This comment letter response contains two parts:

(1) The original submittal from the commenter. (2) A data base printout of EPA’s response to each point raised by the commenter.

Notes about the response letters:

• The response letters were generated by a data base used to track the content of all public

comment submittals and ensure that the Agency responds to each. Each comment letter

was assigned a Letter ID that corresponds to the last four digits of the docket number of the
original comment (as posted on www.regulations.gov).

• Each response letter includes: comment text; an EPA

‐ assigned comment code; and an
individual response. These are described and explained below.

• The data base contains Comment text from the letters submitted by commenters.
Many hard copy letters were scanned into electronic format for inclusion in the data

base. As a result, there may be some typographical errors attributable to optical

character recognition issues. However, all original submittals were reviewed in the

process of drafting responses to ensure that the comment content was understood and
appropriately addressed.

• The content of each comment letter was divided into topic areas and assigned a unique

Comment ID. Additionally, one or more Comment Codes (i.e., unique topic area ID) was assigned to each discrete point raised by a commenter. This information was added to

the data base. To inform final rulemaking decisions, all comments and information

received on a given topic were reviewed by technical experts in each rule area (e.g., on

construction requirements).

• Following decisions on the final rule requirements, Individual responses were drafted
by topic area to ensure completeness and consistency of the responses with the final

rule and other responses to similar comments. Each discrete point made by a

commenter was given a unique response.

• Upon completion of comment responses, all information was entered into the data base.

Each letter response is a compilation of each comment and its individual response, compiled in the order of the original comment letter. As a result of this process, there is
repetition in the response text. The Agency believes this approach ensures completeness

and attention to each comment letter that was submitted.

• All comments in a topic area were reviewed, evaluated, and responded to concurrently.

Responses on each topic area are compiled and are also available in the rulemaking docket.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 1 Underground Injection Control (UIC) Progr am: Federal Requirements for Class VI

Injection Wells for the Geologic Sequestrati on of Carbon Dioxide - Proposed Rule

Comments from Schlumberger Carbon Services

Schlumberger is the world’s leading supplier of oilfield technology, integrated project management and information solutions that optimize reservoir performance. Founded in 1926, the company employs more than 80,000 pe ople of over 140 nati onalities working in approximately 80 countries. Since the earl y 1990’s, Schlumberger has been involved in CO2 injection projects, providing servi ces for subsurface characterization and monitoring, while also investi ng in specific research and de velopment. Leveraging on its internal know how, Schlumberg er has created in 2005 the Sc hlumberger Carbon Services (SCS) activity, which currently focuses on ali gning the group strategy and resources with the current and future CO2 sequestration business environment, while managing the development of comprehensive technologi es and project management services. Schlumberger Carbon Services have both expe rienced geo-technical personnel capable of evaluating all aspects of geol ogic storage as well as the t echnology needed to evaluate, design, construct and monitor storage sites

Schlumberger feels that the proposed rule fo r geologic sequestration of carbon dioxide is a very good start and relatively few changes ar e needed to create a final rule under which geologic CO2 sequestration can become a comme rcial industry and an effective piece in the solution to climate change.

Below we provide comments on the rule la nguage (both general and detailed line-byline), the areas specifically identified for co mment in the preamble, and on other aspects of the preamble.

Comments on areas within the body of the proposed rule

1. Schlumberger asks that the EPA expand th e applicability of Class VI wells to cover wells injecting CO2 that is dissolved in water or brine. The current draft language for Section 146.81(b) states:

This subpart applies to wells used to inject carbon dioxide specifically for the purpose of geologic sequestration, i. e., the long-term containment of a gaseous, liquid or supercritical ca rbon dioxide stream in subsurface geologic formations.

We suggest that the EPA replace the current language with the following language:

This subpart applies to wells used to inject carbon dioxide specifically for the purpose of geologic sequestration, i. e., the long-term containment of aSchlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 2 gaseous, liquid or supercritical ca rbon dioxide stream or carbon dioxide dissolved in water or brine into subsurface geologic formations.

While we recognize today the injecti on of dissolved CO2 raises economic challenges we feel that there may be cas es where the injection of dissolved CO2

will make sense both in terms of economics and in terms of leakage risk. Unlike separate phase CO2, CO2 dissolved in wate r is not less dense than the formation fluid and will not be subject to buoyancy driven leakage.

2. Schlumberger feels that the general prohibition on CO2 injection above the

lowermost USDW should removed from the re gulations. We feel that as long as the injection will not endanger USDWs the elevation with respect to the lowermost USDW is not important. Howeve r, if CO2 injection is allowed above

the lowermost USDW we feel that the EPA must specify that there needs to be a confining unit both above and below the injection zone th at is free of pathways that may allow for leakage of fluids out of the injection zone. The inclusion of a lower confining unit will be important b ecause CO2-saturated brine or water is

more dense than the native formation fluid and will sink.

3. Schlumberger does not support the defau lt post injection site care period of 50 years. We feel that because the characterization and operation of the site will be based on the specific attributes of the site that the length of post injection site care should also be site specific information. In particular the criteria for ending the PISC period should be based on site perf ormance and risk. We support the idea that the director approves fi nal site closure. We s uggest the following language for Section 146.93(b)(1):

(1) The owner or operator shall c ontinue to conduct monitoring as specified in the Director-approved post -injection site care and site closure plan, pursuant to the performance based criteria describe d in 146.93(b)(3).

We suggest the following language for section 146.93(b)(2)

(2) If the owner or operator can dem onstrate to the satisfaction of the Director that the geologic sequestration project no longer poses an endangerment to USDWs, the Director may approve an amendment to the post-injection site care and site clos ure plan to reduce the frequency of monitoring or may authorize site closure.

And we suggest the following language for section 146.93(b)(3)

(3) Prior to authorization for site closure, the owner or operator must demonstrate to the Director, based on monitoring and other site-specific data that no additional monitoring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs, considering the following:.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 3 (i) the estimated magnitude a nd extent of the AOR based on measurements and modeling; (ii) that CO2 movement and pressu re changes match model predictions, (iii) the estimated location of th e detectable CO2 plume based on measurement and modeling (measuring ma gnitude of saturation within the plume or mapping the edge of it); (iv) that there is no evidence of si gnificant leakage of either CO2 or formation fluids that endanger USDWs; (v) that the CO2 plume a nd displaced formation fluid are not expected to migrate in the future in a manner that encounters a potential leakage pathway; and, (vi) that wells at the site are not leaking and have maintained integrity.

4. Schlumberger supports the concept of te sting and monitoring to track the CO2 plume and the associated pressure front. We feel that without this monitoring the validation and updating of the models used to predict the size and shape of the AOR cannot be properly conducte d and that the use of mode ls to predict the size and shape of the AOR will be ineffective. However we feel that the language in section 146.90(g) is too restrictive. The current language states:

(g) Testing and monitoring to track th e extent of the carbon dioxide plume and the position of the pressure front by either monitoring for pressure changes in the first formation overl ying the confining zone or using indirect, geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hol e carbon dioxide detection tools);

We feel that the restrictions placed in this language could adversely impact the efficiency of monitoring and mode ling depending on site conditions. Schlumberger proposes the following alternate language:

(g) Testing and monitoring to track th e extent of the carbon dioxide plume and the position of the pressure front by either monitoring for pressure changes, using geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hol e carbon dioxide detection tools), other techniques that are approved by the director or a combination of techniques if multiple techniques are deemed necessary by the director;

Comments on areas within th e preamble of the rule

1. Schlumberger supports the idea that horizon tal wells may be used for injection for geologic carbon sequestration. Horizontal CO2 injection wells have been successfully and safely used for CO2 injection at the Weyburn project in Saskatchewan, Canada. We feel that there will be sites with conditions that will make the use of horizontal wells necessary.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 4 2. Now that the EPA has introduced the topi cs of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA) we urge the EPA to clarify the roles of both with respect to CO2 injec tion under the UIC program.

Schlumberger supports the EPA in defini ng the injected CO2 stream to exclude

hazardous wastes. We feel that this de finition implies that CO2 itself is not a

hazardous waste under RCRA and that the injected CO2 stream can only be

considered a hazardous waste if it is mi xed with another hazardous waste.

Schlumberger feels that s upercritical and gaseous CO2 do not fit the definition of solid waste under RCRA which is limited to “solid, liquid, semisolid, and contained gaseous materials” and are th erefore not regulate d under RCRA. We encourage the EPA to explore this possibili ty and if in agreement, to adopt and espouse this position in the preamble for the final rule. We further feel that EPA should specify that uncontainerized supercritical CO 2 , like that at injected for CCS,

is not solid waste and therefore not subject to RCRA waste determination requirements.

The preamble of the draft points out that under federally permitted release provision of CERCLA releases in complia nce with a UIC permit are exempt from liability under CERCLA. Schlumberger fails to see how the any releases under the proposed rule that involves both charac terization of the injection stream and characterization of the subsurface can fall outside the federally permitted release provision. We urge the EPA to better clar ify any cases where injection of CO2 in accordance with a UIC permit is not releas ed from liability under the federally permitted release provision of CERCLA. We cannot envision a permit being issued for an injection that could cause an unintended re lease, especially, in light of the information that is required in th e permit application on the composition of the injection stream and on the chemical makeup of the subsurface.

3. In the preamble of the draft U-tube te chnology is specifically called out as a technology available for high pressure fluid sampling. Schlumberger wants point out to the EPA there are other techniques for high pressure fluid sampling the use of wireline conveyed sample bottles. We want to ensu re that no one particular technology is adopted or required for high pr essure sampling. The selection of a single sampling technique (although not in th e rule language) could cause the best available technology to be overlooked now or in the future. We propose that EPA either delete the reference to the U-tube samples of clarify that it is not the only solution available for taking high pressure samples

4. Schlumberger appreciates that the EPA crated the Vulnerability Evaluation Framework (VEF) and we fully support the us e of a logical set of steps to address

the vulnerabilities or risk s associated with geologic carbon sequestration. However, we are concerned that the VE F is not the only method that may beSchlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 5 successful for site evaluation and would lik e EPA to clarify that the VEF is one but not the only approach.

Again we thank the US EPA for this chance to provide comment on the proposed rule. Any questions regarding these comments can be directed to:

Andrew Duguid, Ph.D., PE Senior Wellbore Integrity Engineer

Schlumberger Carbon Services 4449 Easton Way, 2 nd Floor Columbus, OH 43219

Phone: (412) 427-7169

aduguid@slb.comSchlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 6 

### Detailed Line-by-Line Comments

Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
§144.1 Purpose and scope of part 144. - -

(f)(1)(viii) Subpart H of this part sets forth requirements for owners or operators of Class VI injection wells. - -

(g) Scope of the permit or rule requirement. The UIC Permit Program regulates underground injections by six classes of wells (see definition of ‘‘well injection,’’ §144.3).

The six classes of wells are set forth in §144.6. All owners or operators of these injection

wells must be authorized either by permit or rule by the

Director. - -

§144.6 Classification of

wells. - -

(e) Class V . Injection wells not included in Class I, II, III, IV, or VI. Specific types of Class V injection wells are described in §144.81. - -

(f) Class VI. Wells used for geologic sequestration of

carbon dioxide beneath the

lowermost formation containing a USDW. (f) Class VI. Wells used for geologic sequestration of

carbon dioxide. We feel that sequestration can be conducted safely above USDWs as evidenced by the class 2 EOR experience. Also, the restriction to below
the lowest USDW rules out many potential CCS sites.

Subpart B —General Program Requirements - -

§144.15 Prohibition of nonexperimental Class V wells for geologic sequestration. - -

The construction, operation ormaintenance of any nonexperimental Class V geologic sequestration well is prohibited. - We agree, there should be only one class of geologic sequestration well but CO2

class V wells should be grandfathered. 5. Adding Section 144.18 to

read as follows. - -

§144.18 Requirements for - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 7 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

Class VI wells. Owners or operators of Class VI wells must obtain a permit.
Class VI wells are not authorized by rule to inject. - -

Subpart D—Authorization by

Permit - -

§144.36 Duration of permits. - - (a) Permits for Class I and V

wells shall be effective for a

fixed term not to exceed 10 years. UIC Permits for Class II, III and VI wells shall be issued for a period up to the operating life of the facility. - -

7. Section 144.39 is amended by revising the second sentence in paragraph (a) introductory text and by revising the second sentence in paragraph (a)(3) introductory text to read as

follows: - -

§144.39 Modification or

revocation and reissuance of permits. - -

(a) For Class I hazardous waste injection wells, Class II,
Class III or Class VI wells the following may be causes for

revocation and reissuance as well as modification; and for all other wells the following may

be cause for revocation or

reissuance as well as

modification when the permittee requests or agrees. - -

(3) Permits other than for
Class I hazardous waste injection wells, Class II, Class III or Class VI wells may be modified during their terms for this cause only as follows: - -

Subpart E—Permit
Conditions - -

Section 144.51 is amended by revising the first sentence in paragraph (q)(1) and the first sentence in paragraph (q)(2) - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 8 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

to read as:

§144.51 Conditions applicable to all permits. - -

- - (q) (1) The owner or operator of a Class I, II, III or VI well permitted under this part shall establish mechanical integrity prior to commencing injection

or on a schedule determined by the Director. Thereafter the owner or operator of Class I, II, and III wells must maintain mechanical integrity as defined in §146.8 and the owner or operator of Class VI

wells must maintain mechanical integrity as defined in §146.89 of this chapter. - -

(2) When the Director determines that a Class I, II, III

or VI well lacks mechanical integrity pursuant to §146.8 or §146.89 for Class VI of this chapter, he/she shall give
written notice of his/her

determination to the owner or operator. - -

9. Section 144.52 is amended by revising paragraph (a)(8) to

read as follows: - -

§144.52 Establishing permit

conditions. - -

(a)(8) Mechanical integrity. A permit for any Class I, II, III or VI well or injection project

which lacks mechanical integrity shall include, and for any Class V well may include, a condition prohibiting injection operations until the permittee

shows to the satisfaction of the Director under §146.08 or§146.89 for Class VI that the well has mechanical integrity. - -

10. Section 144.55 is amended by revising the first - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 9 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
sentence in paragraph (a) to

read as follows:

§144.55 Corrective Action. - - (a) Coverage. Applicants for Class I, II, (other than existing), III or VI injection well permits shall identify the

location of all known wells within the injection well's area of review which penetrate the injection zone, or in the case of Class II wells operating over the fracture pressure of the injection formation, all known

wells within the area of review penetrating formations affected by the increase in pressure. Applicants for Class VI shall perform corrective action as specified in §146.84. - -

Subpart G—Requirements for Owners and Operators of Class V Injection Wells - -

11. Section 144.80 is amended by revising the first sentence in paragraph (e) and by adding paragraph (f) to

read as follows: - -

§144.80 What is a Class V injection well? - -

(e) Class V. Injection wells not included in Class I, II, III, IV or

VI. - -

(f) Class VI. Wells used for geologic sequestration of

carbon dioxide. - -

PART 146—UNDERGROUND
INJECTION CONTROL
PROGRAM: CRITERIA AND
STANDARDS - -

§146.5 Classification of injection wells. - -

(e) Class V. Injection wells not included in Class I, II, III, IV or

VI. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 10 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(f) Class VI. Wells used for geologic sequestration of

carbon dioxide beneath the
lowermost formation containing an underground source of drinking water (USDW). (f) Class VI. Wells used for geologic sequestration of

carbon dioxide. We feel that sequestration can be conducted safely above USDWs as evidenced by the class 2 EOR experience. Also, the restriction to below
the lowest USDW rules out many potential CCS sites.

Subpart H—Criteria and Standards Applicable to
Class VI Wells - -

§146.81 Applicability. - - (a) This subpart establishes

criteria and standards for underground injection control programs to regulate Class VI carbon dioxide geologic sequestration injection wells. - -

(b) This subpart applies to wells used to inject carbon dioxide specifically for the purpose of geologicsequestration, i.e., the longterm containment of a gaseous, liquid or supercritical

carbon dioxide stream in subsurface geologic

formations. - -

(c) This subpart applies to owners and operators of permit or rule-authorized Class I industrial, Class II, or Class V experimental carbon dioxide injection projects who seek to apply for a Class VI geologic sequestration permit for their

well or wells. If the Director
determines that USDWs will not be endangered, such wells are exempt, at the Director’s discretion, from the casing and cementing requirements at §§146.86(b) and 146.87(a)(1) through (3). (c) This subpart applies to owners and operators of permit or rule-authorized Class I industrial, Class II, or Class V experimental carbon dioxide injection projects who seek to apply for a Class VI geologic sequestration permit for their

well or wells. If the Director
determines that USDWs will not be endangered, such wells are exempt, at the Director’s discretion, from the casing and cementing requirements at §§146.86(b) and 146.87(a)(1) through (3) if the wells were constructed prior to January 1,

2010. We feel that there needs to be

a cutoff date for the grandfathering of wells so eventually all Class 6 wells are

constructed to the same

standardSchlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 11 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(d) Definitions . The following definitions apply to this subpart. To the extent that
these definitions conflict with those in §146.3 these definitions govern: - -

Area of review means the region surrounding the geologic sequestration project that may be impacted by the injection activity. The area of

review is based on computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon

dioxide stream. - -

Carbon dioxide plume means the underground extent, in three dimensions, of an injected carbon dioxide

stream. - -

Carbon dioxide stream means carbon dioxide that has been captured from an emission source (e.g., a power plant), plus incidental associated
substances derived from the

source materials and the capture process, and any

substances added to the stream to enable or improve the injection process. This subpart does not apply to any

carbon dioxide stream that

meets the definition of a

hazardous waste under 40 CFR part 261. Carbon dioxide stream carbon dioxide that has been captured from an industrial process that is injected in any physical

state or dissolved in water or

brine. It includes incidental

associated substances derived

from the source materials and the capture process, and any

substances added to the stream to enable or improve the injection process. This subpart does not apply to any

carbon dioxide stream that
meets the definition of a

hazardous waste under 40 CFR part 261. We want to ensure that dissolved CO2 is specifically allowed as it may allow a solution to the upward buoyancy drive associated with separate phase CO2.

Confining zone means a geologic formation, group of formations, or part of a formation stratigraphically overlying the injection zone
that acts as a barrier to fluid

movement. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 12 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

Corrective action means the use of Director approved

methods to assure that wells
within the area of review do

not serve as conduits for the

movement of fluids into underground sources of drinking water (USDW). - -

Geologic sequestration means the long-term containment of a gaseous, liquid or supercritical

carbon dioxide stream in subsurface geologic

formations. This term does not apply to its capture or transport. Geologic sequestration means the long-term containment of a

carbon dioxide stream in subsurface geologic

formations. This term does not apply to its capture or transport. CO2 stream was already

defined and should e used

here.

Geologic sequestration project means an injection well or wells used to emplace a

carbon dioxide stream

beneath the lowermost formation containing a USDW.

It includes the subsurface

three-dimensional extent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as the

surface area above that delineated region. Geologic sequestration project means an injection well or wells used to emplace a

carbon dioxide stream into an injection zone. It includes the

subsurface three-dimensional

extent of the carbon dioxide plume, associated pressure front, and displaced brine, as

well as the surface area above that delineated region. -

Injection zone means a geologic formation, group of formations, or part of a

formation that is of sufficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through

a well or wells associated with a geologic sequestration project. Injection zone means a geologic formation, group of formations, or part of a

formation that is of sufficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through

a well or wells associated with a geologic sequestration project. -

Post-injection site care means appropriate monitoring and other actions (including corrective action) needed following cessation of injection
to assure that USDWs are not endangered as required under §146.93. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 13 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

Pressure front means the zone of elevated pressure that is created by the injection of

carbon dioxide into the subsurface. For the purposes of this subpart, the pressure

front of a carbon dioxide plume refers to a zone where there is a pressure differential

sufficient to cause the movement of injected fluids or
formation fluids into a USDW. Pressure front means the zone of elevated pressure that is created by the injection of the

carbon dioxide stream into the subsurface, where there is a pressure differential sufficient

to cause movement of the

carbon dioxide stream or
formation fluids into a USDW. -

Site closure the point/time, as determined by the Director following the requirements under §146.93, at which the owner or operator of a GS site is released from post-injection site care responsibilities. Site closure means the point/time, as determined by the Director following the requirements under §146.93, at which the owner or operator of a GS project is released from post-injection site care responsibilities. Suggest using “GS project” to

be consistent with other

definitions

Transmissive fault or fracture

means a fault or fracture that has sufficient permeability and

vertical extent to allow fluids to

move between formations. Transmissive fault or fracture

means a fault or fracture that has sufficient permeability and

vertical extent to allow fluids to move beyond the confining

zone. The term between formations

is insufficient as it could also include multiple zones within a injection zone or between two zones above the confining

unit.

§146.82 Required Class VI permit information. - -

This section sets forth the

information which the owner or operator must submit to the

Director in order to be permitted as a Class VI well. The application for a permit for construction and operation of
a Class VI well must include the following: - -

(a) Information required in 40 CFR 144.31 (e)(1) through (6); - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 14 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(b) A map showing the injection well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number,
or name and location of all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including

structures intended for human occupancy and roads. The map should also show faults, if known or suspected. Only information of public record is required to be included on this

map; (b) A map or electronic file (e.g. GIS file) showing the injection well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number,

or name and location of all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including

structures intended for human occupancy and roads. The map should also show faults, if known or suspected with surface expressions. Only information of public record is required to be included on this

map; This may mean more clarification. It seems strange to have deep faults on a surface map. Is the map to be

of the surface or of the confining unit? Also, any map will be very busy so it may be

useful to be able to submit an
electronic file like a GIS file.

(c) The area of review based on modeling, using data obtained during logging and testing of the well and the formation as required by paragraphs (l), (r), and (s) of this section; - We support this but it may

need to be better clarified that the well must e drilled prior to the permit application

(d) Information on the geologic structure and hydrogeologic properties of the proposed storage site and overlying formations, including: - -

(1) Maps and cross sections of the area of review; - -

(2) Location, orientation, and properties of known or suspected faults and fractures that may transect the confining zone(s) in the area of review and a determination that they

would not interfere with containment; - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 15 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(3) Information on seismic history including the presence and depth of seismic sources

and a determination that the seismicity would not interfere with containment; (3) Information on seismic history of the area including the presence and depth of

seismic sources and a

determination that the seismicity would not interfere with containment; It seems like this requirement is at a larger scale than the AOR (maybe a regional scale) than the other requirements. This should be specified.

(4) Data on the depth, areal extent, thickness, mineralogy, porosity, permeability and capillary pressure of the injection and confining zone(s); including geology/facies changes based on field data which may include geologic cores, outcrop data, seis mic surveys, well logs, and names and lithologic descriptions; (4) Data on the depth, areal extent, thickness, mineralogy, porosity, permeability and capillary entry pressure of the injection and confining zone(s); including geology/facies changes based on field data which may include geologic cores, outcrop data, seis mic surveys, well logs, and names and lithologic descriptions; Should this include capillary pressure or capillary entry pressure?

(5) Geomechanical information on fractures, stress, ductility, rock strength, and in situ fluid pressures within the confining zone; and - -

(6) Geologic and topographic maps and cross sections illustrating regional geology, hydrogeology, and the geologic structure of the local

area. - -

(e) A tabulation of all wells

within the area of review which penetrate the injection or confining zone(s). Such data must include a description of each well's type, construction, date drilled, location, depth, record of plugging and/or completion, and any additional information the Director may require; - How will this be handled if all

of this data is not available for

each well?

(f) Maps and stratigraphic cross sections indicating the general vertical and lateral limits of all USDWs, water wells and springs within the area of review, their positions relative to the injection zone(s)

and the direction of water movement, where known; In -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 16 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

(g) Baseline geochemical data on subsurface formations, including all USDWs in the area of review; (g) Baseline geochemical data on subsurface formations, including all USDWs and geochemically monitored in the area of review; All formations that are or may need to be geochemically

monitored should be included

(h) Proposed operating data: - - (1) Average and maximum daily rate and volume of the carbon dioxide stream; - -

(2) Average and maximum injection pressure; - -

(3) The source of the carbon dioxide stream; and - -

(4) An analysis of the chemical and physical characteristics of the carbon dioxide stream; - -

(i) The compatibility of the

carbon dioxide stream with fluids in the injection zone and minerals in both the injection and the confining zone(s),

based on the results of the formation testing program, and

with the materials used to construct the well; - -

(j) Proposed formation testing program to obtain an analysis of the chemical and physical characteristics of the injection zone and confining zone; - -

(k) Proposed stimulation program and a determination

that stimulation will not interfere with containment; - -

(l) The results of the formation testing program as required in paragraph (j) of this section; - -

(m) Proposed procedure to outline steps necessary to conduct injection operation; - -

(n) Schematic or other appropriate drawings of the

surface and subsurface - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 17 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

construction details of the well;

(o) Injection well construction procedures that meet the requirements of §146.86; - -

(p) Proposed area of review and corrective action plan that meets the requirements under §146.84; - -

(q) The status of corrective

action on wells in the area of review; - -

(r) All available logging and testing program data on the well required by §146.87; - -

(s) A demonstration of mechanical integrity pursuant to §146.89; - -

(t) A demonstration, satisfactory to the Director, that the applicant has met the financial responsibility requirements under §146.85; - -

(u) Proposed testing and monitoring plan required by §146.90; - -

(v) Proposed injection well plugging plan required by §146.92(b); - -

(w) Proposed post-injection site care and site closure plan required by §146.93(a); - -

(x) Proposed emergency and remedial response plan required by §146.94; and - -

(y) Any other information requested by the Director. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 18 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

§146.83 Minimum criteria for siting. - -

(a) Owners or operators of
Class VI wells must

demonstrate to the satisfaction

of the Director that the wells

will be sited in areas with a suitable geologic system. The geologic system must be comprised of: - -

(1) An injection zone of sufficient areal extent, thickness, porosity, and permeability to receive the total anticipated volume of the carbon dioxide stream; - -

(2) A confining zone(s) that is

free of transmissive faults or

fractures and of sufficient areal extent and integrity to contain the injected carbon dioxide stream and displaced

formation fluids and allow injection at proposed maximum pressures and volumes without initiating or propagating fractures in the confining zone(s); and - We support this language as it

is written.

(b) At the Director’s discretion, owners or operators of Class VI wells must identify and

characterize additional zones that will impede vertical fluid movement, are free of faults and fractures that may interfere with containment, allow for pressure dissipation, and provide additional opportunities for monitoring, mitigation and remediation. (b) Owners or operators of Class VI wells must identify

and characterize some additional zones, if they exist, that will impede vertical fluid movement, allow for pressure dissipation, and provide additional opportunities for monitoring, mitigation and
remediation. Vertical faults

and fractures that transect

these zones must be

identified. We believe that a site with a single confining can provide storage integrity, however, we
feel that if there are additional confining layers at the site they should be characterized to get a better estimate of leakage risk to USDWs and possibly identify additional monitoring zones.

§146.84 Area of review and

corrective action. - -

(a) The area of review is the region surrounding the geologic sequestration project that may be impacted by the injection activity. The area of

review is based on (a) The area of review is based on computational modeling that accounts for physical and the chemical properties of all phases of the injected carbon dioxide -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 19 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon

dioxide stream. stream, the associated pressure front, and displaced

brine.

(b) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan to delineate the area of review for a proposed geologic sequestration project, periodically reevaluate the delineation, and perform

corrective action that meets the requirements of this section and is acceptable to the Director. As a part of the permit application for approval by the Director, the owner or operator must submit an area

of review and corrective action plan that includes the following

information: (b) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan to delineate the area of review for a proposed geologic sequestration project, reevaluate the delineation, and perform corrective action that meets the requirements of this

section in a manner and at a frequency acceptable to the Director. As a part of the permit application, the owner or operator must submit an
area of review and corrective action plan that includes the following information:

(1) The method for delineating

the area of review that meets the requirements of paragraph - -

(c) of this section, including the model to be used, assumptions that will be made,

and the site characterization

data on which the model will be based; - -

(2) A description of: - - (i) The minimum fixed frequency, not to exceed 10 years, the owner or operator proposes to reevaluate the area of review; Revision: (i) The owner or operator will reevaluate the AOR after two years, 5 years and then no less frequently than every 5 years for period of injection. This schedule may be relaxed at the
discretion of the director in the post injection period if appropriate data exist to support the change. We feel that a frequency of every 10 years is too long to identify early discrepancies between the site performance and the site model. Seeing early difference will allow for earlier model updating and provide additional reduction in leakage risk and a better understanding of the site.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 20 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(ii) The monitoring and operational conditions that

would warrant a reevaluation of the area of review prior to

the next scheduled reevaluation as determined by the minimum fixed frequency established in paragraph (b)(2)(i) of this section. - -

(iii) How monitoring and operational data (e.g., injection rate and pressure) will be used

to inform an area of review reevaluation; and - -

(iv) How corrective action will

be conducted to meet the requirements of paragraph (d) of this section, including what

corrective action will be performed prior to injection and what, if any, portions of

the area of review will have

corrective action addressed on a phased basis and how the phasing will be determined;

how corrective action will be adjusted if there are changes in the area of review; and how site access will be guaranteed
for future corrective action. (iv) How corrective action will

be conducted to meet the requirements of paragraph (d) of this section, including what

corrective action will be performed prior to injection and what, if any, portions of

the area of review will have

corrective action addressed on a phased basis and how the phasing will be determined;

how corrective action will be adjusted if there are changes in the area of review; and how site access will be arranged
for future corrective action. Future access cannot be fully guaranteed for an area in advance that may not even be

within the boundaries of the initial AOR/ project.

(c) Owners or operators of Class VI wells must perform the following actions to delineate the area of review, identify all wells that require corrective action, and perform

corrective action on those

wells: - -

(1) Predict, using computational modeling, the projected lateral and vertical migration of the carbon dioxide plume and formation fluids in

the subsurface from the commencement of injection activities until the plume movement ceases, pressure
differentials sufficient to cause the movement of injected

fluids or formation fluids into a USDW are no longer present, - We support this as writtenSchlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 21 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
or after a fixed time period as determined by the Director.

The model must:

(i) Be based on detailed geologic data collected to characterize the injection zone, confining zone and any additional zones; and anticipated operating data, including injection pressures,

rates and total volumes over the proposed life of the geological sequestration project; (i) Be based on detailed geologic data collected to characterize the injection zone, confining zone(s), monitoring zones and any additional zones; and anticipated operating data, including injection pressures,

rates and total volumes over the proposed life of the geological sequestration project; We feel that if there are secondary confining units that they should be included in the site model along with any

transmissive zones between the primary and secondary confining units.

(ii) Take into account any geologic heterogeneities, data quality, and their possible impact on model predictions;

and - -

(iii) Consider potential migration through faults, fractures, and artificial penetrations. - -

(2) Using methods approved by the Director, identify all penetrations, including active

and abandoned wells and underground mines, in the area of review that may penetrate the confining zone. Provide a description of each well’s type, construction, date drilled, location, depth, record of plugging and/or completion, and any additional information the Director may require; and - We feel that there needs to be some effort to identify unknown wells using aerial surveys or other methods. We support this language as long as it is interpreted to mean more than just a record search

in areas that that have been explored or produced oil and gas or have had other deep

wells.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 22 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(3) Determine which

abandoned wells in the area of review have been plugged (as required by §146.92) in a manner that prevents the

movement of carbon dioxide or associated fluids that may endanger USDWs. (3) Determine which

abandoned wells identified in 146.84 (c) (2) have been plugged (as required by §146.92) in a manner that prevents the movement of

carbon dioxide or formation fluids that may endanger
USDWs. -

(d) Owners or operators of Class VI wells must perform

corrective action on all wells in
the area of review that are

determined to need corrective action using methods necessary to prevent the

movement of fluid into or between USDWs including

use of corrosion resistant materials, where appropriate. Owners or operators of Class VI wells must perform corrective action using corrosion resistant materials, when appropriate, on all wells identified in 146.84(c)(2) that

are determined to need

corrective action”. -

(e) If monitoring data indicate an endangerment to USDWs, the owner or operator must notify the Director and cease operations as required by §146.94. - -

(f) At the minimum fixed frequency, not to exceed 10 years, as specified in the area

of review and corrective action plan, or when monitoring and operational conditions warrant, owners or operators must: (f) At the same frequency as
the reevaluation of the AOR as specified in 146.84(c ) (2) (i), or when monitoring and operational conditions warrant, owners or operators must: -

(1) Reevaluate the area of

review in the same manner specified in paragraph (c)(1) of this section; - -

(2) Identify all wells in the

reevaluated area of review that require corrective action in the same manner specified in - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 23 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
paragraph (c)(2) of this section;

(3) Perform corrective action on wells requiring corrective

action in the reevaluated area

of review in the same manner specified in paragraph (c)(3) of this section; and - -

(4) Submit an amended area

of review and corrective action plan or demonstrate to the Director through monitoring data and modeling results that

no amendment to the area of

review and corrective action plan is needed. (4) Submit an amended area

of review and corrective action plan or demonstrate to the Director through monitoring data and modeling results that no change to the area of

review and corrective action plan is needed. -

(g) The emergency and remedial response plan (as required by §146.94) and a

demonstration of financial responsibility (as described by §146.85) must account for the entire area of review, regardless of whether or not

corrective action in the area of review is phased. - -

§146.85 Financial responsibility. - -

(a) The owner or operator

must demonstrate and

maintain financial responsibility and resources for corrective action (that meets the requirements of §146.84), injection well plugging (that meets the requirements of §146.92), post-injection site care and site closure (that meets the requirements of §146.93), and emergency and remedial response (that meets the requirements of §146.94) in a manner prescribed by the

Director until: - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 24 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(1) The Director receives andapproves the completed postinjection site care and site closure plan; and - -

(2) The Director determines

that the site has reached the end of the post injection site care period. - -

(b) The owner or operator must provide to the Director, at a frequency determined by the Director, written updates of adjustments to the cost estimate to account for any

amendments to the area of

review and corrective action plan (§146.84), the injection well plugging plan (§146.92), and the post-injection site care and site closure plan (§146.93). (b) The owner or operator must provide to the Director, at the same frequency as the AOR reevaluation, written updates of adjustments to the

cost estimate to account for any amendments to the area

of review and corrective action plan (§146.84), the injection well plugging plan (§146.92), and the post-injection site care and site closure plan (§146.93). We feel that potential changes in the size of the AOR require that all site plans be

reevaluated at the same frequency as the AOR.

(c) The owner or operator must notify the Director of

adverse financial conditions such as bankruptcy, that may affect the ability to carry out injection well plugging and post-injection site care and

site closure. - -

(d) The operator must provide an adjustment of the cost

estimate to the Director if the

Director has reason to believe that the original demonstration is no longer adequate to cover the cost of injection well plugging (as required by §146.92) and post-injection site care and site closure (as required by §146.93). - -

§146.86 Injection well construction requirements. - -

(a) General. The owner or operator must ensure that all
Class VI wells are constructed and completed to: - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 25 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(1) Prevent the movement of
fluids into or between USDWs or into any unauthorized

zones; (1) Prevent the movement of
fluids into or between USDWs or into any unauthorized zones that causes endangerment; -

(2) Permit the use of appropriate testing devices and workover tools; and - -

(3) Permit continuous monitoring of the annulus space between the injection tubing and long string casing. - -

(b) Casing and Cementing of
Class VI Wells. - -

(1) Casing and cement or

other materials used in the
construction of each Class VI

well must have sufficient structural strength and be designed for the life of the geologic sequestration project.

All well materials must be compatible with fluids with which the materials may be expected to come into contact

and meet or exceed standards developed for such materials by the American Petroleum Institute, ASTM International, or comparable standards acceptable to the Director. The casing and cementing program must be designed to prevent the movement of fluids
into or between USDWs. In

order to allow the Director to determine and specify casing and cementing requirements, the owner or operator must provide the following

information: - We support this language as

written.

(i) Depth to the injection zone; - - (ii) Injection pressure, external pressure, internal pressure and axial loading; (ii) Injection pressure, external pressure, internal pressure and axial loading; What is meant by external and internal pressure?

(iii) Hole size; (iv) Size and grade of all casing strings (wall thickness, external diameter, nominal weight, length, joint specification and construction material); - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 26 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(v) Corrosiveness of the carbon dioxide stream, and formation fluids; - -

(vi) Down-hole temperatures; (vi) Down-hole temperatures and pressures; -

(vii) Lithology of injection and confining zones; - -

(viii) Type or grade of cement;

and (viii) Type or grade of cement;

and additives -

(ix) Quantity, chemical composition, and temperature

of the carbon dioxide stream. - -

(2) Surface casing must extend through the base of the
lowermost USDW and be

cemented to the surface. (2) Surface casing must extend through the base of the
lowermost USDW above the injection zone and be
cemented to the surface. In some parts of the US the USDW is very deep and this standard may preclude geologic sequestration in

these areas. (3) At least one long string casing, using a sufficient number of centralizers, must extend to the injection zone and must be cemented by circulating cement to the surface in one or more stages. - We support this language work by Carey et al and crow
et al shows that CO2 can move above the top of the CO2 reservoir, so cementing to surface will provide the best

chance to have maximum

zonal isolation (4) Circulation of cement may be accomplished by staging. The Director may approve an
alternative method of cementing in cases where the

cement cannot be recirculated to the surface, provided the owner or operator can demonstrate by using logs that

the cement does not allow

fluid movement behind the

well bore. - -

(5) Cement and cement additives must be compatible

with the carbon dioxide stream
and formation fluids and of sufficient quality and quantity to maintain integrity over the design life the geologic sequestration project. The integrity and location of the cement shall be verified using technology capable of evaluating cement quality radially and identifying the

location of channels to ensure
that USDWs are not (5) Cement and cement

additives must be suitable for

use with the carbon dioxide
stream and formation fluids and of sufficient quality and quantity to maintain integrity over the project life. The integrity and location of the cement shall be verified using technology capable of evaluating cement quality radially and identifying the

location of channels to ensure
that USDWs are not endangered. Well cements need to site and condition specific. There may be instances or places in the well that will require special

cements. It is also that the cement in the well last as long as the project and post injection period.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 27 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
endangered.

(c) Tubing and packer. - - (1) All owner and operators of Class VI wells must inject fluids through tubing with a packer set at a depth opposite

a cemented interval at the location approved by the

Director. - -

(2) In order for the Director to determine and specify requirements for tubing and packer, the owner or operator must submit the following

information: - -

(i) Depth of setting; - - (ii) Characteristics of the

carbon dioxide stream (chemical content, corrosiveness, temperature, and density); - -

(iii) Injection pressure; - - (iv) Annular pressure; - - (v) Injection rate (intermittent or continuous) and volume of the carbon dioxide stream; - -

(vi) Size of casing; and - - (vii) Tubing tensile, burst, and collapse strengths. - -

§146.87 Logging, sampling, and testing prior to injection well operation. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 28 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(a) During the drilling and
construction of a Class VI injection well, the owner or operator must run appropriate logs, surveys and tests to determine or verify the depth, thickness, porosity, permeability, and lithology of, and the salinity of any formation fluids in, all relevant geologic formations to assure conformance with the injection well construction requirements under §146.86, and to

establish accurate baseline data against which future measurements may be compared. The owner or operator must submit to the Director a descriptive report prepared by a knowledgeable log analyst that includes an interpretation of the results of such logs and tests. At a minimum, such logs and tests

must include: (a) During the drilling and
construction of a Class VI injection well, the owner or operator must run appropriate logs, surveys and tests to determine or verify the depth, thickness, porosity, permeability, and lithology of, and the salinity of any formation fluids in, all relevant geologic formations to assure conformance with the injection well construction requirements under §146.86, and to

establish accurate baseline data against which future measurements may be compared. The owner or operator must submit to the Director a descriptive report prepared by a knowledgeable log analyst that includes an interpretation of the results of such logs and tests. The Director may require such logs and tests as may be needed after taking into account the availability of similar data in the area of the drilling site to

ensure that the data is equivalent to the data as

would be collected based on such logs and tests as:: In well defined areas, these evaluations are frequently unnecessary. The director

should have discretion to select the appropriate requirements necessary to
ensure that sufficient baseline

data and information are available. For example, in an
area where a number of wells are being drilled, the logging of surface hole yields little

useful additional information.

(1) Deviation checks during drilling on all holes constructed by drilling a pilot hole which are enlarged by reaming or
another method. Such checks must be at sufficiently frequent

intervals to determine the

location of the borehole and to

assure that vertical avenues
for fluid movement in the form of diverging holes are not created during drilling; and - -

(2) Before and upon

installation of the surface casing: - -

(i) Resistivity, spontaneous potential, and caliper logs before the casing is installed;

and - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 29 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(ii) A cement bond and variable density log, and a temperature log after the casing is set and cemented. - -

(3) Before and upon installation of the long string casing: - -

(i) Resistivity, spontaneous potential, porosity, caliper, gamma ray, fracture finder logs, and any other logs the Director requires for the given geology before the casing is installed; and - -

(ii) A cement bond and variable density log, and a temperature log after the casing is set and cemented. (ii) Cement evaluation logs after the casing is set and

cemented to evaluate cement quality radially with sufficient resolution to identify channels or changes to the cement quality. Radial is key to finding pathways but the resolution
must be sufficient to see the pathways. See the pathway
identified in Crow et al

(4) A series of tests designed

to demonstrate the internal

and external mechanical integrity of injection wells, which may include: (4) Test(s) designed to

demonstrate the internal and external mechanical integrity of injection wells, which may

include: -

(i) A pressure test with liquid

or gas; - -

(ii) A tracer survey such as oxygen-activation logging; (ii) Diagnostic tools such as oxygen-activation logging; Technical correction

(iii) A temperature or noise log; - - (iv) A casing inspection log, if required by the Director; and - -

(5) Any alternative methods that provide equivalent or

better information and that are required of and/or approved of by the Director. - We interpret that (5) applies to 146.87(a)

(b) The owner or operator

must take and submit to the

Director whole cores or sidewall cores of the injection zone and confining system and formation fluid samples from the injection zone(s). The Director may accept cores from nearby wells if the owner or operator can demonstrate

that core retrieval is not possible and that such cores are representative of (b) The owner or operator

must submit to the Director a report describing whole cores

or sidewall cores representative of the injection zone and confining system and formation fluid samples from the injection zone(s). The Director may accept data from cores and fluid samples from nearby wells if the owner or operator can demonstrate that such data are representative The information required should be sufficient to properly describe the injection and confining zones.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 30 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

conditions at the well. The Director may require the owner or operator to core
other formations in the

borehole. of conditions at the well.

(c) The owner or operator

must record the fluid temperature, pH, conductivity, reservoir pressure and the static fluid level of the injection zone(s). (c) Prior to injection well operation, the owner or operator must record the formation temperature, formation fluid pH and conductivity, and reservoir pressure of the injection zone(s). -

(d) At a minimum, the owner or operator must determine or calculate the following information concerning the injection and confining zone(s): - -

(1) Fracture pressure; - - (2) Other physical and

chemical characteristics of the injection and confining zones;

and - -

(3) Physical and chemical

characteristics of the formation fluids in the injection zone. - -

(e) Upon completion, but prior to operation, the owner or operator must conduct the following tests to verify hydrogeologic characteristics of the injection zone: (d) At any time prior to injection well operation, the owner or operator must determine fracture pressures of the injection and confining

zones and conduct tests to verify hydrogeologic and geomechanical characteristics of the injection zone, e.g.: -

(1) A pump test; or - - (2) Injectivity tests. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 31 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(f) The owner or operator must provide the Director with the opportunity to witness all logging and testing by this subpart. The owner or operator must submit a
schedule of such activities to the Director 30 days prior to conducting the first test and submit any changes to the schedule 30 days prior to the

next scheduled test. (f) The owner or operator must provide the Director with the opportunity to witness all logging and testing by this subpart. The owner or operator must submit a
schedule of such activities to the Director upon spudding the well and submit any changes to the schedule 48 hours prior

to the scheduled test. The changes reflect the realities of flexible rig schedules and consistency with Class II practices.

§146.88 Injection well operating requirements. - -

(a) Except during stimulation, the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone so as to assure that the injection does not
initiate new fractures or propagate existing fractures in the injection zone. In no case may injection pressure initiate fractures in the confining zone(s) or cause the movement of injection or

formation fluids that endangers a USDW. (a) Except during stimulation, the owner or operator must ensure that injection pressure does not exceed 90 percent of the hydraulic fracture pressure of the confining zone so as to assure that the injection does
not initiate new fractures or propagate existing fractures in the confining zone. In no case may injection pressure initiate fractures in the confining zone(s) or cause the movement of injection or

formation fluids that endangers a USDW. Maintaining the integrity of the confining zone is the critical parameter.

(b) Injection between the outermost casing protecting
USDWs and the well bore is prohibited. (b) Injection of the CO2 stream between the outermost casing protecting USDWs and the well bore is prohibited. -

(c) The owner or operator

must fill the annulus between the tubing and the long string casing with a non-corrosive fluid approved by the Director. The owner or operator must

maintain on the annulus a pressure that exceeds the operating injection pressure,

unless the Director determines that such requirement might harm the integrity of the well. (c) The owner or operator

must fill the annulus between the tubing and the long string casing with a non-corrosive fluid approved by the Director. Industry experience with the Class II UIC program does not support this requirement.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 32 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(d) Other than during periods

of well workover (maintenance) approved by

the Director in which the sealed tubing-casing annulus is of necessity disassembled

for maintenance or corrective procedures, the owner or operator must maintain mechanical integrity of the injection well at all times. - -

(e) The owner or operator

must install and use continuous recording devices to monitor: the injection pressure; the rate, volume, and temperature of the carbon dioxide stream; and the pressure on the annulus between the tubing and the long string casing and annulus fluid volume; and must install

and use alarms and automatic down-hole shut-off systems, designed to alert the operator

and shut-in the well when operating parameters such as annulus pressure, injection rate or other parameters approved by the Director diverge beyond permitted ranges and/or gradients specified in the permit; - -

(f) If a down-hole automatic shutdown is triggered or a loss of mechanical integrity is discovered, the owner or operator must immediately investigate and identify as expeditiously as possible the cause of the shutoff. If, upon such investigation, the well appears to be lacking mechanical integrity, or if monitoring required under paragraph (e) of this section

otherwise indicates that the well may be lacking mechanical integrity, the owner or operator must: - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 33 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(1) Immediately cease injection; - -

(2) Take all steps reasonably necessary to determine whether there may have been a release of the injected carbon dioxide stream into any unauthorized zone; - -

(3) Notify the Director within

24 hours (3) Notify the Director within 24 hours of discovery; -

(4) Restore and demonstrate mechanical integrity to the

satisfaction of the Director prior to resuming injection; and - -

(5) Notify the Director when injection can be expected to

resume. - -

§146.89 Mechanical integrity. - -

(a) A Class VI well has mechanical integrity if: - -

(1) There is no significant leak in the casing, tubing or packer;

and - -

(2) There is no significant fluid
movement into a USDW through channels adjacent to the injection well bore. - -

(b) To evaluate the absence of significant leaks under paragraph (a)(1) of this section, owners or operators must, following an initial annulus pressure test, continuously monitor injection pressure, rate, injected volumes, and pressure on the annulus between tubing and long stem casing and annulus fluid volume as specified in §146.88 (e); - -

(c) At least once per year, the owner or operator must use one of the following methods

to determine the absence of significant fluid movement under paragraph (a)(2) of this

section: - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 34 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(1) A tracer survey such as oxygen-activation logging; - -

(2) A temperature or noise log;

or - -

(3) A casing inspection log, if required by the Director. - -

(d) The Director may require any other test to evaluate mechanical integrity under paragraph (a)(1) or (a)(2) of this section. Also, the Director may allow the use of a test to

demonstrate mechanical integrity other than those listed

above with the written approval of the Administrator. To obtain approval, the

Director must submit a written request to the Administrator,
which must set forth the proposed test and all technical data supporting its use. The Administrator must approve the request if it will reliably

demonstrate the mechanical integrity of wells for which its use is proposed. Any alternate method approved by the Administrator will be published

in the Federal Register and may be used in all States in accordance with applicable
State law unless its use is

restricted at the time of approval by the Administrator. - -

(e) In conducting and evaluating the tests

enumerated in this section or others to be allowed by the Director, the owner or operator and the Director must apply

methods and standards generally accepted in the industry. When the owner or operator reports the results of mechanical integrity tests to the Director, he/she shall include a description of the test(s) and the method(s) used. In making his/her - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 35 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

evaluation, the Director must review monitoring and other

test data submitted since the previous evaluation.

(f) The Director may require

additional or alternative tests if the results presented by the owner or operator under paragraph (d) of this section are not satisfactory to the

Director to demonstrate that there is no significant leak in the casing, tubing or packer or significant movement of fluid
into or between USDWs resulting from the injection activity as stated in paragraphs (a)(1) and (2) of

this section. - -

§146.90 Testing and monitoring requirements. - -

The owner or operator of a Class VI well must prepare, maintain, and comply with a testing and monitoring plan to verify that the geologic sequestration project is operating as permitted and is not endangering USDWs. The testing and monitoring plan

must be submitted with the permit application, for Director approval, and must include a description of how the owner or operator will meet the requirements of this section. Testing and monitoring associated with geologic sequestration projects must, at a minimum, include: - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 36 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(a) Analysis of the carbon

dioxide stream with sufficient frequency to yield data representative of its chemical and physical characteristics; - -

(b) Installation and use, except during well workovers as defined in §146.86(d), of continuous recording devices to monitor injection pressure, rate and volume; the pressure

on the annulus between the tubing and the long string casing; and the annulus fluid volume; - 146.86(d) does not exist; perhaps 146.88(d) is what was

intended.

(c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on a quarterly

basis to ensure that the well components meet the
minimum standards for material strength and performance set forth in §146.86(b) by: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed quarterly and may be modified to be less frequent as approved by the

Director based on construction materials, operating conditions, and monitoring history to ensure that the well components meet the

minimum standards for material strength and performance set forth in §146.86(b) by: Allows application of performance based approach.

(1) Placing coupons of the well

construction materials in

contact with the carbon dioxide stream; or (1) Analyzing coupons of the

well construction materials placed in contact with the carbon dioxide stream; or -

(2) Routing the carbon dioxide stream through a loop

constructed with the material used in the well; or (2) Routing the carbon dioxide stream through a loop

constructed with the material used in the well and inspecting the materials in the loop; or -

(3) Using an alternative method approved by the Director; (3) Using an alternative method, materials, or time period approved by the Director; -

(d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may

be a result of carbon dioxide (d) Periodic monitoring of the ground water quality for geochemical changes above the confining zone(s) that may

be a result of carbon dioxide -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 37 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
movement through the confining zone or additional

identified zones: movement through the confining zone or additional

identified zones:

(1) The location and number of monitoring wells must be based on specific information about the geologic sequestration project, including injection rate and volume, geology, the presence of artificial penetrations and other factors; (1) The location and number of monitoring wells must be based on specific information about the geologic sequestration project, including injection rate and volume, geology, the presence of artificial penetrations and

other relevant factors aswarranted by a riskassessment; The monitoring should be designed to reduce risk

(2) The monitoring frequency and spatial distribution of monitoring wells must be

based on baseline geochemical data that has

been collected under §146.82(a)(6) and any modeling results in the area of review evaluation required by §146.84(b); (2) The monitoring frequency and spatial distribution of monitoring wells must be based on geological and geophysical data that has

been collected under §146.82(d) and any modeling

results in the area of review evaluation required by §146.84(b); Geochemical data does not seem have a high degree of relevance in selecting monitoring well sites.

(e) A demonstration of external mechanical integrity pursuant to §146.89(c) at least once per year throughout the duration of the geologic sequestration project; (e) A demonstration of external mechanical integrity pursuant to §146.89(c) at least once per year throughout the life of the well; -

(f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information; (f) A pressure fall-off test or other equivalent test that

identifies reservoir conditions with respect to flow dynamics at least once every five years unless more frequent testing is required by the Director based on site specific information; Allows more flexibility while still providing the needed

information

(g) Testing and monitoring to

track the extent of the carbon dioxide plume and the position of the pressure front by either monitoring for pressure changes in the first formation overlying the confining zone or using indirect, geophysical techniques (e.g., seismic, (g) Testing and monitoring to

track the extent of the carbon dioxide plume and the position of the pressure front. Monitoring outside of the injection zone provides little

information of value for tracking and monitoring the injected plume. Examples of

how to test and monitor could

be included in the Preamble.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 38 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
electrical, gravity, or electromagnetic surveys
and/or down-hole carbon dioxide detection tools);

(h) At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect

movement of carbon dioxide that could endanger a USDW. (h) At the Director’s discretion based on site-specific

conditions and risk-based factors, surface air monitoring and/or soil gas monitoring to

detect movement of carbon dioxide that could endanger a
USDW. In most situations soil and air monitoring does not provide

an effective method of protecting USDWs.

(1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review; (1) The testing and monitoringplan must be based on sitespecific geologic factors,modeling, and riskassessment within the area of review; -

(2) The monitoring frequency and spatial distribution of surface air monitoring and/or soil gas monitoring must
reflect baseline data and the monitoring plan must include how the proposed monitoring will yield useful information on

the area of review delineation and/or compliance with
standards under 40 CFR 144.12; - -

(i) Any additional monitoring, as required by the Director, necessary to support, upgrade, and improve computational modeling of the

area of review evaluation required under §146.84(b) and to determine compliance with
standards under 40 CFR 144.12; and - -

(j) A quality assurance and surveillance plan for all testing and monitoring requirements. - -

§146.91 Reporting requirements. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 39 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
The owner or operator must, at a minimum, provide the following reports to the Director, for each permitted
Class VI well: - -

(a) Semi-annual reports containing: - -

(1) Any changes to the physical, chemical and other

relevant characteristics of the

carbon dioxide stream from the proposed operating data; (1) Any significant changes to the physical, chemical and

other relevant characteristics
of the carbon dioxide stream from the proposed operating data; Minor changes could just be due to uncertainty in

measurements or models

(2) Monthly average,

maximum and minimum values for injection pressure, flow rate and volume, and annular pressure; - -

(3) A description of any event that exceeds operating parameters for annulus pressure or injection pressure as specified in the permit; - -

(4) A description of any event which triggers a shutdown device required pursuant to §146.88(e) and the response taken; - -

(5) The monthly volume of the carbon dioxide stream injected over the reporting period and project cumulatively; - -

(6) Monthly annulus fluid volume added; and - -

(7) The results of monitoring prescribed under §146.90. - -

(b) Report, within 30 days the

results of: - -

(1) Periodic tests of mechanical integrity; - -

(2) Any other test of the injection well conducted by the permittee if required by the Director; and - -

(3) Any well workover. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 40 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(c) Owners or operators must submit reports in an electronic format acceptable to the

Director. At the discretion of the Director, other formats may be accepted. - -

§146.92 Injection well plugging. - -

(a) Prior to the well plugging, the owner or operator must flush each Class VI injection well with a buffer fluid,

determine bottomhole reservoir pressure, and perform a final mechanical integrity test. (a) Prior to the well plugging, the owner or operator must flush each Class VI injection well with a buffer fluid,

determine bottomhole reservoir pressure, and perform a final external mechanical integrity test. Many of the components that would be tested by an internal

MIT are removed or tested during the plugging process.

(b) Well Plugging Plan. The owner or operator of a Class VI well must prepare, maintain, and comply with a plan that is acceptable to the Director. The requirement to maintain and implement an approved plan is directly enforceable regardless of whether the requirement is a condition of the permit. The well plugging plan must be submitted as part of the permit application and must include the following information: - -

(1) Appropriate test or

measure to determine bottomhole reservoir pressure; - -

(2) Appropriate testing

methods to ensure mechanical integrity as specified in §146.89; (2) Appropriate testing

methods to ensure final external mechanical integrity as specified in §146.89(c); Many of the components that would be tested by an internal

MIT are removed or tested during the plugging process. (3) The type and number of plugs to be used; - -

(4) The placement of each plug including the elevation of the top and bottom of each plug; - -

(5) The type and grade and quantity of material to be used in plugging. The material must be compatible with the carbon dioxide stream; and (5) The type and grade and quantity of material to be used in plugging. The material must

be suitable for use with the carbon dioxide stream; and -

(6) The method of placement - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 41 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
of the plugs.

(c) Notice of intent to plug. The owner or operator must notify the Director at least 60 days before plugging of a well. At this time, if any changes have been made to the original well plugging plan, the owner or operator must also provide the revised well plugging plan. At the discretion of the Director, a shorter notice period may be

allowed. - -

(d) Plugging report. Within 60 days after plugging or at the

time of the next semi-annual report (whichever occurs earlier) the owner or operator must submit a plugging report

to the Director. If the semiannual report is due less than 15 days after completion of plugging, then the report must be submitted within 60 days after plugging. The report must be certified as accurate by the owner or operator and by the person who performed the plugging operation (if other than the owner or operator.) (d) Plugging report. Within 60 days after plugging the owner or operator must submit a plugging report to the Director. The report must be certified as accurate by the owner or operator and by the person who performed the plugging operation (if other than the owner or operator.) Simplification

§146.93 Post-injection site

care and site closure. - -

(a) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan for post-injection site care

and site closure that meets the requirements of paragraph (a)(2) of this section and is acceptable to the Director. - -

(1) The owner or operator must submit the post-injection site care and site closure plan as a part of the permit application to be approved by

the Director. - -

(2) The post-injection site care and site closure plan must include the following - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 42 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

information:

(i) The pressure differential between pre-injection and predicted post-injection pressures in the injection

zone; - -

(ii) The predicted position of the carbon dioxide plume and associated pressure front at

site closure as demonstrated

in the area of review evaluation required under §146.84(b); - -

(iii) A description of postinjection monitoring location, methods, and proposed frequency; and - -

(iv) A proposed schedule for submitting post-injection site care monitoring results to the

Director. - -

(3) Upon cessation of injection, owners or operators
of Class VI wells must eithersubmit an amended postinjection site care and site closure plan or demonstrate to the Director through monitoring data and modeling

results that no amendment to the plan is needed. - -

(4) The owner or operator maymodify and resubmit the postinjection site care and site closure plan for the Director’s approval within 30 days of such change. - -

(b) The owner or operator shall monitor the site following the cessation of injection to show the position of the carbon dioxide plume and pressure front and
demonstrate that USDWs are not being endangered. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 43 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(1) The owner or operator

shall continue to conduct monitoring as specified in theDirector-approved postinjection site care and site closure plan for at least 50 years following the cessation of injection. At the Director’s discretion, the monitoring will continue until the geologic sequestration project no longer poses an endangerment to USDWs. (1) The owner or operator

shall continue to conduct monitoring as specified in theDirector-approved postinjection site care and site closure plan, pursuant to the performance based criteria described in 146.93(3). The 50 year default period is not based on any scientific or

technical information and could be considered arbitrary and capricious.

(2) If the owner or operator

can demonstrate to the

satisfaction of the Director before 50 years, based onmonitoring and other sitespecific data, that the geologic sequestration project no longer poses an endangerment to USDWs, the Director may approve anamendment to the postinjection site care and site closure plan to reduce the frequency of monitoring or may authorize site closure before the end of the 50-year period. (2) If the owner or operator

can demonstrate to the

satisfaction of the Director that the geologic sequestration project no longer poses an endangerment to USDWs, the Director may approve anamendment to the postinjection site care and site closure plan to reduce the frequency of monitoring or may authorize site closure. -

(3) Prior to authorization for site closure, the owner or operator must submit to the Director a demonstration, based on monitoring and other site-specific data, that the carbon dioxide plume and pressure front have stabilized

and that no additional monitoring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs. (3) Prior to authorization for site closure, the owner or operator must demonstrate to the Director, based onmonitoring and other sitespecific data that no additional monitoring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs, considering the following:. (i) the estimated magnitude
and extent of the AOR based

on measurements and modeling; (ii) that CO2 movement and pressure changes match model predictions, (iii) the estimated location of the detectable CO2 plume

based on measurement and modeling (measuring magnitude of saturation within Establishes the performance based criteria for selecting the monitoring period.Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 44 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
the plume or mapping the edge of it); (iv) that there is no evidence of significant leakage of either
CO2 or formation fluids that endanger USDWs; (v) that the CO2 plume and displaced formation fluid are not expected to migrate in the
future in a manner that encounters a potential leakage pathway; and, (vi) that wells at the site are not leaking and have maintained integrity.

(4) If such a demonstration cannot be made (i.e., if the carbon dioxide plume and pressure front have not stabilized) after the 50 year period, the owner or operator

must submit to the Director a plan to continue post-injection

site care. Delete No longer necessary

(c) Notice of intent for site

closure. The owner or operator must notify the Director at least 120 days before site closure. At this time, if any changes have been made to the original post-injection site care and site closure plan, the owner or operator must also provide the revised plan. At the discretion of the Director, a shorter notice period may be

allowed. - -

(d) After the Director has authorized site closure, the owner or operator must plug all monitoring wells in a

manner which will not allow movement of injection or - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 45 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale

formation fluids that endangers a USDW.

(e) Once the Director has authorized site closure, the owner or operator must submit a site closure report within 90 days that must thereafter be

retained at a location designated by the Director. The report must include: (e) Once the Director has authorized site closure, the owner or operator must submit a site closure report within 90 days after completion of all closure operations. The report

must include: What is the retention period? Many other programs have a three year limit for retention of

records. EPA is the steward of information at this point of the project, not the owner or operator.

(1) Documentation of appropriate injection and monitoring well plugging as specified in §146.92 and paragraph (c) of this section. The owner or operator must provide a copy of a survey plat

which has been submitted to the local zoning authority designated by the Director. The plat must indicate the location of the injection well relative to permanently surveyed benchmarks. The owner or operator must also submit a copy of the plat to the Regional Administrator of the appropriate EPA Regional Office; (1) Documentation of appropriate injection and monitoring well plugging as specified in §146.92 and paragraph (c) of this section. The owner or operator must provide a copy of a survey plat

which has been submitted to the local zoning authority designated by the Director. The plat must indicate the location of the injection well(s) relative to permanently surveyed benchmarks. The owner or operator must also submit a copy of the plat to the Regional Administrator of the appropriate EPA Regional Office; -

(2) Documentation of appropriate notification and information to such State, local

and tribal authorities as have authority over drilling activities
to enable such State and local authorities to impose appropriate conditions on subsequent drilling activities that may penetrate the injection and confining zone(s); and - -

(3) Records reflecting the nature, composition and

volume of the carbon dioxide

stream. - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 46 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
(f) Each owner or operator of a Class VI injection well must

record a notation on the deed to the facility property or any

other document that is normally examined during title search that will in perpetuity provide any potential purchaser of the property the following information: - -

(1) The fact that land has been used to sequester carbon dioxide; - -

(2) The name of the State agency, local authority, and/or tribe with which the survey plat was filed, as well as the address of the Regional

Environmental Protection Agency Office to which it was submitted; and - -

(3) The volume of fluid injected, the injection zone or

zones into which it was injected, and the period over which injection occurred. - -

(g) The owner or operator must retain for three years following site closure, recordscollected during the postinjection site care period. The owner or operator must deliver

the records to the Director at
the conclusion of the retention period, and the records must

thereafter be retained at a location designated by the Director for that purpose. - -

§146.94 Emergency and remedial response. - -

(a) As part of the permit application, the owner or operator must provide the Director with an emergency and remedial response plan

that describes actions to be

taken to address movement of the injection or formation fluids that may cause an endangerment to a USDW - -Schlumberger Carbon Services Comments on “Requirements for Class VI Injection Wells for the Geologic Seque stration of Carbon Dioxide - Proposed Rule” Contact: Andrew Duguid, Ph.D., P.E. aduguid@slb.com 47 Proposed Rule Schlumberger Suggested Revision Schlumberger

Rationale
during construction, operation, closure and post-closure periods.

(b) If the owner or operator

obtains evidence that the injected carbon dioxide stream and associated pressure front may cause an endangerment to a USDW, the owner or operator must: (b) If the owner or operator

obtains evidence that the injected carbon dioxide stream or associated pressure front endangers a USDW, the owner or operator must: -

(1) Immediately cease injection; (2) Take all steps reasonably necessary to identify and characterize any release; (2) Take all steps reasonably necessary to identify and

characterize the endangerment posed; -

(3) Notify the Director within 24 hours; and (3) Notify the Director within 24 hours of becoming aware of the endangerment; and -

(4) Implement the emergency and remedial response plan approved by the Director. - -

(c) The Director may allow the operator to resume injection prior to remediation if the owner or operator demonstrates that the injection operation will not endanger
USDWs. - -

(d) The owner or operator must notify the Director and obtain his approval prior to conducting any well workover. (d) The owner or operator must notify the Director prior to conducting any well workover in response to any case of endangerment. In critical situations, time spent obtaining approval could adversely affect the ability to conduct operations or

increase the level of endangerment.Letter ID: 0226 Commenter: Andrew Duguid Organization: Schlumberg er Carbon Services

Letter ID: 0226 Comment ID: 23995 Letter Lines: 37 to 40

Comment Code: 1420 1.2.1.1 Support the GS rulemaking

Comment: Schlumberger feels that the proposed ru le for geologic sequestration of carbon dioxide is a very good start and relatively few changes are needed to create a final rule under which geologic CO2 seque stration can become a commercial industry and an effective piece in the solution to climate change.

Individual Response: EPA believes that the creation of a new injection well class (VI) under the existing UIC Program is necessary to enable the use of GS as a climate change mitigation technology in a manner that protects USDWs from endangerment. EPA agrees that the UIC Program, under the authority of the SDWA, provides a strong fram ework for regulating injection of CO2 for GS and adds that the GS regulati on tailors the UIC requirements to address the unique issues associated with large-scale GS including large injection volumes, the relative buoyancy of CO2, its corrosivity in the presence of water, the potenti al presence of impurities in captured CO2, and its mobility within subsurface geologic formations.

Letter ID: 0226 Comment ID: 23996 Letter Lines: 48 to 70

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: 1. Schlumberger asks that the EPA expand th e applicability of Class VI wells to cover wells injecting CO2 that is dissolv ed in water or brine. The current draft language for Sec tion 146.81(b) states:

This subpart applies to wells used to inject carbon dioxi de specifically for the purpose of geologic seque stration, i.e., the long-term containment of a gaseous, liquid or supercritical carbon dioxide stream in subsurface geologic formations.

We suggest that the EPA replace the current language with the following language:

This subpart applies to wells used to inject carbon dioxi de specifically for the purpose of geologic seque stration, i.e., the long-term containment of a gaseous, liquid or supercritical carbon dioxide stream

or carbon dioxide dissolved in water or brine into subsurface geologic

formations.

1While we recognize today the injection of dissolved CO2 raises economic challenges we feel that there may be cases where the injection of dissolved CO2

will make sense both in terms of economi cs and in terms of leakage risk. Unlike separate phase CO2, CO2 dissolved in water is not less dense than the

formation fluid and will not be s ubject to buoyancy driven leakage.

Individual Response: EPA disagrees with the suggested change. §146.81(b) reads as follows: “This subpart applies to any wells used to inject carbon dioxide specifically for the purpose of geologic sequestration, i.e., the long-term containment of a gaseous, liquid, or supercritical carbon dioxide stream in subsurface geologic form ations.” Nothing in the rule precludes the injection of dissolved CO2, as long as the CO2 doe s not meet the definition of a hazardous waste under 40 CFR part 261.

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 23997 Letter Lines: 72 to 80

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost

USDW

Comment: 2. Schlumberger feels that the general prohibition on CO2 in jection above the lowermost USDW should removed from the regul ations. We feel that as long as the injection will not endanger USDWs the el evation with respect to the lowermost USDW is not important. However, if CO2 in jection is allowed above the lowermost USDW we feel that the EPA must specify that there needs to be a confining unit both above and below the injec tion zone that is free of pathways that may allow for leakage of fluids out of the inje ction zone. The inclusion of a lower confining unit will be important because CO2-saturated brine or water is more

dense than the native formation fluid and will sink.

Individual Response: EPA acknowledges that there are lim ited circumstances where injection above the lowermost USDW can be performe d in a manner that protects USDWs from endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 establishes a process by which owne rs or operators can seek a waiv er of the Class VI injection depth requirements for injecti on into non-USDW formations above and/or between USDWs. It establishes: 1) requirements spec ifying information that owners or operators must submit, and Directors must consider, in consultation with PW SS Directors; 2) procedures for public notice of a waiver application and for Director-Regiona l Administrator communicat ion; 3) the waiver issuance process; and, 4) additiona l requirements that apply to owne rs or operators of Class VI wells granted a waiver of the in jection depth requirements to en sure USDW protection above and below the injection zone.

EPA agrees that proper siting, monitoring, and c ontainment capacity are cr itical elements of Class VI injection for GS. However, the Agency also believes that in jection into non-USDW

2formations above and between USDWs presents unique challenges related to movement of CO2 in the subsurface, which requires a unique approach to ensure that USDWs are protected. Therefore, the Agency believes that additional requirements are appropriate and necessary for wells that would inject into non- USDWs above and be tween USDWs.

For additional information on the waiver approa ch, please see the final rule and preamble, as well as EPA's responses to comments on the No tice of Data Availability and Request for

Comment.

Letter ID: 0226 Comment ID: 23998 Letter Lines: 82 to 120

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5260 2.8.2.3 Adjusting the post-injecti on timeframe (seeking comment)

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93)

Comment: 3. Schlumberger does not support the default post injection site care period of 50 years. We feel that because the char acterization and opera tion of the site will be based on the specific attributes of the site that the length of post injection site care should also be site specific information. In particular the criteria for ending the PISC period shoul d be based on site performance and risk. We support the idea th at the director approves fi nal site closure. We suggest the following language for Section 146.93(b)(1):

(1) The owner or operator shall con tinue to conduct monitoring as specified in the Director-approved po st-injection site care and site closure plan, pursuant to the performa nce based criteria described in 146.93(b)(3).

We suggest the following language for section 146.93(b)(2)

(2) If the owner or operator can dem onstrate to the satisfaction of the Director that the geologic sequest ration project no longer poses an endangerment to USDWs, the Director may approve an amendment to the post- injection site care and site closure plan to reduce the frequency of monitoring or ma y authorize site closure.

And we suggest the following language for section 146.93(b)(3)

(3) Prior to authorization for site cl osure, the owner or operator must demonstrate to the Director, based on monitoring and other sitespecific data that no additional monito ring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs, considering the following:.

(i) the estimated magnitude and extent of the AOR based on measurements and modeling; (ii) that CO2 movement and pressure changes match model

3predictions, (iii) the estimated locat ion of the detect able CO2 plume based on measurement and modeling (measuring magnitude of saturation within the plume or mapping the edge of it); (iv) that there is no evidence of significant leakage of eith er CO2 or formation fluids that endanger USDWs; (v) that the CO2 plum e and displaced formation fluid are not expected to migrate in the futu re in a manner that encounters a potential leakage pathway; and, (vi) that wells at the site are not leaking and have maintained integrity.

Individual Response: The PISC requirements in the final GS rule, as specified in §146.93(b), incorporate a combination of a fixed timeframe and a performance standard approach. EPA believes that a default PISC timeframe of 50 year s, with Director's di scretion to shorten or lengthen this timeframe, combined with a site-s pecific Director’s disc retion to create an alternative PISC time frame, ensu res that USDWs are protected. The GS rule offers owners or operators flexibility regarding th e duration of the PISC timeframe by: (1) allowing the Director discretion to shorten or lengt hen the PISC timeframe during the PISC period based on sitespecific data, pursuant to require ments at §146.93(b); or (2) afford ing the Director discretion to allow a Class VI well owner or operator to demo nstrate, based on substa ntial data during the permitting process, that an alternative PISC timeframe may be appropriate if it ensures nonendangerment of USDWs pursuant to requirements at §146.93(c).

EPA expects that the Director would consider th e types of information the commenter describes in determining whether the plume and pressure front no longer pose a risk of endangerment to USDWs and post-injection site care monitoring may be discontinued.

EPA believes that a default post-injection site car e timeframe of 50 years, with flexibility to adjust the timeframe for a limited number of GS projects during the permitting process where

substantial data exists to demonstrate that an alternative timeframe would be protective of USDWs, or based on data collected during the PISC period, is appropriate to address the range of sites where GS is anticipated to occur, to ac commodate site-specific circumstances and various geologic conditions, and addre sses commenters’ concerns, wh ile ensuring USDW protection. Both approaches will utilize si te-specific data, and be based on pressure monitoring and USDW impacts.

EPA is developing guidance to assist owners or operators in evaluating well plugging, postinjection site care, and site closure requirements of §146.92 and §146.93. Additionally, the guidance will assist Directors in evaluating propo sed well plugging plans a nd post-injection site care and site closure plans under §146.92 a nd §146.93. The guidance describes recommended approaches for how an owner or operator coul d plug injection and m onitoring wells; perform post-injection monitoring; demonstrate the appropriateness of an alternative post-injection site care time frame; demonstrate non endangerment; and perform site closure activities. The guidance will be available at h ttp://water.epa.gov/type /groundwater/uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 23999 Letter Lines: 122 to 146

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

4Comment Code: 4650 2.6.5 CO2 plume and pressure fr ont tracking (seeking comment)

Comment: 4. Schlumberger supports the concept of testi ng and monitoring to track the CO2 plume and the associated pressure front. We feel that without this monitoring the validation and updating of the models used to predict the size and shape of the AOR cannot be properly conducted and th at the use of models to predict the size and shape of the AOR will be ineffective. However we feel that the language in section 146.90(g) is too restrictive. The current language states:

(g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pressu re front by either monitoring for pressure changes in the first forma tion overlying the confining zone or using indirect, geophysical techniqu es (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole carbon dioxide detection tools);

We feel that the restrictions placed in this language could adversely impact the efficiency of monitoring and mode ling depending on site conditions. Schlumberger proposes the fo llowing altern ate language:

(g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pressu re front by either monitoring for pressure changes, using geophysic al techniques (e.g., seismic, electrical, gravity, or electromagneti c surveys and/or down-hole carbon dioxide detection tools), other tec hniques that are approved by the director or a combination of techniques if multiple techniques are deemed necessary by the director;

Individual Response: EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or opera tors to monitor directly for pressure changes in the injection zone. EPA belie ves that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. In addition, §146.90(g)(2) requires owners or oper ators to track the position of the CO2 plume using indirect methods (e.g., seismic, electri cal, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), un less the Director determines based on site-specific geology, that such methods are not appropr iate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologi c settings. EPA clarifies that th is determination will be made by the Director based on the site-specific geologi c information submitted by the owner or operator with their permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring pl an will include the site-specific details, technologies, testing and monitoring freque ncies, and other pertinent information.

5EPA is developing guidance on testing and mon itoring to assist owne rs or operators and Directors in evaluating requi rements under §146.90, including pr oposed monitoring plans. The guidance describes available technologies a nd recommended approaches for implementing a testing and monitoring plan, including pre-ope rational geophysical l ogging and testing of injection wells, MITs, injecti on well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pre ssure front, and soil gas and su rface air monitoring which may be required by the UIC Director for specific GS projects. Th e guidance can be found on EPA’s website at http://water.epa.gov/type/gr oundwater/uic/wells_se questration.cfm.

Letter ID: 0226 Comment ID: 24000 Letter Lines: 150 to 155

Comment Code: 3840 2.3.2 Horizontal well drilling techniques (seeking comment)

Comment: 1. Schlumberger supports the idea that horizontal wells may be used for injection for geologic carbon sequest ration. Horizontal CO2 injection wells have been successfully and safe ly used for CO2 injection at the Weyburn project in Saskatchewan, Cana da. We feel that there will be

sites with conditions that will make the use of horizontal wells

necessary.

Individual Response: In this final rule, EPA allows the use of horizontal wells at GS projects. In the proposed rule, EPA sought comment on the appr opriateness of horizontal drilling techniques for Class VI wells, and commenters representing energy companies, el ectric utilities, the oil and gas industry, CCS associations, states, and the public, unanimously suppo rted the concept and provided many reasons why horizonta l wells could be beneficial at GS sites. Based on an evaluation of these comments and additional research by EPA, the Agency has concluded that horizontal wells that are properly constructed, logged, and tested for mechanical integrity (i.e., to meet the requirements of the GS rule) can ensu re the protection of USDW s from endangerment.

Letter ID: 0226 Comment ID: 24001 Letter Lines: 157 to 160

Comment Code: 1630 1.3.3 RCRA/hazardous waste i ssues (seeking comment)

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment)

Comment: 2. Now that the EPA has introduced the topics of the Comprehensive Environmental Response, Compensation, a nd Liability Act (CERCLA) and the Resource Conservation and Recovery Act ( RCRA) we urge the EPA to clarify the roles of both with respect to CO 2 injection under the UIC program.

Individual Response: EPA received many comments regarding the need for clarity with respect to RCRA regulations and statute to CO2 streams that are geologica lly sequestered under the final Class VI UIC well requirements. As a result, EP A has decided to initiate a separate proposed rulemaking specifically to examine the issue of RCRA applicability to CO2 streams being geologically sequestered, including the possible option of a conditional exemption from the

6RCRA requirements for CO2 GS in Class VI wells. EP A will consider these comments as part of its development of that proposal. The Agency w ill consider issues par ticular to RCRA in the context of that separate rulemaking, and recommends that the commenter read that proposed rule when it is published. The Agency notes that commenters who wish to submit comments on the RCRA proposal will need to do so during the comme nt period for that rule. Finally, EPA also notes that the final GS rule, which adds new regulations for Class VI wells under the Safe Drinking Water Act (SDWA), is not maki ng any changes to the RCRA regulations.

EPA clarifies that CO2 itself is not listed as a hazardous s ubstance under CERCLA; however, the CO2 stream may contain a listed hazardous subs tance (such as mercury) or may mobilize substances in the subsurface that could react with ground water to produce listed hazardous substances (such as sulfuric acid). Whether su ch substances may result in CERCLA liability from a sequestration facility depe nds entirely on the composition of the specific CO2 stream and

the environmental media in which it is stored (e.g., soil or ground water). CERCLA exempts from liability, under CERCLA section 107, 42 U. S.C. 9607, certain “federally permitted releases” (FPR) as defined in CERCLA, 42 U.S. C. 9601(10). Class VI permits will need to be carefully structured to ensure that they prevent potential releases from the well which are outside the scope of the Class VI permit.

Letter ID: 0226 Comment ID: 24002 Letter Lines: 162 to 176

Comment Code: 1630 1.3.3 RCRA/hazardous waste i ssues (seeking comment)

Comment: Schlumberger supports the EPA in defi ning the injected CO2 stream to

exclude hazardous wastes. We feel that this definition implies that CO2

itself is not a hazardous waste under RCRA and that the injected CO2 stream can only be considered a haza rdous waste if it is mixed with

another hazardous waste.

Schlumberger feels that supercriti cal and gaseous CO2 do not fit the

definition of solid waste under RCRA wh ich is limited to "solid, liquid, semisolid, and contained gaseous ma terials" and are therefore not regulated under RCRA. We encourage the EPA to explore this possibility and if in agreement, to adopt and es pouse this position in the preamble

for the final rule. We further feel that EPA should specify that uncontainerized supercritical CO2, like that at injected for CCS, is not solid waste and therefore not subj ect to RCRA waste determination requirements.

Individual Response: EPA received many comments regardi ng the applicability of the RCRA regulations and statute to CO2 st reams that are geologically seque stered under the final Class VI UIC well requirements. As a result, EPA has deci ded to initiate a sepa rate proposed rulemaking specifically to examine the issue of RCRA appl icability to CO2 streams being geologically sequestered, including the possible option of a conditional exemption from the RCRA requirements for CO2 GS in Class VI wells. EPA will consider these comments as part of its development of that proposal. The Agency will consider issues pa rticular to RCRA in the context

7of that separate rulemaking, and recommends that the commenter read that proposed rule when it is published. The Agency notes that comment ers who wish to submit comments on the RCRA proposal will need to do so during the comment pe riod for that rule. Finall y, EPA also notes that the final GS rule, which adds ne w regulations for Class VI wells under the Safe Drinking Water Act (SDWA), is not making any ch anges to the RCRA regulations.

Letter ID: 0226 Comment ID: 24003 Letter Lines: 178 to 190

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment)

Comment: The preamble of the draft points ou t that under federally permitted release provision of CERCLA releases in compliance with a UIC permit are exempt from liability under CERCLA. Schlumberger fails to see how the any releases under the proposed rule that involves both characterization of the injection stream and characte rization of the subsurface can fall outside the federally permitted release provision. We urge the EPA to better clarify any cases where injecti on of CO2 in accordance with a UIC permit is not released from liability under the federally permitted release provision of CE RCLA. We cannot envision a permit being issued for an injection that could cause an unintended release, especially, in light of the information that is re quired in the permit application on the composition of the injection stre am and on the chemical makeup of

the subsurface.

Individual Response: CERCLA exempts from liability, un der CERCLA section 107, 42 U.S.C. 9607, certain “federally permitted releases” (FPR ) as defined in CERCLA, 42 U.S.C. 9601(10). Therefore, Class VI requirements and permits will n eed to be carefully structured to ensure that they do not “authorize” inappropriate releases, and would need to prevent potential releases from the well which are outside the scope of the Cla ss VI permit. Furthermore, EPA is promulgating

the GS rule under the authorit y of the SDWA. To the extent the commenter is seeking interpretations of CERCLA and its related provi sions, such as the definition of a federally permitted release, such interpretations are beyond the scope of this rulemaking.

Letter ID: 0226 Comment ID: 24004 Letter Lines: 192 to 202

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)

Comment: 3. In the preamble of the draft u-tu be technology is specifically called out as a technology available for high pressure fluid sampling. Schlumberger wants point out to the epa there are other techniques for high pressure fluid sampling the us e of wireline conveyed sample

bottles. We want to ensure that no one particular tec hnology is adopted or required for high pressure samp ling. The selection of a single sampling technique (although not in the rule language) could cause the best available technology to be ove rlooked now or in the future. We

8propose that epa either delete the reference to the u-tube samples of clarify that it is not the only solution available for taking high pressure samples

Individual Response: EPA recognizes that the collecti on of representative ground water samples from depth poses challenges and that speci al methods, such as U-tubes, will be needed to preserve the integrity of such samples. However, EPA is not requiring the use of U-tubes for sampling under the final rule. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologie s and recommended approaches for implementing a testing and monitoring pla n, including pre-operatio nal geophysical logging and testing of injection wells, MITs, injection well testing during opera tion, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type /groundwater/uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24005 Letter Lines: 204 to 209

Comment Code: 1820 1.4.1.1 Vulnerability Evaluation Framework (VEF)

Comment: 4. Schlumberger appreciates that th e EPA crated the Vulnerability Evaluation Framework (VEF) and we fully support the use of a logical set of steps to address the vulnerabil ities or risks associated with geologic carbon sequestration. However, we are concerned that the VEF is not the only method that may be successful for site evaluation and would like EPA to clarify that the VE F is one but not the only approach.

Individual Response: The Agency clarifies that the VEF is intended to be a risk screening tool, but it is not a required component of the GS site selection proce ss. The UIC Class VI well permit application requirements, including the mi nimum criteria for s iting at §146.83, and the information requirements at §146.82 provide the basis for determin ing whether a proposed GS site is geologically appropriate and the proposed operations are technicall y viable, safe, and will not endanger USDWs.

EPA believes that requiring appr opriate site characterization by the owner or operator and providing an appropriate de gree of flexibility to the Director to evaluate site-specific geologic data will afford the greatest protection of US DWs. The issuance of a UIC Class VI permit is determined based on evaluation of site-specific permit information pursuant to the requirements at §§146.82 and 146.83. The Director may consid er some components of the VEF (e.g., information regarding wells, faults, and pressure changes) when assessing the appropriateness of a site for GS; however, the Director's permit a pproval determination is based on UIC Class VI requirements and not the VEF.

9Letter ID: 0226 Comment ID: 24006 Letter Lines: 230 to 240

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost

USDW

Comment: §144.6 Classification of wells.

Proposed Rule:(f) Class VI. Wells used for geologic sequestration of carbon

dioxide beneath the lowermost formation containing a USDW.

Schlumberger Suggested Revision: (f) Class VI. Wells used for geologic sequestration of carbon dioxide.

Schlumberger Rationale: We feel that se questration can be conducted safely above USDWs as evidenced by the class 2 EOR expe rience. Also, the restriction to below the lowest USDW rules out many potential CCS sites.

Individual Response: EPA acknowledges that there are lim ited circumstances where injection above the lowermost USDW can be performe d in a manner that protects USDWs from endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 establishes a process by which owne rs or operators can seek a waiv er of the Class VI injection depth requirements for injecti on into non-USDW formations above and/or between USDWs. It establishes: 1) requirements spec ifying information that owners or operators must submit, and Directors must consider, in consultation with PW SS Directors; 2) procedures for public notice of a waiver application and for Director-Regiona l Administrator communicat ion; 3) the waiver issuance process; and, 4) additiona l requirements that apply to owne rs or operators of Class VI wells granted a waiver of the in jection depth requirements to en sure USDW protection above and below the injection zone.

EPA adds that it has revised the definition of a Cl ass VI well to read as follows: “Wells that are not experimental in nature that are used for geologic sequestrati on of carbon dioxide beneath the lowermost formation containing a USDW; or, we lls used for geologic sequestration of carbon dioxide that have been granted a waiver of the injection depth requirements pursuant to requirements at §146.95 of this chapter; or, we lls used for geologic sequestration of carbon

dioxide that have received an e xpansion to the areal extent of an existing Class II enhanced oil recovery or enhanced gas rec overy aquifer exemption pursuant to §§146.4 of this chapter and 144.7(d).”

For additional information on the waiver approa ch, please see the final rule and preamble, as well as EPA's responses to comments on the No tice of Data Availability and Request for

Comment.

Letter ID: 0226 Comment ID: 24007 Letter Lines: 242 to 251

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

10Comment Code: 2066 1.5.3.3 Grandfathering construction of Class V wells (seeking comment)

Comment: §144.15 Prohibition of non-experimental Class V wells for geologic sequestration.

Proposed Rule: The construction, operation or maintenance of any nonexperimental Class V geologic se questration well is prohibited.

Schlumberger Suggested Revision: -

Schlumberger Rationale: We agree, ther e should be only one class of geologic sequestration well but CO2 class V wells should be grandfathered.

Individual Response: EPA agrees that many Class V experimental technology wells are designed and constructed to withstand exposure to CO2. The final GS rule provides for the construction of these wells to be grandfathe red per §146.81(c), provided th e owner or operator
can demonstrate to the Director that the wells were engineered and constructed to meet the requirements at §146.86(a) and ensu re protection of USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA clarifies that only the construction requirements are grandfathered and that all other Class VI requirements (reporting, monitoring, mechnical integrity testing, etc.) must be met fo llowing a determination under §146.81(c).

Letter ID: 0226 Comment ID: 24008 Letter Lines: 253 to 264

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost

USDW

Comment: §146.5 Classification of injection wells.

Proposed Rule:(f) Class VI. Wells used for geologic sequestration of carbon

dioxide beneath the lowermost formati on containing an underground source of drinking water (USDW).

Schlumberger Suggested Revision: (f) Class VI. Wells used for geologic sequestration of carbon dioxide.

Schlumberger Rationale: We feel that se questration can be conducted safely above USDWs as evidenced by the class 2 EOR expe rience. Also, the restriction to below the lowest USDW rules out many potential CCS sites.

Individual Response: Please see the response to the comme nter’s suggested revision to §144.6(f).

11Letter ID: 0226 Comment ID: 24009 Letter Lines: 266 to 287

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment)

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 146.86)

Comment: §146.81 Applicability.

Proposed Rule: (c) This subpart applies to owners and operators of permit or rule-authorized Class I industrial, Cla ss II, or Class V experimental carbon dioxide injection projects who seek to apply for a Class VI geologic sequestration permit for their well or wells. If the Director determines that USDWs will not be endangered, such wells are exempt, at the Director’s discretion, from the casing and cemen ting requirements at §§146.86(b) and 146.87(a)(1) through (3).

Schlumberger Suggested Revision: (c) Th is subpart applies to owners and operators of permit or rule-authorized Cl ass I industrial, Class II, or Class V experimental carbon dioxide injection projec ts who seek to apply for a Class VI geologic sequestration permit for their well or wells. If the Director determines that USDWs will not be endangered, such wells are exempt, at the Director’s discretion, from the casing and cementing requirements at §§146.86(b) and 146.87(a)(1) through (3) if the wells were construc ted prior to January 1,

2010.

Schlumberger Rationale: We feel that there needs to be a cutoff date for the grandfathering of wells so eventually a ll Class 6 wells are constructed to the

same standard

Individual Response: EPA agrees that many Class I, Cl ass II, and Class V experimental technology wells are designed and constructed to withstand exposure to CO2. The final GS rule provides for the construction of these wells to be grandfathered per §146.81(c), provided the owner or operator can demonstrate to the Director that the wells were en gineered and constructed to meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA clarifies that only the construction requirements are grandfathered and that all ot her Class VI requirements (reporting, monitoring, mechanical integrity testing, etc.) must be met fo llowing a determination under §146.81(c).

EPA does not plan to institute a "cut-off date" fo r this requirement since conversion is a sitespecific decision. EPA believes that the requireme nt should be based on the specific aspects of the well's construction, not on the da te on which it was constructed.

Letter ID: 0226 Comment ID: 24010 Letter Lines: 289 to 306

Comment Code: 1220 1.1.1.1 Terminology and definitions

12Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Carbon dioxide stream mean s carbon dioxide that has been captured from an emission source (e.g., a power pl ant), plus incident al associated

substances derived from the source mate rials and the capture process, and any

substances added to the stream to enable or improve the inject ion process. This subpart does not apply to a ny carbon dioxide stream that meets the definition of a hazardous waste under 40 CFR part 261.

Schlumberger Suggested Revision:: Carbon dioxide stream carbon dioxide that has been captured from an industrial process th at is injected in any physical state

or dissolved in water or brine. It incl udes incidental asso ciated substances

derived from the source materials and th e capture process, and any substances added to the stream to enable or improve the injection process. This subpart does not apply to any carbon dioxide str eam that meets the definition of a hazardous waste under 40 CFR part 261.

Schlumberger Rationale: We want to ensu re that dissolved CO2 is specifically allowed as it may allow a solution to th e upward buoyancy drive associated with separate phase CO2.

Individual Response: EPA disagrees with the suggested edit. The final definition of carbon dioxide stream at §146.81(d) remains unchanged and reads as: “carbon dioxide that has been captured from an emission source (e.g., a power plan t), plus incidental as sociated substances

derived from the source materi als and the capture process, a nd any substances added to the stream to enable or improve th e injection process. This subpa rt does not apply to any carbon

dioxide stream that meets the definition of a hazardous waste under 40 CFR part 261.” As described above, nothing in the ru le precludes the injection of di ssolved CO2, as long as the CO2

does not meet the definition of a hazardous waste under 40 CFR part 261.

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment EPA has made many revisions to the GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24011 Letter Lines: 308 to 316

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule:Geologic sequestration mean s the long-term containment of a gaseous, liquid or supercritical carbon di oxide stream in subsurface geologic formations. This term does not appl y to its capture or transport.

Schlumberger Suggested Revision: Geol ogic sequestration means the long-term

containment of a carbon dioxide stream in subsurface geologic formations. This term does not apply to its capture or transport.

13Schlumberger Rationale: CO2 stream was al ready defined and should e used here.

Individual Response: EPA disagrees with the suggested cha nge. The final definition of geologic sequestration at §146.81(d) reads as follows: “[T] he long-term containment of a gaseous, liquid, or supercritical carbon dioxide stream in subsur face geologic formations. This term does not apply to carbon dioxide cap ture or transport.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24012 Letter Lines: 318 to 330

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Geologic sequestration projec t means an injection well or wells used to emplace a carbon dioxide stream beneath the lowermost formation containing a USDW. It includes the subsur face three-dimensional extent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as the surface area above that delineated region.

Schlumberger Suggested Revision: Geol ogic sequestration project means an injection well or wells used to empl ace a carbon dioxide stream into an injection zone. It includes the subsur face three-dimensional extent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as the surface area above that delineated region.

Schlumberger Rationale: -

Individual Response: The Agency has modified the defini tion of geologic sequestration project at §146.81(d) to read as follows: “Geologic seque stration project means an injection well or wells used to emplace a carbon dioxide stream beneath the lowermost formation containing a USDW; or, wells used for geologic sequestration of carbon dioxide that have been granted a waiver of the injection depth requirements pur suant to requirements at §146.95; or, wells used for geologic sequestration of car bon dioxide that have received an aquifer exemption expansion.

It includes the subsurface three-dimensional ex tent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as the surface area above th at delineated region.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

14Letter ID: 0226 Comment ID: 24013 Letter Lines: 332 to 342

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Injection zone means a ge ologic formation, group of formations, or part of a formation that is of su fficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through a well or wells associated with a geologic sequestration project.

Schlumberger Suggested Revision: Injec tion zone means a geologic formation, group of formations, or part of a formation that is of sufficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through a well or wells associated with a ge ologic sequestration project.

Schlumberger Rationale: -

Individual Response: EPA disagrees with the suggested edit. The definition of injection zone at §146.81(d) remains unchanged and reads as fo llows: “[A] geologic formation, group of formations, or part of a formation that is of sufficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through a well or wells associated with a geologic sequestration project.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24014 Letter Lines: 344 to 353

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Pressure front means the z one of elevated pressure that is created by the injection of carbon dioxide into the subsurface . For the purposes of this subpart, the pressure front of a carbon dioxide plume refers to a zone where there is a pressure differential sufficient to cause the movement of injected fluids or formation fluids into a USDW.

Schlumberger Suggested Revision: Pressure front means the zone of elevated pressure that is created by the injecti on of the carbon dioxide stream into the subsurface, where there is a pressure differential suffi cient to cause movement

of the carbon dioxide stream or formation fluids into a USDW.

Individual Response: EPA disagrees with the suggested edit . The final definition of pressure front at §146.81(d) is unchanged and reads as follows : “[T]he zone of elevat ed pressure that is created by the injection of carbon dioxide into the subsurface. Fo r the purposes of this subpart,

15the pressure front of a carbon dioxide plume refers to a zone where there is a pressure differential sufficient to cause the movement of injected fluids or formation fluids into a USDW.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24015 Letter Lines: 357 to 367

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Site closure the point/tim e, as determined by the Director following the requirements under §146.93, at wh ich the owner or operator of a GS site is released from post-inject ion site care responsibilities.

Schlumberger Suggested Revision: Site closure means the point/time, as determined by the Director following the requirements under §146.93, at which the owner or operator of a GS project is released from post-in jection site care responsibilities.

Schlumberger Rationale: Suggest using "GS project" to be consis tent with other

definitions

Individual Response: EPA disagrees with the suggested edit. The final definition of site closure at §146.81(d) is unchanged and reads as follows: “T he point/time, as determined by the Director following the requirements under §146.93, at which the owner or operator of a GS site is released from post-injection site care responsibilities.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24016 Letter Lines: 369 to 379

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment: Proposed Rule: Transmissive fault or fractur e means a fault or fracture that has sufficient permeability and vertical extent to allow fluids to move between

formations.

Schlumberger Suggested Revisi on: Transmissive fault or fr acture means a fault or fracture that has sufficient permeability and vertical extent to allow fluids to move beyond the confining zone.

16Schlumberger Rationale: The term between fo rmations is insuffici ent as it could also include multiple zones within a inj ection zone or between two zones above the confining unit.

Individual Response: EPA disagrees with the suggested edit. The final definition of transmissive fault or fracture at §146.81(d) is unchanged and reads as follows: “[A] fault or fracture that has sufficient permeability and vertic al extent to allow fl uids to move between

formations.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0226 Comment ID: 24017 Letter Lines: 381 to 473

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82)

Comment: §146.82 Required Class VI permit information.

Proposed Rule: (b) A map showing the inje ction well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number, or name and lo cation of all injec tion wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsur face cleanup sites, surface bodies of water, springs, mines (surface and subs urface), quarries, water wells and other pertinent surface features including struct ures intended for human occupancy and roads. The map should also show faults, if known or suspected. Only information of public record is required to be included on this map;

Schlumberger Suggested Revision: (b) A ma p or electronic file (e.g. GIS file) showing the injection well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number, or name and location of all injection wells, pr oducing wells, abandoned wells, plugged wells or dry holes, deep stratigraphi c boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, springs, mines (surface and subsurface), quarries, water wells and other pertinent su rface features including structures intended for human o ccupancy and roads. The map should also show faults, if known or suspected with su rface expressions. On ly information of public record is required to be included on this map;

Schlumberger Rationale: This may mean more clarification. It seems strange to have deep faults on a surface map. Is the map to be of the surface or of the confining unit? Also, any map will be very busy so it may be useful to be able

to submit an electronic f ile like a GIS file.

17Proposed Rule: (c) The area of review based on modeling, using data obtained during logging and testing of the well and the formation as required by paragraphs (l), (r), and (s) of this section;

Schlumberger Suggested Revision: -

Schlumberger Rationale: We support this but it may need to be better clarified that the well must e drilled pr ior to the permit application

Proposed Rule: (3) Information on seismi c history including the presence and depth of seismic sources and a determin ation that the seismicity would not interfere with containment;

Schlumberger Suggested Revision: (3) Info rmation on seismic history of the area including the presence and de pth of seismic sources and a determination that the seismicity would not inte rfere with containment;

Schlumberger Rationale: It seems like this requirement is at a larger scale than the AOR (maybe a regional scale) than the other requirements. This should be specified.

Proposed Rule: (4) Data on the depth, ar eal extent, thickne ss, mineralogy, porosity, permeability and capillary pressure of the injection and confining zone(s); including geology/f acies changes based on field data which may include geologic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions;

Schlumberger Suggested Revision: (4) Data on the depth, areal extent, thickness, mineralogy, porosity, permeability and capillary entry pressure of the injection and confining zone(s); including geology/ facies changes based on field data which may include geologic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions;

Schlumberger Rationale: Should this incl ude capillary pressu re or capillary entry pressure?

Proposed Rule: (e) A tabulation of all we lls within the area of review which penetrate the injection or confining z one(s). Such data must include a description of each well's type, construction, date drilled, location, depth, record of plugging and/or completion, and any additional information the Director may require;

Schlumberger Suggested Revision: -

Schlumberger Rationale: How will this be handled if all of this data is not

18available for each well?

Proposed Rule: (f) Maps and stratigraphic cross sections indicating the general vertical and lateral limits of all USDWs, water wells and springs within the area of review, their positions relative to the injection zone(s) and the direction of water movement, where known;

Schlumberger Suggested Revision: In

Schlumberger Rationale: -

Proposed Rule: (g) Baseline geochemical data on subsurface formations, including all USDWs in the area of review;

Schlumberger Suggested Revision: (g) Ba seline geochemical data on subsurface formations, including all USDWs and geoche mically monitored in the area of review;

Schlumberger Rationale: All formations that are or may need to be geochemically

monitored should be included

Individual Response: EPA agrees that deep faults would not be expressed on a surface map, but information on such faults should be provided in cross sections, which are also required as part of the materials that supp ort a permit application.

EPA agrees that submittal of support information electronically is beneficial. The final GS rule requires owners or operators to submit permit a pplications, including su pporting information, to EPA in an electronic format (§146.91(e)).

Regarding seismic information, EPA acknowledges that, due to the nature of seismic events and records, available information w ould likely address an area that is larger than the delineated AoR. EPA clarifies that the intent of this requirements is to ensure that the Director has sufficient

information on which to base a determination of the suitability of a potential project site for GS.

EPA clarifies that information on capillary entry pressure must be submitted. EPA believes that capillary entry pressure measur ements on core samples are nece ssary to quantify the amount of buoyant force the confining zone can maintain befo re failure (World Res ources Institute, 2008).

Regarding the requirement to submit tabulations of all wells within the AoR, EPA acknowledges that public records may not contain data on every artificial penetr ation in the AoR (or all of the data on each well that is required for the tabulation), particularly in areas with many older wells. However, EPA notes that the inventory and review process for GS wells required at §146.84(c)(2) is similar to what is required of Cl ass I and Class II injection well operators, that the AoR and corrective action process for these we ll types has been successful for many years.

EPA adds that the Director has the discretion to require the owner or operator to supplement a data records search, including re quiring ground or airborne surveys for wells, if there is reason to

19believe, based on knowledge of the site or of avai lable data bases, that the incompleteness of available information could compromise USDW protection from endangerment.

Regarding baseline geochemical data, EPA is not specifying for which formations this

information should be submitted to allow flexib ility, but examples may include the following formations: a) the injection zone, b) the conf ining zones, c) containment zones above the confining zones in which any potentially migrating CO2 could be trapped, d) all USDWs, and e) any other geologic zone or forma tion that is important to the proposed monitoring program. The Director has the authority to request additional geochemical data as well.

EPA agrees that not all of the information listed at §146.82 of the proposed regulation will be available at the time the owner or operator deve lops their initia l permit application. In response to comments and based on an evaluation of the proposed requirements at §146.82, the Agency revised this subpart so that the final regulation specifies separate requirements for information to be submitted with the permit application and be fore well construction is approved (at §146.82(a)) and information to be submitted before operati on of the well is aut horized (at §146.82(c)).

EPA is developing guidance on site characterization for GS projects to assist owners or operators and Directors in evaluating permit requirements and applications under §146.82. The guidance provides recommendations regard ing characterizing the region al geology and hydrogeology of a proposed GS site as well as performing th e necessary geochemical, geomechanical, and geophysical analyses of the injection and conf ining zone. The guidance can be found on EPA’s website at http://water.epa.gov/type/gr oundwater/uic/wells_se questration.cfm.

Letter ID: 0226 Comment ID: 24018 Letter Lines: 475 to 485

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83)

Comment: §146.83 Minimum criteria for siting.

Proposed Rule: (2) A confining zone(s) that is free of transmissive faults or

fractures and of sufficient areal extent and integrity to contain the injected carbon dioxide stream and displaced forma tion fluids and allo w injection at proposed maximum pressures and volume s without initiatin g or propagating fractures in the confining zone(s); and

Schlumberger Suggested Revision: -

Schlumberger Rationale: We support th is language as it is written.

Individual Response: EPA acknowledges the comment and the final rule retains the text at §146.83 as proposed.

20Letter ID: 0226 Comment ID: 24019 Letter Lines: 487 to 503

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones (seeking comment)

Comment: Proposed Rule: (b) At the Director’s discre tion, owners or operat ors of Class VI wells must identify and characterize additi onal zones that will impede vertical fluid movement, are free of faults and fractures that may interfere with containment, allow for pressure di ssipation, and provide additional opportunities for monitoring, m itigation and remediation.

Schlumberger Suggested Revision: (b) Owners or operators of Class VI wells must identify and characterize some additional z ones, if they exist, that will impede vertical fluid movement, allow for pressu re dissipation, and provide additional opportunities for monitoring, mitigation and remediation. Vertical faults and

fractures that transect these zones must be identified.

Schlumberger Rationale: We believe that a site with a si ngle confining can provide storage integrity, however, we feel that if there are additional confining layers at the site they shoul d be characterized to get a better estimate of leakage risk to USDWs and possibly identify additional monitoring

zones.

Individual Response: EPA retains the requirement to iden tify additional containment/confining zones, if required by the Di rector, as proposed (§146.83(b)). EPA acknowledges that such additional zones may not be needed in all circumst ances, and clarifies that this requirement is at the Director's discretion, based on his or her understanding of a part icular site. EPA believes that, in some situations, the presence of additional confining and containment zones above the primary (i.e., lowermost) confining zone can improve USDW protecti on. These layers could further impede vertical fluid movement and al low for pressure dissipation, and also provide additional sites for monitoring, mitigation, and re mediation. The Agency's decision is supported by commenters representing states, water associati ons, and an electric utility who assert that these requirements promote a flexible, risk-base d, site-specific approach to characterizing and permitting a site for GS projects, and are intende d to improve understanding of the project as a whole and promote better modeling of the site.

Letter ID: 0226 Comment ID: 24020 Letter Lines: 505 to 517

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3200 2.2 Proposed Area of Review and Corrective Action Requirements (40 CFR 146.84)

Comment: §146.84 Area of review and corrective action.

Proposed Rule: (a) The area of review is the region surrounding the geologic

21sequestration project that may be imp acted by the injection activity. The area

of review is based on com putational modeling that accoun ts for the physical and chemical properties of all phases of the injected carbon dioxide stream.

Schlumberger Suggested Revision: (a) The area of review is based on computational modeling that accounts for phys ical and the chemical properties of all phases of the injected carbon dioxide stream, the associated pressure front, and displaced brine.

Schlumberger Rationale: -

Individual Response: Based on review of all public comments on the AoR definition at 146.84(a), the Agency has modified it to read as follows: The region surrounding the geologic sequestration project where USDWs may be e ndangered by the injecti on activity. The area of review is delineated using computational mode ling that accounts for the physical and chemical properties of all phases of the injected CO2 stream and is based on available site characterization, monitoring, and operational data. The definition in the proposed rule accounted for the varying physical and chemical propertie s of the CO2 including free-phase and waterdissolved CO2, as the commenter suggests. The defin ition in the final rule wi ll continue to do so.

EPA is developing guidance on AoR and corrective act ion at GS Class VI s ites to assist owners or operators and Directors in evaluating requi rements and proposed AoR and corrective action plans under 146.84. The guidance describes EPA's reco mmended approaches for the data to be

considered in an initial AoR delineation, how to apply computat ional modeling to delineate the AoR, performing corrective action at GS sites, and, when appropriate, completing AoR reevaluations. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwat er/uic/wells_se questration.cfm.

Letter ID: 0226 Comment ID: 24021 Letter Lines: 518 to 534

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3400 2.2.2 Corrective Action

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Proposed Rule: (b) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan to delin eate the area of review for a proposed geologic sequestration proj ect, periodically reevalua te the delineation, and perform corrective action that meets the requirements of this section and is acceptable to the Director. As a part of the permit application for approval by the Director, the owner or operator must submit an area of review and corrective action plan that includes the following information:

Schlumberger Suggested Revision: (b) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan to delineate the area of review for a proposed geologic sequestration proj ect, reevaluate th e delineation, and

22perform corrective action that meets the requirements of this section in a manner and at a frequency acceptable to th e Director. As a part of the permit application, the owner or ope rator must submit an area of review and corrective action plan that includes the following information:

Schlumberger Rationale: -

Individual Response: EPA disagrees with the proposed cha nges and retains the provisions as proposed. For additional information on EPA's appr oach to AoR and corrective action, please see the final rule and preamble.

Letter ID: 0226 Comment ID: 24022 Letter Lines: 536 to 548

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Proposed Rule: (i) The minimum fixed fr equency, not to exceed 10 years, the

owner or operator proposes to r eevaluate the area of review;

Schlumberger Suggested Revision: Revi sion: (i) The owner or operator will reevaluate the AOR after two years, 5 y ears and then no less frequently than every 5 years for period of injection. Th is schedule may be relaxed at the discretion of the director in the post injection period if appropriate data exist to suppor t the change.

Schlumberger Rationale: We feel that a frequency of every 10 years is too long to identify early discrepancies between the site performance and the site model. Seeing early difference will allow for earlier model updating and provide additional reduction in leakage risk and a better understand ing of the site.

Individual Response: EPA agrees with commenters that reevaluations of the AoR every ten years may not be sufficient to appropriately model plume and pressure front movement, establish conditions for corrective action, and ensure prot ection of USDWs from endangerment. For these reasons, the Agency changed the minimum freq uency for the AoR reevaluation at §146.84(e) from 10 years to at least every 5 years in the final GS rule. EPA belie ves that this revised frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, and the unique nature of CO2 GS. In addition, the Director has discre tion to require more frequent AoR reevaluation if he or she has reason to believe, based on site-specific information, that a five-year reevaluation schedule is not sufficiently protective of USDWs.

Letter ID: 0226 Comment ID: 24023 Letter Lines: 550 to 567

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3400 2.2.2 Corrective Action

23Comment: Proposed Rule: (iv) How corrective ac tion will be conducted to meet the requirements of paragraph (d) of this section, including what corrective action will be performed prior to injection and what, if any, portions of the area of

review will have corrective action ad dressed on a phased basis and how the phasing will be determined; how corrective action will be adjusted if there are changes in the area of review; and how site access will be guaranteed for future

corrective action.

Schlumberger Suggested Revi sion: (iv) How corrective ac tion will be conducted to meet the requirements of paragraph (d ) of this section, including what corrective action will be pe rformed prior to injec tion and what, if any, portions of the area of review will have corrective action addressed on a phased basis and how the phasing will be determined; how corrective action will be adjusted if there are changes in the ar ea of review; and how site access will be arranged for future corrective action.

Schlumberger Rationale: Future access cannot be fully guaranteed for an area in advance that may not even be within the boundaries of the initial AOR/ project.

Individual Response: EPA is retaining this requiremen t as proposed. The purpose of the corrective action requirement at §146.84(d) is to ensure that a ll wells in the AoR that have the potential to cause the movement of CO2 or other fluids in to or between USDWs receive appropriate corrective action. In general, to meet this requirement, the owner or operator will most likely need to obtain the right of access to wells that may require corrective action, and demonstrate they have done this in their pr oposed AoR and corrective action plan. In the AoR and corrective action plan, the owner or operato r must describe how site access will be guaranteed for future correct ive action. §146.84(b)(2)(iv).

Letter ID: 0226 Comment ID: 24024 Letter Lines: 569 to 577

Comment Code: 3310 2.2.1.1 Comments in favor of requiring computational models to delineate the AoR (seeking comment)

Comment: Proposed Rule: (1) Predict, using computationa l modeling, the projected lateral and vertical migration of the carbon dioxi de plume and formati on fluids in the

subsurface from the commencement of injection activities until the plume movement ceases, pressure differentials sufficient to cause the movement of injected fluids or formation fluids into a USDW are no longer present,

Schlumberger Suggested Revision: -

Schlumberger Rationale: We support this as written

Individual Response: EPA acknowledges the commenter’s support; the final GS rule retains the provision with minor modifications to require the use of existing data in predicting the AoR.

24Letter ID: 0226 Comment ID: 24025 Letter Lines: 579 to 592

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3110 2.1.1 Proposed siting requirements (i.e., injection/confining zones, trapping mechanism)

Comment: Proposed Rule: (i) Be based on detailed geol ogic data collected to characterize the injection zone, confining zone and any additional zones; and anticipated operating data, including injection pressu res, rates and total volumes over the proposed life of the geologi cal sequestration project;

Schlumberger Suggested Revision: (i) Be based on detailed geologic data

collected to characterize th e injection zone, confini ng zone(s), monitoring zones and any additional zones; and an ticipated operating data, including injection pressures, rate s and total volumes over th e proposed life of the geological sequestration project;

Schlumberger Rationale: We f eel that if there are seconda ry confining units that they should be included in the site m odel along with any transmissive zones between the primary and s econdary confining units.

Individual Response: EPA agrees that all geologic data about the site, in cluding confining zone(s) and transmissive zones, should be a ddressed in the model but disagrees that the suggested revision is necessary. EPA clarifies th at the AoR delineation model must be based on detailed geologic data collected to characteri ze the injection zone, c onfining zone and any additional zones ( §146.84(c)(1)(i)).

Letter ID: 0226 Comment ID: 24026 Letter Lines: 594 to 606

Comment Code: 3440 2.2.2.2 Evaluation of wells in the AoR (e.g., types of data to be reviewed)

Comment: Proposed Rule: (2) Using methods appr oved by the Director, identify all penetrations, including ac tive and abandoned wells and underground mines, in the area of review that may penetrate the c onfining zone. Provide a description of each well’s type, construction, date drilled, location, depth, record of plugging and/or completion, and any additi onal information the Director may require; and

Schlumberger Suggested Revision: -

Schlumberger Rationale: We feel that there needs to be some effort to identify unknown wells using aerial surveys or othe r methods. We support this language as long as it is interpreted to mean more th an just a record search in areas that that have been explored or produced oil and gas or have had other deep wells.

25Individual Response: For most GS sites, relying on databa se and other public records searches (i.e., of "known" artificial penetrations) will be sufficient to meet the requirements at §146.84(c)(2). However, the Agency recognizes that there may be situations where additional surveys or research to locate wells may be approp riate. For example, the Director may determine that ground or airborne surveys fo r wells are appropriate, e.g., if there is reason to believe that the incompleteness of information on known wells could compromise USDW protection from endangerment. EPA adds that under §146.84(c)(2), th e Director has the disc retion to require the owner or operator to conduct a dditional searches. EPA adds that all corrective action must be performed pursuant to the approved AoR and corr ective action plan, which affords the Director the discretion to require any additi onal information needed to ensu re that all necessary corrective action is performed. EPA is issui ng guidance on how to identify a ll wells that require corrective action; the guidance also describes the data that EPA recommends to be c onsidered in an initial AoR delineation, how to apply computational modeling to delineate the AoR, performing corrective action at GS sites, and, when a ppropriate, completing AoR reevaluations. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwater /uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24027 Letter Lines: 608 to 617

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3400 2.2.2 Corrective Action

Comment Code: 5100 2.8.1 Injection well plugging activ ities (seeking comment) (40 CFR 146.92)

Comment: Proposed Rule: (3) Determine which abandone d wells in the area of review have been plugged (as required by §146.92) in a ma nner that prevents the movement of

carbon dioxide or associated flui ds that may endanger USDWs.

Schlumberger Suggested Revision: (3) De termine which abandone d wells identified in 146.84 (c) (2) have been plugged (as required by §146.92) in a manner that prevents the movement of carbon dioxide or formation fluids that may endanger

USDWs.

Schlumberger Rationale: -

Individual Response: EPA acknowledges the comment. Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS Rule. See the final ru le and preamble for further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24028 Letter Lines: 619 to 629

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3400 2.2.2 Corrective Action

26Comment: Proposed Rule: (d) Owners or operators of Class VI wells must perform corrective

action on all wells in the area of review th at are determined to need corrective action using methods necessary to prevent th e movement of fluid into or between USDWs including use of corrosion resist ant materials, wh ere appropriate.

Schlumberger Suggested Revi sion: Owners or operators of Class VI wells must perform corrective action using corrosion re sistant materials, when appropriate, on all wells identified in 146.84(c)(2) that are determined to need corrective

action".

Schlumberger Rationale: -

Individual Response: EPA revised the text at §146.84(d) to re quire the use of materials that are "compatible with the carbon dioxide stream" In stead of corrosion resi stant materials. EPA believes this language change addresses commenters ' concerns and is also consistent with other language regarding materials requirements in the GS rule. EPA did not make the other suggested changes. See the final rule and preamble fo r further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24029 Letter Lines: 631 to 639

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Proposed Rule: (f) At the minimum fixed frequency, not to exceed 10 years, as specified in the area of review and corre ctive action plan, or when monitoring and operational conditions warrant, owners or operators must:

Schlumberger Suggested Revision: (f) At the same fre quency as the reevaluation of the AOR as specified in 146.84(c ) (2) (i), or when monitoring and operational conditions warrant, ow ners or operators must:

Schlumberger Rationale: -

Individual Response: EPA disagrees with the proposed cha nges and retains the provisions as proposed. EPA believes that the commenter’s sugge sted edit has substantiv ely the same meaning as the proposed text. For additional informa tion on EPA's approach to AoR and corrective action, please see the final rule and preamble.

Letter ID: 0226 Comment ID: 24030 Letter Lines: 641 to 650

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3700 2.2.5 Comments on the requirement for an AoR and corrective action plan

27Comment: Proposed Rule: (4) Submit an amended area of review and corrective action plan or demonstrate to the Director through m onitoring data and modeling results that

no amendment to the area of review a nd corrective action plan is needed.

Schlumberger Suggested Revision: (4) S ubmit an amended area of review and corrective action plan or demonstrate to the Director through monitoring data and modeling results that no change to the area of review a nd corrective action plan is needed.

Schlumberger Rationale: -

Individual Response: EPA disagrees with the suggested cha nge and believes the proposed text

is clear as written. For additional information on EPA's approach to AoR and corrective action, please see the final rule and preamble.

Letter ID: 0226 Comment ID: 24031 Letter Lines: 652 to 667

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5400 2.9 Proposed Financial Respons ibility and Long-Term Care Requirements

Comment: §146.85 Financial responsibility.

Proposed Rule: (b) The owner or operator must provide to th e Director, at a frequency determined by the Director, writte n updates of adjustments to the cost estimate to account for any amendments to the area of revi ew and corrective action plan (§146.84), the injection well pl ugging plan (§146.92), and the postinjection site care and si te closure plan (§146.93).

Schlumberger Suggested Revision: (b) The owner or operator must provide to the Director, at the same fr equency as the AOR reeval uation, written updates of adjustments to the cost estimate to acc ount for any amendments to the area of review and corrective action plan (§1 46.84), the injection well plugging plan (§146.92), and the post-injection site car e and site closure plan (§146.93).

Schlumberger Rationale: We feel that pot ential changes in th e size of the AOR require that all site plans be reevalua ted at the same frequency as the AOR.

Individual Response: EPA agrees that it is important to periodically update cost estimates that support financial responsibility determinations. The final GS rule, at §146.85(c), requires the owner or operator to provide annual updates to the cost estimate to account for any amendments to the AoR and corrective action plan, the injectio n well plugging plan, the PISC and site closure plan, and the emergency and remedial response plan. Owners or operators must also adjust the estimates for inflation annually under §146.85(c)(2). EPA adds that the Director can also require the owner or operator to provide an adjustment of the cost estimate if the Director determines

28that the original demonstration is no longer ad equate, as specified at §146.85(e). See the final rule and preamble for further discussion of EPA' s final approach to financial responsibility.

Letter ID: 0226 Comment ID: 24032 Letter Lines: 669 to 677

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 146.86)

Comment: §146.86 Injection well constr uction requirements.

Proposed Rule: (1) Prevent the movement of fluids into or between USDWs or into any unauthorized zones;

Schlumberger Suggested Revision:(1) Preven t the movement of fluids into or between USDWs or into any unauthorized zones that causes endangerment;

Schlumberger Rationale: -

Individual Response: EPA disagrees with the suggested ed it. EPA believes that protection of USDWs from endangerment and prevention of fluid movement between formations is paramount, and believes that the language as proposed meets the standards in SDWA §1421. Appropriately designed and constructed wells ar e necessary to prevent endangerment to USDWs and maintain integrity of the well throughout the lifetime of a GS project . This is the foundation of the requirements for construction and pre-op erational testing of Class VI wells at §§146.86

and 146.87.

Letter ID: 0226 Comment ID: 24033 Letter Lines: 679 to 692

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment)

Comment: Proposed Rule: (1) Casing and cement or othe r materials used in the construction of each Class VI well must have sufficient structural strength and be designed for the life of the geologic sequestration project. All well materials must be compatible with fluids with which the ma terials may be expected to come into

contact and meet or exceed standards developed for such materials by the American Petroleum Institute, ASTM International, or comparable standards acceptable to the Director. The casing and cementing program must be designed to prevent the movement of fluids into or between USDWs. In or der to allow the Director to determine and specify casing and cementing requirements, the owner or operator must provide the following information:

Schlumberger Suggested Revision: -

Schlumberger Rationale: We support this language as written.

29Individual Response: EPA agrees that cement that is co mpatible with the CO2 and formation fluids will enhance Class VI well integrity and has retained this provision in the final rule. EPA also agrees that developing technology in the field of acid-resistant cement will provide the industry with future benefits. In the interest of USDW protection, the Agency requires that the materials used in Class VI wells must be compa tible with fluids with which they may come in contact, as required in §146.86(b)(1).

Letter ID: 0226 Comment ID: 24034 Letter Lines: 694 to 700

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3820 2.3.1 Well construction procedures

Comment: Proposed Rule: (ii) Injection pressure, exte rnal pressure, intern al pressure and axial loading;

Schlumberger Suggested Revi sion: (ii) Injection pressu re, external pressure, internal pressure and axial loading;

Schlumberger Rationale: What is meant by external and internal pressure?

Individual Response: The internal and external pressure me ntioned in §146.86(b)(1)(ii) refers to pressure on the well casing. Internal pressures could be caused by cement or annular fluids; external pressures could be caused by cementing against the borehole or pressure head from

formations. See the discussion of Class VI well construction requirements in the preamble to the

final GS rule for additional information. A dditionally, EPA is developing guidance on the construction of Class VI wells. This guida nce will be available on EPA’s website at http://water.epa.gov/type/groundwater /uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24035 Letter Lines: 702 to 706

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 146.86)

Comment: Proposed Rule: (vi) Down-hole temperatures;

Schlumberger Suggested Revi sion: (vi) Down-hole temper atures and pressures;

Schlumberger Rationale: -

Individual Response: EPA believes the requirement at 146.86(b)(1)(ii), which requires consideration of Injection pressure, external pressure, in ternal pressure, and axial loading addresses this concern, and therefore the proposed change is unnecessary.

30Letter ID: 0226 Comment ID: 24036 Letter Lines: 714 to 721

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3822 2.3.1.1 Depth of surface casing (seeking comment)

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment)

Comment: Proposed Rule: (2) Surface casing must exte nd through the base of the lowermost

USDW and be cemented to the surface.

Schlumberger Suggested Revision: (2) Surf ace casing must extend through the base of the lowermost USDW above the injection zone and be cemented to the surface.

Schlumberger Rationale: In some parts of th e US the USDW is very deep and this standard may preclude geologic se questration in these areas.

Individual Response: EPA disagrees with the suggested edit or that th e surface casing requirements in the GS rule preclude injecti on below deep USDWs. The final GS rule at §146.86(b)(2) requires that surface casing extend th rough the base of the lowermost USDW and be cemented to the surface through the use of a singl e or multiple strings of casing and cement. It does not, however, specify how cementing must be accomplished, and gives flexibility to the owner or operator to propose alternate methods - to provide a sufficient amount of cement to meet the standard that USDWs are protected from endangerment. EPA notes that there are many potential ways to meet the requirement , such as the use of staged cementing.

EPA recognizes concerns regardi ng construction of Class VI wells where the lowermost USDW is very deep. To further address comments on d eep injection wells, the final GS rule at §146.95 includes requirements for owners or operators that seek a waiver of the injection depth requirements. Owners or operators of wells opera ting under injection depth waivers must comply with additional construction require ments to ensure that wells used to inject above or between USDWs are protective. See the discussion of the wa iver approach in the preamble to the final GS

rule for additional information.

Letter ID: 0226 Comment ID: 24037 Letter Lines: 723 to 731

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment)

Comment: Proposed Rule: (3) At least one long stri ng casing, using a sufficient number of centralizers, must extend to the inje ction zone and must be cemented by circulating cement to the surface in one or more stages.

Schlumberger Suggested Revision: -

Schlumberger Rationale: We support this langua ge work by Carey et al and crow et al shows that CO2 can move above the top of the CO2 reservoir, so cementing to

31surface will provide the best chance to have maximum zonal isolation

Individual Response: EPA agrees that the requirement for long-string casing of Class VI wells at §146.86(b) will offer the best protection agai nst fluid movement behind the casing, between formations, and above the injec tion zone and will ensure competency of Class VI wells and protect USDWs from endangerment. The buoyant na ture of CO2 dictates deep well construction procedures that address movement of fluid be hind the casing and provide necessary barriers to CO2 leakage outside of the injection zone. In developing the constructio n requirements for Class VI wells, EPA reviewed the work cited by Care y et al. (2007) and Cr ow et al. (2008). EPA agrees that they offer important justification for the establishment of tailored requirements.

Letter ID: 0226 Comment ID: 24038 Letter Lines: 733 to 750

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3864 2.3.3.2 Use of corrosion-resistant cements (seeking comment)

Comment: Proposed Rule: (5) Cement and cement addi tives must be compatible with the

carbon dioxide stream and formation flui ds and of sufficient quality and quantity to maintain integrity over the design life the geologic sequestration project. The integrity and location of the cement shall be verified using technology capable of evaluating cement quality radially and identifying the

location of channels to ensure that USDWs are not

Schlumberger Suggested Revision: (5) Ce ment and cement additives must be

suitable for use with the carbon dioxide stream and formation fluids and of sufficient quality and quantity to maintain integrity over the project life. The integrity and location of the cement sha ll be verified using technology capable of evaluating cement quality radially and identifying th e location of channels to ensure that USDWs are not endangered.

Schlumberger Rationale: Well cements need to site and conditi on specific. There may be instances or places in the well that will require special cements. It is

also that the cement in the well last as long as the project and post injection period.

Individual Response: EPA recognizes that each GS project will be unique and, for this reason, the rule provides flexibility regarding the selectio n and use of cements for Class VI wells that are appropriate to the site-specific conditions of the project. With the permit application, the owner or operator must submit well construction proc edures, as specified at §146.82 (a)(12), that

demonstrate that the well as c onstructed will prevent unacceptable fluid movement; allow the use of appropriate testing devices and workover to ols; and allow continuous monitoring of the annulus space between the injection tubing a nd long-string casing, as specified at §146.86(a). The Director will evaluate the procedures in the context of geological and proposed operating

data about the site. EPA adds that the rule does not specify cements to be used; rather, it provides owners or operators with the flex ibility to choose, as long as the cements are compatible with the

CO2 stream and formation fluids and of sufficient qual ity and quantity to maintain integrity over

32the design life of the GS projec t, as specified at §146.86(b)(5).

See the discussion of Class VI well construction requirements in the preamble to the final GS rule for additional information. Additionally, EP A is developing guidance on the construction of Class VI wells. This guidance will be available on EPA’s website at http://water.epa.gov/type/groundwater /uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24039 Letter Lines: 752 to 784

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: §146.87 Logging, sampling, and testing prio r to injection well operation.

Proposed Rule: (a) During the drilling and construction of a Class VI injection well, the owner or operator must run a ppropriate logs, surveys and tests to determine or verify the depth, thickness, porosity, permeability, and lithology of, and the salinity of any formation fluids in, all relevant geologic

formations to assure conformance w ith the injection well construction requirements under §146.86, and to establish accurate baseline data against which future measurements may be compare d. The owner or operator must submit to the Director a descriptive report prepared by a knowledgeable log analyst that includes an interpretation of the results of such logs and tests. At a minimum, such logs and tests must include:

Schlumberger Suggested Revision: (a) Du ring the drilling and construction of a Class VI injection well, the owner or operator must run appropriate logs, surveys and tests to determine or veri fy the depth, thickness, porosity, permeability, and lithology of, and the salin ity of any formation fluids in, all relevant geologic formations to assure conformance with the injection well construction requirements under §146.86, and to establish accurate baseline data against which future measurements may be compared. The owner or operator must submit to the Director a descriptive report prepared by a knowledgeable log analyst that includes an interpretation of the results of such logs and tests. The Director may require such logs and te sts as may be needed after taking into account the availability of similar data in the area of the drilling site to ensure that the data is equivalent to the data as would be collected based on such logs and tests as::

Schlumberger Rationale: In well defined areas, these evaluations are frequently unnecessary. The director should have di scretion to select the appropriate requirements necessary to ensure that su fficient baseline data and information are available. For example, in an ar ea where a number of wells are being drilled, the logging of surface hole yiel ds little useful additional

information.

33Individual Response: EPA disagrees that the requirements for logs, surveys, and tests are unnecessary. All logs, surveys, a nd tests listed at §146.87( a) are necessary to verify information about the injection and confining zones and ensure that the well is being drilled and cased as approved, and has mechanical integrity. This inform ation is needed to demonstrate that the well can be operated and tested in a manner that pr otects USDWs from endangerment. While the tests do provide information on some of the same items, each test provides unique pieces of information that build on each other and allow for interpretations not possi ble with a single test.

EPA notes that the Director ha s the discretion at §146.87(a)(5) to approve alternative methods that provide equivalent or better information. EP A believes that logs and tests must be performed on each well drilled regardless of existing in formation about the area to account for the complexity of CO2 injection well construction and the buoyancy of CO2. Existing lithologic and geologic information may lack the details need ed for site-specific we ll design and the geology needed to support protection of USDWs from endangerment.

Letter ID: 0226 Comment ID: 24040 Letter Lines: 786 to 794

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (ii) A cement bond and vari able density log, and a temperature log after the casing is set and cemented.

Schlumberger Suggested Revisi on: (ii) Cement evaluation logs after the casing is set and cemented to evaluate cement quality radially with sufficient resolution to identify channels or cha nges to the cement quality.

Schlumberger Rationale: Radial is key to finding pathways but the resolution must be sufficient to see the pathways. S ee the pathway identified in Crow et al

Individual Response: EPA agrees with the suggested change. In the final GS rule, §146.87(a)(2)(ii) reads as follows: "A cement bond and variable density log to evaluate cement quality radially, and a temp erature log after the casi ng is set and cemented."

Letter ID: 0226 Comment ID: 24041 Letter Lines: 796 to 803

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (4) A series of tests desi gned to demonstrate the internal and external mechanical integrity of injection wells, which may include:

Schlumberger Suggested Revision: (4) Test(s) designed to demonstrate the internal and external mechanical integrity of injection wells, which may

include:

34Schlumberger Rationale: -

Individual Response: EPA disagrees that the suggested edit is necessary, and the final rule retains the text as proposed.

Letter ID: 0226 Comment ID: 24042 Letter Lines: 805 to 810

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (ii) A tracer survey such as oxygen-activation logging;

Schlumberger Suggested Re vision: (ii) Diagnostic tools such as oxygenactivation logging;

Schlumberger Rationale: Technical correction

Individual Response: EPA disagrees that the allowing the us e of unspecified "diagnostic tools" would provide the same amount of information as the requirement to perform a tracer survey.

The track record for tracer surv eys in evaluating mechanical inte grity has been proven over time. The Agency clarifies that a tracer survey is one of the mechanical integrity tests that may be required by the Director or used by the owner or operator.

Letter ID: 0226 Comment ID: 24043 Letter Lines: 812 to 817

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (5) Any alternative methods that provide equivalent or better information and that are required of a nd/or approved of by the Director.

Schlumberger Suggested Revision: -

Schlumberger Rationale: We interpre t that (5) applie s to 146.87(a)

Individual Response: EPA clarifies that the Director has the discretion at §146.87(a)(5) to approve alternative logging, samp ling, and testing methods that pr ovide equivalent or better information than those specified in §146.87(a)(1 -4). The Director may not allow MIT methods that have not been approved by EPA, pursuant to §146.89(e).

Letter ID: 0226 Comment ID: 24044 Letter Lines: 819 to 835

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

35Comment: Proposed Rule: (b) The owner or operator must take and submit to the Director

whole cores or sidewall cores of the in jection zone and confining system and formation fluid samples from the injec tion zone(s). The Director may accept cores from nearby wells if the owner or operator can demonstrate that core retrieval is not possible and that such cores are representative of conditions at the well. The Director may require the owner or operator to core other

formations in the borehole.

Schlumberger Suggested Revision: (b) The owner or operator mu st submit to the Director a report describing whole cores or sidewall cores representative of the injection zone and confining system a nd formation fluid samples from the injection zone(s). The Director may accept data from cores and fluid samples from nearby wells if the owner or operator can demonstrate that such data are representative of cond itions at the well.

Schlumberger Rationale: The informati on required should be sufficient to properly describe the injec tion and confining zones.

Individual Response: EPA clarifies that it is not the Agency's intent that physical cores be submitted to the Director. In the final GS rule, EPA has revised the first sentence of §146.87(b) to read as follows: "The owner or operator mu st take whole cores or sidewall cores of the injection zone and confining system and formati on fluid samples from the injection zone(s), and must submit to the Director a detailed report pr epared by a log analyst that includes: well log analyses (including well logs), core analyses, and formati on fluid sample information...."

EPA clarifies that §146.87(b) allows informati on on cores from nearby wells to be submitted only if the operator can demonstrate that core re trieval is not possible an d that cores from nearby wells are representative of conditions at the Cla ss VI well. If the Direct or approves the use of alternate cores and determines that additional logs, such as video logs, are necessary to evaluate the site, he/she has authority under §146.87(a)(5) to require additional information.

Letter ID: 0226 Comment ID: 24045 Letter Lines: 837 to 845

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (c) The owner or operator mu st record the fluid temperature, pH, conductivity, reservoir pressure and the st atic fluid level of the injection zone(s).

Schlumberger Suggested Revision: (c) Pr ior to injection well operation, the owner or operator must record the forma tion temperature, formation fluid pH and conductivity, and reservoi r pressure of the injection zone(s).

Schlumberger Rationale: -

36Individual Response: EPA clarifies that all logging, sampli ng and testing for ch aracteristics of the injection zone required in §146.8 7 are, as defined in the title to that section, to be performed prior to injection well operation. EPA adds that §146.82(c)(7) requires that the Director evaluate the results of all logging and testing prior to authorizing injection.

Letter ID: 0226 Comment ID: 24047 Letter Lines: 858 to 871

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule:(f) The owner or operator must provide the Director with the opportunity to witness all logging and testing by this subpart. The owner or operator must submit a schedule of such act ivities to the Direct or 30 days prior to conducting the first test and submit any changes to the schedule 30 days prior to the next scheduled test.

Schlumberger Suggested Revision: (f) Th e owner or operator must provide the Director with the opportunity to witn ess all logging and testing by this subpart. The owner or operator must subm it a schedule of such activities to the Director upon spudding the well and submit any changes to the schedule 48 hours prior to the scheduled test.

Schlumberger Rationale: The changes reflect the realities of flexible rig schedules and consistency with Class II practices.

Individual Response: EPA disagrees that the 30-day notif ication requirement is unreasonable. The 30-day notification mirrors the current requ irement for logging and testing of new Class I wells, as described in §146.66. Acknowledging the developing nature of CO2 GS, EPA believes that involvement by the permitting authority in each project will provide much needed field data for assurance of USDW protec tion from endangerment and will help update and refine the permitting process. Adequate timing of notification will ensure the Director's ability to be

involved.

Letter ID: 0226 Comment ID: 24048 Letter Lines: 873 to 891

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4110 2.4.1.1 Injection pressure limitations

Comment: §146.88 Injection well operating requirements.

Proposed Rule: (a) Except during stimulation, the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection zone so as to assure th at the injection doe s not initiate new fractures or propagate exis ting fractures in the injection zone. In no case may

37injection pressure initiate fractures in the confining zone(s) or cause the movement of injection or formati on fluids that endangers a USDW.

Schlumberger Suggested Revision: (a) Ex cept during stimulation, the owner or operator must ensure that injection pre ssure does not exceed 90 percent of the hydraulic fracture pressure of the confini ng zone so as to assure that the injection does not initiate new fractures or propagate existing fractures in the confining zone. In no case may injection pressure initiate fractures in the confining zone(s) or cause the movement of injection or formation fluids that endangers a USDW.

Schlumberger Rationale: Maintaining the integrity of the confining zone is the critical parameter.

Individual Response: EPA agrees that maintaining the integrity of the confining zone is critical in order to protect USDWs from endangerment. Ho wever, EPA also believes that the injection pressure should not exceed 90 percent of the fract ure pressure of the injection zone. The final rule retains this provision at §146.88(a). EPA be lieves that the 90 per cent requirement, which was suggested by IOGCC and permit writers wh om EPA consulted when writing the regulation, is a satisfactory margin of safety for well operation.

Letter ID: 0226 Comment ID: 24049 Letter Lines: 847 to 856

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: (e) Upon completion, but prior to operation, the owner or operator must conduct the following tests to verify hydrogeologic characteristics of the injection zone:

Schlumberger Suggested Revision: (d) At any time prior to injection well operation, the owner or operator must determine fracture pressures of the injection and confining z ones and conduct tests to ve rify hydrogeologic and geomechanical characteristics of the injection zone, e.g.:

Schlumberger Rationale: -

Individual Response: EPA disagrees that the suggested edit is necessary, and the final rule retains the text as proposed.

Letter ID: 0226 Comment ID: 24050 Letter Lines: 893 to 899

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4000 2.4 Proposed Injection Well Operat ing Requirements (40 CFR 146.88)

38Comment: Proposed Rule: (b) Injecti on between the outermost cas ing protecting USDWs and the well bore is prohibited.

Schlumberger Suggested Revision: (b) Inje ction of the CO2 stream between the outermost casing protecting USDWs a nd the well bore is prohibited.

Schlumberger Rationale: -

Individual Response: EPA retains the provision as propos ed, and clarifies that injection between the casing and the well bore is prohibited. This is consistent with requirements for other injection well classes in the UIC program.

Letter ID: 0226 Comment ID: 24051 Letter Lines: 901 to 912

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4000 2.4 Proposed Injection Well Operat ing Requirements (40 CFR 146.88)

Comment: Proposed Rule: (c) The owner or operator must fill the annulus between the tubing and the long string casing with a non-corrosive fluid approved by the Director. The owner or operat or must maintain on the annulus a pressure that exceeds the operating injection pressure, unless the Director determines that such requirement might harm the integrity of the well.

Schlumberger Suggested Revision: (c) The owner or operator must fill the annulus between the tubing and the long string casing with a non-corrosive fluid approved by the Director.

Schlumberger Rationale: Industry experien ce with the Class II UIC program does not support this requirement.

Individual Response: EPA believes that maintaining an annulus pressure that is higher than the injection pressure, as required at §146.88(c), will ensure that if there are leaks in the tubing, the annulus fluid will move into the tubing, rather than the injectate moving out of the tubing and potentially along the outside of the well. EPA believes this requirement is appropriate and necessary for Class VI wells given the potential high volumes and superc ritical nature of the CO2 injectate, potential geomechanical stresses in the wellbore, and the potential for movement

of the CO2 in the event of a mechanical integrity loss.

Letter ID: 0226 Comment ID: 24052 Letter Lines: 914 to 919

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4000 2.4 Proposed Injection Well Operat ing Requirements (40 CFR 146.88)

Comment: Proposed Rule: (3) Notify the Director within 24 hours

39Schlumberger Suggested Revision: (3) No tify the Director within 24 hours of discovery;

Schlumberger Rationale: -

Individual Response: The final rule text at §146.88(f) now reads, "If a shutdown (i.e., downhole or at the surface) is triggere d or a loss of mechanical integr ity is discovered." Therefore the notice required at §146.88(f)(3) must be provide d within 24 hours of an automatic shut-off device being triggered or a loss of mechanical integrity being discovered. EPA believes this provision is necessary to ensure timely re sponse to potential USDW endangerment.

Letter ID: 0226 Comment ID: 24053 Letter Lines: 921 to 931

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: §146.90 Testing and monitoring requirements.

Proposed Rule: (b) Installation and use, ex cept during well wor kovers as defined in §146.86(d), of continuous recording devi ces to monitor inje ction pressure, rate and volume; the pre ssure on the annulus between the tubing and the long string casing; and the annulus fluid volume;

Schlumberger Suggested Revision: -

Schlumberger Rationale: 146.86(d) does not exist; perhaps 146.88(d) is what was

intended.

Individual Response: EPA acknowledges the comment; the fina l rule contains the suggested

revision.

Letter ID: 0226 Comment ID: 24054 Letter Lines: 933 to 945

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4630 2.6.3 Corrosion monitoring

Comment: Proposed Rule: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on a quarterly basis to ensure that the well components meet the minimum standards for material strength and perfor mance set forth in §146.86(b) by:

Schlumberger Suggested Revision: (c) Corrosi on monitoring of the well materials for loss of mass, thickness, cracking, pitt ing and other signs of corrosion must be performed quarterly and may be modified to be less frequent as approved by

40the Director based on construction ma terials, operating conditions, and monitoring history to ensure that the well components meet the minimum standards for material strength and perfor mance set forth in §146.86(b) by:

Schlumberger Rationale: Allows applica tion of performance based approach.

Individual Response: EPA believes that corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well material s. The CO2 stream for a GS project may also contain small volumes of impurities that could co ntribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring at §146.90(c), as proposed.

Letter ID: 0226 Comment ID: 24055 Letter Lines: 947 to 953

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4630 2.6.3 Corrosion monitoring

Comment: Proposed Rule: (1) Placing coupons of the we ll construction materi als in contact with the carbon dioxide stream; or

Schlumberger Suggested Revision: (1) An alyzing coupons of th e well construction materials placed in contact with the carbon dioxide stream; or

Schlumberger Rationale: -

Individual Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has ma de many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24056 Letter Lines: 955 to 962

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4630 2.6.3 Corrosion monitoring

Comment: Proposed Rule: (2) Routing the carbon dioxide stream through a loop constructed with the material used in the well; or

Schlumberger Suggested Revision: (2) Rou ting the carbon dioxide stream through a loop constructed with the material used in the well and inspec ting the materials in the loop; or

Schlumberger Rationale: -

Individual Response: Based on its evaluation of all public comments and input on the proposed

41rule and NODA and Request for Comment EPA has ma de many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24057 Letter Lines: 964 to 969

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4630 2.6.3 Corrosion monitoring

Comment: Proposed Rule: (3) Using an alternativ e method approved by the Director;

Schlumberger Suggested Revision: (3) Usi ng an alternative met hod, materials, or time period approved by the Director;

Schlumberger Rationale: -

Individual Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has ma de many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24058 Letter Lines: 971 to 980

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4660 2.6.6 Geochemical monitoring

Comment: Proposed Rule: (d) Periodic monitori ng of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide movement through the confining z one or additional identified zones:

Schlumberger Suggested Revision: (d) Periodic monitoring of the ground water quality for geochemical changes above the c onfining zone(s) that may be a result of carbon dioxide movement through the conf ining zone or additional identified

zones:

Schlumberger Rationale: -

Individual Response: EPA did not make the suggested cha nge. Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the fi nal rule and preamble for further discussion on EPA's final approach.

Letter ID: 0226 Comment ID: 24059 Letter Lines: 982 to 992

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4650 2.6.5 CO2 plume and pressure fr ont tracking (seeking comment)

42Comment: Proposed Rule: (1) The location and number of monitoring wells must be based on specific information about the geologic sequestration proj ect, including injection rate and volume, geology, the pr esence of artificial penetrations and other factors;

Schlumberger Suggested Revision: (1) The location and number of monitoring wells must be based on specific information about the geologic sequestration project, including injection rate and volume, geology, the presence of artificial penetrations and other relevant fact ors as warranted by a risk-assessment;

Schlumberger Rationale: The monitoring should be designed to reduce risk

Individual Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment. EPA retains the requirement regard ing placement of monitoring wells, but adds that any additional relevant site-specific information must be considered in the development of the testing and monitoring plan to ensu re USDW protection from endangerment.

EPA is developing guidance on testing and mon itoring to assist owne rs or operators and Directors in evaluating requi rements under §146.90, including pr oposed monitoring plans. The guidance describes available technologies a nd recommended approaches for implementing a testing and monitoring plan, including pre-ope rational geophysical l ogging and testing of injection wells, MITs, injecti on well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, a nd soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. Th e guidance can be found on EPA’s website at http://water.epa.gov/type/gr oundwater/uic/wells_se questration.cfm.

Letter ID: 0226 Comment ID: 24060 Letter Lines: 994 to 1005

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4660 2.6.6 Geochemical monitoring

Comment: Proposed Rule: (2) The monitoring fre quency and spatial distribution of monitoring wells must be based on baseli ne geochemical data that has been collected under §146.82(a) (6) and any modeling results in the area of review evaluation required by §146.84(b);

Schlumberger Suggested Revision: (2) The monitoring frequency and spatial distribution of monitoring wells must be based on geological and geophysical data that has been collected under §146.82( d) and any modeling results in the

area of review evaluati on required by §146.84(b);

Schlumberger Rationale:Geochemical data does not seem have a high degree of relevance in selecting monitoring well sites.

43Individual Response: EPA believes that baseline characteri zation of the site, including the geochemical data and initial modeling, will be hi ghly valuable in selection of monitoring well locations and in refining plans for monitoring frequency. The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were coll ected during the initial site characterization and the area of review evaluation at §146.90(d)(2). The details of the geochemical monitoring will be based on site-specific information and described in the Director-approved testing and monitoring plan.

Letter ID: 0226 Comment ID: 24061 Letter Lines: 1007 to 1015

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4546 2.5.2.2 MIT frequency (seeking comment)

Comment: Proposed Rule: (e) A demonstr ation of external mechani cal integrity pursuant to §146.89(c) at least once per year thro ughout the duration of the geologic sequestration project;

Schlumberger Suggested Revision: (e) A de monstration of external mechanical integrity pursuant to §146.89(c) at leas t once per year thr oughout the life of the well;

Schlumberger Rationale: -

Individual Response: EPA is retaining the language as proposed. EPA clarifies that the monitoring and testing plan requirements in §146.90 cover the period pr ior to well plugging. External MITs are not required onc e a well is plugged, as this test would no longer be possible in a plugged well. If a well is plugged prior to site closure, no further MITs are required for that

well.

Letter ID: 0226 Comment ID: 24062 Letter Lines: 1017 to 1027

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4640 2.6.4 Pressure fall-off testing (seeking comment)

Comment: Proposed Rule: (f) A pressure fall-off te st at least once every five years unless more frequent testing is required by the Director based on site specific information;

Schlumberger Suggested Revision: (f) A pressure fall-off test or other equivalent test that identifies reservoir conditions with respect to flow dynamics at least once every five years unle ss more frequent test ing is required by the Director based on s ite specific information;

Schlumberger Rationale: Allows more flexibility while still pr oviding the needed

44information

Individual Response: EPA believes that pressure fall-off testing is necessary for GS wells. Pressure fall-off tests are designe d to verify that modeled proj ections of reservoir pressure decline agree with measured pressure decline profiles. These tests can be useful in AoR

calculations and reevaluations and may also indicate mischaracter ization of site geology and the presence of leakage pathways. EP A therefore believes that pressu re fall-off testing is conducted at least once every five years a nd the final GS regulation includes this requirement at §146.90(f). Pressure fall-off tests may be conducted in conj unction with other well performance tests (i.e., mechanical integrity testing) to en sure safe and effective operations.

Letter ID: 0226 Comment ID: 24063 Letter Lines: 1029 to 1040

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4650 2.6.5 CO2 plume and pressure fr ont tracking (seeking comment)

Comment: Proposed Rule: (g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pre ssure front by either monitoring for pressure changes in the first formation overlying the confining zone or using indirect, geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hol e carbon dioxide detection tools);

Schlumberger Suggested Revision: (g) Test ing and monitoring to track the extent of the carbon dioxide plume and th e position of the pressure front.

Schlumberger Rationale:Monitoring outside of the injection z one provides little information of value for tracking and monito ring the injected plume. Examples of

how to test and monitor could be included in the Preamble.

Individual Response: As described above, EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g )(1), requires all GS project ow ners or operators to monitor directly for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and moveme nt of the pressure front and CO2 plume. In addition, §146.90(g)(2) requires owners or operators to tr ack the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless th e Director determines based on site-specific geology, that such methods are not appropriate.

Letter ID: 0226 Comment ID: 24064 Letter Lines: 1042 to 1051

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking comment)

Comment: Proposed Rule: (h) At the Director’s di scretion, surface air monitoring and/or

45soil gas monitoring to detect movement of carbon dioxide that could endanger a

USDW.

Schlumberger Suggested Revision: (h) At the Director’s discretion based on sitespecific conditions and risk- based factor s, surface air mon itoring and/or soil gas monitoring to detect movement of car bon dioxide that could endanger a USDW.

Schlumberger Rationale: In most situa tions soil and air monitoring does not provide an effective met hod of protecting USDWs.

Individual Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at a ll GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for th e purpose of USDW protection will be sitespecific.

In the final rule, at §146.90(h), the decision to re quire such monitoring as an additional measure to ensure USDW protection rests with the Direct or as a means of identif ying leaks that may pose a risk to USDWs and informing emergency notifi cation of a Class VI owner or operator and UIC Director in the event of a USDW endangerm ent, pursuant to requirements at §146.91(c).

The Agency believes that surface air and soil ga s monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensu re USDW protection. EPA also acknowledges that surface air a nd soil gas measurements are subj ect to variabili ty and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude thei r use. The decision to use surface monitoring and

the selection of monito ring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on poten tial risks to USDWs

within the AoR.

Letter ID: 0226 Comment ID: 24065 Letter Lines: 1053 to 1060

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)

Comment: Proposed Rule: (1) The testing and monito ring plan must be based on potential vulnerabilities within the area of review;

Schlumberger Suggested Revision: (1) The testing and monitoring plan must be based on site-specific geologic factors, modeling, and risk-assessment within the area of review;

Schlumberger Rationale: -

Individual Response: EPA anticipates that the testing and monitoring plan wi ll address sitespecific geologic factors, mode ling, and risk-assessment. EPA is developing guidance on how best to develop the various required project plan s, including the testing and monitoring plan. The

46guidance can be found on EPA’s website at http://water.epa.gov/type/groundwat er/uic/wells_se questration.cfm.

Based on its evaluation of all public comment s and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussi on on EPA's final approach.

Letter ID: 0226 Comment ID: 24066 Letter Lines: 1062 to 1072

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: §146.91 Reporting requirements.

Proposed Rule: (1) Any changes to the phys ical, chemical and other relevant

characteristics of the carbon dioxide str eam from the proposed operating data;

Schlumberger Suggested Revision: (1) Any significant changes to the physical,

chemical and other relevant characteristi cs of the carbon dioxide stream from the proposed operating data;

Schlumberger Rationale: Minor changes c ould just be due to uncertainty in

measurements or models

Individual Response: EPA retained this provision as pr oposed. The final rule at §146.91(a)(3) requires reporting of all exceedances of operating parameters. EPA disagrees with the suggestion to report only "significant" exceedances. Making a determination as to whether an exceedance is "significant" is not the purpose of the requirement. EPA believes that the ability of an operator toconsistently meet operating requirements and avoid exceedances provides evidence of a wellmanaged GS project that is in compliance with the Class VI permit. If multiple exceedances occur, the Director should be aware of such occurrences and determine whether these indicate non-compliance at the site, and require the appropriate course of action (e.g., a well workover, modification of operating parameters, or imposition of a penalty). Please see the final rule and the discussion of testing and monitoring in the preamble for additional information.

EPA clarifies that the rule, at §146.91(c), also requires operators to notify the Director, within 24 hours, of any event that may cause endangerment to a USDW. If such ev ents occur outside of business hours (e.g., over night), operators must report to the Director within 24 hours, and permitting agencies have staff and procedures to respond to these types of calls 24 hours a day, 7 days a week.

Letter ID: 0226 Comment ID: 24067 Letter Lines: 1074 to 1086

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

47Comment Code: 5100 2.8.1 Injection well plugging activ ities (seeking comment) (40 CFR 146.92)

Comment: §146.92 Injection well plugging.

Proposed Rule: (a) Prior to the well pluggi ng, the owner or operator must flush each Class VI injection well with a buffe r fluid, determine bottomhole reservoir pressure, and perform a final mechanical integrity test.

Schlumberger Suggested Revision: (a) Prior to the well plugging, the owner or operator must flush each Class VI injec tion well with a buffer fluid, determine bottomhole reservoir pressure, and perform a final external mechanical integrity

test.

Schlumberger Rationale: Many of the components that would be tested by an

internal MIT are removed or test ed during the plugging process.

Individual Response: EPA agrees that only an external MIT is required, and has modified the GS rule at §146.92(a) to require owners or opera tors to perform a final external mechanical integrity test prior to the well plugging.

Letter ID: 0226 Comment ID: 24068 Letter Lines: 1088 to 1095

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5100 2.8.1 Injection well plugging activ ities (seeking comment) (40 CFR 146.92)

Comment: Proposed Rule: (2) Appropriate testing methods to ensure mechanical integrity as specified in §146.89;

Schlumberger Suggested Revisi on: (2) Appropriate testing methods to ensure final external mechanical integrity as specified in §146.89(c);

Schlumberger Rationale: Many of the components that would be tested by an

internal MIT are removed or test ed during the plugging process.

Individual Response: EPA agrees that only an external MIT is required, and has modified the GS rule at §146.92(a) to require owners or opera tors to perform a final external mechanical integrity test prior to the well plugging.

Letter ID: 0226 Comment ID: 24069 Letter Lines: 1097 to 1104

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5100 2.8.1 Injection well plugging activ ities (seeking comment) (40 CFR 146.92)

48Comment: Proposed Rule: (5) The type and grade and quantity of material to be used in plugging. The material must be compatible with the carbon dioxide stream; and

Schlumberger Suggested Revision: (5) The ty pe and grade and quant ity of material to be used in plugging. The material must be suitable for use with the carbon dioxide stream; and

Schlumberger Rationale: -

Individual Response: EPA believes, considering the potentia lly corrosive nature of CO2 when it is in contact with water, that the requirement that the material must be compatible with the CO2 stream is appropriate. The final rule retains this requirement.

Letter ID: 0226 Comment ID: 24070 Letter Lines: 1106 to 1120

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5100 2.8.1 Injection well plugging activ ities (seeking comment) (40 CFR 146.92)

Comment: Proposed Rule: (d) Plugging report. Within 60 days after plugging or at the time of the next semi-annual report (whichever occurs earlier) the owner or operator must submit a plugging report to the Direct or. If the semi-annual report is due less than 15 days after completion of plugging, then the report must be submitted within 60 days after plugging. The report must be certified as accurate by the owner or operator and by the person who performed the plugging operation (if other than th e owner or operator.)

Schlumberger Suggested Revision: (d) Pl ugging report. Within 60 days after plugging the owner or operator must s ubmit a plugging report to the Director. The report must be certified as accura te by the owner or operator and by the person who performed the plugging operati on (if other than the owner or operator.)

Schlumberger Rationale: Simplification

Individual Response: EPA has revised the text at §146.92(d) to reduce confusion. The final rule text reads, "Within 60 days afte r plugging the owner or operator must submit a plugging report to

the Director."

Letter ID: 0226 Comment ID: 24071 Letter Lines: 1122 to 1152

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment)

Comment Code: 5260 2.8.2.3 Adjusting the post-injecti on timeframe (seeking comment)

49Comment: §146.93 Post-injection site care and site closure.

Proposed Rule: (1) The owner or operator shall continue to conduct monitoring as specified in the Director-approved post-i njection site care and site closure plan for at least 50 years following the cessation of in jection. At the Director’s discretion, the monitoring will continue until the geologic sequestration project no longer poses an endangerment to USDWs.

Schlumberger Suggested Revision: (1) The owner or operator sh all continue to conduct monitoring as specified in the Director-approved post -injection site care and site closure plan, pursuant to th e performance based criteria described in 146.93(3).

Schlumberger Rationale: The 50 year default period is not based on any

scientific or technical information a nd could be considered arbitrary and capricious.

Proposed Rule: (2) If the owner or operat or can demonstrate to the satisfaction of the Director before 50 years, base d on monitoring and other site-specific data, that the geologic sequestration proj ect no longer poses an endangerment to USDWs, the Director may approve an amendm ent to the post-injection site care and site closure plan to reduce the frequenc y of monitoring or may authorize site

closure before the end of the 50-year period.

Schlumberger Suggested Revision: (2) If th e owner or operator can demonstrate to

the satisfaction of the Director that the geologic sequestra tion project no longer poses an endangerment to USDWs, the Director may approve an amendment to the post- injection site care and site cl osure plan to reduce the frequency of monitoring or may author ize site closure.

Schlumberger Rationale: -

Individual Response: EPA disagrees that a post-injection si te care timeframe of 50 years is

excessive in most cases or is arbitrary and capricious. EPA proposed a default post-injection site care timeframe of 50 years based on a review of research studies, industry reports, and existing environmental programs. This analysis was in cluded in an EPA-prepared background document that is available in the federal docket, titled "Computational Modeling of Underground Injection

of Carbon Dioxide for Determination of Area- of-Review and Potential Risk to Underground Sources of Drinking Water." EPA assessed vari ous default timeframes based on additional

review of research studies and evaluation of public comments. While numerous commenters suggested that EPA shorten the monitoring timeframe, none of the commenters provided

sufficient data or other evidence to warrant a ch ange in the proposed timeframe. While the 10- or 30-year timeframe suggested by some of thes e commenters may be within the timeframe suggested in some studies, EPA believes that the potential risks of endangering USDWs will likely not decline within these timeframes a nd available data, including data submitted by

50commenters, do not support a different defau lt timeframe. However, EPA recognizes that alternative timeframes may be appropri ate under limited, specific circumstances.

For this reason, the GS rule offers owners or op erators flexibility regarding the duration of the PISC timeframe by: (1) allowing the Director discretion to shorten or lengthen the PISC timeframe during the post-injecti on period based on site-specific da ta, pursuant to requirements at §146.93(b); or (2) affording the Director discretion to allow a Class VI well owner or operator to demonstrate, during the permitting process based on substantial data, that an alternative PISC timeframe may be appropriate if it ensu res non-endangerment of USDWs pursuant to requirements at §146.93(c).

EPA believes however, that to ensure USDW protection from enda ngerment, a default timeframe for post-injection site care will be necessary in al l but a limited number of cases. This default 50 year post-injection site care ti meframe represents a reasonable and protective monitoring period based on a review of research studies, industr y reports, and existing environmental programs, and evaluation of public comments.

EPA believes that a default post-injection site car e timeframe of 50 years, with flexibility to adjust the timeframe for a limited number of GS projects during the permitting process where

substantial data exists to demonstrate that an alternative timeframe would be protective of USDWs, or based on data collected during the PISC period, is appropriate to address the range of sites where GS is anticipated to occur, to ac commodate site-specific circumstances and various geologic conditions, and addre sses commenters’ concerns, wh ile ensuring USDW protection. Both approaches will utilize si te-specific data, and be based on pressure monitoring and USDW impacts.

EPA is developing guidance to assist owners or operators in evaluating well plugging, postinjection site care, and site closure requirements of §146.92 and §146.93. Additionally, the guidance will assist Directors in evaluating propo sed well plugging plans a nd post-injection site care and site closure plans under §146.92 a nd §146.93. The guidance describes recommended approaches for how an owner or operator coul d plug injection and m onitoring wells; perform post-injection monitoring; demonstrate the appropriateness of an alternative post-injection site care time frame; demonstrate non endangerment; and perform site closure activities. The guidance will be available at h ttp://water.epa.gov/type /groundwater/uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24072 Letter Lines: 1154 to 1175

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93)

Comment: Proposed Rule: (3) Prior to authorization for site closure, the owner or operator must submit to the Director a de monstration, based on monitoring and other site-specific data, that the carbon dioxide plume and pre ssure front have stabilized and that no additional monitoring is needed to assure that the geologic sequestration proj ect does not pose an endangerment to USDWs.

51Schlumberger Suggested Revision: (3) Prio r to authorization for site closure, the owner or operator must demonstrate to the Director, based on monitoring and other site-specific data that no additional monitoring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs, considering the following:. (i) the estima ted magnitude and extent of the AOR based on measurements and modeling; (ii) th at CO2 movement and pressure changes match model predictions, (i ii) the estimated location of the detectable CO2 plume based on measurement and modeling (measuring magnitude of saturation within (iv) that there is no evidence of significant leakage of either CO2 or formation fluids that endanger USDWs; (v) that the CO2 plume and displaced formation fluid are not expected to migr ate in the future in a manner that encounters a potential leakage pathway; and, (vi) that wells at the site are not leaking and have maintained integrity.

Schlumberger Rationale: Establishes the pe rformance based criteria for selecting the monitoring period. the plume or mapping the edge of it);

Individual Response: The post-injection site care require ments in the final GS rule, §146.93(b), incorporate a combination of a fixed timefra me and a performance standard approach. Specifically , the GS rule offers owners or ope rators flexibility regard ing the duration of the PISC timeframe by: (1) allowing the Director discretion to shorten or lengthen the PISC timeframe during the post-injecti on period based on site-specific da ta, pursuant to requirements at §146.93(b); or (2) affording the Director discretion to allow a Class VI well owner or operator to demonstrate, during the permitting process based on substantial data, that an alternative PISC timeframe may be appropriate if it ensu res non-endangerment of USDWs pursuant to requirements at §146.93(c).

EPA believes however, that to ensure USDW protection from enda ngerment, a default timeframe for post-injection site care will be necessary in most cases. The default 50 year post-injection site care timeframe represents a reasonable and prot ective monitoring period based on a review of research studies, industry reports, and existing environmental programs, and evaluation of public

comments. EPA believes that a default post-injection site car e timeframe of 50 years, with flexibility to adjust the timeframe for a limited number of GS projects during the permitting process where

substantial data exists to demonstrate that an alternative timeframe would be protective of USDWs, or based on data collected during the PISC period, is appropriate to address the range of sites where GS is anticipated to occur, to ac commodate site-specific circumstances and various geologic conditions, and addre sses commenters’ concerns, wh ile ensuring USDW protection. Both approaches will utilize si te-specific data, and be based on pressure monitoring and USDW impacts. EPA is developing guidance to assist owners or operators in evaluating well plugging, postinjection site care, and site closure requirements of 146.92 and 146.93. Additionally, the guidance will assist Directors in evaluating propo sed well plugging plans a nd post-injection site care and site closure plans under 146.92 a nd 146.93. The guidance describes recommended approaches for how an owner or operator could plug injection and monito ring wells; demonstrate the appropriateness of an alternative post-inject ion site care time frame; perform post-injection

52monitoring; demonstrate non endangerment; and pe rform site closure act ivities. The guidance will be available at http://water.epa.gov/t ype/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0226 Comment ID: 24073 Letter Lines: 1186 to 1196

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93)

Comment: Proposed Rule: (e) Once the Director has au thorized site closure, the owner or operator must submit a site closure report within 90 days that must thereafter be retained at a location designated by th e Director. The report must include:

Schlumberger Suggested Revision: (e) On ce the Director has authorized site closure, the owner or operator must submit a site closure report within 90 days after completion of all closure ope rations. The report must include:

Schlumberger Rationale: What is the reten tion period? Many other programs have a three year limit for retention of records. EPA is the steward of information at this point of the project, not the owner or operator.

Individual Response: EPA disagrees that the owner or opera tor should not be responsible for record retention such as site closure reports. EPA believes that the requirements that the owner or operator retain for ten years following site closure, records collected during the post-injection site care period at §146.93(f) and §146.93(h) are a ppropriate for the post-injection and site closure period to ensure that data are availabl e to support non-endangerment demonstrations and to address any concerns that may arise following site closure. This data will also support EPA's review of project data as part of the adaptive rulemaking approach.

Letter ID: 0226 Comment ID: 24074 Letter Lines: 1198 to 1214

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93)

Comment: Proposed Rule: (1) Documentation of appr opriate injection a nd monitoring well plugging as specified in §146.92 and paragraph (c) of this section. The owner or operator must provide a copy of a survey plat which has been submitted to the local zoning authority designated by the Director. The plat must indicate the location of the injection well relative to permanently surveyed benchmarks. The owner or operator must also submit a copy of the plat to the Regional Administrator of the appropr iate EPA Regional Office;

Schlumberger Suggested Revision: (1) Docu mentation of appropriate injection and monitoring well plugging as specified in §146.92 and paragraph (c) of this

53section. The owner or operator must provi de a copy of a survey plat which has been submitted to the local zoning authority designated by the Director. The plat must indicate the loca tion of the injection well(s) relative to permanently surveyed benchmarks. The owner or operato r must also submit a copy of the plat to the Regional Administrator of th e appropriate EPA Re gional Office;

Schlumberger Rationale: -

Individual Response: The GS regulation at §146.93(g) requires the owner or ope rator to record a notation on the deed to the facility property or other similar document examined during a title

search that the land has been used to sequester CO2 on the deed to the facility property at the

time of site closure.

Letter ID: 0226 Comment ID: 24075 Letter Lines: 1216 to 1252

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5800 2.13 Comments on emergency and re medial response (40 CFR 146.94)

Comment: §146.94 Emergency and remedial response.

Proposed Rule: (b) If the owner or operator obtains evidence that the injected

carbon dioxide stream and associ ated pressure front may cau se an endangerment to a USDW, the owner or operator must:

Schlumberger Suggested Revision: (b) If the owner or operator obtains evidence that the injected carbon dioxi de stream or associated pr essure front endangers a USDW, the owner or operator must:

Schlumberger Rationale: -

Proposed Rule: (2) Take all steps re asonably necessary to identify and characterize any release;

Schlumberger Suggested Revision: (2) Take all steps reasonab ly necessary to identify and characterize the endangerment posed;

Schlumberger Rationale: -

Proposed Rule: (3) Notify the Director within 24 hours; and

Schlumberger Suggested Revision: (3) No tify the Director within 24 hours of becoming aware of the endangerment; and

Schlumberger Rationale:-

Proposed Rule: (d) The owner or operator mu st notify the Director and obtain his

54approval prior to conducting any well workover.

Schlumberger Suggested Revision: (d) Th e owner or operator must notify the Director prior to conducting any well workover in response to any case of endangerment.

Schlumberger Rationale:In critical situat ions, time spent obtaining approval could adversely affect the ability to conduct operations or increase the level of endangerment.

Individual Response: After consideration of comments, EPA has finalized the rule language in §146.94(b) as proposed. In the introductory section of §146.94(b), EPA clarifie s that the pressure front, as defined in §146.81, is a zone where the pr essure differential is sufficient to cause the movement of injected fluids or formation flui ds into a USDW. Therefor e, displaced formation fluids are implicitly included in the requirements for §146.94. EPA al so clarifies that owners or operators must take action when the CO2 stream or pressure front may cause endangerment. In order to prevent the endangerment of USDW s, as required under §1421 of the SDWA, EPA expects the owner or operator to act preemptiv ely and not wait until endangerment has occurred. This language is consistent w ith existing UIC requirements fo r other well classes and EPA’s authority under the SDWA.

EPA clarifies that the Agency e xpects that owners or operators should take care not to damage the well when ceasing injection under §146.94(b)(1). At §146.94(b)(2), EPA is maintaining the requirement to “characterize the release.” In or der to prevent the enda ngerment of USDWs, as required under §1421 of the SDWA, EPA expects th e owner or operator to act preemptively and not wait until endangerment has occurred. This language is co nsistent with existing UIC requirements for other well classes and EPA’s authority under the SDWA.

Concerning commenters’ suggestions for §146.94(b)(3 ), EPA clarifies that the 24 hours begins when the owner or operator obtains evidence of possible endangerment. EPA believes the rule language is clear on this requirement.

Since proposal, EPA has modified the final regu latory language at §146.94( d) to clarify what

constitutes a workover to address a well failur e (which invokes remedi al actions) and what constitutes a maintenance-type workover. For ma intenance-type workovers (i.e., those that are scheduled in advance), the owner or operator must notify and gain approval from the Director prior to beginning the workover. In the final GS regulation, EPA has moved this requirement to the reporting requirements at §146. 91(d) to clarify its intent.

Regarding concerns that notifica tion could delay responses, EPA cl arifies that the GS rule, at §146.94(b), describes procedures owners or opera tors must take in emergency situations. Specifically, upon determining that there is a problem with the we ll that may endanger a USDW, the owner or operator must firs t cease injection, then take all steps reasonably necessary to identify and characterize any release, notif y the Director, and implement the approved emergency and remedial response plan, which ma y include a well workover. EPA believes that ceasing injection (which the ow ner or operator would do immediately and before notifying the

55Director) is the immediate action necessary to pr event or mitigate endangerment of USDWs, as required under the SDWA.

Letter ID: 0226 Comment ID: 24970 Letter Lines: 1177 to 1184

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 5260 2.8.2.3 Adjusting the post-injecti on timeframe (seeking comment)

Comment: Proposed Rule: (4) If such a demonstra tion cannot be made (i.e., if the carbon dioxide plume and pressure front have not stabilized) after the 50 year period, the owner or operator must submit to the Director a plan to continue postinjection site care.

Schlumberger Suggested Revision: Delete

Schlumberger Rationale: No longer necessary

Individual Response: As described above, EPA believes that a default post-injection site care timeframe of 50 years, with allowance of Direct or's discretion to shorten or lengthen this timeframe or approve an alternat ive PISC timeframe, is appropriate to ensure that USDWs are protected, while accounting for the variety of site -specific circumstances that may come in to play at GS sites. EPA expects that the Direct or would consider the types of information the commenter describes in determining whether the plume and pressure front no longer pose a risk of endangerment to USDWs and post-injection site care monitoring may be discontinued.

Letter ID: 0226 Comment ID: 24971 Letter Lines: 708 to 712

Comment Code: 1240 1.1.1.3 Suggested changes/ed its to rule language

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment)

Comment: Proposed Rule: (viii) Type or grade of cement; and

Schlumberger Suggested Revision: (viii) T ype or grade of cement; and additives

Schlumberger Rationale: -

Individual Response: EPA agrees with the suggestion that §146.86(b)(1)(viii) be revised to also address cement additives. In the final GS rule, the subparagraph reads as follows: "Type or grade

of cement and cement additives."

56