# Attachment O

Leaks

Dave Picard

Clearstone Engineering, Ltd.PEER REVIEW: OIL AND NATURAL GAS SECTOR LEAKS

1. Did this paper appropriately characterize the different studies and data sources that quantify VOC and methane emissions from leaks in the oil and natural gas sector?

Response: The paper identified all the key studies and data sources that quantify VOC and methane emissions from leaks in the oil and natural gas sector. However, the following are a

few areas where th is information could have been better characterized:

• Wh ile t he study touches on the matter, it should make a more clear distinction

between : (1) quantifying emissions for the purpose of environmental reporting and (2) the quantification of emissions for the purpose of building a health, safety,

environmental o r business case for leak repairs. A leak at surface facilities may be defined as the loss of process fluid past a seal, mechanical connection or minor flaw at a rate that is in excess of normal tolerances allowed by the manufacturer or applicable health, safety and environmental standards. Those leaks in the first category should be fixed wherever this is economical to do (i.e., based on direct repair or replacement costs and the value of the process fluid being lost), while those in the latter category mu st be fixed regardless of the cost. Some companies prefer to simply detect and repair leaks and avoid the cost of quantifying them unless the leak is deemed uneconomical to repair and the significance of the leak from a health, safety and environmental per spective is in question.

• Other than indicating they should not be applied to individual components, no indication is given regarding the accuracy of the leak

- rate correlation and different emission factor methods and how the accuracy is impacted by the nu mber of components considered. For example, the leak

- rate correlations are extremely weak correlations and have uncertainty bands of ±2 to 3 orders of magnitude when applied to individual screening values. In general, screening values are a poor indicator of the

leak rate

.

• There is no discussion on how reliable the average facility

- level or process unit

- level component counts are, or discussion of the challenges of getting accurate component counts. It is much easier to train someone to operate a leak dete ction device than it is to train them to recognize what equipment is in active service and what service each component is in. So, developing component counts can be a noteworthy source of uncertainty. The potential issues of developing component counts fro m process drawings should also be acknowledged.

• A number of studies have been cited that contain information on the amount of CH 4 and, in some cases, VOC emissions from leaks per facility. It would be useful to compare these data to the GRI/US EPA 1996 data used to derive the facility

- level emission factors applied in the presented emission inventory estimates. There may be value in combining the data sets to get a larger, more statistically representative, data set upon which to base the emission factors.

2. Please comment on the approaches for quantifying emissions and on the emission factors

used in the data sources discussed. Please comment on the national estimates of emissio ns and emission factors for equipment leaks presented in this paper. Please comment on the activity data used to calculate these emissions, both on the total national and regional equipment counts.



### 1Response: See the comments provide under Item 1 above.

3. Are the emission estimating procedures and leak detection methods presented here equally applicable to both oil and gas production, processing, and tr ansmission and storage sectors?

Response: The presented leak detection methods are all aimed at detecting leaked gases and vapors in air at or downwind of the source

. These emissions are primarily related to equipment components in Gas/Vapor, LPG and LNG service. The presented detection methods are equally applicable to oil and natural gas production, processing and transmission and storage sectors for the purpose of targeting these types of leaks.

Components in crude oil or NGL service tend to have low or no methane emissions and any leakage is generally readily detected by visual means. Components in this type of service mostly occur at oil production facilities and at production and processing facilities handling wet natural gas. L eak

- prone components in crude oil or NGL service will normally feature drip pans to capture any leakage that occurs less any evaporation losses

. The presented leak detection methods are much less applicable these types of leaks.

4. Are there ongoing or planned studies that will substantially improve the current understanding of VOC and methane emissions from leaks and availab le techniques for detecting those leaks? Please list the additional studies you are aware of.

Response: I am not aware of any additional studies other than the work currently in progress through the Environmental Defense Fund.

5. Are there types of wells sit es, gathering and boosting stations, processing plants, and transmission and storage stations that are more prone to leaks than others? Some factors that could affect the potential for leaks are the number and types of equipment, the maintenance of that eq uipment, and the age of the equipment, as well as factors that relate to the local geology. Please discuss these factors and others that you believe to be important.

Response: 

### F ugitive emissions management requires ongoing attention. Leaking

components, e ven after successful repair, will eventually reoccur without proper inspection and maintenance. It is also recognized that different types of components and service applications have different leak potentials, and therefore, will require different

levels o f attention.

This is apparent in Table 1 below even though it includes compressor seals as a leak category which is not the focus of the oil gas sector leaks white paper. If the leak potential (i.e., average emission rate per component) for a connector is set to 1 (see the final right

- hand column in Table 1), then the leak potential for block valves is 9 times greater, the value for control valves is 37, open

- ended lines is 205, a reciprocating compressor seal is 2400 and so on. Based on these statistics, their percentage contribution to total fugitive emissions and their leak frequencies, leak detection efforts should be

focused mostly on the top 5 categories shown in Table 1, namely: blowdown systems, centrifugal compressor seals, reciprocating compressor seals, pressure relief valves and

open

- ended lines. Collectively, these five categories account for only 1.2 percent of the

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### total component population but contribute more than 88 percent of the total emissions from fugitive equipment leaks.

The amount of leakage at a facility will be related to the number of high

- leak

- potential components employed at the facility, the quality of the facility’s inspection and maintenance program, the toxicity or odor potential of the process fluids, and (to some extent) the age of the facility.

Facilities that suffer from neglect, regardless of whether they are new or old will, will have greater leak frequencies than those that do not. Facilities that are experiencing dramatic declines in throughput, are believed to be approaching the end of their useful life or have gone through numerous ownership changes are most likely to suffer from neglect. Components that ar e in sour or odorized service will tend to have lower leak frequencies and large leaks than components in sweet gas service.

Components in fuel gas service tend to have greater leak frequencies than components in process gas service.

The amount of emission s from a leaking component is generally independent of the size of the component.

Leakage into vent systems, compressor seals, pressure relief valves and open

- ended lines tend to be the most common sources of big leaks. Still, components such as connector s Table 1 : Sample leak statistics for gas transmission facilities.

Source Number

of

Sources 1 

### Leak Frequency 2 

### Average

Emissions (kg/h/source) 2 

### Percent of Component Population Contribution

to Total

Emissions (%) Relative

Leak

Potential

Station or Unit Blowdown System 219 59.8 3.41E+00 0.131 53.116 7616

Compressor Seal

– Centrifugal 103 64.1 1.27E+00 0.062 9.310 2838

Compressor Seal

– Reciprocating 167 40.1 1.07E+00 0.100 12.764 2400

Pressure Relief Valve 612 31.2 1.62E

- 01 0.366 7.062 362
Open

- ended Line 928 58.1 9.18E

- 02 0.555 6.070 205

Orifice Meter 185 22.7 4.86E

- 02 0.111 0.641 109

Control Valve 782 9 1.65E

- 02 0.468 0.919 37

Pressure Regulator 816 7 7.95E

- 03 0.488 0.462 18

Block Valve 17029 2.8 4.13E

- 03 10.190 5.011 9

Connector 145829 0.9 4.47E

- 04 87.264 4.644 1

Other Flow Meter 443 1.8 9.94E

- 06 0.265 0.000 0.02

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### and valves can, on occasion, also be major leak sources. Examples of situations where this or other unexpected significant leak contributions may occur include the following:

• Connections left untightened after a scheduled turnaround or maintenance which go unnoticed due to high background noise levels or because the component is in a difficult to access or infrequently visited location (e.g., at high elevation location or on a pipe rack).

• Holes that have developed in equipment or piping due to corrosion, abrasion or damage.

• Components that have been improperly installed or that were neglected to be installed (e.g., a pressure gauge removed during maintenance work is not put back into its port and the valve on the port is in an open or partially open posit ion).

• Major failures of valve stem packing systems (e.g., blowout of the packing material).

6. Did this paper capture the full range of technologies available to identify leaks at oil and natural gas facilities?

Response: The paper did not discuss area and building monitoring systems, use of

odourant s, and mass balance techniques

. A discussion of building and area monitoring systems is warranted as there is sometimes a perception that these are effective in detecting leaks; they are only effective in detecti ng leaks that are either sufficiently large to appreciably affect the air quality of the monitored building or area, or are located very close to the gas sensors used by the sensors.

7. Please comment on the pros and cons of the different leak detection technologies. Please discuss efficacy, cost and feasibility for various applications.

Response:

• OGI

– this technology provides the ability to visualize leaks in real time and record

the information. Such information has proven to be much more compelling evidence for management to approve the time and resources needed to control leaks than the output of other technologies. The technology is not as sensitive as other technologies

in detecti ng leaks, but it is much more efficient in finding the big leaks that contr ibute most of the leakage emissions. The key disadvantage of the technology is the high capital cost of the instrument.

• Method 21

– These methods are more sensitive than the OGI and have much lower capital cost s , but are more time

- consuming to apply, are susceptible to fouling, and require regular calibration and servicing.

• Soap Solution

– this is a simple technique that has good se nsitivity, the lowest capital

cost and is not affected by interferences from other nearby sources

. It cannot be

app lied to cold or hot surfaces and can be time

- consuming to apply.

• Remove Monitoring

– This method requires favorable wind conditions, needs t o be able to accurately measure small perturbations in pollutant concentrations above background levels, is susceptible to interferences from other nearby sources, does not



### 4distinguish between leakage and our other emission sources, can be costly , requires a much greater level of training and knowledge to apply and does not pinpoint the location of individual leaks. Rather, it provides a practicable means of measuring

total emissions from a facility or process area

.

• Acoustical

– this method does not disting uish between natural gas leaks and leaks of other types of gases such as steam, air or nitrogen. Moreover, the method should not be used after a rain or in an area where soap tests have just been performed as the wetted surfaces may adversely affect the de tection capability of the method. The technology is moderately priced.

8. Please comment on the prevalence of the use of the different leak detection technologies at oil and gas facilities. Which technologies are the most commonly used? Does the type of facility (e.g., well site versus gathering and boosting station) affect which leak detection technology is used?

Response: In the absence of a formal leak detection program, leaks are largely detected based on OVA techniques by operations and maintenance s taff as they conduct their normal activities, and by building and area monitoring systems. However, where formal leak surveys are required there is an overwhelming tendency for upstream oil and natural gas companies to

either invest in OGI cameras or retai n service providers that use OGI cameras.

9. Please provide information on current frequencies of revisit of existing voluntary leak detection programs in industry and how the costs and emission reductions achieved vary with different frequencies of revisit.

Response: No information available.

10. Please comment on the potential for using ambient/mobile monitoring technologies in conjunction with OGI technology. This would be a two

- phase approach where the ambient/mobile monitoring technology is used to detect th e presence of a leak and the OGI technology is used to identify the leaking component. Please discuss efficacy, cost and feasibility.

Response: While the proposed strategy is a pragmatic approach to efficiently finding noteworthy sources of leakage, it has not been widely adopted. This is largely due to the lack of readily available and practicable ambient/mobile monitoring technologies and/or service providers.

11. Please comment on the cost of detecting a leak when compared to the cost to repair a leak.

Multi ple studies described in this paper suggest that detecting leaks is far more costly than repairing leaks and, due to generally low costs of repair and the subsequent product recovery, it is almost always economical to repair leaks once they are found. Plea se comment on this

overall conclusion.

Response: The statement that leaks are far more costly to find than to repair is a generality. Many leaks are easy to fix and simply require the tightening of a connector or packing gland, but these are not necessaril y the leaks that contribute most to total leakage at a

site.



### 512. If the conclusion is correct that it is almost always economical to repair leaks once they are found, then how important is the quantification of emissions from leaks when implementing a

progra m to detect and repair leaks?

Response: The quantification of emissions is not necessary to drive a repair decision if the leaking component is easy and inexpensive to fix or if the amount of emissions is clearly sufficient to pose a health, safety, or en vironmental concern (e.g., if it causes personal, area or building monitoring systems to alarm). Quantification is more important where companies adopt leak reductions as a key performance indicator

.

13. Please comment on the state of innovation in leak detect ion technologies. Are there new technologies under development that are not discussed in this paper? Are there significant advancements being made in the technologies that are not described in this paper?

Response: There is a reasonable amount of innovation underway to develop more powerful and cost

- effective leak detection and quantification systems. Most of this effort is focused on developing lower cost gas sensors, intelligent multi

- sensor fixed monitoring systems that incorporate information o n the site structures and meteorological data to detect and quantify leaks, and manned and unmanned vehicle

- based plume transect systems for quantification of emissions.



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