# Attachment M

Leaks

Matt Harrison

URS Corporation

### Comments on



## Oil and Natural Gas Sector Leaks

Draft dated April, 2014

Submitted to:

Carrie Richardson Fry RTI, International

Submitted by:

Matthew Harrison

June 16, 2014

Overview As requested, I have reviewed the draft white paper titled “Oil and Natural Gas Sector Leaks” prepared by the U.S. EPA Office of Air Quality Plan ning and Standards (OAQPS), dated April 2014. My review is limited to my areas of experien ce.

I have only been asked to comment upon this Leaks p aper, however, the papers on Compressors and the paper on Pneumatic devices and the paper on Hydraulically fractured oil wells have significant overlap in the upstream production segm ent.

This review document is grouped into two sections: responses to the charge questions for reviewers that appear in the white paper, and addit ional specific comments, organized by page

number.Responses to Charge Questions

1. Did this paper appropriately characterize the diffe rent studies and data sources that quantify

VOC and methane emissions from leaks in the oil and gas sector?

Response: In general, the paper does an adequate jo b of summarizing the studies and sources of data. However, it summarizes each source independen tly, and does not do much intercomparison between all the studies. It would be us eful to have comparisons and conclusions about the differences between all the sources.

Natural gas is used as a surrogate for VOC and meth ane emissions as in almost all the cases, this is appropriate for traditional leak sources wh ere it is the produced natural gas that is

emitted.

A primary issue in this reviewer’s opinion is an im proper scope of this paper that defines “leaks” to include tank emissions such as flashing emissions, breathing emissions, and malfunctions of other equipment that result in emis sions from tanks (such as gauging hatches left open, or stuck dump valves on separators that allow gas to blow through to a tank). These tank sources are extremely different from other traditio nal leak sources and should not be grouped together as “leaks”.

Leaks from traditional sources come from sealed sur faces, such as flange gaskets, valve stem packing, screwed fittings, pressure relief val ve seats, etc., and these traditional leak sources could be near zero if perfectly design ed and maintained. That is not the case for tank emissions, which are a designed emiss ion point of a completely different

character.

While some of the detection techniques that are dis cussed for leaks may be applicable to find and locate tank issues, it is erroneous for th e paper to group tank sources with other leak sources simply by making the definition of “le ak” broad enough to cover tank emissions. Either the title of the paper needs to be “Leaks and Tank Emissions”, or the subjects need to be split into separate documents. EPA already split out an important source, pneumatic devices, even though these pneuma tic devices can be detected and measured by some of the same techniques used to add ress leaks. The rationale appears to be because the control techniques for pneumatics wi ll be different than leak repairs. The same can be said for tank emissions.

In fact, the paper states that emissions from impro perly operating tanks controls are designated to be leaks, or leaks from tanks where t he emissions are not exceeding the required state or federal control limits. These ar e not leaks, but defects in control systems, or inadequate design, or permitting issues . Only a portion of the tank emissions are called leaks by the paper, whereas any emission from a traditional sealed equipment source is a leak. This inconsistency needs to be r emedied by treating tanks independently. Tanks can be an important source of emissions, and should be addressed by a white paper, but using appropriate context.The Greeley CO report stated that 72% of emissions measured were from storage tanks,

but there was no mention in the white paper of the amount of that emission that would

have been considered an exceedance and thus a “leak ”2. Please comment on the approaches for quantifying em issions and on the emission factors

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

Response: In some areas, the paper criticizes (or states limitations) of particular emission detection approaches, or measurement approaches. L imitations stated for the OGI really exist for other techniques as well. This white paper lis ts limitations for the OGI that are true, but are not differentiators. The OGI write up in 3.1.2 lis ts limitations cited such as “when the technology is used appropriately”, and can be affec ted “by high or variable wind conditions”, and “is dependent upon the training and expertise o f the operator”. This is true, but is also true for many other techniques. The current write up ap pears to offer this as a unique limitation or consideration of the OGI, but it is not unique.

The white paper lists the Acoustic Leak detector in 3.1.3, and cites limitation in URS/UT 2011 for “through-valve leak detection device”. This is not the only citation available, as Subpart W allows this device for reporting as one option on c ompressors. Authors of the EPA “Leaks” white paper should note that the URS/UT 2011 citati on source was re-written and a new final version was published without reference to any VPAC results. My personal experience with the through valve device has been that it has not offer ed verifiable results, especially where used in noisy, high vibration environments, such as near co mpressors. This seems especially true for the very large valves that are found downstream of prod uction. However, most of these will likely be discussed in more detail in the compressor paper re views.

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

Response: In general, these techniques are applicab le to most sectors. Once you are dealing with the vapor phase of produced natural gas, then the pipes and packed fittings carrying or handling that gas can leak and can be detected usin g the same general array of measurement and detection techniques.

The downwind techniques discussed in Section 3.1.4 may be more easily applicable to a single large site that is readily and easily differentiate d from the background, such as a large gas processing plant, a large transmission and storage station. In those cases, there are often access roads around, upwind and downwind of a facility, an d the emission signal is large. In upstream production, access is often much more limited, and the site is often remote, and a single well pad may not be large enough to differentiate as easily.

4. Are there ongoing or planned studies that will s ubstantially improve the current understanding of VOC and methane emissions from lea ks and available techniques for detecting those leaks? Please list the additional s tudies you are aware of.Response: I am not aware of any new techniques that are not already mentioned in the white

paper.

I am aware of other natural gas supply chain studie s that are being conducted by a consortium of operating gas companies and the Environmental De fense Fund (EDF). These EDF instigated studies will show new measured results for traditio nal leaks at gas processing and gathering, and at Transmission and Storage. There will also b e one on Distribution systems, but that is outside the scope of this “Leaks” white paper. My understanding is that these papers will be published later in 2014. EPA should make use of th ese results in the EPA white paper on

“Leaks”.

There are some existing studies on whole basin area s, such as the NOAA study that looked at airplane and tower measurements of the Denver Jules berg basin. There have been similar flyover studies of other basins. However, these st udies have many limitations, and cannot separate out all the sources, such as pneumatics, t anks, compressors, etc from the leaks. Also they are highly dependent upon meteorology and the ability to estimate and remove other unrelated sources of emissions in the same area.

As mentioned in the introduction, natural gas leaks are appropriately used as a surrogate for methane and VOC leaks from traditional leak sources . For non-tank related sources, that is an appropriate surrogate, especially since the operati ng companies usually have a gas speciation analysis on the contained stream.

My experience with the commercially available HiFlo w device is that it has some service factor issues. When operating, the device provides a reas onable quantification. However, it often requires maintenance. I am also aware of some new research by Conestoga Rovers & Associates (CRA) that may comment upon the effecti veness of the commercially available HiFlow Instrument under certain conditions of methane concentration in the inlet gas less than 85 mol %. CRA has shared with me that they believe an issue may exist with the HiFlow device in these low methane circumstances. This low percent of methane occurs in upstream production and less so in midstream and further in the supply chain. Their work has not yet been published, and likely will require further research before bei ng fully understood and tested.

5. Are there types of wells sites, gathering and bo osting stations, processing plants, and transmission and storage stations that are more pro ne to leaks than others? Some factors that could affect the potential for leaks are the number and types of equipment, the maintenance of that equipment, and the age of the equipment, as we ll as factors that relate to the local geology. Please discuss these factors and others that you be lieve to be important.

Response: The University of Texas Methane report, P hase 1, did find regional differences existed in the upstream production data for equipment leak emissions. However the cause of these differences is not definitively known. There was n o single variable (age, well type, geology, etc.) that had a strong correlation to leak rate. The st udy did not gather information on maintenance practices, such as DI&M nor LDAR.6. Did this paper capture the full range of technol ogies available to identify leaks at oil and

natural gas facilities?

Response: To my knowledge, yes.

The industry has, of course, had sensory approaches (where a company operator hears or sees a leak) for as long as there has been an industry. T hese approaches are not standardized.

I did think the 3.1.4 section should have developed the Picarro cavity ring down measurement method in detail, as that is in common use for down wind approaches. My understanding is that they now offer a new coupling of data handling and installation that produces a quantification of flux, though this likely needs to be vetted by many users.

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

Response: I do not have any detailed data on leak d etection technology costs that go beyond what is mentioned in this paper. I think it is cle ar that expense of the survey needs to be minimal, to keep a positive ROI for the entire leak detection and repair process. Therefore, though OGI is a good method for greatly reducing th e manhours needed to screen a large number of components, a less expensive method of de termining where to apply the OGI, rather than applying it to all components, would be benefi cial.

Since most of the sites in many recent studies had very low emissions, and a smaller fraction of sites had the large leakers, it is very important t o minimize any costs associated with the initial screening approaches.

8. Please comment on the prevalence of the use of t he 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 stat ion) affect which leak detection technology is

used?

Response: The best respondents for this question wo uld be the operating companies, rather than researchers, academia, or NGO’s. EPA appears to hav e only one operating company, Southwestern Energy, as an official peer reviewer f or this paper. EPA may want to expand that in order to gather the best response to this questi on (and others as well).

In my experience, OGI and HiFlow appear to be in vo luntary use in many companies, in that the major oil and gas producers own the devices. Howev er, the extent of the surveys for all company assets is not known to this reviewer. Downs tream, in gas processing, transmission and storage, use the OGI commonly as part of required S ubpart W reporting.

9. Please provide information on current frequencie s of revisit of existing voluntary leak detection programs in industry and how the costs an d emission reductions achieved vary with different frequencies of revisit.Response: I have no information on frequencies of voluntary leak detection programs and the

effectiveness of any different frequencies. I do k now some of the upstream companies with voluntary programs appear to have a goal of an annu al frequency. Also, there would be expected diminishing returns by increasing frequenc ies; the largest leaks would likely be the ones found when a first-ever survey was done, and s ubsequent visits are likely to find fewer of the largest leaks. Therefore increasing frequency may not be cost effective.

EPA should note that surveys more frequently than a nnual increase the cost of the surveys, but without further research, the effect on emission re ductions is unknown. It is likely that a positive return annual LDAR program could be made to have a negative ROI simply by increasing the survey frequency to a level of diminishing returns.

10. Please comment on the potential for using ambient/m obile monitoring technologies in conjunction with OGI technology. This would be a tw o-phase approach where the ambient/mobile monitoring technology is used to det ect the presence of a leak and the OGI technology is used to identify the leaking componen t. Please discuss efficacy, cost and feasibility.

Response: There are many difficulties with ambient/ mobile monitoring, including calculating emissions from concentration and atmospheric modell ing. A major difficulty with ambient/mobile monitoring for screening is determin ing what is an acceptable baseline. A mobile monitoring would require a threshold, wherei n a site above this threshold would then be inspected by OGI. However, the threshold should d epend upon many things, such as the size of the facility. A 10 well facility would be expected to have more emissions than a single well facility, and a different single well facility with high liquids production may have higher tank flash emissions than the previous single well site. However, downwind measurement crews usually have little to no information about the equ ipment and production at a site. The practical application of an ambient/mobile monitoring thresho ld may prevent its use as a screening tool.

If this EPA whitepaper continues to focus on tanks, then perhaps the permitted site emissions, that included emissions from tanks, could potential ly be used as a threshold. However, a downwind snapshot may still be made over insufficie nt time duration to get an actual daily average. Tank emission may vary over time with the variation in liquid flow from a well, with cycle of separator dumps to the tan (when flash occ urs), and other factors. A measurement at a particular moment might be a poor representation of the annual average.

11. Please comment on the cost of detecting a leak when compared to the cost to repair a leak. Multiple studies described in this paper suggest th at 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. Please comment on this

overall conclusion.

Response: It makes sense that it would almost alway s be economical to repair a leak once found, so long as the repair can be made without affecting the normal operation of the site. However, where shut downs are required for repairs, the cost of lost production can drastically affect the cost of repair.The white paper does comment, and cites other paper s that comment on the fact that the cost of survey is very important and must be minimized to m ake any repair program cost effective.

12. If the conclusion is correct that it is almost alwa ys economical to repair leaks once they are found, then how important is the quantification of emissions from leaks when implementing a program to detect and repair leaks?

Response: If the assumption is that all found leak s are repaired, then quantification is likely not

needed.

Quantification is needed for certain other things, such as National Emissions Inventories. However, quantification for the purposes of Nationa l Emissions Inventories can be determined from sampling of a subset of operations across the US in broader studies, rather than by requiring each site to quantify each leak. In the case of national inventories, it may be more valuable to know general emissions end results of a program where every found leak is repaired, so that the emission per component are known for pr ograms with LDAR, and as a baseline, measurements could also be made for programs with n o LDAR requirements at all. These emissions could be determined by industry studies t hat sample various operations across the US, rather than by emissions required to be measured fo r every single found leak by every operator, every time.

If there were to be a future LDAR regulation, then quantification might be an allowed option. If there were such an option, such quantification migh t allow an owner/operator to decide which leaks to repair, or to prioritize the repairs. Th ere are other parts of the supply chain, such as Distribution, just downstream of the scope of this white paper, where decades of Public Utility Commission practice s recognize that certain small leaks do not require repair for safety nor for gas loss reasons. They recognize the cost of repai rs can be high, and Distribution companies are allowed to grade their leaks in Class 1, 2 , an d 3, with grade 3 leaks being monitored but not mandatorily repaired. Since the white paper recogn izes that there is a skewed distribution of leaks (i.e. 80% of the leaks caused by 20% of the l eakers), then it makes sense that the most cost effective repairs are the largest leakers.

This philosophy, suggested in the question, also as sumes that all repairs cost the same, which is not always the case. Some repairs can be made easi ly and on line, some require a shutdown, but only of one piece of equipment for which there is a spare, and some might require shutdown of the facility. These have differing costs.

It depends whether the cost of survey already inclu ded the cost of HiFlow quantification.

13. Please comment on the state of innovation in leak d etection technologies. Are there new technologies under development that are not discuss ed in this paper? Are there significant advancements being made in the technologies that ar e not described in this paper?

Response: I am not aware of new leak detection tech nologies, but the amount of activity in the natural gas supply chain has brought recent analysi s (such as the Picarro cavity ring downdevice), and efforts such as research and recent te chnology development challenges by EDF may

lead to other innovations.Specific Editorial Comments and Questions

Page 2: the third paragraph states “the projected groth is primarily led by.....” The sources mention only gas development plays, and should also mention oil plays, which is driving most drilling now.

Page 9: define “Unit-specific” when the term is use d.

Page 16: “the GHGRP covers a subset of national emi ssions...” The paper should cite the percent coverage EPA expected for oil and gas. I r ecall that was covered in preamble and technical support documents and was >85%. Cite the best number available. It is too undefined as printed.

Page 17: first 2 paragraphs cite “emission factors” in the Subpart W regulation. Summarize the source of those factors.

Page 18: The top of the page mentions the NEMS regi ons that are only cited as NEMS regiona in the bottom of the page. Make the citati on when first introduced, please.

Page 29: first full paragraph: “components that wer e identified in the surveys”. This is a confusing statement. Was there a larger population of unidentified components? Or does this mean simply “all of the components surveyed”

Page 29: Same paragraph “(Vented emissions are not considered leaks for the purposes of this paper).” Does “this” refer to the whitepaper or to the CL, 2013 study? Also, hopefully you have a final version that can now be cited.

Page 31: Section 2.10 (IICF paper). I believe ther e is some published API analysis and constructive criticism of this paper that should be reviewed by EPA.

Page 36; Define “mean repair life”

Page 39: Section 3.1.2. Spell out Infrared (IR)

Page 41: First sentence under OGI ends with “quant ifying the emissions is difficult.” This should say “is not currently possible.” After all, you later state there is no way to do it.

Page 42: define or footnote “Normally Pressured Lan ce”