Exploration and Production Technologies
 
Assessing Fugitive Methane Emissions Using Natural Gas Engines in Unconventional Resource Development Last Reviewed December 2016

DE-FE0013689

Goal
The project goal is to create an inventory of diesel engines, their use, and their emissions during unconventional well development. The first project objective is to analyze the benefits of operating these or similar engines on dual fuel or dedicated natural gas to determine regulated and non-regulated emissions and fuel cost reductions. The next objective is to determine the effects of operating these or similar engines and fugitive methane emissions based on the operation of current technologies using a variety of natural gas compositions. The final objective will be to examine new catalyst formulations that can be used in conjunction with these developing technologies to minimize these new sources of fugitive methane emissions associated with unconventional well development.

Performers
West Virginia University (WVU), Center for Alternative Fuels, Engines and Emissions (CAFEE), Morgantown, WV 26571

CATCO®

Background
Production of unconventional gas wells demands a significant cost in diesel fuel used to power extraction equipment. The industry is moving toward substituting domestic natural gas for diesel fuel in order to reduce operating costs. Ideally, local wellhead gas would be utilized, but this solution is undermined by engine control and emissions problems in the near term. In addition, pending and future greenhouse gas emission regulations, which include methane emissions, have the potential to slow this change.

Dual fuel retrofit strategies will be implemented in the near term to reduce the risk to unconventional gas producers; however, the strategies will evolve to include dedicated stoichiometric natural gas engines in the long term to realize the greater cost benefit of utilizing domestic natural gas. Switching from diesel to dual fuel or dedicated natural gas engines also has the potential to reduce local and regional emissions inventory loading to the atmosphere from these sites.

 

CAFEE will collaborate with its project partners to assess fugitive methane emissions when utilizing domestic natural gas for the prime movers and transportation at unconventional gas drilling sites. Specifically, CAFEE will identify and characterize the impacts of fugitive methane emissions using dual fuel (natural gas and diesel) and dedicated natural gas engines as replacements for the diesel-powered units that currently dominate unconventional well site operations. This effort will include assessing fugitive methane emissions at unconventional well site locations, as well as for the on-site supply pipeline, compression systems, storage tanks, engine fuel lines, crank case vents, and unburned fuel in the exhaust. This effort will provide industry with data, assessment, conclusions, and strategies for mitigating fugitive methane emissions through the utilization of natural gas for the prime movers and transportation used in unconventional gas production.

Impact
The successful completion of this project will provide the natural gas industry with information needed to implement low-cost, robust technologies that will promote production and utilization of U.S. energy resources while simultaneously mitigating risk to the public, oil and gas personnel, and the environment.

Accomplishments (most recent listed first)

  • WVU obtained the additional funds necessary to expand the in-use data collection effort, adding three additional field testing campaigns, bringing the total number of field measurement campaigns to six. WVU worked with the industry’s largest drilling contractor to obtain additional site access at up to three additional locations, which included two dedicated natural gas fleets operating on compressed natural gas (CNG) and field gas as well as the previously mentioned diesel only/dual fuel operation in east Texas.
  • WVU researchers completed the last in-field data collection effort in West Virginia during October 2016. The rig was equipped with Waukesha L7044GSI dedicated natural gas engines that were fueled on field gas.
    • 16 hours of in-use data collected
    • Pre-/Post TWC measurements
    • Higher CO2 emission than Tier 2 diesel
    • Lower CO and NOx emissions than Tier 2 diesel
    • Lower CH4 emissions than dual fuel conversions
    • Fuel conversion efficiency from 18.4 to 24.4%
    • TWC was effective at reducing emissions to at or below certification requirements
  • WVU researchers completed the first in-field data collection effort for a dedicated natural gas rig in West Texas during June 2016. The rig was equipped with Waukesha L7044GSI dedicated natural gas engines that were fueled compressed natural gas.
    • 16 hours of in-use data collected
    • Pre-/Post TWC measurements
    • Higher CO2 emission than Tier 2 diesel
    • Higher CO emissions than Tier 2 diesel
    • Similar post-catalyst NOx emissions as compared to Tier 2 diesel
    • Lower CH4 emissions than dual fuel conversions
    • Fuel conversion efficiency from 13 to 22%
    • TWC was not effective at meeting emissions requirements – CO
    • Likely improper air/fuel control (lower fuel conversion efficiency)
  • WVU researchers have developed a draft journal publication on the effects of dual fuel operation on efficiency and emissions from dual fuel drilling and well stimulation engines and will be submitting this article to Environmental Science and Technology. Due to the availability of additional funding, the paper will now include data on dedicated natural gas engines.
  • WVU researchers finalized cycle development methodologies and implemented cycles on a dedicated natural gas engine. The researchers have developed a publication on this methodology and the results, which was published in the Journal of the Air and Waste Management Association:
    Johnson, D., Heltzel, R., Nix, A. and Barrow, R., 2016, “Development of Engine Activity Cycles for the Prime Movers of Unconventional, Natural Gas Well Development,” Journal of the Air &Waste Management Association, DOI:10.1080/10962247.2016.1245220
  • WVU is also finalizing its national inventory estimates for emissions. The study targets emissions from the prime-movers of unconventional well development operating as diesel only and as a function of dual fuel and dedicated natural gas market penetration. The highly impactful results of this article will be submitted to a journal such as the Proceedings of the National Academy of Sciences (PNAS).

All Additional Accomplishments:

  • WVU completed cycle development methodology and developed three prime-mover test cycles which were implemented on a scaled dedicated natural gas engine within the WVU engines laboratory. A smoothing method was applied to the final results of the MCMC and generic algorithms candidate cycles. All cycles passed regression criteria and scoping tests were conducted and compared to conventional emissions test cycles within the most recent quarterly report.
  • WVU completed on-site evaluation of an Altronic-GTI dual fuel kit for unconventional drilling. The kit was installed on a CAT 3512C engine which was operated on field gas in east Texas.
    • Collected emissions pre- and post-catalyst in diesel only and dual fuel modes.
    • More than 32 hours of data collected.
    • ECU did not broadcast real engine fuel flow rate and load parameters due to the third party nature of the dual fuel kit – boost and fuel flow rate were used to determine engine load.
    • LLT substitution rate – 19%.
    • SS substitution rate – 54%.
    • Net increases in carbon dioxide (CO2) emissions.
    • Dual fuel CO and NOx emissions above regulation limits.
    • 15-21% of the natural gas supplied to the engine lost via crankcase and uncombusted methane in the exhaust.
    • Decrease in fuel conversion efficiencies of 33%.
    • 28-58% increase in CO2 equivalent emissions.
  • WVU conducted additional research activities at an active Marcellus site in Westover, WV. WVU researches collected emissions and fuel consumption data over 12 stages of well stimulation in Westover, WV, from a CAT 3512B HD engine outfitted with CAT Dynamic Gas Blending Kit.
    Results from this activity include:
    • Average natural gas substitution ratio of 52.2%.
    • Pre-catalyst CO2 emissions increased by a factor of 40 over diesel only operation. Post catalyst CO2 emissions were still 12.7 times higher than diesel only operation.
    • Dual fuel operation yielded a 12% decrease in NOx emissions, though variations in load and emissions were not statistically different for post catalyst emissions.
    • Total methane lost was 18.8-27% (23% average) of the natural gas substituted to the engine (1.5%crankcase).
    • 12.8% decrease in fuel conversion efficiency.
    • Greenhouse gas (GHG) equivalent over 3 times higher for dual fuel operation compared to diesel only.
  • WVU successfully collected engine activity data for 12 additional stages, over a 24-hour period, for hydraulic fracturing engines equipped with CAT3512 B HD engines at the Westover, WV, field site.
  • WVU successfully created a drilling cycle for further engine tests using Markov Chain, Monte Carlo cycle development tool along with SG smoothing. This accomplishment will assist WVU researchers in completing future project-related activities.
  • WVU successfully collected emissions and fuel consumption data over 64 hours of horizontal drilling in Westover, WV, from a CAT 3512C engine outfitted with CAT Dynamic Gas Blending Kit.
    Additional details/results associated with this activity include;
    • Rig operated only two engines at a time.
    • 16 hours of data collected in each following configuration: diesel fuel only pre- and post-catalyst and dual fuel operation pre- and post-catalyst.
    • Data separated into low load transient (LLT) and high load steady state (SS) operation.
    • LLT substitution 19.3%.
    • SS substitution 63.5%.
    • Dual fuel operation increased engine out CO2 emissions by 5-20 times, but incorporation of DOC reduced CO2 to below diesel only pre-catalyst levels.
    • During SS operation, NOx emissions decreased by 20% compared to diesel only operation.
    • 16-20% of natural gas substituted was lost as unburned methane from the exhaust and crankcase (1-2% of total).
    • SS – 2.3 times higher GHG equivalent footprint.
    • LLT – 1.7 times higher GHG equivalent footprint.
    • SS – decrease in fuel to electricity conversion efficiency of 13.6%.
    • LLT – decrease in fuel to electricity conversion efficiency of 13.6%.
  • WVU successfully collected 311 hours (233 useful) of horizontal drilling engine activity data during operations at the Westover, WV, active drilling site.
  • WVU successfully collected engine activity data from six Cummins QSK 50 hydraulic fracturing engines/pumps in WV. Collected over 25 hours of speed and load data for 15 well stages. Researchers were able to corroborated additional stage duration and engine speed from five additional engines.
  • Emissions and fuel economy data were collected on common operating points of a Cummins QSK 10 under cooperation with Baker-Hughes. Data included engine operation as diesel only and dual fuel with two separate oxidation catalysts. This engine is used for hydraulic stimulation of wells.
    • Diesel only operation with catalysts decreased both CO2 and THC emissions.
    • Three load levels of dual fuel operation showed reductions in diesel fuel consumption of 50-56%.
    • Total efficiency of the engine over these three modes decreased by 10%.
    • Crankcase methane emissions were about one percent of exhaust methane slip.
    • Total methane lost was 13-26% of the natural gas substituted to the engine.
    • CO2 equivalent emissions increased compared to diesel only operation – due to efficiency and methane slip.
    • PM emissions were reduced by 6-43% with the combined effects of the catalyst and dual fuel operation.
    • A catalyst focused on methane mitigation showed only a modest 3% reduction in methane emissions.
  • WVU performed a comprehensive literature review of available dual fuel and natural gas technologies, well site fueling infrastructure, diesel fuel consumption rates of the prime movers, and emissions regulations. The comprehensive review was summarized in a journal article published in a special edition of Energy Technology.
    Johnson, D., Heltzel, R., and Nix, A., “Trends in Unconventional Well Development – Methane Emissions Associated with the Use of Dual Fuel and Dedicated Natural Gas Engines,” Energy Technology, Wiley, 2014. DOI:10.1002/ente.201402088.
  • WVU researches updated multiple miniature stand-alone data loggers. These loggers were implemented in on-road prime movers and are collecting activity data for cycle development. On-road data collection has been completed.
  • A scaled dedicated natural gas engine (Cummins-Westport ISL-G 8.9L) has been obtained and installed in the WVU test cell.
  • A Cummins ISX 15L engine is currently being outfitted with a dual fuel system.
  • Researchers completed a draft literature review of currently available dual-fuel and natural gas technologies, well site fueling infrastructure, diesel fuel consumption rates of the prime movers, and emissions regulations.
  • Researchers updated three miniature stand-alone data loggers that were implemented in on-road prime movers to collect activity data for cycle development. Three new mechanical engineering graduate students are now gaining hands-on experience in conducting field measurements.

Current Status (December 2016)
Researchers have obtained data beyond the minimal requirements for activity data and in-use fuel economy and emissions data for Phase 1 objectives. WVU has obtained an additional 12 month no-cost extension to continue research on Phase 2 of the program. WVU obtained additional funding necessary to collect additional in-use data from drilling activities (total of six field campaigns) while maintaining all portions of Phase 2 – including research on the effects of fuel quality on dual fuel conversion kits and dedicated natural gas engines. WVU has published a cycle development paper in the Journal of Air and Waste Management Association, and has developed two additional publications regarding in-use emissions and a national emissions inventory. Researchers have completed scoping tests on a dedicated natural gas engine within the laboratory and will be completing tests under Tasks 5 and 6 in the coming quarter. The project did experience delays in obtaining natural gas fuel blends, but both fuel blends are currently in-house and the engine will be reinstalled and tested this quarter. WVU researchers are currently working with catalyst manufacturer CATCO to develop a methane oxidation catalyst for laboratory testing to reduce methane emissions from dual fuel or dedicated natural gas engines.

Project Start: October 1, 2013
Project End: September 30, 2017

DOE Contribution:  $1,828,637
Performer Contribution: $514,910
Note: The original DOE contribution for this project was $1,499,830 with WVU contribution of $410,813. Modified budget in June, 2016 by $328,807 (DOE contribution), with an additional $104,097 contributed by WVU.

Contact Information:
NETL – William Fincham (william.fincham@netl.doe.gov or 304-285-4268)
West Virginia University – Dr. Andrew Nix (Andrew.Nix@mail.wvu.edu) or 304-293-0801)