|Assessing Fugitive Methane Emissions Using Natural Gas Engines in Unconventional Resource Development
||Last Reviewed 6/14/2016
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.
West Virginia University (WVU), Center for Alternative Fuels, Engines and Emissions (CAFEE), Morgantown, WV 26571
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.
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 is working to obtain the additional funds necessary to expand the in-use data collection effort. WVU is currently working with the industry’s largest drilling contractor to obtain additional site access at up to three additional locations, which will include two dedicated natural gas fleets operating on either compressed natural gas (CNG) or field gas as well as another dual fuel or diesel only operation.
WVU researchers are preparing for the first additional site visit at the end of May. The site will be operating Waukesha LS7044 engines in the West Texas region. These engines will be operating on CNG.
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.
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, and it is currently under review with the Journal of the Air and Waste Management Association.
WVU is also finalizing its national inventory estimates for emissions. The paper targets emissions from the prime-movers of unconventional well development operating as diesel only and as a function of dual fuel 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).
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.
All Additional Accomplishments:
- WVU successfully utilized activity data from two engine and pump configurations to create steady-state hydraulic fracturing cycle for engine tests.
- 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.
- 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.
- WVU researchers successfully operated a 8.9L ISL-G over cycles. Original cycles failed regression and a subsequent method using Savitzky-Golay (SG) for input data smoothing was developed for additional testing.
- 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 (June 2016)
Researchers have obtained 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 is also working to obtain additional funding necessary to collect additional in-use data from drilling activities 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 submitted a cycle development paper to 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. 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: March 31, 2016
DOE Contribution: $1,499,830
Performer Contribution: $410,813
NETL – William Fincham (firstname.lastname@example.org or 304-285-4268)
West Virginia University – Dr. Andrew Nix (Andrew.Nix@mail.wvu.edu) or 304-293-0801)