|Assessing Fugitive Methane Emissions Using Natural Gas Engines in Unconventional Resource Development
||Last Reviewed 12/1/2015
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 Secured a field site in West Texas to conduct a study for the evaluation of dedicated natural gas engine (Waukesha) for unconventional drilling.
WVU Secured field site in East Texas to conduct a study to evaluate GTI dual fuel kits for unconventional drilling.
Marcellus Shale Energy and Environmental Laboratory project related accomplishments:
- 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.
- 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. They were able to corroborated additional stage duration and engine speed from five additional engines.
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 (December 2015)
Researchers continue to collect off-road emissions and fuel consumption data. They are proactively engaged in the Marcellus Shale Energy and Environmental Laboratory project with operations planned for early spring 2016. WVU researchers are currently working on the development of a method to present emissions inventories for the unconventional well development sector. They have collected the minimum amount of data necessary to complete inventory work and develop cycles for Phase II of the program. They continue to process this data per the defined project tasks. WVU Researchers are currently working with catalyst manufacturer CATCO to develop a methane oxidation catalyst for laboratory testing to reduce emissions specific duel fuel engine operation. WVU is contemplating a possible no cost time extension for the award.
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)