Robert Heltzel

Regulated Gaseous Emissions from In-use High Horsepower Drilling and Hydraulic Fracturing Engines

Unconventional well development is an energy intensive process, which relies heavily on diesel fuel to power high-horsepower engines. To reduce emissions and fuel costs, and increase natural gas utilization, industry has employed a limited number of dual fuel compression-ignited and dedicated natural gas spark-ignited engines. However, little in-use data are available for conventional engines or these new technologies. We measured regulated gaseous emissions from engines servicing the unconventional natural gas well development industry to understand better their in-use characteristics such that insight into real world emissions factors could be developed for use by researchers, regulators, or industry. Data collection efforts were limited by low utilization of these new technologies, therefore these data may not be representative of the current distribution of engines either nationally or by shale play. Emissions and fuel consumption were collected from two drilling engines operating as Tier 2 diesel only and dual fuel, two drilling engines that were dedicated natural gas, and two hydraulic fracturing engines operated as diesel only and dual fuel. Emissions for diesel only operation were below Tier 2 certification standards for carbon monoxide and non-methane hydrocarbon plus oxides of nitrogen. Dual fuel engines require use of oxidation catalysts to reduce carbon monoxide and non-methane hydrocarbon emissions resulting from this mode of combustion. For dual fuel engines with diesel oxidation catalysts, carbon monoxide emissions were reduced below Tier 2 diesel only standards by an order of magnitude. Dual fuel operation showed varied effects on non-methane hydrocarbon plus oxides of nitrogen emissions depending on configuration. These variations were mainly driven by some technologies increasing or decreasing oxides of nitrogen emissions. One dual fuel drilling engine failed to meet Tier 2 standards, as it did not include a diesel oxidation catalyst. Of the two dedicated natural engines tested, one had a failed catalyst and did not meet off-road standards for spark-ignited engines; however, emissions from the engine with the properly functioning catalyst were well below standards. Dedicated natural gas engines also demonstrated potential to meet Tier 2 carbon monoxide regulations while producing significantly lower oxides of nitrogen emissions than diesel only or dual fuel engines.

Estimated Emissions from the Prime-Movers of Unconventional Natural Gas Well Development Using Recently Collected In-Use Data in the United States

Natural gas from shale plays dominates new production and growth. However, unconventional well development is an energy intensive process. The prime movers, which include over-the-road service trucks, horizontal drilling rigs, and hydraulic fracturing pumps, are predominately powered by diesel engines that impact air quality. Instead of relying on certification data or outdated emission factors, this model uses new in-use emissions and activity data combined with historical literature to develop a national emissions inventory. For the diesel only case, hydraulic fracturing engines produced the most NO x emissions, while drilling engines produced the most CO emissions, and truck engines produced the most THC emissions. By implementing dual-fuel and dedicated natural gas engines, total fuel energy consumed, CO2, CO, THC, and CH4 emissions would increase, while NO x emissions, diesel fuel consumption, and fuel costs would decrease. Dedicated natural gas engines offered significant reductions in NO x emissions. Additional scenarios examined extreme cases of full fleet conversions. While deep market penetrations could reduce fuel costs, both technologies could significantly increase CH4 emissions. While this model is based on a small sample size of engine configurations, data were collected during real in-use activity and is representative of real world activity.

Development of Engine Activity Cycles for the Prime Movers of Unconventional, Natural Gas Well Development.

ABSTRACT With the advent of unconventional natural gas resources, new research focuses on the efficiency and emissions of the prime movers powering these fleets. These prime movers also play important roles in emissions inventories for this sector. Industry seeks to reduce operating costs by decreasing the required fuel demands of these high horsepower engines but conducting in-field or full-scale research on new technologies is cost prohibitive. As such, this research completed extensive in-use data collection efforts for the engines powering over-the-road trucks, drilling engines, and hydraulic stimulation pump engines. These engine activity data were processed in order to make representative test cycles using a Markov Chain, Monte Carlo (MCMC) simulation method. Such cycles can be applied under controlled environments on scaled engines for future research. In addition to MCMC, genetic algorithms were used to improve the overall performance values for the test cycles and smoothing was applied to ensure regression criteria were met during implementation on a test engine and dynamometer. The variations in cycle and in-use statistics are presented along with comparisons to conventional test cycles used for emissions compliance. Implications: Development of representative, engine dynamometer test cycles, from in-use activity data, is crucial in understanding fuel efficiency and emissions for engine operating modes that are different from cycles mandated by the Code of Federal Regulations. Representative cycles were created for the prime movers of unconventional well development—over-the-road (OTR) trucks and drilling and hydraulic fracturing engines. The representative cycles are implemented on scaled engines to reduce fuel consumption during research and development of new technologies in controlled laboratory environments.