Semester

Summer

Date of Graduation

2022

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Andrew Nix

Committee Co-Chair

Wade Huebsch

Committee Member

Wade Huebsch

Committee Member

Derek Johnson

Abstract

In the past twenty years natural gas production in the United States has significantly increased. This is largely due to technological advancements in unconventional methods of horizontal drilling and hydraulic fracturing. With these new and improved technologies, the United States has been able to increase its natural gas dry production per year by 14.5 trillion cubic feet per year from 2001-2021, a 74.1% increase. Horizontal drilling allows the wellbore to have more contact with the source rock, thus allowing more hydrocarbons to be extracted. Hydraulic fracturing allows oil and gas companies to have access to low permeable source rock, previously uneconomical to pursue. With hydraulic fracturing or “fracing” comes emissions from the heavy-duty engines used to power fluid pumps that drive the frac fluid into the ground. To evaluate the emissions from various engine types, a MATLAB model was developed and improved based on a model created by partner, BJ Energy Solutions. This model was also expanded by evaluating emissions for engines operating in the Marcellus shale play.

The model was developed utilizing Environmental Protection Agency (EPA) standardized methodologies, data from previously conducted studies, as well as engine manufacturer data sheets. This model was created to accurately predict emission values and rates from greenhouse and non-greenhouse gases on fracing well sites. Seven engines were compared using the model: direct drive turbine, natural gas reciprocating, Tier 2 and Tier 4 diesel and dual fuel, and large turbine. Five shale plays were put into the model: Haynesville, Permian, Montney/Duvernay, Marcellus, and SCOOP/STACK (South Central Oklahoma Province/Sooner Trend Anadarko Canadian Kingfisher). A total of eight cases were ran with five varying parameters: shale play, pumping pressure, fluid flow rate, and Tier 2 and Tier 4 Dual Fuel substitution ratios. Each case assumed the same amount of pumping hours per day at 17 and only the Marcellus case differed in stage length.

Each of the cases are equivalent to one days’ worth of fracing, a total of 17 pumping hours. For Cases 1 through 6 over all the engines the average total CO2e emissions was 2342 Metric Tons. The Titan direct drive engine had the best CO2e values at 21.7% less than the average and the Tier 2 Dual Fuel engine had the worst CO2e values at 32.9% greater than the average. Cases 7 and 8 were used to look at the effects of changing the substitution rate on dual fuel engines. Cases 7 and 8 are the same as Cases 1 and 4, respectively, except the substitution rate was decreased by 15%. This led to a 2.2% increase in total CO2e emissions from the Tier 4 engine and a decrease of 4.4% in total CO2e emissions from the Tier 2 engine. For all eight cases over all the engines the average total non-greenhouse gas emission rate was 29.6 g/kw-hr. The Titan direct drive engine had the best non-greenhouse gas rate at 64.0% less than the average. The Tier 2 diesel engine had the worst non-greenhouse gas rate at 152.3% greater than the average. All these calculated values were compared against the BJ Energy Solutions model. The CO2e values were normalized to g/kW-hr using shaft horsepower and hydraulic horsepower then compared to published research studies.

When normalized using shaft horsepower the natural gas reciprocating engine had the lowest emissions and the Tier 2 dual fuel engine had the highest. When hydraulic horsepower (which accounts for driveline losses) was used the Titan engine had the lowest emissions while the Tier 2 dual fuel engine still had the highest. The shaft-power normalized GHG emissions from the diesel and dual fuel engines were compared to data in the published literature with good agreement.

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