Characterization of the Interactions between Shale Cementation and Fracture Pump Resistance, and the Subsequent Contributions to Air Emissions from Eagleford Shale Hydraulic Fracturing Operations

Abstract

Natural gas is the fastest growing primary energy fuel, with demand increasimg more rapidly than any other energy source. With advances in horizontal drilling and hydraulic fracturing, shale formations have become an economically viable source for oil and natural gas. The Texas’ Eagleford shale has long been known as the source rock for Austin Chalk and the giant East Texas field, and is now being considered as a formidable self-sourced oil and gas reservoir with increasing economical potential to extract the shale’s oil and gas. However, the reservoir itself is not vertically homogenous between the upper and lower members. During hydraulic fracturing, the differences in petrofacies cause the fracturing engine pumps to work at higher load factors in 2 the more tightly cemented, clay-rich, layers. Fracture pump engines operate at ten to twelve percent higher load factor when fracturing shale gas formations without carbonate intersititial layering. As fracturing pump engines operate at a load factor higher than forty percent, the engines consume exponentially increasing amounts of diesel fuel. The augmentation of fuel consumption generates higher emissions of nitrous oxide, carbon dioxide and carbon monoxide. Calculations performed using industry and regulatory air emissions modeling scenarios reveals that emissions are most affected by load factor resulting from formational cementation, and not engine horsepower, repetitions per minute, or hours in operation.