(298a) Novel Fracturing Process Utilizing Natural Gas

Hydraulic fracturing is used to increase oil and natural gas production by injecting high-pressure fluid (primarily water) into a rock formation to fracture the rock and release trapped oil and natural gas. This method was developed to increase yield and make production feasible in areas that would not be viable using traditional drilling technologies. Hydraulic fracturing does have some drawbacks, however, including excessive water use and the large environmental footprint associated with that water usage. Other fracturing fluids such as carbon dioxide and propane have been tested to try to reduce the environmental impact, but the related processes are expensive and have only been implemented on a limited scale.

In the past year, under a Department of Energy (DOE) program, a novel process has been developed that utilizes natural gas as the fracturing fluid. Using natural gas requires minimal water consumption because the fracturing fluid is composed mostly of produced natural gas from adjoining wells. One challenge associated with using produced natural gas is designing and optimizing a mobile process to produce the flow rate and pressure required for fracturing. As a part of the DOE program, several different thermodynamic cycles were considered for processing the natural gas. Options included direct compression and various refrigeration cycles to produce liquefied natural gas, which was then pumped to high pressure before vaporization. Each of these cycles was evaluated and the optimal cycle was then designed in detail. Some of the factors considered in the selection included specific power, cost, size, weight, and mobility. This presentation reviews the various designs that were considered and outlines the method used to select the optimal process. A description of the final detailed design is presented.