Stimuli-Responsive Rheoreversible Fracturing Fluids for Unconventional Oil and Gas Extraction

Even the most pessimistic US Energy Information Administration (EIA) models predict a near-doubling of U.S. production of tight oil by 2035 as crude production from other sources remains static or diminishes. As a result, the development of specialized fracturing fluid systems has been a constant research and development focus driven by the strong need for optimization of fracture propagation and permeability enhancement. To optimize and lessen environmental impact of reservoir stimulation, an environmentally benign, CO2-activated, rheoreversible fracturing fluid is presented. This fracturing fluid enhances permeability due to in situ volume expansion triggered by the presence of CO2. Our results show 100 % volume expansion of PNNL fracturing fluids at temperatures relevant to tight oil reservoirs. This rapid volume expansion created fracture networks in highly impermeable crystalline rock cores with permeability values up to 3 orders of magnitude higher than the permeabilities obtained when using conventional fracturing fluids. The chemical mechanism, phase-change behavior, and rheology of this fracturing fluid at tight oil temperatures and pressures are presented.