Carbon dioxide (CO2) has been used for decades in enhanced oil recovery (EOR) and enhanced coal bed methane (ECBM) operations to improve production of oil and gas. The high affinity of CO2 for organic matter in shale such as the kerogen has also been well documented, but supercritical CO2 as a fracturing fluid in unconventional reservoirs has not been achieved on a commercial scale. It’s low viscosity and negligible dissolution of viscosifying polymers make it a poor substitute for aqueous slickwater fracturing fluids. In this study we propose a stimulation fluid system for shale whereby CO2 is alternated with slickwater, as the proppant carrier, yet laden with strong oxidizer. The oxidizer reacts with the kerogen, increasing organic matter porosity and permeability of the source rock. The kerogen with its enhanced surface area also serves as a substrate for CO2 sorption and eventually a permanent storage reservoir for the CO2. The oxidizer and the low viscosity CO2 work in tandem to penetrate deep into the shale formation minerals intertwined with the organic matter frameworks to enhance methane production while adsorbing large volumes of CO2. The alternating oxidizer-CO2 concept has no equivalent to date in unconventional hydraulic fracturing operations.

Alternate injection of oxidizer-CO2 fluid systems into unconventional source rock to enhance gas production

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