Simultaneous geological CO2 sequestration and gas production from shale gas reservoirs: brief review on technology, feasibility, and numerical modeling

Shale gas reservoirs are important unconventional sources that have been utilized and developed recently. Methods for improving production from shale gas plays focus mainly on depletion by hydraulic fracturing and horizontal well drilling. Large shale gas reserves are in the adsorbed state, which need special techniques for their recovery. CO2 injection process can enhance shale gas recovery (ESGR) through competitive adsorption between CO2 and methane as well as providing CO2 sequestration for reducing CO2 emissions. This paper presents a critical review of the most updated studies on using CO2 for enhancing shale gas recovery (ESGR) and also laboratory and field trials of CO2 capture and storage in shale gas formations. The main objective of this study is to discuss the main mechanisms and components involved, and also the challenges of performing CO2-ESGR. Feasibility assessment of CO2-ESGR for field trials is complicated and requires extensive laboratory studies and modeling and simulation of this process. Fully detailed numerical modeling and important governing equations of CO2-ESGR are discussed here which can be helpful in process optimization for achieving maximum CO2 storage and shale gas production simultaneously.