Experimental Study on the Effect of Supercritical CO2 on Mechanical Properties and Fracture Characteristics of Longmaxi Shale

Conventional hydraulic fracturing techniques typically consume large amounts of water when producing shale gas. Fracking fluids may cause environmental pollution. In contrast, supercritical carbon dioxide (scCO2) (above 31.8°C, 7.29 MPa) can displace CH4 in reservoirs. Achieve CO2 sequestration while increasing the gas production. We studied mechanical properties and fracture characteristics a under action scCO2, nitrogen, helium, by comparing triaxial compression tests samples with seven coring angles. The results show that: (1) scCO2 effectively reduced compressive strength weakened anisotropy shale; (2) caused content dolomite, calcite, illite to decrease 4.7%∼13.5%, respectively; (3) produced micropores microfractures 10 times larger than original size microstructure. These microstructures help improve seepage gathering gas, leading enhanced recovery storage.