Study on the Alteration of Pore Parameters of Shale with Different Natural Fractures Under Supercritical Carbon Dioxide

Supercritical CO2 (scCO2) holds promise for enhancing the efficiency of deep shale gas development while simultaneously sequestering carbon. This research, pivoting on the unique features of scCO2 fracturing, investigated how the porosity of shale with varying fracture types (no fracture or NF; axial natural fracture or AF; and transversal natural fracture or TF) changes under scCO2 seepage. The results indicated that, at temperatures surpassing the critical point, the shale's porosity consistently increased with CO2 injection. Notably, the rise was more prominent at elevated temperatures.

Additionally, under a fixed temperature, pressure changes had a more pronounced effect on shale porosity than temperature variations. Experimental multi-field couplings of shale under scCO2 seepage validated these findings. In all tested scenarios, porosity increased after CO2 injection, with experimental results aligning closely with numerical simulations. The insights from this research could be pivotal for optimizing CO2 injection techniques in scCO2 fracturing, balancing efficient gas extraction with environmental carbon sequestration.