Numerical simulation of the feasibility of supercritical CO2 storage and enhanced shale gas recovery considering complex fracture networks

In recent years, the greenhouse gas control has been a hot issue. A solution of injecting supercritical CO2 (scCO(2)) in Longmaxi shale gas formation (in Southwest China) is proposed in this study. To evaluate the feasibility of this method that storing CO2 and enhanced gas recovery (EGR) simultaneously, we first carried out isothermal adsorption experiments on samples from Longmaxi formation to describe the adsorption behavior of CH4 and CO2, and a generalized Ono-Kondo Lattice (OK) model was applied to predict adsorption amount of pure CH4/CO2 and their binary mixtures under supercritical, high-pressure conditions. In addition, discrete fracture network (DFN) model was adopted to characterize the complex hydraulic fracture networks constructed from micro-seismic monitoring (MSM) data and engineering analysis. The porous flow in shale matrix was modeled with the multiple interacting continua (MINC) and fractal theories. A multiscale compositional numerical model based on unstructured tri-prism grids was finally developed and solved by control volume finite element (CVFE) method. The simulation results of base and CO2 injection cases presented that scCO(2) huff 'n' puff in Longmaxi formation might be an effective method for CO2 storage and EGR, and the orthogonal experiments were designed to optimize scenarios in the field application and obtain a maximum balanced result of EUR and CO2 storage capacity (CSC) for multistage fractured horizontal well (MFHW) with complex fracture networks in shale.

Automated summary

This study evaluates the feasibility of injecting supercritical CO2 in Longmaxi shale gas formation for CO2 storage and enhanced gas recovery through isothermal adsorption experiments and simulation models, suggesting it as a potentially effective method for the desired outcomes.