An integrated model for carbon geo-sequestration considering gas leakage

Abstract

Carbon geo-sequestration is a promising method for mitigating global warming and climate change. Depleted shale gas reservoirs with high adsorption capacities, excellent sealing properties, and complete infrastructure are potential sites for CO2 storage. However, hydraulic fracturing and extensive CO2 injection can result in fault reactivation, leading to CO2 migration and an increased risk of environmental contamination. Given this problem, a partially permeable boundary is introduced to characterize permeable faults. Herein, a novel methodology based on rate transient analysis that considers CO2 adsorption, diffusion, and leakage is proposed for evaluating the CO2 storage capacity of depleted shale gas reservoirs. The analytical solution for a multiple fractured horizontal well with finite conductivity is derived from the principle of potential superposition, Laplace transform, and correction functions. Subsequently, according to the analytical solutions, a rapid and robust CO2 storage capacity assessment technique is established. Using field data of the Marcellus shale, a sensitivity analysis is performed to analyze the effects of the reservoir and well parameters on the injection performance, carbon storage potential, and CO2 leakage risk. The results indicate that the proposed model is consistent with previously reported semi-analytical models and numerical simulations. The injection rate and cumulative leakage ratio increase with the leakage ratio, resulting in gas migration and an increased risk of leakage. Reservoirs with large drainage radii, high Langmuir volumes, and small Langmuir pressures are suitable for carbon sequestration, significantly increasing the adsorption capacity and reducing the leakage risk. In this study, a novel method is used to calculate the analytical solution for multiple fractured horizontal wells, which allows a rapid and practical CO2 geo-sequestration capacity assessment for CO2 storage projects.