Estimating Carbon Storage Capacity of Depleted Shales with Flow Regime Diagnosis and Transient Analysis

Abstract Recently, many attempts have been made to estimate carbon storage capacity of depleted shales. In this paper, based on flow regime diagnosis and transient analysis, a quick and reasonable semi-analytical method for estimating CO2 storage capacity of depleted shales is introduced. Our semi-analytical method has the capability to estimate carbon storage capacity of depleted shales by considering effective diffusion, gas adsorption, and stress-sensitivity phenomenon of the permeability. By combining Laplace transforms, Pedrosa's substitution, and Stehfest numerical inversion, a CO2 seepage model for an injection well with constant injection rate is solved. With these solutions, CO2 storage capacity can be easily estimated at an arbitrary injection rate. We verify the semi-analytical method against the numerical method. In addition, the influence of some critical parameters on CO2 storage capacity are studied. Accurate determination of maximal carbon storage capacity in depleted shales is significant. This study presents a new semianalytical approach to efficiently estimate the maximal carbon storage capacity. Our study provides an improved understanding of calculating the maximal carbon storage capacity in depleted shales.