Effects of multiphase transport in multiscale pore network on carbon storage and enhanced shale oil recovery: An experimental and numerical study

CO 2 injection in shale oil reservoirs has emerged as a promising technique for simultaneously achieving CO 2 geological storage and enhancing shale oil recovery. This study investigates the potential of CO 2 injection into shale oil reservoirs with natural fractures for carbon storage and enhanced oil recovery through a combination of experimental and numerical simulations. It focuses on the synergistic effects on carbon storage capacity and oil recovery efficiency. A series of CO 2 injection experiments using online NMR T 2 and stratified T 2 technology were conducted to validate the feasibility of carbon storage and oil recovery in shale oil reservoirs. The shale samples consist of three distinct pore space systems: kerogen, inorganic matrix, and shale bedding fractures. A coupled multiscale-multiphase simulation model was developed to facilitate a comprehensive analysis of the underlying mechanisms. In the model, kerogen, inorganic matrix, and shale bedding fractures are defined as triple-continuum media. The model integrates the mechanisms of molecular diffusion, adsorption, and viscous flow to accurately represent the mass transport processes during CO 2 injection in shale oil reservoirs. Within this framework, a series of mass transport partial differential equations were derived to describe the CO 2 injection process. The finite element method was used to numerically solve these equations, and the proposed model was validated against experimental results. Sensitivity analyses yielded the following results: (1) The shale bedding fractures are not only key reservoir spaces for shale oil but also the key mass transfer channels for shale oil and CO 2 during CO 2 injection. Increasing the permeability of the shale bedding fractures can significantly improve oil recovery efficiency and CO 2 adsorption amount. (2) The kerogen content and organic porosity have a significant impact on CO 2 adsorption amount and shale oil recovery factor, respectively. (3) High production pressure is essential for maximizing carbon storage capacity. Simultaneously, increasing injection pressure can effectively enhance carbon storage and shale oil recovery.