Temperature perturbation and induced pressure under convective-conductive heat flow during wellbore CO2/CH4 injection/production

Thermal-hydraulic-mechanical (THM) responses of wellbores and those inside porous formations are of significant interest for injection design and forecast in energy extraction and production processes. In this study, a THM formulation incorporating conductive-convective heat transfer mechanism was developed. Closed-form solutions for temperature and pressure perturbations are developed incorporating the THM-induced effects near a cylindrical wellbore are analyzed. Solutions for both high-permeability and low-permeability formations were presented, simulating two separate processes, a convective-conductive and a conductive heat transfers, respectively. A Laplace transform technique was used and the inversely transformed solution was solved numerically. Solutions subject to type I-III boundary conditions are solved and analyzed, corresponding to different engineering processes in various rock formations. CO2/CH4 injection for sequestration and storage purposes were used as an example. The storage capacity and injectivity analysis are conducted with the acquired spatial and temporal changes in temperature and pore pressure inside the poroelastic medium and at the wellbor. Once the supercritical conditions are surpassed, the impacts of phase and thermal-hydraulic (TH) characteristics changes due to injected gas on injectivity, capacity, post-production safety, and operating design were highlighted.