Thermally Induced Fracturing: An Optimized Workflow for Exploiting Software Capabilities for CCS Applications

Thermally Induced Fracturing (TIF) relates to the fracture generation due to the horizontal stress reduction because of cold fluid injection. An evaluation of this complex phenomenon, which involves geomechanics, fluid dynamics in porous media, and thermodynamics, is essential in any CCUS project. The scope of this paper is to show and compare the workflow followed with two commercial software, a multi-physics multipurpose one (COMSOL Multiphysics®) and a compositional reservoir simulator (CMG GEM®), to perform Thermo-Hydro-Mechanical (THM) simulations to assess possible TIF occurrence. A preliminary validation is performed against a literature analytical model, followed by a real case study application. The real case evaluation starts with a 2D planar model built in COMSOL Multiphysics® to investigate TIF occurrence in reservoir and the possible temperature interference between wells. Subsequently a 2D near wellbore radial model is built with both software to evaluate TIF in reservoir and at reservoir-caprock interface. Results show that both models have good agreement with the literature analytical model confirming that the two software can evaluate TIF occurrence, demonstrating good match for what regards the real case study in terms of effective hoop stress reduction. COMSOL Multiphysics® is suitable for well scale/small scale models with simplified geometry and fluid compositions, and fast in terms of computational time; CMG GEM® is instead a compositional reservoir simulator with the capabilities to model geomechanics and thermal phenomena on a wider scale.