Geologic Carbon Storage for Shale Gas Recovery

We consider the feasibility of a novel Carbon Capture, Utilization and Storage (CCUS) concept that consists in producing oil and gas from hydrocarbon-rich shales overlying deep saline aquifers that are candidates for CO2 storage. Such geological overlapping between candidate aquifers for CO2 storage and shale plays exists in several sedimentary basins across the continental US. Since CO2 reaches the storage formation at a lower temperature than the in-situ temperature, a thermal stress reduction occurs, which may lead to hydraulic fracturing of the caprock overlying the aquifer. In this work, we use a thermo-hydro-mechanical approach for modelling a caprock-aquifer-baserock system. We show that hydraulic fracturing conditions are induced within the aquifer by thermal stress reduction caused by cooling and that hydraulic fractures eventually propagate into the lower portion of the shale play. Nonetheless, fracture height of penetration in the caprock is considerably short after 10 years of injection, so the overall caprock sealing capacity is maintained. To maximize the benefit of the proposed CCUS method, CO2 injection should be maintained as long as possible to promote the penetration depth of cooling-induced hydraulic fractures into organic-rich shales. Though drilling a horizontal well in the lower portion of the shale to produce hydrocarbons from the induced hydraulic fractures may not be technically feasible, hydrocarbons can still be produced through the injection well. The production of hydrocarbons at the end of the CO2 storage project will partly compensate the costs of CCS operations. © 2017 The Authors.This study was partially supported by the Louisiana Board of Regents — Research Competitiveness Subprogram (RCS) under contract #43950. V.V. acknowledges financial support from the “TRUST" project (European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement n 309607) and from “FracRisk" project (European Community's Horizon 2020 Framework Programme H2020-EU.3.3.2.3 under grant agreement n 640979).Peer reviewe