Geological CO₂ sequestration in multi‐compartment reservoirs: Geomechanical challenges

Abstract

[1] Sequestration of large amounts of CO 2 within deep underground reservoirs has been proposed as a potential approach for reducing atmospheric emissions of greenhouse gases. A CO 2 sequestration project should address the associated environmental and safety issues and, in this respect, the importance of geomechanics has recently been widely recognized. Geomechanics is even more important when fluid injection is planned in faulted reservoirs. How much CO 2 can be safely injected into multi-compartment reservoirs? Are geomechanical constraints more restrictive than flow-dynamic constraints? These and other questions are addressed in the present study using a three-dimensional finite element-interface element geomechanical model. We simulate the possible mechanical failure in both the injected formation and the caprock, the fault/thrust reactivation, and the ground surface displacement in a faulted reservoir of the offshore northern Italy, where seismic surveys provided an accurate characterization of the faulted geological structure. Based on reliable petrophysical/geomechanical properties from well logs and pore overpressure as predicted by a fluid-dynamic model, the results show that the injection of 1 10 6 ton/a of CO 2 may be performed over a few years only. Thereafter, part of the injected formation fails by shear stress. A number of parametric scenarios are investigated to address the major uncertainties on the geomechanical response to CO 2 injection. The modeling outcome suggests that shear failure and faults/thrusts reactivation can occur much before attaining the hydraulic fracturing pressure, hence representing two major constraints for a safe and permanent containment.

Analytical model of well leakage pressure perturbations in a closed aquifer system

“…CO 2 is to be injected in a block delimited by faults and covering an area of 4.64 km 2 (equivalent reservoir radius is $1200 m). On the basis of the hydrocarbon accumulation and field history, the limiting faults may be sealing and the reservoir is considered closed [40,41], restricting the amount of CO 2 injection because of geomechanical constraints [42]. A high overpressure may jeopardize mechanical stability of the caprock (e.g.…”

Efficient global optimization of reservoir geomechanical parameters based on synthetic aperture radar-derived ground displacements

“…Equation 2 is solved numerically by FEs using the code GEPS3D (Geomechanical Elasto-Plastic 3D Simulator developed at the University of Padova), which follows the infinite pore pressure gradient formulation (Gambolati et al, 2001). GEPS3D has been successfully used in several geomechanical applications over the past few years (Teatini et al, 2000(Teatini et al, , 2011Ferronato et al, 2003;Janna et al, 2012;Castelletto et al, 2013). An advanced block factored sparse approximate inverse with incomplete LU factorization preconditioner (Janna et al, 2010) is implemented in GEPS3D to effectively solve on parallel supercomputers the typically large linear systems arising from FE implementation.…”

“…Advanced 3D viscoelastoplastic models have been used to reproduce the geomechanical behavior of complex, multipool, faulted reservoirs worldwide (Ferronato et al, 2003;Vasco et al, 2010;Teatini et al, 2011;Castelletto et al, 2013;Rinaldi and Rutqvist, 2013). Despite significative developments, model reliability in predicting localized (e.g., along fault systems) and/or distributed (e.g., land subsidence) deformations of subsurface systems due to change in pore pressure is hampered by large uncertainties in model parameters.…”

Gas injection may have triggered earthquakes in the Cogdell oil field, Texas

“…There have been preliminary monitoring and modeling of the consequences of SCCO 2 injection in the Kelly-Snyder (SACROC) unit (25,26). The presence of detectable seismic activity in the Cogdell field and its absence in the apparently similar Kelly-Snyder and Salt Creek fields makes these fields attractive candidates for detailed geomechanical modeling, as has been recently applied to CO 2 injection sites near the coast of Italy (27). It would be informative to apply similar analyses to the Cogdell field, incorporating information about faulting, our reported epicentral locations, and Texas Railroad Commission (RRC) data concerning extraction/ injection rates at individual wells.…”

“…As in our previous investigation of triggered seismicity in the Barnett Shale of northeast Texas (9), the present study is an apt example of a positive but unanticipated benefit of the USArray Temporary Array, part of the National Science Foundation-funded EarthScope program. EarthScope was conceived and funded before recent concerns about possible hazards from earthquakes triggered by water injection associated with disposal of hydrofracturing wastes (27) or by SCCO 2 injection for carbon sequestration (11,28,29). Analysis of USArray data makes it possible to determine accurate epicenters for small events and evaluate their proximity to nearby wells; it is plausible that similar analysis could provide critical information about possibly triggered earthquakes elsewhere.…”