Status of CO₂storage in deep saline aquifers with emphasis on modeling approaches and practical simulations

Abstract

Carbon capture and storage (CCS) is the only viable technology to mitigate carbon emissions while allowing continued large-scale use of fossil fuels. The storage part of CCS involves injection of carbon dioxide, captured from large stationary sources, into deep geological formations. Deep saline aquifers have the largest identified storage potential, with estimated storage capacity sufficient to store emissions from large stationary sources for at least a century. This makes CCS a potentially important bridging technology in the transition to carbon-free energy sources. Injection of CO 2 into deep saline aquifers leads to a multicomponent, multiphase flow system, in which geomechanics, geochemistry, and nonisothermal effects may be important. While the general system can be highly complex and involve many coupled, nonlinear partial differential equations, the underlying physics can sometimes lead to important simplifications. For example, the large density difference between injected CO 2 and brine may lead to relatively fast buoyant segregation, making an assumption of vertical equilibrium reasonable. Such simplifying assumptions lead to a range of simplified governing equations whose solutions have provided significant practical insights into system behavior, including improved estimates of storage capacity, easy-to-compute estimates of CO 2 spatial migration and pressure response, and quantitative estimates of leakage risk. When these modeling studies are coupled with observations from well-characterized injection operations, understanding of the overall system behavior is enhanced significantly. This improved understanding shows that, while economic and policy challenges remain, CO 2 storage in deep saline aquifers appears to be a viable technology and can contribute substantially to climate change solutions.

The Influence of Hydraulic Fracturing on Carbon Storage Performance

“…CO 2 storage targets are typically saline aquifers or depleted oil/gas reservoirs overlain by low‐permeability caprocks. Deep saline aquifers are expected to have the largest storage potential (Celia et al, ; McGrail et al, ). An essential consideration in the design and operation of a CO 2 storage complex is to secure the integrity of the caprock to prevent CO 2 leakage from the storage reservoir.…”

3D Pressure‐limited approach to model and estimate CO2 injection and storage capacity: saline Mount Simon Formation

“…The underground CO 2 plume movement and distribution, extension, and magnitude of the induced injection pressure, and possible and potential risks and hazards associated with this phenomenon both during and after injection have been analyzed by many research and study groups . Nevertheless, one major concern is that the effective amount of CO 2 that needs to be injected and stored in the saline formations to have a known effect on climate change is far beyond the amounts that have been injected so far . Consequently, one of the most important tasks in CCS research is to estimate the most feasible capacity of these formations to hold and store CO 2 for many years.…”

Robust simulation of sharp-interface models for fast estimation of CO2 trapping capacity in large-scale aquifer systems

“…As a results, VE simulations will typically be orders of magnitude faster and consume significantly less memory than conventional 3D simulators. In [23,43], the authors report a simulation of CO 2 migration under the caprock at Sleipner, for which a VE simulator running for a few minutes on a single core produced forecasts with similar accuracy as a 3D simulation with TOUGH2 running for several hours on one hundred cores.…”

“…Apart from the open-source implementation, the novelty of our work lies in a flexible and robust formulation that unifies work from the early period of reservoir simulation [15][16][17][18], when practical numerical aspects were primarily in focus, with recent extensions of the VE framework [19] that focus more on physical effects related to large-scale CO 2 injection. The validity of the simplifying assumptions underlying VE models has been studied both with respect to spatial [20] and temporal [21] scales, and the utility of VE models is thoroughly discussed in, e.g., [22,23]. Early studies focused on VE models with a sharpinterface assumption [24][25][26], and models that only account for the basic effects of buoyant migration were successfully used to simulate long-term migration in the Utsira [27] and Johansen [28] aquifers.…”