Capillary heterogeneity trapping of CO₂ in a sandstone rock at reservoir conditions

Abstract

[1] The storage of CO 2 in deep subsurface porous rocks is being developed worldwide for the mitigation of emission from large industrial sources such as power plants and steel manufacturing. A main concern of this technology is in ensuring that the upwardly buoyant CO 2 does not migrate to the surface. Simulation studies suggest that substantial amounts of CO 2 can be trapped within permeable sections of a reservoir by capillary forces and intra-reservoir heterogenities, but there is little experimental observation of these phenomena. We report the results of CO 2 core flooding experiments at high pressure and temperature performed to investigate the impact of natural capillary heterogeneity in a sandstone rock on CO 2 saturation buildup and trapping. CO 2 and water were injected through a Mt. Simon sandstone core at 9 MPa pore pressure and 50°C. The core had two regions of distinct capillarity: An upstream 10 cm long region of the core consisted of a relatively high permeability and homogenous sand. A downstream 3 cm long region of the core consisted of a low permeability region characterized by significant crossbedding and a high capillary entry pressure for CO 2 . During a drainage process of CO 2 displacing water, CO 2 builds up upstream of the capillary barrier. Once in place, CO 2 on the upstream side of the barrier cannot be displaced during 100% water flooding leading to trapped saturations that are a factor 2-5 times higher than what would be expected from residual trapping alone.

Fundamental study of CO2-H2O-mineral interactions for carbon sequestration, with emphasis on the nature of the supercritical fluid-mineral interface.

“…The effectiveness of this mechanism has been demonstrated experimentally. In a CO 2 flooding column experiment, it was found that a thin layer of reduced porosity at the exiting end of the column greatly increases (by a factor of 2-5 times) the residual CO 2 trapping in the core [123].…”

Simulations of long‐column flow experiments related to geologic carbon sequestration: effects of outer wall boundary condition on upward flow and formation of liquid CO2

“…For lower permeability media, residual trapping is expected to increase as the CO 2 residual saturation S gr increases. S gr is a history-dependent property that is correlated to the maximum historical CO 2 saturation S gmax , and the maximum possible CO 2 residual saturation S grmax , a fixed material property, through the Land 16 32 ).…”

Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

“…The pore-and micro-scale transport properties of sandstone reservoirs have been well characterized in the petrophysics literature [10][11][12][13], as sandstones contain a large portion of global petroleum reserves [10]. Recently, carbonate saline aquifers have been identified as suitable carbon dioxide sequestration sites due to their high porosity, effective stratigraphic trapping, and global abundance [14,15].…”