Supercritical CO2 flow through a layered silica sand/calcite sand system: Experiment and modified maximal inscribed spheres analysis

► X-ray CT observations of scCO2 flow through silica and calcite sample. ► Observations compared to modified maximal inscribed spheres modeling. ► Maximal inscribed spheres modeling used pore structure from micro computed tomography. ► scCO2 flow in the upstream silica sand was different than in the downstream silica. ► Downstream silica sand may be affected by calcite dissolution/precipitation. A core-scale experiment in which supercritical carbon dioxide (scCO2) was flowed through a brine-saturated sample consisting of a layer of silica sand, a layer of calcite sand, and another layer of silica sand from inlet to outlet was performed, and compared to a similar experiment in which nitrogen was flowed through the same sample at the same orientation, effective stress, and temperature. The core-scale experiments were monitored using X-ray computed tomography to examine the flow paths of the fluids. Both nitrogen and scCO2 showed gravity override, however both flowed through a very narrow pathway through the calcite sand, and a broader pathway through the silica sand. Synchrotron computed microtomography volumes were acquired for sub-samples of each type of sand and reconstructions of the sand samples were analyzed using the maximal inscribed spheres method modified for mixed-wet conditions to estimate characteristic curves for a number of contact angles. These characteristic curves are used to explain and interpret the experimental results.