Insight investigation of miscible SCCO2 Water Alternating Gas (WAG) injection performance in heterogeneous sandstone reservoirs

摘要

In this manuscript, we present the results of a systematic approach to investigate the impact of core scale heterogeneity on the efficiency of miscible CO2 water-alternating-gas (WAG) flooding performance. Both vertical (by layering two axially-cut half plugs with differing permeability) and horizontal (stacking two smaller core samples with differing permeability in series) heterogeneities are explored. In the layered or vertically heterogeneous sample, the permeability ratio (PR) defines the ratio between the permeability values of each half plug. Our special sample construction technique using either a thin impermeable Teflon sheet to prevent flow communication or a thin tissue to promote flow communication has enabled us to investigate the effect of crossflow between half plug on the performance of the WAG flood. For the stacked composite or the horizontally heterogeneous core samples, short cylindrical core segments were used each with a different permeability value. We have also investigated the effect of the EOR injection mode (i.e. secondary vs. tertiary) on our results. For this study, core flooding experiments were performed using n-C10, brine and CO2 at a temperature of 343 K and a pressure of 12.4 MPa.