The Effects of Crossflow and Permeability Variation on Different Miscible CO2 injection Schemes Performance in Layered Sandstone Porous Media

Abstract

Summary Supercritical carbon dioxide (SCCO2) injection in hydrocarbon reservoirs is documented as important means to achieve hydrocarbon potential whilst mitigating the greenhouse gas effect. However, reservoir heterogeneity significantly affects subsurface multiphase flow behaviour thereby oil recovery factor, thus triggering intrinsic uncertainties to manage and predict reservoir performance. In this manuscript, we present the results of a systematic approach to investigate the influences of crossflow and permeability variations in layered core samples on the efficiency of miscible continuous SCCO2 and water alternating gas (WAG) flooding performance. Here, we manufactured heterogeneous porous media by stacking two hemi cylindrical sample (each sample has a different permeability) together. Placing either a lint free tissue paper or a Teflon sheet allowed us to investigate the impact of crossflow on displacement efficiency. The core flooding experiments were conducted under miscible conditions at a reservoir temperature of 343 K and pressure of 17.23 MPa using n C10, synthetic brine and SCCO2. Two different SCCO2 flooding schemes were used; namely, continuous injection of SCCO2 and water alternating SCCO2. The results obtained from heterogeneous porous media indicate that permeability variations in layered porous media have significantly impact the ultimate recovery for both continuous and WAG flooding. It is also found that crossflow in the layered sample has an appreciable effect on the ultimate oil recovery (i.e. increasing oil recovery by 4.8% as a maximum) when injecting SCCO2 continuously. However, as the permeability variations between layers increases a considerable channelling of the injected SCCO2 through the high permeability layer is dominated which reduces the amount of additional oil mobilised by crossflow. In contrast to the findings of continuous injection of SCCO2, the effect of crossflow during WAG flooding is negatively impacts the recovery factor. Such an outcome by WAG flooding may be attributed to the achievement of conformance control under the non communication layers which otherwise cannot due to occurrence of preferential flow paths. Thus, the results of this study provide insight into the importance of crossflow in layered porous media to overcome the current challenges in capturing the importance of geological uncertainties in the current and future SCCO2 IOR/EOR projects.