Oil production performance and reservoir damage distribution of miscible CO2 soaking-alternating-gas (CO2-SAG) flooding in low permeability heterogeneous sandstone reservoirs

Miscible CO 2 -SAG flooding is an enhanced form of flooding, which mitigates the inadequate -crude oil interaction by adding a soaking period just after breakthrough (BT). The addition process results in improvements recovery residual during secondary process, may vary across reservoir, and lead to differential changes distribution permeability decline wettability variation due asphaltene precipitation. In this work, simple miscible experiments were carried out at reservoir conditions (90 °C, 23 MPa) on low long composite cores with progressively decreasing direction injection. show that overall factor (RF) was 72.8% 11% higher than (61.8%). RFs individual core plugs decreased along (i.e., decreases initial permeabilities). occurs more for those high saturation close outlet. Consequently, improved lower cores, particularly medium sized pores these cores. By contrast, 8–20%, 1.0–4.5% flooding. injection end showed slight increase, continued decrease However, greater led homogeneous increase decline. consistent larger middle had biggest values SAG • Oil outlet, leads