Study on the Production Law of Crude Oil in Conglomerate Reservoirs by Chemical Flooding Based on CT Scanning

The conglomerate oil reservoirs in Xinjiang Oilfield face challenges such as complex microscopic oil displacement mechanisms and low sweep efficiency in chemical flooding development due to their complex modal pore structures. (multimodal and fine-biased pore-throat distributions, high pore-throat ratios, and low coordination numbers) To clarify the rules of oil mobilization in pore-throats under different chemical flooding schemes, the 3D characteristics of the pore space in the conglomerates of the Karamay Oilfield were studied through CT scanning technology. Among them, compared with Type I conglomerates, Type III and Type II conglomerates have poor pore connectivity, a relatively higher proportion of unconnected pore spaces, and stronger pore heterogeneity characteristics. The oil displacement efficiency of Type I conglomerates by water flooding can reach 39.86%, and the water flooding effect is the most obvious. The oil displacement efficiency of Type II conglomerates can reach 39%, and that of Type III conglomerates can reach 24%. It can be seen that the remaining oil content in the cores of the three types of conglomerates has significantly decreased, and the remaining oil is mainly concentrated in the large pores surrounded by small pore throats. Performing binary flooding or ternary flooding after water flooding for the three types of conglomerates still has a certain effect on the remaining oil in the cores. Among them, the effect of performing chemical flooding after water flooding for Type II conglomerates is the best, which can increase the oil displacement efficiency by 11%. Combining with the real-time displacement imaging of chemical flooding under CT scanning technology, the results show that due to the existence of unconnected pores and tortuous and complex pore spaces, a large amount of clustered remaining oil exists after water flooding. Both binary flooding and ternary composite flooding can effectively reduce the clustered remaining oil.Through the quantitative statistics of the remaining oil, the mobilization degree of the remaining oil below 2.5 ~ 3 μm has significantly decreased, and the main remaining oil mobilization range is mostly concentrated in the pore spaces above 3 ~ 5 μm, and this part of the remaining oil is mostly concentrated in Type II conglomerates.