Study on Remaining Oil Distribution and Utilization Status Under Different Displacement Methods Based on Nuclear Magnetic Resonance Technology

To clarify the distribution and utilization of remaining oil under different displacement methods. This study combines core displacement experiment with nuclear magnetic resonance technology to carry out displacement simulation experiments of continuous water flooding, water flooding converted to CO2 flooding, and water flooding converted to polymer flooding. The pore space was divided by the NMR T2 relaxation time, the distribution and utilization of remaining oil in different pore spaces under different displacement modes were analyzed. The result showed that the oil was mainly distributed in the medium and large pores in the irreducible water state, and the oil-water displacement mainly occurred during the process of continuous water flooding. Compared with continuous water flooding, water flooding converted to CO2 flooding and water flooding converted to polymer flooding increased the utilization of remaining oil in small pores while maintaining recovery of remaining oil in medium and large pores. When comparing the oil displacement efficiency among these methods, the effect of water flooding converted to CO2 flooding proved superior to both continuous water flooding and water flooding converted to polymer flooding.