The Mechanism of Near Miscible Flooding of Natural Gas in Bohai Low Permeability Reservoir

Abstract

AbstractIn view of the problems in water flooding of low permeability reservoirs in Bohai, the physical simulation method is used to explore the natural gas flooding mechanism of low permeability reservoirs in Bohai. Based on the analysis of the principle of slim tube experiment and long core displacement experiment, recognizing the necessity of judging miscible and near miscible pressure by long core displacement experiment in low permeability reservoir. Based on the mechanism of multiple contact and miscibility of natural gas, the reasonable core length of low permeability natural gas flooding experiment is optimized through laboratory experiments. Through the long core test of natural gas, the near miscible displacement pressure range and the near miscible displacement mechanism of natural gas are obtained. The results show that the core length of natural gas miscible displacement experiment in low permeability should be more than 160 cm; the pressure range of natural gas near miscible displacement in target oilfield is 29 MPa–39 MPa; the miscible process of natural gas flooding is the process that formation fluid multi-contact injected gas phase and continuously enriches to gradually eliminate the interfacial tension. The near miscible pressure range measured in long core displacement experiment is wider than that measured in slim tube experiment. The miscibility pressure is also slightly lower. This study will have a certain guiding significance for the promotion of gas flooding technology in offshore low-permeability reservoir.KeywordsNear miscible floodingLong core testMultiple contact enrichment