Study On CO₂ Immiscible Flooding Technology In Low Permeability Reservoir Of Daqing Oilfield

In recent years,under the background of large reserves of high permeability conventional reservoirs,how to effectively exploit low permeability oil and gas resources is an important measure to ensure energy security in china.At present,China's low permeability oil and gas resources distribution has oil and gas,reservoir types,wide distribution and the gas containing oil,marine and continental oil and gas has the characteristics,has proven reserves in low permeability reserves ratio is very high,accounting for more than the storage the amount of 2/3,great development potential,low permeability oil and gas field has become the main battlefield of oil and gas development.CO₂ is not affected by the flooding because the salinity and temperature of the reservoir control,low cost,suitable for mining mining,oil production rate is more high,especially for more effective exploitation of low permeability reservoir and special types of reservoir,so the exploitation of low permeability reservoirs at home and abroad when using CO₂ drive mode.In this paper,the effect of CO₂ non miscible flooding in low permeability reservoirs in the Daqing oilfield is studied in the laboratory.PVT formation,take physical simulation to simulate the formation of oil injected into the change of CO₂ after the formation of oil and gas phase and PVT,determined that CO₂ flooding relative permeability curve,the research into the changes of rock properties to CO₂ formation.The results of this study indicated that the Daqing oilfield water flooding reservoir with Qing new high residual oil saturation,water two-phase range is narrow,early and rising speed of water,water permeability,water permeability and endpoint effect has the characteristics of higher high saturation.In the CO₂ displacement operation,the CO₂ flooding is superior to water flooding,and the difference between them is nearly 700 times.At the same time,the permeability of rock increases and the hydrophilicity of rock increases.When continuous injection of CO₂ into the formation,the relevant physical parameters of formation oil changes,the formation of oil viscosity and density decreased,the underlying saturation pressure,dissolved gas oil ratio,compression coefficient,volume coefficient,average dissolution coefficient,shrinkage and expansion coefficient increased.With the increase of CO₂ pressure,gas breakthrough recovery,gas breakthrough time,oil change rate and ultimate recovery rate increase,improve the ability of CO₂ injected,CO₂-oil interfacial tension decreased,oil and gas production increased.The smaller the reservoir rock permeability,the higher the efficiency of CO₂ flooding.Therefore,it is very suitable to use CO₂ flooding to produce oil in Daqing oilfield.