Interfacial Characteristics And Application Research On CO₂-Formation Oil System

Face on the growing CO2 flooding technology in oilfield, further understanding mechanism of CO2 flooding becomes the key to solving many technical problems.The gas-liquid system miscibility means that order of magnitude of gas-liquid interfacial tension reaches 10-3. Oil and gas interfacial tension change is the essential characteristic of miscibility. Up to now, in the domestic and foreign research results, the research results considering the pure CO2 and hydrocarbon changes in the interface have not been reported. Thus, the research about the interface characteristic between CO2 and formation oil systems/pure hydrocarbon components has important significance for miscible CO2 flooding technology.Based on the previous results, high temperature and pressure calculation method of interfacial tension and improved testing methods were established. Measuring the interfacial tension between pure hydrocarbons and CO2, oil-gas interfacial change of the CO2-formation oil system during the miscibility, the interface mass transfer process and component change rule were analyzed. New method of MMP was proposed.The results of this thesis are shown below:(1) Utilizing Young-Laplace equation, we establish a theory method of calculating oil-gas interfacial tension, increasing the measuring applicability, develop the software, and achieve the integration of measurement-image analysis-calculation.(2) Using IFT measure method established by this thesis, we obtain a relation between CO2 and pure hydrocarbon of IFT (aromatic)> IFT (cycloalkanes)> IFT (alkanes), fit out a MMP correlation between pure hydrocarbon components and CO2 and provides a reliable mathematical relationship for establishing a new MMP prediction method.(3) Based on macro long-core displacement experiments, the interface characteristics of CO2 and formation oil contact front during the flow and asphalting deposition feature are studied.By means of CT scanning, CO2 miscible and immiscible flooding are identified. The oil recovery of CO2 miscible flooding was significantly higher than non-miscible flooding.(4) We get movement regularity of oil and gas interface in micro-displacement experiments. The results show that:after water flooding, it's feasible to implement CO2 flooding. (5) According to the composition characteristics of continental sedimentary crude oil, we use pure hydrocarbons MMP correlation with ACE to establish a kind of MMP predictive equation of CO2-formation oil system, providing a new calculation method for reservoir engineering design.