用界面张力法测定CO2与原油的最小混相压力

采用悬滴法,测定了在模拟地层温度为356.5K、压力为8.54~23.43MPa时的CO₂与原油间的界面张力.实验发现,CO₂与原油间的界面张力随压力的增加近似呈线性下降趋势.对该数据进行了线性回归,并用外推法计算出当界面张力为零时的最小混相压力为24.17MPa,与实验观测达到一次接触混相状态时的压力(23.43MPa)相比,相对误差为3.16%.采用界面张力确定CO₂与原油间的最小混相压力,既可通过直接观测接触混相状态确定,也可利用所测界面张力数据进行估算,操作简单易行,且耗时少.

Determination of the minimum miscibility pressure of CO2 and crude oil system by vanishing interfacial tension method

The interfacial tension data of CO2 and reservoir crude oil were measured by the pendant-drop method under the simulated-formation conditions of temperature of 356.5K and pressure ranging from 8.54MPa to 23.43MPa. The test result indicated that the interfacial tension of CO2 and reservoir crude oil decreased almost linearly as increasing pressure. The minimum miscibility pressure was determined by linearly regression of these data and extrapolating the regressed line to the point with interfacial tension of zero. The determined minimum miscibility pressure agrees well with the pressure observed by experiment. The minimum miscibility pressure of CO2 and reservoir crude oil could be determined either by the miscible phase picture or by the interfacial tension data. The vanishing interfacial tension method is easy in operation and needs less time than the other experimental methods.