CO_2驱替实验压力变化特性

在CO2驱油试验区的开发初期,地层压力并没有明显上升,为了查明其原因,开展一维填砂模型和二维砂岩模型物理模拟实验研究。一维填砂模型CO2驱替实验显示:在相同压力下,随着CO2溶解量的增加,蒸馏水、盐水和原油3种流体的密度均上升后趋于稳定。结合液体升压过程中的体积缩小量计算及蒸馏水溶解实验,确认CO2在油相和水相中因溶解而导致液相体积缩小效应是填砂模型中压力降低的主要原因。在二维砂岩模型CO2驱替实验过程中也存在压力降低现象,对产出液体积倍数与驱替体积倍数关系曲线分析后提出:CO2在渗流时能进入油、水所不能进入的微小孔隙从而导致注入压力降低,相对而言CO2在液相中的溶解效应可以忽略。孔隙度计算及不同生产控制方式下碳酸盐岩岩心的CO2驱替实验验证了分析结果。图4表2参15

Pressure characteristics in CO2 flooding experiments

In the initial period of CO2 flooding,formation pressure of reservoir does not increase obviously.Physical simulation experiments were designed to study this phenomenon.In the 1-D infill-sand model,it is found that,under the same pressure,the densities of distilled water,salt water and crude oil increased with the CO2 dissolution,and then tended to be stable.By the volume decrease calculation of the liquid and the distilled water dissolution experiment,it is confirmed that the effect of CO2 dissolved in oil...