扎尔则油田泥盆系F4顶层油藏注富气混相驱实验

在扎尔则油田F4顶层油藏开展富气混相驱,具有良好的储层物性和流体性质条件。长细管实验研究了注入富气组成对混相驱效果的影响,确定了目前地层压力、温度条件下注入富气的最小混相组成,并揭示注入富气组成在影响驱油效率的同时,也影响驱油速度,且在近混相驱范围内对富气驱效果的影响更为强烈。长岩心驱替实验表明:开发初期注富气效果要好于水驱后注富气,但水驱后注入最小混相组成流体仍可获得非常高的驱油效率,高含水油藏注富气混相驱有望大幅度提高原油采收率;随着富气注入量的增加,混相驱最终采收率也增加,但存在增幅减缓的"拐点",原因是轻烃组分超越原油流动,使有效驱替容积部分损失,气油比的"台阶"式变化将是经济确定富气注入量的重要标志;在富气注入量较小时,连续注入比气水交替注入效果好,建议扎尔则油田小型先导试验采用连续注气方式。

Laboratory experiment of enriched-gas miscible flooding in top layer of Devonian F4

There are the favorable conditions of reservoir property and fluid property for enriched-gas miscible flooding in top layers of Devonian F4 in Zaraitine Oilfield. Experimental displacements with differently-enriched gases had been carried out in a slim tube, by which the minimal miscible composition under the conditions of present reservoir pressure and temperature was determined and the mechanism that the composition of injected enriched-gas affects both flooding efficiency and oil production rate, especially in the process of miscible flooding, was unveiled. Long core tests concluded that the gas injection before water flooding was better than thatafter water flooding, however, a remarkably high oil recovery was gained ultimately, proving that there still existed a great potential for enriched-gas displacement in high water cut zone. The ultimate recovery with miscible flooding increased as a large amount of enriched gas was injected, but there was a turning point of production rate slowed down because the light hydrocarbon component overstepped the oil flow to lose the volume of effective displacement. Thereby, the properly proposed and injected amount of enriched gas should be determined economically upon the time when the first jump of GOR was found. With small injected amount of enriched gas, the effect of continuous gas injection was better than WAG pattern. Continuous gas injection was recommended for small-scale pilot test in Zarzaitine Oilfield.