致密砂岩储层微观水驱油效率及其主控因素

Microscopic water flooding efficiency and main controlling factors of tight sandstone reservoir

为了解决鄂尔多斯盆地吴起油田长7储层水驱过程中单井产量低、含水上升快、剩余油分布复杂等问题,采用自主设计研发的高温、高压微观模型加持器,对研究区长7储层的真实取样岩心开展微观水驱油渗流实验,通过辅以铸体薄片、扫描电镜、X射线衍射、高压压汞和核磁共振实验,研究了不同孔隙结构类型下的微观水驱油渗流特征,探讨了储层物性、微观孔隙结构、可动流体参数、黏土矿物、驱替压力和注水体积对水驱油效率的影响。结果表明:研究区长7储层微观注水驱替特征以网状驱替和树枝状驱替为主,均匀驱替次之,少见蛇状驱替。不同类型驱替特征的驱油效率、残余油分布特征存在较大差异,均匀驱替驱油效率最高为48.84%,蛇状驱替驱油效率最低为31.73%;75%的残余油以簇状和油膜状赋存于孔喉内。水驱油效率的影响因素是多方面的,其中可动流体参数是比其它物性参数更能准确反映与驱油效率之间关系的参数。研究结果为该区不同类型储层开发方案的调整提供了理论依据。

Aiming at the problems of low single well production,fast water cut rise and complex residual oil dis‐tribution during the water flooding of Chang 7 reservoir in Wuqi Oilfield,Ordos Basin,microscopic water flood‐ing seepage experiment was carried out on real core samples of Chang 7 reservoir in the study area by using self-designed high-temperature and high-pressure micro-model holder.Combined with cast thin slice analysis,scan‐ning electron microscopy,X-ray diffraction,high pressure mercury penetration and NMR testing,the micro‐scopic water flooding seepage characteristics under different pore structure types were studied.The effects of res‐ervoir physical properties,microscopic pore structure,movable fluid parameters,clay minerals,displacement pressure and water injection volume on water flooding efficiency were discussed.The results show that the char‐acteristics of microscopic water flooding of Chang 7 reservoir are mainly reticular displacement and dendritic dis‐placement,followed by uniform displacement and rare serpentine displacement.There are great differences in displacement efficiency and residual oil distribution among different types of displacement characteristics.The displacement efficiency of uniform displacement is the highest(48.84%),and that of serpentine displacement is the lowest(31.73%).75%of the remaining oil occurs in the pore throat as clusters and oil films.There are many factors affecting water flooding efficiency,among which movable fluid parameters are more accurate than other physical parameters to reflect the relationship with oil displacement efficiency.The research results provide a the‐oretical basis for the adjustment of the development schemes of different reservoir types.