裂缝性低渗透油藏不同含水阶段剩余油动用比例研究

Study on utilization ratio of remaining oil in fractured low permeability reservoirs at different water cut stages

为探究裂缝对低渗透油藏驱油效果的影响,通过采用玻璃模型微观驱油实验、微观解剖实验和天然岩心驱油实验,研究水驱开发过程中不同含水阶段裂缝性油层驱油效果,进而得到在裂缝的作用下各类剩余油的动用状况。结果表明,随着含水率的增加,簇状剩余油饱和度降低,幅度较大,膜状、盲端状、油滴状和柱状类剩余油饱和度增大;有裂缝模型剩余油饱和度高于无裂缝模型,驱替液在裂缝中窜流,降低波及体积;模型渗透率增大,簇状剩余油饱和度增加,其他类型剩余饱和度降低。微观解剖实验表明:剩余油分布变化规律与光刻玻璃模型大体一致,从而证明制作的光刻玻璃模型的可靠性。从人造岩心水驱油实验看出,低渗透岩心水驱规律曲线呈现“S”型,裂缝岩心比无裂缝岩心见水早,裂缝和基质渗透率比值(kf/km)越大,无水采收率越小。

In order to explore the effect of fractures on oil displacement in low permeability reservoirs,the oil displacement effect of fractured reservoirs in different water cut stages was studied by a series experiments on glass model micro-oil displacement,micro core dissection and natural core oil displacement,and then the utilization status of various remaining oil under the action of fractures was obtained.The results showed that the saturation of cluster residual oil decreased with the increase of water cut,while the saturation of film,blind end,droplet and column residual oil increased.The residual oil saturation of the fractured models were higher than that of the non-fractured ones,the displacement fluid was channeling in the fractures,and the swept volume was reduced.When the model permeability increased,the cluster residual oil saturation increased,but the other types of residual saturation decreased.The distribution and variation rules of residual oil in micro core dissection experiments were generally consistent with that of the photolithographic glass model,thus proving the reliability of the photolithographic glass model.Seen from the core water flooding experiment,the water flooding law curve of low permeability core was an“S”curve.Water breaks through earlier in the fractured cores than that in the non-fracture ones.And the larger the permeability ratio of fracture to matrix(kf/km)was,the smaller the anhydrous recovery would be.