非均质油藏水驱后剩余油分布实验研究及潜力评价

为更好揭示非均质油藏水驱后剩余油分布规律和动用条件,在冀东油田非均质性强的不同区块中,通过改进电阻率测试含油饱和度的方法,研究了影响电阻率与含油饱和度对应关系的主要因素,开展了在不同非均质性岩心中水驱后聚合物驱的不同位置含油饱和度对比实验。结果表明:渗流速度对饱和水的岩心电阻率曲线影响不大;地层水矿化度对水驱中岩心电阻率影响较大,矿化度从1 629 mg/L增加到3 847 mg/L时,岩心电阻率下降了10~10~2数量级;在矿化度一定条件下,渗透率越低,喉道间彼此连通的概率越小,宏观上的岩心电阻率越高;对于纵向非均质油藏,水驱后开采潜力区域为正韵律分布下中渗层的远井地带和低渗层;且随非均质程度的增强,水驱后该区域开采潜力越大;对于纵向非均质油藏水驱后聚合物驱,使高渗层的含油饱和度从0.55~0.58降低到0.28~0.38,使中渗层含油饱和度从0.87降低到0.58~0.63,降低幅度为33.33%~49.09%;使低渗层的含油饱和度从0.92~0.95降低到0.66~0.83,聚合物驱能很好的携带中高渗层的残余油滴,对低渗层远井地带动用效果较差。

Experimental research and potential evaluation about remaining oil distribution after water flooding in heterogeneous reservoir

In order to reveal remaining oil distribution and flooding conditions after water flooding in heterogeneous reservoir, the relationship between the resistivity and oil saturation is carried out with the improved resistivity method in different heterogeneous blocks in Jidong oilfield. Then the experiment about oil saturation in different positions of core before and after polymer flooding is carried out. The results show that the velocity has little effect on the resistivity of core with saturated water. The core resistivity decreases by 10~102 magnitude when the salinity increases from 1629 mg/L to 3847mg/L. In certain condition of salinity, the lower the permeability is, the smaller the probability of connected throat becomes, and the higher the core resistivity is. In the vertical heterogeneous reservoir, the exploitation potential area is the zone far from well of the middle- permeability layer and low-permeability layer. And with the enhancement of heterogeneity degree, the exploitation potential area becomes larger. The oil saturation of high-permeability layer reduces from 0.55~0.58 to 0.28~0.38 after polymer flooding. Also the oil saturation of middle-permeability layer decreases from 0.87 to 0.58~0.63, reducing by 33.33%~49.09%. And the oil saturation of low-permeability layer decreases from 0.92~0.95 to 0.66~0.83. The polymer can flood the residual oil in middle and high permeability layers, but cannot make the zone far from well in low permeability layer.