鄂尔多斯盆地致密油储层覆压孔渗特征实验研究

Experimental Study on Overburden Porosity and Permeability Characteristics of Tight Oil Reservoirs in Ordos Basin

覆压下岩石的孔渗变化往往会对油藏的后续开发产生一定影响。为了研究鄂尔多斯盆地致密油储层覆压孔渗特征,利用YC-4型覆压孔渗测定仪对鄂尔多斯盆地133块致密油岩心进行了覆压孔渗实验,并利用同步辐射成像技术,分析了3块不同渗透率岩心的微观孔隙结构特征。研究结果表明:(1)相对孔隙度比值和相对渗透率比值与有效覆压有很好的相关关系,随上覆压力的增加,其相对孔隙度比值和相对渗透率比值变化均较大,与传统的认识不同;(2)在油层条件下,其相对孔隙度、渗透率比值以及不可逆渗透率损失与渗透率均具有很好的半对数关系,在油层条件下的孔隙度、渗透率的值与在地面的孔渗差异较大,其影响不可忽略;(3)致密油岩心的渗透率越低,其微观非均质性越强,孔隙连通性越差。

The change of porosity and permeability of rock under overburden often has a certain influence on the subsequent deve-lopment of the reservoir. In order to study the overburden porosity and permeability characteristics of tight oil reservoirs in the Ordos Basin, the YC-4 overburden porosity and permeability tester was used to conduct overburden porosity and permeability experiments on 133 tight oil cores in the Ordos Basin. Meanwhile, synchrotron radiation imaging technology was used to analyze the microscopic pore structure characteristics of 3 cores with different permeability. The results show these as follows. The relative porosity ratio and relative permeability ratio have a good correlation with the effective overburden pressure. With the increase of overburden pressure, the relative porosity ratio and relative permeability ratio change greatly, which is different from the traditional understanding.Under reservoir conditions, the relative porosity, permeability ratio, and irreversible permeability loss all have a good semi-logarithmic relationship with permeability. The values of porosity and permeability under reservoir conditions are quite different from those on the ground, and their influence cannot be ignored.The lower the permeability of tight oil cores, the stronger the microscopic heterogeneity and the worse the pore connectivity.