致密储层物性下限确定新方法及其应用

New methods to determine physical property lower limit of tight reservoir and their application

         文中应用储层孔隙度、渗透率、储层产能、压汞测试和致密储层临界孔喉半径等分析资料，提出了2种求取致密储层物性下限的新方法：一是利用储层物性与产能相结合的经验统计法，分别对工业油层和低产油层储层物性按累计概率丢失10%进行统计分析，确定工业油层的物性下限为孔隙度7.20%、渗透率0.050×10^-3 微米平方，低产油层的物性下限为孔隙度4.50%，渗透率0.030×10^-3 微米平方；二是利用致密砂岩临界孔喉半径与压汞资料相结合的函数拟合法，所确定储层物性下限为孔隙度4.48%，渗透率0.023×10^-3 微米平方。考虑到经验统计法得到的低产油层储层物性下限值与函数拟合法得到的值近乎一致，故取该下限值作为研究区致密储层的物性下限。研究区储层孔喉分布特征亦表明，物性低于该下限值的储层，其孔喉整体小于致密储层临界孔喉，为无效储层。

In this paper, using the analysis data such as reservoir porosity, permeability, productivity, mercury injection test and the critical pore throat radius of tight reservoir, two new methods to obtain the physical property lower limit of tight reservoir are proposed. One is that using the statistical method combining with physical property and reservoir productivity, the statistical analysis of physical property according to losing the cumulative probability 10% is performed for the commercial oil layer and low yield oil layer. The physical property lower limit of commercial reservoir is ?准=7.20%，K=0.05 md. The physical property lower limit of low yield oil layer is ?准=4.50%, K=0.03 md． The other is that using the fitting function method combined with the critical pore throat radius of tight sandstone and mercury injection data, the physical property lower limit of reservoir is determined, the result is ?准=4.48%, K=0.023 md. Considering the almost consistency of the physical property lower limit value obtained by statistical analysis and the value obtained by fitting function method for the low yield oil layer, therefore, the physical property lower limit of ?准=4.48%, K=0.023 md is taken as the lower limit value of tight reservoir in this study area. The pore throat distribution characteristics also show that for the reservoir with the physical property lower limit less than this value, its pore throat is smaller than that of the critical throat of tight reservoir on the whole, so it is invalid reservoir．