致密砂岩储层物性下限确定新方法及系统分类

扶余油层致密砂岩储层是大庆油田目前勘探开发的新目标，但对其储层物性的下限缺乏明确界定。因此，采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%作统计分析，确定工业油层物性下限为：孔隙度=7.1%，渗透率 =0.08 mD，低产油层物性下限为：孔隙度=5.6%，渗透率=0.047mD。 再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，确定储层物性下限为：孔隙度=4.46%，渗透率=0.041mD，该值与低产油层储层物性的下限值较为接近，故将其作为致密砂岩储层的物性下限。依据致密储层物性下限、工业油层物性下限及常规储层物性分类界限，将砂岩储层系统分为致密Ⅲ类、致密Ⅱ类、致密Ⅰ类、低孔渗、中孔渗、高孔渗和特高孔渗储层。致密砂岩储层物性下限的确定和储层系统的分类可为致密油储层产能的计算及储层评价提供参数指标和技术支撑。

A new method for determining physical property lower limit of tight sandstone reservoir and reservoir system classification

Tight sandstone reservoir of Fuyu oil layer is a new target of current exploration and development, but there lacks clear definition of the property lower limit.By using statistical method combining physical properties with reservoir productivity, this paper carried out statistical analysis of physical properties respectively on the commercial oil layer and low yield oil layer according to the cumulative probability loss 10%. The physical property lower limit of commercial reservoir is φ=7.1%，K=0.08 mD. The physical property lower limit of low yield oil layer is φ=5.6%, K= 0.0047 mD. Based on function fitting method combining tight sandstone critical pore throat radius with mercury injection data, it is determined that the physical property lower limit is φ=4.46%, K=0.041mD. Considering the lower limit value being close to the lower limit of low yield oil layer, we took the lower limit value as the physical property lower limit of tight reservoir. Based on the physical property lower limit of the tight and commercial reservoir and the conventional reservoir classification boundaries, we classified sandstone reservoir system into class Ⅲ, class Ⅱ and class Ⅰ of tight reservoir, and low, middle, high and extra-high porosity and permeability reservoir. The determination of tight reservoir physical property lower limit and reservoir system classification can provide important parameters and technical supports for productivity calculation and evaluation of tight reservoir.