Abstract:

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.

Key words: low resistivity oil layer, tri-water model, saturation evaluation, Zhujiang Formation, Pearl River Mouth Basin