Sedimentary facies and diagenesis control on petrophysical properties of sandstone reservoirs: A case study from the Permian Sulige Gas Field, Ordos Basin (Central China)

Abstract

The sedimentary characteristics and petrophysical properties of the reservoir of the second/lower member of the Lower Permian Shanxi Formation (P1s2) in Sulige Gas Field, Central China are studied by means of thin section petrography and scanning electron microscopy. This article highlights the relationship between reservoir quality and sedimentary environments, explains the differences in reservoir petrophysical properties in different sedimentary environments, discusses the influence of clastic components and authigenic minerals on the reservoir, and finally, provides the basis for the prediction of relatively high‐quality reservoir in P1s2 of the study area. The results show that the sandstones formed as a meandering river deposit in the south of the study area are fine‐grained, mainly composed of lithic fragments of quartz sandstone, metamorphic, and volcanic rock lithic fragment, with high content of matrix and poor sorting, average porosity of 5.09%, and average permeability of 0.20 × 10−3 μm2. The braided river sedimentary deposits in the north are coarse‐grained, mainly composed of quartz sandstone sedimentary rock lithic fragment, with low content of matrix, good sorting, and more developed dissolution pores. The average porosity is 6.16%, and the average permeability is 0.53 × 10−3 μm2. Among the authigenic minerals, siderite, calcite, and illite block, the pores between the grains reduce the porosity. Siliceous cement often indicates better reservoir petrophysical properties. The siliceous cement is more common in braided river deposits in the north area, in which the channel bar detailed facies are conducive to retain more primary pores or form secondary pores, thus forming better reservoirs.