Accumulation characteristics of tight sandstone gas reservoirs in the Upper Paleozoic in the Shenfu block of the Ordos Basin

Abstract

The Shenfu gas field on the eastern margin of the Ordos Basin is one of the key blocks of CNOOC’s land tight sandstone gas field development in recent years. In order to further analyze the physical properties and accumulation and evolution characteristics of the Upper Paleozoic tight sandstone gas reservoirs in the Shenfu block, we characterized of the reservoir pore structure, diagenetic evolution, and natural gas accumulation stages, combined with fluid inclusions, the types of tight sandstone gas reservoirs in the Upper Paleozoic are studied, revealing the main controlling factors for the natural gas accumulation in the study area. Studies have shown that the core porosity of tight sandstone reservoirs in the Upper Paleozoic in the Shenfu block is less than 10%, and the permeability is less than 1mD. Compaction and cementation are the main factors for reservoir tightness. The results of porosity evolution and homogenization temperature of fluid inclusions indicate that the Upper Paleozoic sandstone tightness is formed during the Middle-Late Triassic-Early Jurassic, which is earlier than the Late Jurassic-Early Cretaceous period of large-scale natural gas accumulation.