Accumulation Characteristics and Main Controlling Factors of Tight Gas in the Upper Paleozoic in the Eastern Margin of Ordos Basin—A Case Study of Jiaxian Block, Shenmu Gas Field

The Jiaxian block in the eastern margin of Ordos Basin is a new optimized allocation block of Jidong oilfield, which is currently in the early stage of exploration and development. The study of tight gas accumulation characteristics and main controlling factors in the Upper Paleozoic is beneficial to guide the efficient exploration and development of this area. Based on the analysis of the development and sedimentary characteristics of the Upper Paleozoic source rocks in the eastern margin of Ordos Basin, the distribution characteristics of reservoir and cap rock are analyzed, Analyze the relationship between source and reservoir allocation, The characteristics of tight gas accumulation and main controlling factors of tight gas accumulation are defined, Establish tight gas accumulation and control model in target area. The results show that, There are three types of Upper Paleozoic source-reservoir assemblages in Jiaxian block: active inner assemblage, near source assemblage and far source assemblage, The reservoir has the characteristics of “first compact, then reservoir formation”, Extensive coal measure source rock and large area reservoir overlap each other, Close migration and efficient accumulation of natural gas. There are five types of gas accumulation modes: active and internal gas, tight sandstone gas, limestone gas, near tight sandstone gas and far tight sandstone gas, The interlayer reservoir control model of “strong hydrocarbon supply capacity of source rocks, priority of hydrocarbon accumulation in source and near source, and selective accumulation in far source” and the interlayer reservoir control model of “sedimentary sand control, microphase controlled reservoir, superior reservoir control” are established. The research results reveal the huge exploration and development prospect of tight gas in Jiaxian block.