Abstract: The complex distribution of gas and water in the Upper Paleozoic gas reservoirs of Qingyang Gasfield restricts the efficient development of the gas field. To solve this problem, we comprehensively utilized data from drilling and logging wells, 3D seismic, gas testing and production to systematically carry out study on the classification of formation water types, the distribution pattern of gas and water and the controlling factors, so as to clarify the main control factors for the distribution of gas and water. The results show that:the formation water in the study area is primarily distributed in the Shan 1 Member, with the water-producing layers in the He 8 Member being relatively limited.On a plane, a high water-bearing area in the center and medium water-bearing areas in the west and east can be delineated. The formation water can be categorized into structural low-lying trapped water,interlayer fracture water, and isolated lens-body water. Structural low-lying trapped water is distributed in the western part of the study area,influenced by regional tectonic characteristics and the intensity of hydrocarbon generation; interlayer fracture water is primarily found in the central part of the study area, controlled by the fault system;isolated lens body water is distributed in the eastern part of the study area, mainly controlled by the heterogeneity of the reservoir and the migration distance.This achievement provides theoretical reference for the study of gas-water distribution in tight sandstone gas reservoirs under complex structural backgrounds, as well as for the study of natural gas accumulation. It also offers geological basis for the subsequent efficient development of gas fields.

Key words: gas-water distribution, control factors, tight sandstone gas reservoir, Upper Paleozoic, Qingyang Gasfield, Ordos Basin