Study On Reservoir Forming Mode Of Reservoirs With Tilted Gas-water Contact In Kuqa Foreland Thrust Belt

Kuqa depression in Tarim Basin is rich in natural gas resources,in which the natural gas production in piedmont zone accounts for more than 70% of the total production of Tarim Oilfield.After the discovery of Kela 2 gas field,Dabei,Keshen and other large oil and gas fields have been successively discovered in Kela Su structural belt in Kuqa area,especially in Keshen block,Keshen 2,Keshen 8 and other large gas reservoirs have been successively discovered.At the initial stage of development,it is considered that the gas reservoir in this area belongs to conventional structural gas reservoir,and there is a unified pressure system and oil-gas-water interface in a single gas reservoir.However,in the rolling development practice,it is found that with the increase of drilling in individual wells,the water invasion rate is too fast,the gas water interface rises sharply,and the pressure and production decrease significantly,while the oil pressure and production of other wells in the gas reservoir are relatively stable.These anomalies lead to that the development plan formulated earlier is no longer suitable for the subsequent efficient development of reservoirs in this area,which brings great challenges to the sustainable and stable production in the later period.In view of these problems,this paper has carried out extensive investigation and research,but similar phenomena are rare in the development of reservoirs at home and abroad.In this paper,S9 gas reservoir in Keshen area is taken as the main research object.Starting from the dynamic data of gas reservoir and regional geological background,the regional geological characteristics of this area,including evolution characteristics,structural characteristics,sedimentary characteristics,reservoir characteristics and gas reservoir characteristics,are systematically analyzed by means of combining seismic,geological and logging methods,and various factors that may lead to the above special phenomena are analyzed in detail,It is believed that the reason for the above special phenomena is that some gas reservoirs in this area belong to inclined gas water interface gas reservoirs.The inclined gas water interface indicates the general distribution of oil,gas and water in the gas reservoir to some extent.The research on gas reservoirs with inclined gas water interface is of great guiding significance for the reserve evaluation and calculation,the formulation and adjustment of development policies,and the optimization and deployment of development well locations for similar gas reservoirs.