Research On Dynamic Analysis And Countermeasures Of Horizontal Wells In Tainan Gas Field

Located in eastern SeBei tectonic belt of Qinghai Qaidam Basin, Tainan gas fieldis a typical unconsolidated sandstone gas reservoir which contains an area of 32 square kilometers and 95.162 billion cubic meters gas in place. It is one of the main gas exploration regions in Qaidam Basin with great development prospects. According to the characteristics of thin reservoir and poor permeability of unconsolidated sandstone gas reservoirs, some good results have been achieved after putting horizontal well development into use recently in Tainan gas field. However, the horizontal well production declines quickly with the gas recovery increasing, water influx and sand inflow problem getting worse, and they both affect each other, which finally restricts the effectiveness of horizontal well development.According to these problems, on the basis of previous studies and combination of gas reservoir engineering and reservoir simulationthis theories, this paper studies about the water and sand production dynamic state in Tainan gas field, evaluating its production performance in horizontal wells and finally making a reasonable development of horizontal wells in the next periods.In this paper, we analyse the water dynamics state of horizontal wells by using water technical methods firstly, which identifies the main water source of horizontal wells is the edge water. Then, we use gas reservoir engineering method to study the water invasion regularity of the water layer and find that the main factors affecting water invasion include recovery degree, the differential pressure and permeability of reservoir. Secondly, based on analysing the sanding mechanism of multilayer unconsolidated sandstone gas reservoirs, we study the water production dynamic state through acknowledging that water breakthrough and fast gas production rate are the main reason of formation sand production in horizontal wells. By taking these problems into consideration, we choose the appropriate method to calculate the critical sanding pressure difference of horizontal wells, optimizing the productivity formula of horizontal wells that are suitable for Tainan gas field and evaluating the productivity in order to study the influence of water invasion, pressure, horizontal section length, the reservoir permeability and reservoir effective thickness on horizontal well productivity. Furthermore, we carry out proration plan in horizontal wells on the basis of gas reservoir engineering method. Through the above research work, we finally formulate a corresponding countermeasures for water and sand problems that will give effectively guidance to the reasonable development of horizontal wells in Tainan gas field in the next step.