Gas And Water Two-phase Seepage Model And Parameter Inversion Of Hydraulic Fracture Network In Shale Reservoir

The WY shale gas reservoir in Southwest China is rich in resources and has broad development prospects,and it is one of the main positions for increasing natural gas reserves and production in China.The shale gas reservoir has complex reservoir conditions and special dynamic characteristics of gas and water production after fracturing.The current gas and water two-phase production interpretation model is difficult to accurately invert the parameters of complex hydraulic fracture network,and it is difficult to evaluate hydraulic fracturing effectiveness and make high-efficiency development strategies.Therefore,it is imminent to establish a gas and water two-phase seepage model suitable for the target area and invert the key parameters of the hydraulic fracture network.Firstly,based on the geological and development performance data of the target area,this thesis divided the gas and water production dynamic models of typical wells,and quantitatively evaluated the gas and water decline characteristics under different dynamic models.The three-level system of stimulated area,water invasion layer and main fracture in shale gas reservoirs after fracturing are classified.Then a seepage mathematical model considering shale matrix gas adsorption analysis,water invasion layer and gas-water twophase flow in main fracture were established in Laplace space and semi-analytical solution method was also developed.Further we identified the typical stages of gas and water flow under different dynamic modes,and formed a fracturing network parameter inversion method based on dynamic fitting of gas-water two-phase production,which was used to determine the pressure of typical wells in WY shale gas reservoirs.Fracture network parameters were inverted,and the stimulation effects of fractured wells in different shale reservoirs were compared and analyzed.The research results show that the shale gas and water production decline patterns in the WY area can be divided into two types: "convex type" in which gas and water are coproduced and "jizi type" in which water is first produced and then gas is produced.The slow decline of gas production conforms to hyperbolic decline,Water conforms to exponential decline.The "convex type" gas-water mainly exhibits 3 flow stages,including water-phase boundary-controlled flow,gas-phase linear flow,and gas-phase boundary-controlled flow;The gas-water flow in the "jizi type" well shows five flow stages,water boundary-controlled flow,gas bilinear flow,gas linear flow,and gas boundary-controlled flow.The length of the fracturing main fracture of a typical well in WY is about 90 m,the permeability of the stimulated area is on the order of 0.001 m D,the thickness of the water invasion layer is less than 1m,and the permeability of the water invasion layer is lower than that of the stimulation area.The water invasion layer is thin,and the permeability of the water invasion layer is one order below that of the matrix.Based on the gas and water two-phase seepage model and the fracturing network inversion method established in this paper,the current shale gas and water two-phase production dynamic analysis model and the fracturing network interpretation method are improved.The results provide theoretical basis and practical guidance for evaluating hydraulic fracturing effectiveness and making high-efficiency development strategies...