Study On Fracture Parameters Of Fractured Tight Gas Reservoir

With the conventional oil and gas resources are decreasing,and unconventional oil and gas reservoirs have gradually changed into the focus of exploration and development.Tight gas reservoirs are abundant in oil and gas and has great potential for development.The reservoir has the characteristics of natural fracture and low matrix permeability.In the development process of tight gas reservoir,which is usually in need of fracturing the reservoir.According to different reservoir conditions,the influence of fracture parameters on the productivity is different.According to the characteristics of a reservoir,we should choose what kind of fracture shape,and how the fracturing parameters affect the fracturing effect,which is one of the problems that need to be solved to realize the reasonable and efficient development of tight gas reservoirs.Based on the discrete fractured network model,the numerical model of fracturing gas well production in fractured tight gas reservoirs is established by using the finite element method.Based on this,the fracturing parameters are studied.First of all,the natural fracture network model with random distribution was established by Monte-Carlo simulation method,and embedded fracturing fracture shape of irregular in natural fracture network model,get the fractured tight gas reservoir discrete fracture network model.Then according to the theory of finite element discrete gas seepage mathematical model:matrix system uses triangle element,the fracture system adopts line element to discretize region,which is selected the quadratic Lagrange interpolation function.Based on the equivalent integral principle and variational principle,the functional of the differential equation of the original flow is obtained.Furthermore,the element characteristics of matrix system and fracture system are analyzed.Finally,the finite element numerical model of gas seepage is established by analyzing the overall characteristics,and the model is solved and verified.Based on the fracture gas well productivity prediction model of fractured tight gas reservoir,the fracture parameter optimization is studied,and the following conclusions are obtained:(1)when the reservoir permeability is low,it is better to use the network fracturing to achieve better fracturing effect.When the reservoir permeability is relatively high,it can be considered that the conventional fracturing can be used to achieve the same effect as the network fracturing.(2)In the early production period,the main fracture conductivity of the fracture network is the key factor to restrict the yield.In the later stage of production,the branch fracture conductivity and the volume of stimulated reservoirs of the fracture network are the main factors affecting the production.(3)Under the condition of different reservoir permeability,there is an optimal value of the main fracture conductivity and the branch fracture conductivity.The optimal value of the branch fracture conductivity is affected by the reservoir permeability more than the main fracture conductivity.(4)Under the same fracturing scale,in the early production period,the smaller the volume of stimulated reservoirs,the higher the fracture density,the higher the cumulative gas production.However,with the increase in the number of years of production,the larger the volume of stimulated reservoirs,the better the ability of stable production,the higher the cumulative gas production.This paper,based on the discrete fractured network model,the tree-like branching structure fracturing network is characterized by fracture as mesh restrictive condition,which has realized the fracturing complex fracture network irregular characterization,as well as provides a new method to describe the complex fracture.And the simulation results provide a theoretical basis for the optimization of tight gas reservoir fracturing technology,and provides ideas and means for the optimization of network fracturing fracture parameters.