Design And Application Of Fracture-production Integration System For Horizontal Wells In Shale Gas Reservoir

In this paper,the problem of fracture-production integration system for horizontal wells in shale gas reservoir is analyzed and studied.Firstly,exploitation of shale gas by horizontal wells is divided into four main stages according to different hydrodynamic characteristics: fracturing,stuffy well,flowback and production.Secondly,each stage is separately studied,and then each stage is joined together to form a fracture-production integration system.Finally,the main productivity factors for horizontal are analyzed with the system to improve the development efficiency of shale gas.The results provide new theories and ideas.Specifically,in the fracturing stage,according to the basic parameters of natural fracture distribution,two-dimensional space natural fracture and artificial fracture parameters are characterized by statistical method.Based on the intersection criterion of artificial fracture and natural fracture,a fracture network extension model considering branch fracture is established,and its communication effect is analyzed and discretized;in the fracturing stage,a fracture network extension model considering fracturing is established.Mathematical models of fluid filtration and imbibition are established,and the optimum stuffy well time is determined according to the criterion of water absorption and fracturing of shale in fracturing fluid.In the backflow stage,a mathematical model of backflow considering critical backflow of proppant is established,and the variation of conductivity of support fracture with backflow is calculated.In the production stage,a gas-water two-phase seepage mathematical model considering multi-stage seepage is established.The influence of multi-stage seepage is analyzed.Finally,the evaluation of physical parameters and the optimization of fracturing parameters are carried out in the integrated system of fracturing and production formed at different stages from the perspective of the whole development.The results show that the size and shape of fracture mesh have an impact on the subsequent stuffy well,backflow and production.Under the same physical parameters,the more complex the fracture mesh is,the greater the imbibition and filtration of fracturing fluid during imbibition and backflow,the better the effect of pre-production development;the prolongation of stuffy well time can improve the initial production,but there is a marginal decline effect;The longer the nozzle is,the higher the backflow rate is,the less the reservoir water content is in the initial stage of production,but the lower the initial production pressure is,that is,it has both positive and negative effects on the development effect,so we can not blindly pursue high backflow rate;diffusion and slippage mainly affect gas production,and there are sensitive intervals,and stress sensitivity has an impact on gas-water production,which is the key factor to increase and stabilize production.