Fracturing Fluid Flowback Simulation Of Fractured Horizontal Well In Shale Gas Reservoirs

Shale gas reserves are abundant in our country.In recent years,the exploration and development of shale gas has received more and more attention.The permeability of shale gas reservoirs is extremely low,and horizontal well volume fracturing is the key technology for commercial exploitation.After the conventional gas reservoir is fractured,if it is not returned in time,it will often cause serious water lock damage and seriously affect the gas well productivity.Compared with conventional reservoirs,the flowback ratio of shale gas reservoirs is usually lower,and the flowback ratio of some shale gas wells is even less than 5%.It is necessary to study the factors affecting the fracturing and flowback of shale gas reservoirs.Based on the extensive investigation of domestic and foreign literatures,in view of the characteristics of shale gas reservoir and volume fracturing horizontal wells,this paper has carried out in-depth numerical simulation of fracturing fluid backflow in shale gas reservoir fracturing horizontal wells,mainly completed the following work:(1)Based on the embedded discrete fracture model,the single-phase gas seepage in the reservoir was simulated.The model was verified by CMG a reservoir numerical simulation software.The reasonable mesh size was proposed by grid sensitivity analysis.Finally,the model was proposed.It extended to the simulation of fluid seepage in complex fracture morphology.(2)Characterization of complex fracture networks formed by volumetric fracturing of shale reservoirs using embedded discrete crack model and dual media model.The comprehensive consideration of complex fracture morphology,main fracture limited diversion,shale gas adsorption and desorption,Knudsen Diffusion,slippage effect,stress sensitivity,capillary pipetting effect of shale reservoir fracturing horizontal well gas-water two-phase double-permeability fracturing fluid return-flow model.(3)Based on the finite difference method,the seepage equations and boundary conditions in the model are discretized,and the finite difference equations solution format is obtained.Using MATLAB programming,a numerical simulation program for fracturing fluid flowback in horizontal wells of shale reservoirs was prepared.(4)The gas-water two-phase flow law in the process of flowback was simulated.The impact of main fracture permeability,fracturing scale,shale gas adsorption and desorption,slippage,diffusion,capillary force,shut-in time on fracturing fluid flowback and productivity of shale gas were studied.The gas-water two-phase seepage model of the shale gas reservoir fracturing horizontal well established in this paper is of great significance for the backflow simulation and production dynamic prediction of shale gas wells,and can guide the field fracturing flowback optimization design.