Study Of Production Decline Analysis And Productivity Prediction For Multiple-fractured Horizontal Wells

Tight reservoirs are characterized by complex geological conditions,low permeability and poor reservoir physical properties,and low production capacity by conventional methods.At present,volume fracturing technology has become the main method of tight reservoir development.Through volume fracturing,micro-fractures can be generated near the main fracture to form the region of stimulated reservoir volume(SRV)with significantly improved reservoir properties,which improves the overall flow rate of reservoir fluids,effectively improves the flow status of reservoirs,and improves oil well productivity.The production decline analysis of multiple-fractured horizontal wells is a practical method to obtain tight oil reservoir parameters,and the productivity prediction based on these parameters is of great significance for the production of tight oil reservoirs.In this paper,the control area of a single fracture is divided.A mathematical model of unstable flow in multiple-fractured horizontal well with equal length fracture is established.Furthermore,considering the different parameters of fracture length,spacing and fracture conductivity after fracturing,a mathematical model of unstable flow in multiple-fractured horizontal well with unequal length fracture after fracturing is established.Laplace transform and Stehfest numerical inversion were used to solve the problem.Based on the principle of material balance,the production decline analysis theory of multiple-fractured horizontal wells is established.The typical curve of production decline for multiple-fractured horizontal wells is drawn.According to the characteristics of typical curve,they can be divided into linear flow in stimulated reservoir volume area,interporosity flow,pseudo-steady flow of transition area,linear flow in unstimulated area and boundary effect flow period.Sensitivity analysis of asymmetrical factors such as fracture length,fracture spacing and fracture conductivity is carried out.Based on the productivity prediction principle of variable bottomhole flow pressure in multiple-fractured horizontal wells,the productivity prediction curve of variable bottomhole flow pressure is drawn.The influence of fracture length,fracture spacing and fracture conductivity on the productivity predicted curve of variable bottom flow pressure is analyzed.A production decline analysis and productivity prediction method for tight oil multiple-fractured horizontal wells was established to avoid the shortage of pressure buildup test data and long shut-in pressure measurement time in tight reservoirs affecting production.At the same time,the problem that the variable bottom flow pressure production is difficult to predict is solved.The production data of the example well was interpreted,and the reservoir and fracture parameters were obtained.On this basis,the productivity prediction of variable bottomhole pressure is carried out.This study provides scientific basis for the analysis of production data and productivity prediction of multiple-fractured horizontal wells.