Study Of Well Test Analysis For Multiple-Fractured Horizontal Wells In Tight Oil Reservoirs

Tight reservoirs are widely distributed in China and have abundant reserves.However,due to the low permeability,conventional development methods cannot be used to obtain better development results.Horizontal well combined with volumetric fracturing technology can effectively develop tight reservoirs,increase reservoir reformation volume,and increase production.In the actual production of oilfields,well testing techniques are often used to understand reservoir characteristics and obtain reservoir dynamic parameters.Therefore,multiple-fractured horizontal wells testing technology is of great significance.To this end,Study of Well Test Analysis for Multiple-Fractured Horizontal Wells in Tight Oil Reservoirs was carried out.Based on the unstable flow theory of multiple-fractured horizontal wells in tight reservoirs,the physical model of densely cutting fracturing horizontal wells and fracture network fractured horizontal wells are established according to different fracturing methods of tight reservoirs: densely cutting fractured horizontal wells consider matrix systems and artificial fracture systems,fracture network fractured horizontal wells consider matrix systems,micro-fracture systems,and artificial fracture systems.The mathematical model is solved by Galerkin weighted residual finite element method,and the bottom hole pressure is obtained.The typical well test curves of pressure drop and pressure recovery of horizontal wells in tight reservoirs are drawn,and the sensitivity analysis of the well test curves is given.Based on the similarities and differences between the pressure recovery curve and the pressure drop curve,the pressure field maps of different flow stages are drawn and sensitivity analysis is carried out to facilitate a more intuitive understanding of reservoir pressure distribution.It is found through research that the well test typical curve of the densely cutting fractured horizontal well is divided into six flow stages: fracture bilinear flow,SRV(Stimulated Reservoir Volume)region linear flow,SRV regional depletion flow,composite linear flow,late pseudo radial flow and boundary pseudo steady flow.The fracture network fractured horizontal well well test typical curve is divided into six flow stages: SRV region linear flow,SRV region depletion flow,turbulent flow,composite linear flow,late pseudo-radial flow and boundary pseudo-steady flow.Comparing the pressure drop test curve and the pressure recovery test curve of the densely cutting fractured horizontal well and the fracture network fractured horizontal well respectively,it is concluded that the pressure recovery curve and the pressure drop curve start to deviate in the SRV region depletion flow,and the pressure recovery derivative curve is down in the boundary pseudo steady flow stage,and the pressure drop derivative curve appears as an upturn line with a slope of 1,and the pressure drop curve and the pressure recovery curve deviate more from the SRV region depletion flow.The pressure recovery curve and the pressure drop curve have different test curves under different mobility ratios: the smaller the mobility ratio,the greater the difference between the inner and outer zones,and the closer the slope of the pressure drop derivative curve in the SRV region is to 1,the slope of the pressure recovery derivative curve in the SRV region is away form 1.The larger the ratio,the smaller the difference between the inner and outer regions.The greater the matrix permeability of the non-SRV region,the less obvious or even the disappearance of the SRV region.The earlier the well test curve transitions to the late pseudo-radial flow and the boundary pseudo-radial flow.According to the pressure field of different flow stages,it can be seen that fracture fractured horizontal wells can improve reservoir properties more effectively.By comparing the numerical solution of the well test model with the analytical solution of Zerzar,the correctness of the multiple-fractured horizontal well model is verified.Finally,the well test data of the example well is interpreted,and the parameters of the actual well and reservoir are obtained,which is the volume fracturing horizontal well.The interpretation of well test data provides a theoretical basis.