Well Test Analysis For Fractured Horizontal Well With Partially Closed Fractures

In general,when using the conventional fractured horizontal well model for analysis,the interpretation results of fractures half-length and conductivity are less than the actual value.The reason is that the model is impossible to consider complex phenomena such as partial closure of fractures.In this paper,based on the objective phenomenon that the hydraulic fracture of the horizontal well is partially closed,each hydraulic fracture is divided into near-wellbore fracture sections with small closure and even unclosed and a far-wellbore fracture section where a significant closure phenomenon occurs.The fracture model is established by using the principle of mass conservation,Darcy's law and boundary element method.The reservoir model is established by the point source method and superposition principle,and the fracture seepage model is adopted.Combined with the reservoir seepage model,the well test model of fractured horizontal well with partially closed fractures is established,the typical plates are drawn,and the sensitivity analysis of each model parameter is carried out.In the model,there are three parameters describing the partially closed feature of the fractures: the near-wellbore fracture conductivity coefficient,the far-wellbore fracture conductivity coefficient and the near-wellbore fracture half-length.As these three parameters become larger,the more obvious the linear flow phase of the fractures,the lower the derivative curve of this stage.However,compared with the three parameters,the far-wellbore fracture conductivity coefficient has the greatest influence on the curve and the near-wellbore fracture conductivity is the smallest.It shows that in the actual production process,the effect of increasing the closing effect of the fracture far-wellbore fracture is far greater than the conventional reservoir reform near the wellbore.Then,based on the non-Darcy flow characteristics of the gas,a well test model of fractured horizontal well with partially closed fractures considering the high velocity non-Darcy flow is established.If the influence of the high-speed non-Darcy is ignored during well testing,the interpretation result of the far-wellbore fracture conductivity coefficient is less affected,but the interpretation of the near-wellbore fracture coefficient and the near-wellbore fracture half-length are much smaller than the actual value.Therefore,in the well testing of tight gas reservoirs,the high velocity non-Darcy effect of gas in the fractures cannot be ignored.Finally,based on these two well test models,it integrates conventional models,and uses QT,C++ and Matlab programming to develop well test interpretation software for low permeability reservoir.Well test analysis is carried out on two actual wells using the well test software,which verifies the practicality of the well test model in this paper.