Semi-Analytical Models For Multiple-Fractured Horizontal Wells In Compartmental Reservoirs

Recently,multiple fracturing and volume fracturing techniques have become the main means to improve the productivities of unconventional oil and gas reservoirs.Due to reservoir features,for example,small pore spaces,low permeability,strong heterogeneity and so on,the inter-porosity flow will occur between adjacent regions with different properties.Therefore,conventional well test interpretation models are no longer applicable.In this paper,a study on compartmental reservoirs is carried out.Using the point source function theory,boundary element method and finite difference coarse meshing method,the Green function expressions of partially penetrated,fully penetrated linesource,slanted line-source and plane-source are derived.The transient seepage in complex fractures which are created by the multiple fracturing and volume fracturing is also studied.A fast calculation method with good convergence and high accuracy is obtained.A model of partially penetrated well in multi-layered vertical compartmental reservoir is established.Firstly,the partially penetrated line source and partially penetrated plane source are obtained by integrating the point source in rectangular closed reservoir.Then different regions are coupled on the condition of same pressure and continuous flow at the interface.Finally,solving the linear equations by Guass elimination and Stehfest numerical inversion,the bottomhole pressure is obtained and the inter-porosity flow which is caused by different properties between layers is quantitatively investigated.In order to deal with nonlinear flow around the fracture tips,a model of multiplefractured horizontal well(MFHW)in the horizontal compartmental reservoir formed by channel deposition is established.The calculation results show that the semianalytical model can deal with complicated seepage problems with high accuracy.Meanwhile,it also greatly reduces the number of grid division which accelerates the calculation speed.According to the obtained results,new Blasingame type curves are established and the flow stages are divided.In addition,a parametric analysis is also conducted to screen the critical parameters affecting the seepage characteristics of MFHWs.Finally,the shape of stimulated volume reservoir(SRV)which is more close to the situation is simulated for the MFHWs with SRV in radial compartmental tight oil reservoirs.New type curves are obtained and effects of reservoir heterogeneity caused by volume fracturing,SRV shapes,fracture conductivity and length are also analyzed.The applicability of the semi-analytical model is verified by a field example.