Well Test Theory And Interpretation Method Of Multi-Fractured Horizontal Wells Based On The Discrete Fracture Model

Multi-Fractured Horizontal Well is the key technology in the development of tight oil/gasreservoirs, well testing theory and interpretation method of multi-fractured horizontal wellsare not suitable at present, so it is necessary to establish a set of testing theory andinterpretation method for complex fracturing techniques and different reservoir types. Basedon artificial fractures shape, multi-fractured horizontal well can be divided into conventionalfractured horizontal wells and horizontal wells in complex fracture system, and four typesreservoirs including single porosity reservoirs, dual porosity reservoirs, composite reservoirsand shale gas reservoirs are considered, where seven basic models of multi-fracturedhorizontal wells are built. Firstly, a point source mathematical model is established in singleand dual porosity reservoirs which involve pseudo-steady and non-steady cross flow.Analytical pressure and productivity solutions of conventional fractured horizontal wellboreare obtained by using Laplace transform, mirror mapping and the principle of superpositionmethod with different outer boundaries, and then flow stages and the effects of the relevantparameters are investigated. Meanwhile, mathematic model of horizontal wells in complexfracture system are established in single and porosity reservoirs. Using unstructured meshgeneration and the main fracture reducing dimension method by discrete fracture model, andthen the finite element method is applied to solve this model. The accuracy of new methodwas verified by comparing with classic analytical solution and the impact of artificial mainfractures and branches conductivity on horizontal well pressure and productivity are analyzed.Secondly, a new fractured horizontal well model of composite reservoir is constructed toconsider the effect of stimulated reservoir volume; the composite reservoir is divided intothree regions of artificial main fractures, the stimulated reservoir volume and un-stimulatedarea. The discrete fracture model, dual and single continuum models are used in artificialmain fractures, the stimulated reservoir volume and un-stimulated area respectively, the finiteelement method is applied to solve fractured horizontal well model of composite reservoir.There are five flow stages of the fractured horizontal well in composite reservoir includingmain fracture linear flow, pseudo-steady flow of transition region, cross flow, pseudo-radialflow and pseudo-state flow of outer boundary, and the approximate formula for stimulated reservoir volume size are derived by the flow time of pseudo-steady flow of transition region.Finally, based on dual continuum and composite reservoir model, the mathematical unsteadyflow models incorporating desorption of adsorbed gas are established in shale gas reservoir,where the gas adsorption amount accord with the Langmuir adsorption isotherm equation. Thewellbore pressure and productivity of fractured horizontal wells are obtained by Laplaceanalytical and finite element numerical method, then the effect of the desorption parametersare investigated...