Staged Fractured Horizontal Well Flow Simulation Of Low Permeability Reservoir Based On The Discrete Crack Model

Oil reserve of low permeability reservo irs is abundant and widely distributed. But because of its low permeability, poor connectivity and high flow resistance, natural productivity of oil wells is very low and unable to meet the needs of economic development. At present, fracturing technology in horizontal well is a major means for the development of low permeability reservoir. Study on simulation methods of fractured well’s production performance of low permeability reservoir can describe the flow feature and effectively optimize the spatial distribution of horizontal well and the crack. It has significant meaning to improve the yield of oil and gas reservoirs. The research on mathematical modeling, numerical simulation based on the Non- linear seepage and the combination of matrix horizontal well and matrix fracture made some progress.Firstly, this paper elaborated on the basic idea and principle of simulation of mimetic finite difference method based on the single-phase flow problem. Then this method is applied to the oil- water two phase flow problems in reservoir numerical simulation, the correctness and applicability of the method is verified by a numerical example. By the basic idea and principle of mimetic finite difference method can be found that its format structure just be based on a single grid nodes and information. So this method is suitable for any complicated grid in theory and very suitable for the angular point grid existed in geological modeling and reservoir numerical simulation of the hybrid grid. Secondly, This paper established the mathematical model which is suitable for matrix and fracture and described the discrete geometry of discrete crack model. Then, saturation equations are dispersed using the mimetic finite difference method and upstream finite volume format, and finally the discrete crack model is applied to low permeability reservoirs. The results showed that the application of darcy seepage flow model in low permeability reservoirs can make bigger production than the actual, in the meanwhile, non-darcy seepage flow model can better describe the nonlinear seepage characteristics of low permeability reservoirs and get a more accurate production data. Thirdly, this paper considered the influence of frictional pressure drop in horizontal wellbore and established its equations. Then these equations and reservoir equations and crack area equations are connected. At last, the mathematical model and its solve is given. The result shows that, from the toe to heel, wellbore flow and friction loss gradually increased, and the incremental is bigger at the position of cracks. Finally, the exploitation of data instances of fractured horizontal well was analyzed using the model. Through the comparison, the longer the crack near the injection well, the greater the fracture conductivity, the smaller the fracture spacing, the speed of injected water invading into fractures is faster. That will reduce the sweep efficiency of injected water, so the oil recovery is low. For different positions of well network, we can set different fracture parameters. Nearby the injection wells, we can shorten the fracture length, reduce the fracture conductivity and increase the crack spacing to delay the water breakthrough time into horizontal well and expand injection profile and efficiency. In the far distance from water injection wells, we can increase the crack length, conductivity and crack distance to improve the productivity of fractured horizontal wel.