Research On Seepage Flow Lawand Optimization Of Horizontal Wells With Selective Completion In Low Permeability Reservoir

Low permeability oil and gas reservoir is widely distributed in China, which has huge resource potential. In recent years it accounted for 70% of new proved reserves of oil and gas. In view of the nonlinear flow in low permeability reservoir, the development of low permeability reservoir is difficult. Because of the advantage of horizontal well, the development of low permeability reservoirs with horizontal well has been more and more widely applied. However, during the development of horizontal wells, because of the bottom water or edge water, the water cut increases, which affects the development of horizontal well. Usually we use selective completion for the horizontal wells.In this paper, the fluid flow in low permeability reservoirs and the optimization of selective completion are researched deeply. We mainly completed the following work:First, using the potential superposition principle, mirror image principle and the theory of infinitesimal line congruence, three fluid flow models of low permeability reservoirs with selective completion were built up, which included the closed boundary, bottom water boundary and edge water boundary. The threshold pressure gradient was introduced in these three fluid flow models.Second, based on the theory of seepage flow mechanics and fluid mechanics, the calculation models of pressure drop in horizontal wellbore with selective completion were built up, which included the open hole completion and the perforation completionThird, on the basis of fluid flow models and the calculation models of pressure drop, six coupling models with selective completion were presented. And then the change rules of oil production were discussed with the change of parameters such as threshold pressure gradient and thickness of layer. The plots of typical curves are given, which are useful for the horizontal wells with selective completion in low permeability reservoir.Four, for the six coupling models,six new optimization models for the horizontal wells with selective completion in low permeability reservoir were developed, which take the production as the objective function and take the length and location of horizontal intervals asthe optimization variables. Applying the genetic algorithm and writing the numerical stimulation software, the optimal segmentation schemes were presented. By designing the open degree and the number of horizontal intervals, the sensitivity analysis for the factors affecting the productivity of optimization models was carried out.The optimization research in this paper has provided the important theory support for the horizontal wells with selective completion in low permeability reservoir. And it has important theoretical and practical significance for the exploitation of low permeability reservoir.