Optimization Of Parameter Coarsening Methods For Low Permeability Reservoirs Considering The Distribution Of Barriers And Interlayers

The existence of the interlayer is one of the important reasons for the heterogeneity of the reservoir.It has the function of hindering and blocking the migration of fluid in the reservoir and has a controlling effect on the distribution and mining of the remaining 0il.In the construction of geological models,the number of grids is usually used to capture the micro-structures and interlayers in the reservoir,and a fine reservoir geological model is established to maximize the true geological characteristics of the reservoir.In the current fine geological model,the number of grids can reach millions or even tens of millions.However,considering the current limited computer performance,it is necessary to merge some of the meshes and reduce the number of meshes,that is,to coarsen the mesh attributes.Since the geological information is inevitably lost in the roughening process,how to make the roughened geological model contain as much geological information as possible in the original model,and it can be accepted by numerical simulation on the scale of calculation.Important practical significance.In addition,for low-permeability reservoirs,there are many interlayers and strong heterogeneity,and the rationality of grid coarsening is more important for the prediction of its productivity.This paper has carried out the following research work on this issue.Firstly,the traditional method of equivalent permeability coarsening is reviewed.Based on the traditional classical permeability coarsening method,a "comparative-average algorithm"is proposed,which can better preserve the reservoir interlayer and the boundary of the sandstone.Secondly,the river sedimentary facies are the representative of low-permeability heterogeneous reservoirs.The heterogeneity and typical interlayer distribution patterns are compared and analyzed.The distribution pattern is divided into interlayer continuous distribution and interlayer.There are two typical modes of intermittent distribution.Thirdly,the ideal geological model of continuous distribution between interlayers and discontinuous distribution between interlayers is established.The coarsening algorithm is used to roughen the permeability and according to the static heterogeneity parameters(permeability grade difference,coefficient of variation,non-homogeneous coefficient)and dynamic production parameters(daily product oil,daily liquid production,oil recovery,water see time,etc.)to compare the results before and after roughening,preferably the optimal roughening algorithm and coarse Step by step.Fourthly,by comparing the calculation efficiency and the calculation error,the harmonic-arithmetic averaging method is selected to coarsen the permeability,and then the lateral and vertical grid step length is reasonably roughened.The optimization results show that the horizontal grid step should not be Beyond the width of the interlayer,the longitudinal grid step size should not exceed the thickness of the barrier.Fifth,for low-permeability reservoirs,the distribution of the interlayer of the reservoir can be analyzed to better determine the plane roughening and longitudinal coarsening steps.The roughened model and the original model have better Goodness of fit.The accuracy of the model is guaranteed on the base of improving the calculation efficiency and facilitating the use of the model.Sixth,the optimization method proposed in this paper is applied to the actual model.The optimized step size can not only improve the calculation efficiency but also make the model before and after the roughening have small differences and meet the engineering needs.Therefore,the roughening method and roughing step size screened in this paper have guiding significance for actual production simulation.