Water Production Law Of Fractures In Carbonate Reservoirs And Countermeasures For Water Shutoff

Carbonate reservoirs are widely distributed and have a high proportion of reserves;therefore,they have a very important position in the world.Due to its diverse types of reservoir space,the strong heterogeneity and complex flow mechanism in carbonate reservoir,the understanding of water flooding is limited,resulting in poor effect of increasing oil after water control measures.In the past,the understanding of the law of water production mainly refers to the water production characteristics corresponding to the reservoir space,while the fractures in the carbonate reservoir are the main seepage channels,and there have flow interference between different scaled fractures and affect the oil wells production dynamics.Therefore,it is of great significance to study the law of water production in fractures and its dynamic identification method in order to develop effective water shutoff countermeasures in the later stage.In this paper,the oil-water two-phase discrete fracture model is established firstly.An optimization method is used to mesh the fracture,which can obtain triangular mesh to characterize the fracture accurately and finely.The conductivity between different meshes is calculated,and the model is solved by automatic differential algorithm.Then,a typical discrete fracture model was designed based on the method we design above.The effects of fracture relative width,absolute width,oil-water viscosity ratio and fracture length on fracture flow interference were studied.The fracture interference degree is evaluated by the small fracture flow ratio,the residual oil saturation in the fractures and the degree of utilization.Our study find that the fracture interference law is divided into two types: flow competition and flow shielding,and the boundary between the two types is obtained.We find that the water production type can be divided into fracture competition and fracture shield mode.The water cut characteristics were study for each water production mode.For the diagnosis of fracture water production mode,several commonly used dynamic diagnostic methods were evaluated.It was found that the water cut derivative curve can identify the fracture production mode effectively.Considering the production data of real oil fluctuates greatly,a dynamic identification method was optimized by the data denoising method and the diagnosis of the field well was carried out.Finally,a typical model of fracture competition effluent and fracture shielding effluent is established.The numerical simulation of classification water shutoff countermeasures is carried out,and countermeasures for classification water shutoff control are given according to the simulation results.