Numerical Simulation Method Sduty For Development Effect Of Reef Limestone Doublet Type Pore-Throat Structure Reservoir

L oilfield is an large offshore reef limestone oilfield in China which developed pores、fractures and holes.The development level of various pore media in different layers of reservoir is different.In general,the reservoir heterogeneity in vertical reservoir is serious.There are few research achievements on reef limestone oil fields at home and abroad.Few cases can be used for reference.Since the oil field was put into production,water-free oil production period in oilfield is very short.Less than three months of production,the comprehensive water-cut of oil field is up to 56.3%.In late development of oil field,the water-cut grew rapidly.The speed of production decline is fast.Through the discovery of capillary pressure test data,a representative reservoir in the oilfield is the characteristic reservoir of doublet type pore-throat structure.The permeability contribution value of the reservoir core is provided by a few large pores.Therefore,this paper starts with the characteristics of micro pore structure.On the basis of the study of the characteristics of the microcosmic and macro percolation of the reservoir,acquaint the main factors affecting the characteristics of oilfield development which can provide valuable experience for the adjustment of later development methods.In this paper,based on comprehensive analysis of various testing data,production data and geological characteristics of oil field,there is a clear understanding of the seepage law and development characteristics of the doublet type pore-throat structure characteristic reservoir by application of fluid seepage theory and reservoir numerical simulation software.This paper carried out the following research about the doublet type pore-throat structure reservoir and obtained some achievements.(1)Through the capillary pressure curve test data,CT scan and so on,the characteristics of micro pore-throat structure of the reservoir core of doublet type pore-throat structure are analyzed.It is clear that water drive recovery is low and the water cut is rising fast,which is the result of the water channeling along the advantage percolation channel.(2)Utilization of macro water driving experiment,this paper analysed the macroscopical seepage law of reservoir core of doublet type pore-throat structure.The results showed that the relative permeability curves put up the following characteristics:①Weak seepage capacity of water phase under residual oil saturation;②The single phase flow area of the fluid was wide and the two phase co-permeable zone was narrow;③1he relative permeability of oil phase decreased rapidly when the water saturation rose.(3)This paper analysed the pressure gradient of oil field under single well state by using one source and one sink seepage theory.The results showed that increasing the production pressure can increase the use of the capillary and increase the efficiency of the oil.(4)In order to improve the speed of numerical simulation,the dual medium reservoir model can be transformed into an single medium reservoir model by treating equivalently the parameters of the dual medium reservoir model.However,the equivalent treatment of key parameters has a clear limit on the pore medium of the reservoir.The method is no longer applicable beyond a certain extent.(5)The influence of other physical parameters on the final oil recovery of the oil field was significant.To control the other physical parameters of the oil field,the final recovery can be improved properly.Reducing the viscosity ratio of oil and water can be used as one of the main directions for the later recovery.