The Phase Distribution Character Analysis Of Reversing Water-oil Displacement In Micro-pore Structure

As an important technology to improve the recovery of low permeability reservoirs,the reverse drive oil technology has achieved good displacement effect in field experiment of jilin oilfield.At present,most of the researches on the flow of oil displacement by Chinese scholars are carried out in laboratory experiments,and the oil and water flow problems in the process of water flooding are seldom studied from the microscopic perspective.To solve this problem,this paper uses a combination of experiments,theoretical analysis and numerical simulation,combining the basic theories of multiphase fluid mechanics,graphics and computational fluid dynamics.From the microscopic point of view,the distribution characteristics of the oil-water phase around the positive water flooding process,the choice of the optimal commutation timing for the directional oil displacement process,and the displacement pressure,rock wettability,and the influence of oil-water interfacial tension on the distribution of oil-water phase in the microscopic pores of the reversing water flooding oil was studied.Through a large number of simulation calculations,the distribution of oil and water in the microscopic pores of the reversing water flooding was visually demonstrated.The quantitative analysis of the factors affecting the distribution of the oil-water phase in the microscopic pores of the reversing water flooding oil is carried out.The main findings are as follows:(1)The studies have shown that the water phase during positive water flooding progresses in the microscopic pores in the shape of a large hole in the mainstream,eventually stabilizing the volume fraction of the oil phase in the pores around 0.4.(2)The phase distribution of oil and water in microscopic pores of reversing water flooding oil is very different from the oil and water phase distribution of positive water flooding.By analyzing the change of the oil phase volume fraction in microscopic pores,it was found that the optimal commutation timing of commutating water flooding is the formation of a mainstream large-diameter channel for forward water flooding.At this time,reversing water flooding is the most effective method of flooding.The volume fraction of the oil phase is less than 0.1 in the forward water flooding microscopic system;(3)Displacement pressure,rock wettability,and oil-water interfacial tension all affect the oil displacement effect of reversing water flooding,the rock wettability of reversing phase distribution in microscopic pore water flooding effect is very obvious.However,when reciprocating water flooding is performed on the hydrophilic reservoir,only the oil-water interfacial tension parameter is changed,and the oil displacement effect of the reversing water flooding oil is not significantly improved.Through the above research,the characteristics of the phase distribution in the microscopic pores of reversing water flooding are theoretically explained,which provides a new idea for studying the theory of reversing water flooding.Further more,the theory of fluid flow in the microscopic pores of reversing water flooding has been developed.