Experimental Study On Enhanced Oil Recovery By Injection Of Supercritical Rich Gas In Reef Limestone Reservoir

The LH11-1 reservoir is the first large strong bottom water massive reef limestone oilfield found in China,and the initial oil in place of the oil field are very rich.In early stage,the main development of oilfield water flooding,but with the continuous development,because of the reef limestone reservoir in complex geological conditions and serious heterogeneity,bottom water along the crack and other advantages of seepage channel channeling,resulting in the high water cut of adjustment wells on oilfield production areas,water cut rising fast.The study found gas injection of miscible flooding reservoir can solve the unfavorable mobility ratio,mobility oil wet and low displacement efficiency,in the LH11-1 reservoir condition,the gas injectied is the supercritical fluid,with its high density,low viscosity and high diffusivity and strong mass transfer characteristics,if we can achieve a note supercritical gas miscible flooding in LH11-1 reservoir,can make oil and gas interfacial tension disappears,can greatly improve the efficiency of oil displacement.In view of the above development problem,,we made a combination of full diameter core tube experiment of water flooding and gas drive and other experimental methods to carry out the top in the LH11-1 supercritical gas reservoir,bottom water drive oil central,obtain the following understanding:(1)The LH11-1 reservoir is a typical reservoir of undersaturated heavy oil reservoir with high viscosity and high density,the pressure difference of reservoir pressure and saturation pressure is high,indicated that LH 11-1 reservoir is a with elastic energy shortage,the development period can be taken gas injection to supplement the formation energy recovery method.The temperature and pressure conditions of reservoir to meet the supercritical condition of,besides,N2 and Methane has poor effects on viscosity reduction so C02 and rich gas was taked into consideration to improve the development effect choose(2)By comparison of the experimental results of gas injection expansion in crude oil samples,After the two supercritical gas injection into the formation,the saturation pressure,expansion coefficient and dissolved gas oil ratio of the crude oil will increase,which will have good viscosity reduction effect for the formation crude oil,which can improve the oil displacement efficiency.(3)Through analyzing the two-phase flow characteristics of the relative permeability curve of gas and water flooding and the combination of full diameter core gas injection and water flooding experiment,we found that the top injection of supercritical gas is longitudinal gravity stability displacement,and the oil displacement efficiency is higher than that of the bottom formation water drive.(4)Based on the above research,we build a well group concept model,through optimizing the design parameters of injection and production well network,injection speed and injection quantity,the dynamic index of production is predicted,and the better development effect of the recommended top injection super critical gas rich and bottom water flooding method on the oil of LH11-1 reef limestone reservoir is found.Through the above research,we make the EOR clear of that top gas injectionand and bottom water injection,it provides a theoretical support for the adjustment and development plan in the middle and later stage of LH11-1 development.