Study On Mechanism And Development Plan Optimization Of Hot Water Flooding In Tight Oil Reservoir

Hot water flooding is commonly applied to the development of heavy oil reservoirs, andgood effect is obtained. But for the tight reservoirs, there are no systematic researches onmechanism and technique of hot water flooding and no releva nt field tests have yet been done.Aimed at EOR of tight reservoirs, the mechanism and development plan optimization in anactual block of hot-water injection development were researched.Mixing oil and gas samples supplied by the oilfield and getting rese rvoir fluid samplesfollowing the principle of matching the bubble point pressure. The phase behavior, interfacialtension, high temperature and high pressure displacement and casting thin sections analysistests were taken to research the influence of hot water injection on crude oil properties,interaction between rock and fluid, petrophysical property of the reservoirs. Then enhancedoil recovery mechanism of hot water flooding is analyzed from these three aspects. Resultsshow that, with the increasing of the injected water temperature, the bubble point pressure oftight oil reservoir increases constantly, but the increasing extent reduces gradually and bubblepoint pressure and temperature curve approximately shows―S‖shape; formation oil volumefactor increases significantly which can highly supply the formation energy and raise theformation pressure; the density of formation oil decline sharply which is conducive to theflow of oil in the formation porous media; the reduction of oil/water viscosity ratio falls littlewhich has little effect on EOR; at the same time, the oil/water interfacial tension, irreduciblewater saturation and the residual oil saturation both decrease, common percolation area of twophases is widen and general shape of the curve turns better; the oil threshold pressure gradientdecreases and it has a power function to the temperature, which can reduce the minimuminjection-production pressure deeply in the case of well pattern fixed; injection pressure fallsand it can relieve the situation effectually that the water well―can’t be injected‖; also, thepore characteristics of reservoir rocks mainly becomes better, and the effect of waterdisplacing oil will turn better.On the basis of laboratory experiment，the model of thermal flooding test area inchangqing tight reservoir was built using reservoir numerical simulation technology to optimize the parameters of hot water injection and then analysed the development effect bythe optimum parameters. The results show that, the optimum temperature of injection water is100℃，the optimum water injection rate is25m3/d and the optimum injected water volume is30×104m3;15years later, the recovery percent of hot-water injection development is22.527％， higher than that of conventional water injection by2.18%. Results of theresearching can provide theoretical basis and technical support for development of hotinjection in tight reservoirs.