Large-scale Experimental Study On Water Injection And Gas Injection In FQ Pore-type Carbonate Reservoirs

FQ reservoir is a large oil reservoir dominated by cretaceous and third series carbonate, which has great geological reserves. The reservoir space of oil bearing layer is mainly primary porosity and has few fractures. In reservoir, crude oil viscosity is small and formation water is in high salinity and formation elastic energy is sufficient. The reservoir is mainly developed by depletion, during the development, because layer and inter layer liquid production capacity is different, some wells water cut rises fast and oil production wells declines quickly Resulting in the difficulty of reservoir steady production.According to the basic geological features of the reservoir, by using the similarity theory, the drive similarity criterion of porous carbonate reservoir is deduced, the mutual conversion of three-dimensional physical model parameters and oilfield actual parameter is realized, the three-dimensional physical model of carbonate rock reservoir is firstly designed and produced in the domestic.The model Ⅰ is similar to the Mishrif layer of FQ reservoir, it can simulate positive rhythm sedimentary in vertical plane. In this model, two horizontal and three vertical wells is deployed on plane and four groups of water flooding experiment and three gas drive experiments are carried out. The Model Ⅱ is similar to the Asmari layer of FQ reservoir, dolomite and sandstone alternate appearance vertically. In this model, five vertical wells are deployed on plane and three groups of water flooding experiment and three groups of gas flooding experiments are carried out.Seven sets of experiments were studied in model Ⅰ:the effect of crude oil aging of 3-D physical model experimental results; The effects of different injection ways on reservoir ultimately recovery degree; the development mode of first gas injection after water flooding towards the effect of reservoir recovery degree; the difference between natural gas injection and nitrogen injection displacement efficiency of oil; the difference between top gas injection and the bottom gas injection of displacement efficiency of oil.Six experimental groups were studied in Model Ⅱ:the effect of water flooding after depletion and water flooding directly towards the ultimately recovery degree of thin mutual layer; the effect of stable fluid production rate in the late period of water flooding; the effect of displacement efficiency between natural gas injection,nitrogen injection and CO2 well coordinated throughput and CO2 flooding;the effect of water injection medium converting to gas injection in oil recovery improvement.The three-dimensional physical simulation experiment is conducted in this paper, combined with reservoir engineering methods, the water drive characteristic curve and oil and water phase permeability experiment and recovery degree and water content change are studied. The results show that the depletion approach can prolong the oil production without water period and improve the recovery of carbonate rock reservoir; horizontal wells and vertical wells combined developing can improve the sweep efficiency and thereby enhance oil recovery; water injection after gas injection can expand the injected medium swept volume; gas injection after water flooding can effectively reduce reservoir water cut, slow speed; CO2 injection oil displacement efficiency is the highest in three gas, while the CO2 can cause the corrosion of pipeline, but nitrogen free corrosion.Through the result of three-dimensional physical simulation experiment, combining injection oil and produced oil viscosity determination, chromatographic analysis, the mechanisms of improving oil recovery can be included as follows:enlarge the sweep volume, water control and increasing the oil, reduce the viscosity of crude oil, dredge oil flow channel and reduce interfacial tension, extraction of light hydrocarbon component of this kind of reservoir by gas injection. Through my research in this paper, The method to develop the pore type carbonate reservoir are depletion, waterflood, gas-alternating-water flooding.