Experimental Study On The Combination Of Deep Conformance Control And Cyclic Water Injection To Improve The Oil Recovery Of Low-permeability Fractured Reservoirs

The first block of Chaoyanggou Oilfield is a fractured low-permeability reservoir.Due to the existence of fracture,the water breakthrough of the production well during the water flooding process is directional.And after the water breakthrough,the water cut rises faster,and the injection pressure of the injection well is low,resulting in invalid water injection and liquid production.In response to the problems in the injection process,the oilfield has adopted measures such as cyclic water injection,deep conformance control,and water plugging to improve oil recovery.However,with the ever increasing water cut,the efficiency of a single measure to increase the oil recovery gradually decreases.Theoretical study found that the combination of deep conformance control and cyclic water injection has a synergistic effect on enhancing oil recovery.Therefore,this article will carry out laboratory experiments to evaluate the oil displacement effect of the combination of deep conformance control and cyclic water injection according to the characteristics of the first block of Chaoyanggou Oilfield.And verify its effectiveness in improving oil recovery.Mainly achieved the following results:(1)Analyzed the influencing factors of polymer gel performance.According to the optimization of the main influencing parameters in the laboratory,the formula of the organic chromium system was optimized,and the gel performance of the system was evaluated.The test results found that the system has good salt resistance,thermal stability and shear resistance.The core flooding experiment was carried out to evaluate the injection and plugging properties of the system,and three formulas that met the on-site construction conditions were determined(2)Carried out flooding experiment.According to the characteristics of the reservoir,three kinds of permeability levels of long cores with fractures were produced.Evaluated the oil displacement effects of three formulas,and optimized the amount of polymer gel,reasonable injection timing and injection method in deep conformance control.The experimental results found that the reasonable dosage of polymer gel is 0.1?0.15 PV.The reasonable time for deep conformance control is when the water cut reaches 60%?80%.The reasonable injection method is 0.015 PV front slug + 0.15 PV main slug + 0.02 PV rear slug.(3)Carried out a flooding experiment combining deep conformance control and cyclic water injection.The slab core was produced by simulating the waterflooding development mode of the first block of Chaoyanggou Oilfield to study the oil displacement effect after the two measures are combined.It was found that after the measures,the liquid interpenetration volume of the matrix/fracture was increased by 7.36 times.It shows that the combination of two measures has a synergistic effect,which can increase the oil recovery.And optimized the injection parameters of the measures.The result found that the reasonable dosage of polymer gel is 0.1?0.15 PV.The timing of cyclic water injection is when the water cut is about 80%.The reasonable rounds of cyclic water injection are 4 times.The water injection intensity of cyclic water injection needs to be determined by the water injection capacity of oilfield.