Research On Oil Displacement Performance Of Surfactant Compound System

Fossil oil has been widely exploited.After conventional exploitation,50%~70% crude oil still remains in reservoirs in the form of residual oil which can't be exploited.Therefore,it is particularly important to exploite reservoir resources effectively.In terms of enhancing oil recovery,surfactant flooding has attracted lots of attention due to its wide application range and large increase.However,the existing surfactants have been fatigued to enhance oil recovery,and there are still some shortcomings in the mechanical interpretation.In this paper,Shaanxi crude oil was used as the oil sample.The rock sample of an oil field was used as the simulated core.The surface/interfacial tension test,the wettability performance test and core flooding experiment were carried out.Finally,in order to explore the mechanism of surfactant flooding,the recovered oil was analyzed by GC-MAS and post-harvest rock samples were analyzed by SEM.Firstly,anionic surfactant sodium dodecyl benzene sulfonate,amphoteric surfactant cocamidopropyl betaine,anion-nonionic surfactant fatty alcohol polyoxyethylene ether sulfate,nonionic surfactant fatty alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether were selected as oil flooding agent.The surface/interfacial tension and wettability performance of surfactant solutions were tested at different concentrations.Subsequently,core flooding experiments were carried out.The results showed that when the concentration was 1000 mg/L,the recovery rate could be increased by 5.77%,7.69%,9.80%,9.62% and 7.69%,respectively;and when the concentration was 2000 mg/L,the recovery rate could be increased by 7.69% and 9.80%,11.76%,11.32%,and 9.61%,respectively.In order to enhanced recovery,sodium dodecyl benzene sulfonate,cocamidopropyl betaine and nonylphenol ethoxylate were selected to carry out the two-two compounding study.The results showed that each system had a synergistic effect and can enhance recovery.When the mass ratios of SDBS/OP10,SDBS/CAB and OP10/CAB system are 1:9,1:1 and 1:1 respectively,the recovery ratio is the highest,which increased by 12.73%,10.96% and 10.00%,respectively.Subsequently,according to the economic evaluation,that is,considering its relationship with price,concentration and recovery factor,SDBS/OP10 system with mass ratio of 5:1 and concentration of 1000 mg/L is the best.Finally,oil displacement mechanism is further discussed through the analysis of oil components and the SEM of core.In the study of the produce oil component,it was found that the compounding system can interact with the higher carbon number hydrocarbons in the crude oil than the single system.The rock surface was observed by SEM.The surfactant can “peel” the crude oil from the rock surface,and the compounding system is stronger than the single system.After the oil flooding process,a small amount of surfactant remained on the rock surface.