| In recent years,chemical flooding technology has been widely applied in the industry due to its significant effect in improving oil recovery and mature technology.Both indoor and field experiments have shown that emulsification can further improve the oil displacement effect of chemical flooding,but there is no quantitative evaluation index for the degree of emulsification.According to indoor experimental research,it has been found that there are significant differences in recovery rates among systems with different emulsification degrees in rock cores with different permeability.Therefore,providing a feasible emulsification degree indicator and studying the matching relationship between emulsification degree and permeability is of great significance for oilfield production.The paper mainly conducted research on the performance of different systems and matched experiments on emulsification degree and permeability.Firstly,conduct a study on the performance of surfactant systems.By measuring the oil/water interfacial tension,emulsification performance,and anti adsorption performance of different surfactants,select the best surfactant with good performance.Secondly,the selected surfactants were used to study the performance of polymer surfactant and alkali surfactant binary systems.Afterwards,the performance of the ternary system was studied,and systems with different emulsifying degrees were screened by changing the concentration of surfactants and alkalis.Generate emulsion through the short core method and study the seepage law of the emulsion.Finally,three sets of formulations with different degrees of emulsification were selected to study the oil displacement effects of different degrees of emulsification.The research results indicate that the interfacial tension between BHS-01 A and BHS-01 B can reach 10-2m N/m in a single system,exhibiting strong emulsifying and anti adsorption properties.The performance of the polymer surfactant binary system is superior to that of a single surfactant system;The alkali surfactant binary system has lower interfacial tension than a single surfactant system.By changing the alkali concentration,the emulsification degree of the alkali surfactant can be changed.The alkali concentration range is 0.1%～0.2% when the emulsification degree is strongest,and 0.7%～1.0% when the emulsification degree is weakest.In the ternary composite system,BHS-01 A surfactant has lower interfacial tension compared to BHS-01B;By changing the concentration of surfactants and alkalis,there are significant differences in the emulsification performance of different ternary system formulations.When the emulsification degree is strongest,the concentration range of surfactants is 0.2%～0.3%,and the alkali concentration range is 0.1～0.3%.When the emulsification degree is weakest,the concentration range of surfactants is 0.3～0.4%,and the alkali concentration range is0.5%～1.0%.Through short core seepage experiments,it has been proven that there is the generation of emulsion at the front edge of the displacement during the long core oil displacement process.At the same time,as the emulsification strength weakens,the migration ability of the emulsion gradually increases,but the retention ability of the emulsion does not improve.Through oil displacement experiments,it was found that the high permeability core and strong emulsification degree system have good oil displacement effects,and the chemical flooding recovery rate is 30.49%;The medium permeability core and medium emulsification degree system have good oil displacement effect,with a chemical recovery rate of 25.18%;In low permeability rock cores,the weak emulsification degree system has good oil displacement effect,with a chemical flooding recovery rate of 21.24%.The strong emulsification degree is suitable for high permeability oil layers,the medium emulsification degree is suitable for medium permeability oil layers,and the weak emulsification degree is suitable for low permeability oil layers. |
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