| Currently, the main oil fields of Daqing have entered later stage of development with water cut increasing rapidly. Nowadays the water cut has been up to more than 80%. It is difficult for the existing flooding technology to meet the requirement of the oil field development. The oil production of main oil reservoirs of Daqing oil field is in a decreasing trend, and the overall output is severely restricted by the shortage of remaining. In order to ensure the high and stable production of oil field, oil field development has transferred gradually from class ? and ? reservoirs to class ? reservoir with poor geological conditions but large amount in place. Screening oil displacement agent suitable for thin and poor reservoir is the core. Chemical flooding technology is preferred, which applies to chemicals with low cost, high efficiency, and easy injection and production. With Flash EA 1112 elements analyzer and XPS energy spectrum, it is proved that type B III has six kinds of chemical elements, including C, H, O, N, S and Si. The results show that the molecular structure of the type BIII polymer has amide group and sulfuric acid group. This essay starts a research with physical and chemical properties of polymer surfactant. A comparison of type BIII polymer surfactant, type III polymer surfactant and common polymer with medium molecular weight has been made from 8 aspects, including viscosity increasing, viscosity stabilizing, emulsifying, ability to form emulsion of oil in water, ability to reduce interfacial tension, the ability of anti salt, the ability of anti pH value interference and ability to flow in porous media. The results showed that the polymer surfactant is well suitable for class III reservoir. Through the transmission and migration experiments in porous media, the results show that type B III polymer surfactant can produce displacement pressure difference both in the first half and the second half of the core, and has the ability to improve the residual oil recovery in the reservoir. The study of flooding mechanism showed that BIII polymer surfactant in aqueous solution can form strong rigidity "network" structure with lager molecular coils, which is good for increasing displacement pressure under strong transmission and migration ability; Type B III polymer surfactant aqueous solution has strong ability to emulsify crude oil, which can improve the oil displacement washing efficiency; when the concentration of polymer surfactant is higher than 1200 mg / L, the oil-water interfacial tension is reduced to 10-1mN/m; Emulsifying and deep profile modification and displacement make polymer surfactant of BIII high oil displacement ability. On the basis of pilot test, combined with lab core flooding, the scheme of polymer surfactant injection for class III reservoir is determined, that is slug injection(0.1 PV x 1300 mg/L+0.5 PV x 800 mg/L+0.4 PV x 600 mg / L). Injection of 669.0mg/L.PV polymer surfactant increased oil 22 thousand tons cumulatively, oil recovery increased by 9.05% periodically. the recovery factor of center well increased by 10.12%, the cumulative oil incremental 10.1 thousand tons, increasing 53.7 tons of oil by injection 1 ton of polymer surfactant. So type B III polymer surfactant has a good application in the field. |
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