Alkali-free compound flooding composition

Abstract

The invention relates to an alkali-free compound flooding composition. The composition consists of the following components by weight percent: 0.1 to 0.4% of composite surfactant, 0.1 to 0.25% of polymer, 0 to 1.0% of sodium chloride or sodium sulfate, and the balance of water. The composite surfactant is petroleum sulfonate and non-ionic surfactant alkanolamide, and the weight ratio of the petroleum sulfonate to the non-ionic surfactant alkanolamide is (5 to 95): (95 to 5). The polymer is polyacrylamide or salt resistance polymer, and the average molecular weight is 12 to 35 million. The oil-water interfacial tension is ultra low under an alkali-free condition. The invention has adaptability to oil and water and has the capacity for resisting bivalent cation. The test of the interfacial tension under an oil deposit temperature condition shows that the interfacial tension is stable and good for a long time. The effect of alkali-free flooding is equivalent to the effect of alkali flooding. The invention can avoid the adverse influence of scale formation and emulsification on the oil extraction when no alkali exists and the salt is added in alkali-free condition, thereby the investment cost of the aftertreatment of the produced liquid is reduced.

Description

Technical field [0001] The invention relates to a chemical combination flooding composition for tertiary oil recovery, in particular to an alkali-free composite flooding composition and its application in tertiary oil recovery. Background technique [0002] At present, most of CNPC's main oilfield waterflooding development oilfields have entered the "double high" development stage with high water cut and high recovery. It is more difficult to further improve the recovery factor. At the same time, with the increasing pressure on oil demand and the further deepening of the exploitation of old oilfields, the importance of tertiary oil recovery technology will become more apparent. The chemical combination flooding technology has been proved by field tests to be one of the effective methods to greatly improve the recovery rate of water flooding in high water-cut oil fields. The chemical combination flooding technology is a new method developed in the late 1980s that can greatly incr...

AI Technical Summary

Problems solved by technology

For example, Daqing Oilfield has achieved good oil-increasing effect in the field test of ASP ASP flooding in strong alkali system using domestic heavy alkylbenzene sulfonate surfactant, but some new problems continue to appear in the field test research, such as The test formula system used a relatively high concentration of strong alkali. In some test areas, it was found that the oil wells were seriously scaled and the pump inspection period was shortened, which increased the technical difficulty and additional costs of oil production, and even directly affected the normal production of the oil wells; secondly, Since the high concentration of alkali has a great influence on the viscosity of the three-component system, in order to achieve the designed mobility control ability, the concentration of the polymer in the formulation system has to be increased, thereby increasing the cost of the oil displacement agent; Severe emulsification, difficult dehydration treatment, and increased oil production costs

In addition, the adaptability of surfactants to different reservoir conditions is not strong, and the source of surfactant raw materials is insufficient, resulting in insufficient quantity supply, etc.

The development of petroleum sulfonate suitable for weak alkali ASP flooding system has made great progress, but there are still problems such as the adaptability of product performance to oil and water and the improvement of product quality stability. Scaling will be weakened, but not eliminated

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