Alkali/surfactant/polymer (ASP) flooding technology has become an important way to enhance the oil recovery and improve the recoverable reserves. However, in the large-scale application, the disposal and reuse of ASP produced water meet lots of difficulties and challenges, especially with the water cut rising of the benefited oil wells and the appearance of polymer, alkali and surfactant in sequence in produced liquid. Many traditional disposal methods are suffering double restriction of purifying effect and economical efficiency, also, the discharge of the disposed water is faced with a variety of pressure, such as facilities pollution, healthy and environmental threat. Therefore, environmental friendly disposal and beneficial reuse of produced water have become one of the technical bottlenecks for the promotion of ASP flooding. A laboratory investigation of evaluating the microcosmic emulsification properties of ASP flooding produced water was carried out recently. A combined disposal process for the water was presented and assessed. The feasibility of produced water reuse for preparing polymer solution during the chemical flooding oilfield development at high water-cut stage was validated.

The results show that there are surplus negative charges on ASP flooding produced water interface. The oil droplet size in the water diminishes with the increase of the chemicals, and particles are easy absorbed on oil-water interface to further prevent the coalescence of oil droplets. The sludge accumulation was decreased more than 70.0% due to the physical comprehensive effects of the combined disposal process including sedimentation with aeration, lateral flow coalescence, dissolved air flotation and micro-flocculation suspended sludge blanket filtration. The power and agent expense was reduced 60.0% and secondary pollution was decreased remarkably. The produced water after disposal could not only meet the re-injection standard of high permeability reservoir, but also can be reused to preparing polymer solution, and the viscosity loss control ability is desirable. The treatment option presented in this paper would contribute more to establishing a health, safety and environment (HSE) system.

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