Study Of Treatment Technology & Reinjection Problem For Enhanced Oil Recovery Produced Water

Recently, the quality of produced water has changed obviously with the development of polymer flooding technology in Daqing Oilfield. The viscosity of produced water rised, degree of emulsification increased, and the suspended particles became small and small, which caused the poor quality of treated produced water, so the recovery effect was influ-enced. Furthermore, the petroleum consume increased year after year in China. To assure the national strategical safe of petroleum, more and more"3-low"petroleum deposits (low production, low permeability, and low abundance) were exploited, the requirement for quality of injected water became rigid. To meet the demand of oilfield recovery, it is ur-gent to research the high and new purification and recycling technology for enhanced oil recovery produced water. In this paper, some research work on theory and application was conducted from oil removal, filtration and fine filtration process unit.In the high efficiency oil removal technology aspect, the theory study and application experiment of air sparged liquid-liquid hydrocyclone was carried out, enlightened by the air sparged solid-liquid hydrocyclone. Firstly, the strength and movement of dispersed phase was analyzed in theory, it was proved that the air bubble-oil drop polymer trend to move to the axes of hydrocyclone. Secondly, using CFD method, the characteristics of oil-air-water flow field were studied, including velocity distribution, pressure distribution, turbulent motion energy and its dissipation distribution. The characteristics and separation effect under different air injection methods were simulated. Thirdly, the separation ex-periment of air sparged liquid-liquid hydrocyclone was carried out at Lab. The major structure parameters of the hydrocyclone were optimized, the reasonable air injection method and performance parameters were determined through 4 groups of air injection experiments. Finally, the process experiment for treatment polymer flooding produced water was done in oilfield, the process parameters were determined, and the treatment ef-fects were evaluated. The experimental results indicated that air sparged hydrocyclone in-tegrated the hydrocyclone and floatation. Compare with conventional two-stage settling process, air sparged hydrocyclone has many advantages, such as high oil removal effi-ciency, short settle time; it has a good application prospect.In the filtration technology aspect, the experiment of treatment ASP produced water with hydrophilic fibre ball filtration. Firstly, the hydrophilic fibre balls were obtained by the surface modification of hydrophobic fibre balls, and its surface quality was measured at Lab. Using hydrophilic fibre ball as filter medium, a new type of filter was designed to treat ASP produced water in pilot-scale experiments. The obtained results indicated that this type of filter had high capability and efficiency for the treatment of ASP produced water.In the fine filtration technology aspect, the polymer flooding produced water was treated by PVDF ultrafiltration membrane. The performance parameters were determined, including performance differential pressure, surface velocity, and concentrate multiple, washing period and so on. The working life was doped out. The pollution principle was illuminated through analyzing the pollutant on membrane surface. Experimental results indicated the quality of water treated by UF membrane, could meet the"511"water qual-ity and the water quality were steady. So, UF membrane has a good prospect for using in the deepness treatment process.Furthermore, rock core flooding experiment was done. The results proved that the high polymer concentration of produced water could injure the low permeability stratum. To protect the stratum, decrease injection pressure and increase recovery ratio, the poly-mer concentration of injected water should be restricted.In this paper, the study on produced water purification and recycling process was conducted systematically. It is significant for improvement of injected water quality and increasing oil recovery ratio.