Study On Oil-water Emulsification Behavior And Separation Characteristic Of High Concentration Polymer Flooding Produced Liquids

High concentration polymer flooding(HCPF) has been one of the enhanced oil recovery(EOR) methods since conventional polymer flooding in the main reservoirs of Daqing Oilfield because its higher viscoelasticity can improve the oil displacement efficiently. However, due to more hydrolyzed polyacrylamide(HPAM) is produced, the oil-water mixture is emulsified easier and separated more difficult. In order to analyze the emulsification behavior of HCPF produced liquid, which is sampled from production wells with different polymer-containing concentrations and water cuts, a laboratory investigation of evaluating the Zeta potential, oilwater interfacial property, rheological property and micro-morphology of the produced liquid was recently carried out. The oil-water separation technology with security-efficient pulse power supply is presented and the electrochemical dehydration process is optimized.The results indicate that HCPF produced liquid is characterized by strong electronegativity, high viscosity, and strong emulsification tendency and stability. The emulsification effect of the low water cut produced liquid is more obvious as the polymer-containing concentration rising up, leads to the phase inversion point, at which the emulsion transformed from water-in-oil(W/O) to oil-in-water(O/W) or water-in-oil-in-water(W/O/W), decreased in different degrees. Comparing with the previous AC-DC power supply dehydration, electrodispersion and current leakage could be avoided and the time length of high dehydration current could be shortened greatly when pulse power supply was used. Under the optimized separation technology and operation parameters, water content in oil is less than 0.3% and oil content in the separated water is less than 1000mg/L, and the oil-water interface is tidy and clear, which meet the produced liquid disposal standards. As the surface matching technology of EOR, this separation technology is significant for promoting the construction of HCPF demonstration project and improving the petroleum development and production efficiently.