| The polymer flooding technology has been applied in first and second types of oil reservoirs in China,but it is immature technology in third type of reservoirs which is characterized by high salt,high calcium and magnesium content.Therefore,Sinopec has proposed the Enhanced oil recovery technology by suspension microcrystalline polymer flooding for third type of reservoirs.A suspension microcrystalline polymer system is formed by adding a crystal agent and dispersant in the common polymer solution to enhance the viscosity of the polymer and improve the recovery of crude oil.In this paper,the present situation of produced water treatment technology of polymer flooding and water flooding at home and abroad is investigated.The water quality characteristics of the suspension microcrystalline polymer flooding in high calcium and magnesium reservoirs are analyzed.Three kinds of produced water samples?PFPW,HPFPW and SMPFPW?were simulated and prepared,and their water quality characteristics with oil content,particle size distribution,zeta potential,viscosity were quantitatively studied.The results show that calcium and magnesium ions,polymers,dispersants and nucleation agents will increase the oil content and viscosity of the produced water,reduce the particle size of the oil beads,and lead to the difficulty of produced water treatment.The results of the research on treatment process of SMPFPW show that the current water treatment process of water flooding produced water in an oil field,which consist of gravity sedimentation unit and primary corundum&anthracite?volume ratio 1:1?composite filtration unit,can be applied to the treatment of SMPFPW with polymer concentration less than 100 mg.L-1.Effluent water quality of the process,oil content,suspended solids and the diameter median of suspended solids meet the indicators of the“Water Quality Standard and Practice for Analysis of Oilfield Injecting Water in Clastic Reservoirs”?SY/T 5329-2012?.For SMPFPW with a polymer content of 300 mg.L-1,three treatment processes were experimentally studied,which consist of different combinations of gravity settling unit,chemical flocculation unit and filtration unit.According to the experimental results,the recommended treatment process of the produced water is gravity sedimentation—primary composite filtration of corundum&anthracite?volume ratio 1:1?—secondary composite filtration of corundum&anthracite?volume ratio 1:1?. |
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