Rheological Study Of Aqueous Solution Of Partially Hydrolyzed Polyacrylamide

Most of oilfields have been in the mid-late period of development at domestic with some problems such as the bigger producing fluid volume, the higher water content, the lower oil concentration and so on. So in order to improve the oil recovery, the polymer (partially hydrolyzed polyacrylamide, PHPA) flooding technology has been widely used in our country. At present, polymer solution (PHPA solution) is prepared by fresh water then diluted by wastewater bring about the large waste of fresh water; While direct emission of large number of oily wastewater produced from the process of oil production causes serious environmental pollution. Therefore the treatment of oily wastewater and the research of resource utilization arouses the wide range of attention.This thesis firstly described the rheology of PHPA solution about the impact factors includes temperature, electrolytes, pH and crude oil concentration, which results in understanding the key limiting factor of preparing the polymer flooding using wastewater; then performed the treatment efficiency of simulated oily wastewater by nano-microbubble technology and studied the feasibility of preparing polymer (PHPA) oil displacement system with treated wastewater instead of fresh water, in order to provide the basic basis of treatment of oily wastewater and its resource utilization.The research content and results of this thesis as follows:(1) Creep and oscillation experiments were performed to measure the zero-shear viscosity (ηo) and storage modulus (C’) of aqueous solution of partially hydrolyzed polyacrylamide (PHPA), respectively. The overlapping concentration (C*) and crossover concentration (C**) of PHPA solution were determined through the dependence of ηo on solution concentration (C). Effects of temperature, pH and electrolytes (NaCl, CaCl2and AlCl3) on C*and C*were investigated. The results show that as temperature and electrolyte concentration are raised, ηo and G’ decrease while C*and C**increase gradually. The higher the electrolyte cation valence is, the more obvious the induced variation of viscosity and critical concentrations of PHPA solution is. With pH increasing, ηo and G’ increase initially and decrease subsequently while C*and C**decrease first and increase afterwards.(2) The factors such as mineralization and oil concentration of simulated oily wastewater on the viscosity of PHPA solution directly prepared were studied. The results showed that the main influencing factor on decreasing the viscosity of PHPA was mineralization.(3) Nano-microbubble technology was performed to dispose simulated produced water in order to study the feasibility of using the oily produced water after treating to prepare polymer solution. The results were the oil concentration and salinity of simulated produced water were dramatically decreased and the value of pH was increased; It can increase the viscosity retention rate of polymer solution which was prepared by the simulated produced water. Nano-microbubble technology possesses tremendous development potential for oilfield wastewater treatment because of its simple operation, the lower cost and the higher efficiency of treatment.