Study On The Degradation And Stability For Flooding Polymers

At present, most of the oil layers are of high temperature and high salinity in EOR. In view of this, polymers used in oil field must have effective thickening properties, temperature tolerance, brine tolerance and resistance to shear force in order to achieve the ideal effect. In polymer flooding technology, the viscosity and long-term stability of polymer fluids are not only one of important index but also the key factor of polymer flooding effectiveness. A lot of literature research and practice tests show that the viscosity of polymer fluids has a direct impact on performance of polymer flooding agent solution.In the laboratory condition, we simulated the influencing factor in the different oil reservoir to study the degradation rules of flooding polymers. By chemical methods we studied the rules of thermal degradation, chemical degradation and shear degradation, in order to provide the theory basis for the improving the solution properties of flooding polymers under different oil deposit condition and achieve the improvement of viscosity and stability. Based on the above considerations, the purpose of this dissertation is focused on evaluation of flooding polymers, synthesis and characterization of viscosity stabilizer and their practical applications. The main work and experimental results are as follows:(1) Combined with the actual reservoir conditions of target oilfield, in the laboratory condition, the effects on viscosity and stabilization for flooding polymer (SNF and AP-P4) were studied under thermal degradation, chemical degradation, shear degradation in the different oil deposit, and were characterized by measuring the chemical structure, hydrolysis degree, thermal analysis, viscosity changes and molecular weight change, dynamic light scattering and so on. It is found that these three kinds of degradation methods can all decrease the viscosity of flooding polymers (SNF and AP-P4), in which shear degradation is most obvious for the reduction of viscosity. The results from IR and TGA show that the chemical structures for SNF and AP-P4 don't basically change during the degradation. (2) Glycoluril and tetramethylol acetylenediurea were synthesized and can be used as viscosity stabilizer. The chemical structure and stability of glycoluril and tetramethylol acetylenediurea were studied by 1HNMR, dynamic laser light scattering, viscosity and viscoelasticity and so on. Glycoluril and tetramethylol acetylenediurea can be used as viscosity stabilizers for AP-P4. The results showed that glycoluril and tetramethylol acetylenediurea can obviously increase the viscosity of the system for AP-P4, in which glycoluril is better than tetramethylol acetylenediurea. Glycoluril can be used as viscosity stabilizer for SNF and can better increase the viscosity of the system for SNF.(3) The polymeric surfactant with quaternary ammonium salt (PQ) was synthesized by cationic ring open polymerization using boron trifluoride diethyletherate as cationic catalyst. The chemical structure and aggregation behavior of polymeric surfactant PQ were studied by 1HNMR, surface tension, static light scattering, dynamic laser light scattering, electrical conductivity and fluorescence measurement. In addition, PQ can be used as viscosity stabilizer, and the viscosity stability results from between flooding polymer (SNF) and PQ also suggest that the mixed system can greatly improve salt resistance and thermal stability and has the high practical application performance.