Study On The Performance Of High Temperature And High Salt Flooding Polymer

China is the most industrialized country in the technology of tertiary oil recovery across the whole world, the research and application of polymer flooding technology going ahead in the world. Reservoir A belonging to high temperature and high salinity reservoir, its formation temperature109℃, salinity up to117615.8mg/L, till now has entered a period of high water stage, facing the problem of stabilizing oil and controlling water in middle and later periods of the oilfield development. Irreversible hydrolysis of general polymers will occur at temperature above75℃. Its viscosity will greatly decrease when the salt content higher than30000mg/L, even phase separation happening and leading to precipitation. So polymer flooding technology is rarely used in this kind of harsh condition. In recent years, researchers are working on a new type of polymer which resisting salt and temperature. The zwitterionic polymer can be applied to high temperature and high salinity reservoir as the oil displacement agent due to anti-polyelectrolyte effect. In this paper, studying on zwitterionic polymers’ performance of resisting high temperature and high salinity in laboratory under the condition of reservoir A will provide a scientific basis for field application selection and synthesis of polymer under harsh condition.Firstly, this paper synthesizes zwitterionic polymers PADA, PSBA and partially hydrolyzed polyacrylamide HPAM, using infrared spectroscopy to prove three polymers synthesizing successfully, in the meanwhile, testing their intrinsic viscosity and molecular weight. Then, zwitterionic polymers’mechanism of resisting temperature and salt is researched by means of viscosity, rheology, dynamic light scattering and environmental scanning electron microscopy combining macroscopic properties with microstructure. Finally, the seepage and flooding capacity of zwitterionic polymers are tested at high temperature and high salt under simulating the formation conditions of reservoir A, comparing with HPAM before aging. The experimental results show that:In terms of macroscopic properties, although the initial viscosity of zwitterionic polymers PADA and PSBA are not as good as HPAM, the properties of resisting temperature, salt and thermal stability are much better than HPAM. With the increasing of salt concentration, the viscosity and viscoelasticity of PADA decrease while PSBA increase. All of these prove that the performance resisting salt of PSBA solution is superior to PADA solution and its high viscoelastic is helpful to increase oil displacement efficiency. In the same time, PADA has a better stability compared with PSBA.In the way of micro structure, with the increasing salt concentration, the molecular size distribution peak of PADA solution moving to the small size,<Rh> value declines. Conversely, the molecular size distribution peak of PSBA solution moving to the large size, hydrodynamic radius<Rh> value increases. As the temperature rises, the molecular size distribution peak of the two polymers both move to large size then moving to small size,<Rh> value increasing firstly and decreasing later. Scanning three kinds of polymers by using environmental scanning electron microscopy, in distilled water, the branch chains of three polymers from coarse to fine are HPAM> PADA> PSBA. In the salt water, the structure of HPAM becomes loose and branch chains become thinner while PADA changes little except for the covering salt crystals. However, the network skeleton of PSBA becomes thick and dense. Once again proving that the performance resisting salt of PSBA is excellent, PADA following.In the aspect of flooding capacity, the flooding ability of zwitterionic polymers is significantly better than HPAM. For zwitterionic polymers, from the beginning of aging to aging after60d, the flow resistance established by PSBA solution is always higher than PADA solution. At the process of simulating flooding oil, polymer flooding of HPAM solution without aging enhances EOR3.85%, total recovery60.54%. After aging60d, PADA enhances oil recovery9.26%, total recovery65.54%, while PSBA enhances oil recovery12.92%, total recovery69.87%.Both two kinds of zwitterionic polymers show a certain oil displacement effect in high temperature and high salt conditions, of which PSBA standing out because of its superior heat resistance, salt resistance, mobility control ability and flooding capacity. This result opens up a new road for the application of polymers in high temperature and high salt reservoir, providing technical support with very important significance.