The Preparation And Performance Evaluation Of High-Temperature Resistant Polymer Gel At Medium Or Low Temperature

The heavy-oil reservoirs in China are generally distributed in medium or low temperature sandstone formations.Due to the strong heterogeneity of reservoirs,profile adjustment operations are required before steam flooding.The commonly used profile control agents are generally divided into two categories:the one has good performance in medium or low temperatures,but high dehydration rate or degradation with high temperature.Current gel profile control agents cannot achieve effective profile adjustment for heavy oil reservoirs,and it is urgently needed to develop a novel gel profile control agent with good gelation in medium or low temperature and enough stability in high temperature.In this paper,HPAM-G01 compound cross-linking system,HPAM-PR organic cross-linking system and AM-G02 newly crosslinking system are studyed on improving the temperature resistance of gels.The control variable method was used to analyze the effect of different types and mass fraction of polymer,crosslinker,cross-linking agents,additives and pH value on gel properties.The gel strength was evaluated by code method and a rheometer.The temperature resistance of the gel was examined at a high temperature of 140°C.The microstructure of the gel was studied by scanning electron microscopy.The experimental results show that the preferred formula of HPAM-G01composite cross-linking system is:0.8%w S001+0.15%w G01+0.2%w Z01+0.4%w Z02+0.05%w KA,and the gelation time is 12h at 70°C.The gel viscosity after gelation reachs 17000 mPa·s at a shear rate of 1.5 s^-1 and can be stable at a high temperature of140°C for 90 days.The gel is an elastic-based viscoelastic colloid,and has a microscopically three-dimensional network structure with pore diameters of 20 to 40?m.The optimal formulation of HPAM-PR organic cross-linking system is:0.8%w S001+0.8%w PR?F/P=4?+0.25%w T01+0.05%w KA,and the gel time is 13h at 70°C.The post-gel viscosity reachs 18,000 mPa·s at a shear rate of 1.5 s^-1,and can be stable at140°C for 90 days and the strength is reduced to E-grade.The gel is a viscoelastic colloid based on elasticity and has a three-dimensional cellular network structure with a hole diameter of about 20?m.The optimal formulation of the AM-G02 newly crosslinking system is:5.6%w AM+0.35%w G02+0.04%w KB?pH=4?,and the gelation time is 20 h at 70°C.The gel viscosity after gelation is The shear rate of 1.5s^-1was 30 Pa·s,and it can be stable at 160°C for 90 days.The gel has a large viscoelastic modulus,and is a strongly viscoelastic colloid based on elasticity.The microstructure is a three-dimensional cellular network structure.The hole diameter is about 15?m.There is also a micro-crosslinked network inside the hole.The diameter of the hole is about0.5?m.