Study On Performance Of Salt Tolerance And Temperature Resistance Functional Polymer And Its Oil Displacement Efficiency

Most of China's oil fields have entered a period of high water-bearing oil recovery,and polymer flooding enhanced oil recovery technology has become an important technical means to increase production and stabilize production in major oil fields.Widely research and application of polymer flooding is mostly partially hydrolyzed polyacrylamide(HPAM).Due to that the HPAM is not salt tolerant and temperature resistant,it is difficult to apply to complex reservoirs with high salinity.This thesis systematically studies the salt tolerant and temperature resistant mechanism of two functional polymers used in oilfield applications and their emulsification and oil displacement,and provides a basis for their practical application in oil fields.The molecular structure of functional RH-4 and KLP-6 polymers was clarified by infrared and nuclear magnetic resonance means.The network microstructure of the RH-4polymer in brine solution was obtained by scanning electron microscopy(SEM)and the salt thickening mechanism was proposed.The thermal analysis of the KLP-6 polymer was carried out by differential scanning calorimeter.The temperature thickening mechanism of temperature resistant KLP-6 polymer was discussed.The apparent viscosity of functional RH-4 and KLP-6 polymers solutions was studied by means of a viscometer with factors such as concentration,temperature and salt type.The rheological properties of the functional RH-4and KLP-6 polymers aqueous solution under shear rate were studied by rheometer.The emulsification law of two functional polymers at high salinity was investigated by bottle test and optical microscope.The relationship between viscoelasticity and emulsifying properties of the two polymers was discussed.Finally,the oil displacement efficiency of the two functional polymers was evaluated by the homogeneous model and heterogeneous model system and the oil displacement mechanism was explored.The results show that the apparent viscosity of the RH-4 polymer solution decreases first and then increases with the increase of salt concentration,and has good viscosity increasing performance under high salt conditions.SEM results show that the network structure of the RH-4 polymer becomes more denser under high salinity.When the salinity reaches 80000 mg/L,the thickening ability of the system is basically the strongest.The salt thickening property is mainly due to the fact that the internal salt bond induced by the carboxyl betaine base group changes with the salt concentration.The viscosity increasing property and salt tolerance mechanism of salt tolerant RH-4 polymer were obtained.The apparent viscosity of KLP-6 solution decreases firstly with the increase of temperature,but when the temperature is higher than the critical association temperature(T_cass),the viscosity of the polymer solution increases with the increase of temperature,and it has temperature thickening characteristic.The decrease in the water solubility of the alkyl polyoxyethylene ether groups in the polymer as the temperature increases is the main cause of the temperature increasing phenomenon of the polymer.Shear experiments showed that the KLP-6 solution was a shear thinning fluid.In addition,compared to HPAM,KLP-6 polymer exhibits good viscoelasticity at low concentrations,and viscoelasticity increases with increasing temperature.The temperature resistant KLP-6 polymer viscosity increasing properties and the temperature thickening mechanism were obtained.The KLP-6 polymer has better emulsifying ability than the RH-4 polymer.By comparing the viscoelastic properties of the same concentrations of RH-4 and KLP-6 polymers,it was found that the KLP-6 polymer has stronger viscoelasticity and emulsifying properties.The higher the viscoelasticity of the polymer,the higher the strength of the resulting network structure,and the better the emulsified crude oil can be coated to make the resulting emulsion more stable.Under the condition of equal viscosity(15m Pa·s),the oil displacement efficiency of the RH-4 polymer and KLP-6 polymer after water flooding in different models is much higher than that of HPAM.Mainly due to the emulsification of functional polymers.The enhanced oil recovery rates of the RH-4,KLP-6and HPAM after water flooding on the sand-filled pipe model were 28.0%,25.3%and 16.5%,respectively.The recovery factors after water flooding on homogeneous cores were 29.5%,16.0%and 13.1%,respectively.The oil displacement efficiency of the RH-4 polymer on the homogenous model is higher than that of the KLP-6 polymer,but not on homogeneous core.The enhanced recovery rate of the RH-4,KLP-6 and HPAM after water flooding is 13.9%,15.3%and 4.2%,respectively,KLP-6 polymer has higher oil displacement efficiency than RH-4 polymer.The Jiamin and retention play a certain profile control effect,such that the displacement caused by the increase in swept volume.In addition,core CT scanning imaging and microscopic simulated displacement have also confirmed that the KLP-6 polymer has strong emulsification retention and expansion of strong swept volume capacity.The two types of functional polymers have broad application prospects in high temperature and high salt reservoirs.