Research On The Effect Of Multi-stage Shear On The Performance Of Polymer Solutions For Oil Displacement

With the rapid development of economy,China's demand for oil is growing with each passing day.As a result,enhancing oil recovery has become a common concern of all countries in the world.As an important method of enhancing oil recovery,the orientation of polymer flooding is high temperature,high salinity and heavy oil reservoirs.The polymer solution will be affected by shearing effect in the process of formulating to inject into the formation,and the shearing effect has a certain influence on the properties of the polymer solution which has a direct impact on its oil displacement efficiency.Aa a result,studying the properties of the polymer solution in the formation is very important.Aiming at the reservoir conditions of SZ36-1 oilfield,various multi-stage shear methods were established to simulate the shear suffered in the process of formulating to inject into the formation.The impact of multi-stage shear to the polymer solution properties can be studied through the measurement of properties of polymer solutions after sheared by different shear methods.The results show that the shearing effect has great impact on the viscosity of the AP-P4 solution and AP-P8 solution.The initial shearing effect has the largest impact on the viscosity of polymer solution in the continuous shear while the impact of second stage and third stage shearing effect is much smaller.The resistance factor and residual resistance factor of the polymer solution has a further reduction on the basis of last stage shear effect.The storage modulus and loss modulus of AP-P4 solution and AP-P8 solution increase as the frequency increases whether the polymer solutions were sheared or not.The storage modulus and loss modulus of the two polymer solutions were significantly reduced after the single-stage shear,and after the subsequent secondary and tertiary shear effect,the storage modulus and loss modulus will be further reduced,but the decrease is not significant.The viscosity of the two polymer solutions decreases with the increase of shear rate,showing the pseudo plastic rheological properties whether the polymer solutions were sheared or not.After the single-stage shearing effect the viscosity of the two polymer solutions decreases significantly under different shear rates,and the viscosity has a certain degree of decline after one more each shearing effect,but the decline range is much smaller than the single-stage shear.Among the three single-stage shearing effects,the shearing effect of near wellbore shearing simulation device has the largest influence on the properties of polymer solution,while the shearing effect of WARING Stirrer and near wellbore shearing simulation device has the largest influence on the properties of polymer solution among the three two-stage shearing effects.After one more stage of shearing effectthe long-term stability of the AP-P4 solution will become worse and worse.The shearing effect can destroy the network structure of the polymer solution.By comparing the properties of the polymer solution sheared by different shear methods and the actual data of the oilfield shows that three-stage shear model is closer to the actual situation of SZ36-1 oilfield,which can simulate the shear suffered in the process of injecting polymer solution from the ground into the formation better.There is a certain reference value for analyzing the changes of the properties of polymer solution in the process of injecting into the formation.