Selection and performance evaluation of heat resistant polymer in Henan oilfield

Considering the characteristics of physical reservoir properties of the Shuanghe VIIdown layer series, such as high formation temperature (96. 5°C) and low permeatbility (0. 374 μm2 ), the heat resistant polymers used in the 3rd or above reservoirs were screened and evaluated. Performance evaluations of five kinds of polymers (named 100622,100621, SNF,2#, 1#) was conducted on temperature tolerance, salt resisting properties and oil displacing capacity. The results showed that the SNF polymer with the viscosity-average molecular mass 2.7 × 107 and the hydrolysis degree 26.03% had excellent capacity of heat resistance, salt tolerance and oil-displacement capacity. The retention of viscosity of the SNF polymer solution with the concentration of 1500 mg/L was 110. 8% after the thermal oxidative aging for 90 d at the temperature of 96°C in the condition of oxygen content <1.0 mg/L. The results of core displacement experiment showed that the oil recovery increased with increasing the polymer concentration due to the improved viscoelasticity, and the proper concentration range was 1500 -2000 mg/L. The larger the slug size, the higher the oil displacement efficiency, and the improvement weren' t obvious when the slug size were above 0. 5 PV, the suitable sizes of injected slugs was 0. 5 PV.