Abstract: In the standard of thermal production,there is no way to exploit the extremely heavy oil with the viscosity more than 10×10~4 mPa?s.Through the horizontal well and the steam soak assistant by the injection of CO_2,the heavy oil in Z411 block of Wangzhuang oil field is effectively produced while the viscosity of degassed oil is over 74×10~4 mPa?s. the mechanism of oil displacement by CO_2 and the steam soak are introduced and the production evaluation method is presented.The evaluation results show that the method is suitable to the production at the area.