Abstract: Subcool is a conventional parameter, by which we can diagnose the state of steam assisted gravity drainage (SAGD) production, but this method extremely relies on the monitoring of temperature and pressure in wellbore. According to this, a new simplified method for the state diagnosing work is proposed, which can be a substitution for using the conventional subcool parameter. In the case study, just by using pressure in downhole and oil pressure at wellhead, the wellbore apparent density can be calculated in condition of artesian flow, which is the same as the function of subcool production state diagnosing. The case study of I well group in SAGD pilot test area of Xinjiang Fengcheng oilfield indicates that it is of a good guiding effect in the field heavy oil production and control.

Key words: SAGD, heavy oil reservoir, artesian flow, wellbore apparent density