Abstract: Production mechanism of pair of horizontal wells by steam-assisted gravity drainage (SAGD) process is studied from the monitoring data and analytical method. Analysis shows that the fluid in steam chamber flows mainly by gravity drainage with low pressure gradient. The fluid flow below the steam-liquid interface between the steam injection well and production well is dominated by pressure drive, different from the gravity drainage in the steam chamber, with relatively high pressure gradient. Sub-cool control is optimized using discretization wellbore model based on the understanding of pressure gradient distribution of production well. The result indicates that sub-cool control ranging from 10℃ to 15℃ is consistent with the field analysis results.

Key words: SAGD, horizontal well, steam chamber, steam-liquid interface, heavy oil