A steam chamber generally rises steadily in the channel sands of Athabasca oil sands during a SAGD operation. It is commonly known that steam chamber growth rate is mainly dependent to permeability. Once the steam chamber reaches the upper boundary, it starts to expand laterally. This is the basic concept of steam chamber growth of SAGD process in fine sands.
However, the growth of steam chamber measured through the analysis of temperature changes from observation wells behaves different in many instances than the commonly accepted steam chamber growth concept, explained above. In these observation wells, the steam chamber deviates from the usual behavior; sometimes stops and then resumes rising or shrinking, or even disappears during SAGD process. This can be caused by the specific nature of steam fingering phenomenon during SAGD operation.
Many simulation studies have been conducted to understand the steam rising phenomenon during SAGD operations. At the top of the steam chamber, steam fingers seemed to be created where steam flows through and the steam chamber expands vertically. If steam fingering actively develops, steam chamber grows steadily as expected. However, activity of fingering can be disturbed under certain conditions, which can result in various alterations in the growth of steam chamber.
In this paper, the steam fingering phenomenon during SAGD process is discussed with actual measured field data from four SAGD projects; UTF Phase A, UTF Phase B, Hangingstone and Surmount.