This paper presents a simulation study of a steam assisted gravity drainage(SAGD) process applied to the Hanging stone tar sands reservoir. Two pairs of500 m long horizontal wells installed from the surface are considered.
The study was conducted to forecast recovery performance and to furtherunderstand the oil production mechanism. Results predicted that more than 60%of the oil can be produced in 6 years of operation with a steam-oil ratio ofless than 3.0. The study was extended to provide a visual understanding of theflow behavior of steam, oil and water in the reservoir. The fluid flow diagramsrevealed that oil is displaced mainly by steam condensate and that convectiveenergy carried by steam condensate dominates the heat transfer mechanism.
The authors applied this recovery mechanism concept to the study of sub coolingtemperature optimization for the steam trap control. The results of thisreservoir dynamics study are presented.
Finally the role of this process's geomechanical effects are brieflydiscussed.
The Hanging stone oil sands reservoir is located near Fort McMurray. Thereservoir is jointly owned by Petro-Canada, Imperial Oil, Canadian Occidentaland Japan Canada Oil Sands (JACOS). The bitumen viscosity at reservoircondition is over 1,000,000 m Pas and will not flow naturally.
JACOS is going to use a Steam Assisted Gravity Drainage (SAGD) process toextract bitumen from the Hangingstone reservoir. A cyclic steam stimulation(CSS) process was extensively tested for the same reservoir over a decade. Through a numerical simulation study of the performance, it was found that thebitumen is difficult to produce at economically feasible rates using the CSSprocess for the subject reservoir (1).
JACOS has been participating in the Underground Test Facility (UTF) projectsince 1991 when Phase A of the project was completed. From its participation, JACOS has received all of the field data plus operating and drillingexperience. UTF's field data has been extensively analyzed through numericalsimulation. Based on the analysis of the data, it was decided to drill twopairs of 500 m horizontal wells in 1997 and to start operating the SAGD processin 1998. The expected well performance calculated using a thermal simulator ispresented in the paper. Following the base case run, a series of parametricstudies were conducted. Some interesting results, such as the oil recoverymechanism obtained from the study, are also included.
Although many uncertainties still exist in both the recovery concept andoperational procedure for the SAGD process, promising potential for itsapplication has been demonstrated in Phases A and B of the UTF project(2,3). One major uncertainty is whether the geomechanical change Of the formationduring the process is an important aspect or not. The role of geomechanicaleffect in the growth of the steam chamber and well performance is alsopresented. A new oil recovery mechanism is required when the geomechanicalchange of the formation occurs in the reservoir. A brief description of therecovery mechanism under the influence of the geomechanical formation change isalso discussed.
