Bitumen production from the Athabasca Oil Sands in northeast Alberta, Canada typically uses steam-assisted gravity drainage (SAGD) techniques. For shallow bitumen resources, low pressure, SAGD (LP-SAGD) and expanding solvent, LP-SAGD (SLP-SAGD) techniques are viable options for such developments as these methods maximize bitumen production and control steam-oil ratios (SORs), while maintaining asset integrity throughout the life of the project.
In Alberta, applications requesting approval for pilot-scale, thermal exploitation of bitumen resources are submitted to the Energy Resources Conservation Board for review. As part of the application process, thermal reservoir simulation studies are often conducted, forecasting 10 years of asset development using SAGD.
The authors recently completed a 3D, pseudo-component, thermal, reservoir simulation study of the proposed Clearwater West, Phase 1 Pilot Project located southeast of Fort McMurray, Alberta. The simulation program, STARS™, was used for this investigation. Three potential development strategies for the Pilot Project were evaluated. These strategies included LP-SAGD, where 100% coldwater equivalent (CWE) steam is continuously injected into the reservoir for 10 years. The other cases were SLP-SAGD, where the injection stream consists of 75% CWE steam and 25% solvent is continuously injected into the reservoir for either 10 years or for 7 years, followed by wellpair blowdown and the termination of solvent injection. Comparisons of key modelling parameter results, such as steam chamber development, bitumen production and recovery, SORs and solvent loss, were completed for all development strategies. A sensitivity study was also conducted.