Architecture and Sequence Stratigraphic Framework of the Oil Sands at the Hangingstone SAGD Project, Alberta, Canada

Abstract

3D seismic studies have provided compelling evidences that point bar deposits of tidal-influenced meandering river in the McMurray Formation represent the main reservoir of the Athabasca oil sands. The deposits show a heterogeneous lithology which could affect the SAGD (steam-assisted gravity drainage) performances. However, the lithology related with channel migrations and the sequence stratigraphic framework of the oil sands have not been studied in enough detail. Therefore, the oil sands in the JACOS Hangingstone Project were studied to resolve the issues. The oil sands, with thickness of 50 m, directly overlies the carbonate basements. At least four meandering valleys which intersect each other are recognized on the top of the basement. Scroll patterns (SPs) were particular features recognized in seismic depth slices of the oil sands and were interpreted as horizontal slices of accretion surfaces of point bars. The oil sands reservoirs were divided into two areas based on whether the SPs can be recognized or not. The deposits without the SPs were locally eroded by the deposits with the SPs. In the area with the SPs, the migration and filling processes of the channel were revealed based on the 3D interpretation of the SPs and well data. The channel migrated laterally and downstream, and was abandoned with sinuosity of 1.3. The abandoned channel was estimated 1000 m wide and 40 m deep. In the area without the SPs, point bar deposits with thickness of 30 m are overlain by shallow marine deposits including “McMurray A1 Sequence (A1: the upper most McMurray Formation)” with thickness of 20 m. From the above, the oil sands are interpreted to be deposited as follows. 1) During relative base level (RBL) rise, meandering rivers developed on the basements. 2) During subsequent RBL fall, the rivers cut into the basements and when RBL fell more the river systems could not maintain. 3) Recurring events of 1)-2) occurred at least four times. 4) During RBL rise, meandering rivers developed and when RBL rose further the rivers were not able to catch up the rising RBL and shallow marine incursions occurred. 5) During RBL fall, incised valleys developed with the erosion of deposits of 1)-4). 6) During RBL rise, large-scale meandering rivers developed in the valleys. The areas without and with the SPs were deposited during 1)-4) and 6), respectively. The 6) deposits was interpreted to be the upper most part of the Formation, because of the 6) deposits eroded the “A1”.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016