ABSTRACT: The Slave Point Formation Exploration Play in the Hamburg-Cranberry Area of Northern Alberta

BLOY, GRAEME, and RON MCKELLAR, Husky Oil, Calgary, Alberta, Canada

The Slave Point Formation in the Hamburg-Cranberry area presents a difficult exploration target. A combination of poor porosity prediction and seismic difficulties in the interpretation of porosity presence has resulted in an elusive play. When successful, this play has substantial rewards. For example, the dolomitized Hamburg Slave Point "A" pool has 9200 million cubic meters of recoverable gas and 16 cubic meters NGL/millioncubic meters gas; in contrast, the undolomitized Cranberry pool has 10,953 million cubic meters of recoverable gas and 377 cubic meters NGL/millioncubic meters gas. The differences in lithology and the types of hydrocarbon present in the Slave Point reservoirs are controlled by diagenetic processes.

The Hamburg and Cranberry pools are located north of the Peace River arch, in an area of downwarp. Isopach and paleogeographic maps of the Slave Point Formation confirm the presence of this low relief trough, which extends from east of Cranberry into British Columbia. Isopachs of the overlying and onlapping Waterways Formation also confirms the presence of this trough.

The reservoirs are stratigraphic traps within mudbanks of variable areal extent (one to tens of square kilometers) and are sealed by the overlying Waterways Formation and laterally by the Otter unit. The Otter unit, which is devoid of any fauna, was deposited after the mudbanks but prior to the Waterways Formation and is bound by hardgrounds.

The dominant constituents of the mudbanks are peloids. The peloids probably originated from microbial and/or chemical reactions and are indicative of a low energy depositional setting. The biota within these banks is limited to a few stromatoporoid forms, corals, and algae indicative of a stressed environment.

The best-developed porosity in these reservoirs is located in the northeast side and/or in the upper portion of the mudbanks. This porosity development is facies related in proximal margin packstones.

In the limestone reservoirs, porosity appears to have resulted from the survival of microporosity and subsequent interconnection due to dissolution prior to hydrocarbon emplacement. In contrast, the dolostone reservoirs appear to have developed following a burial dolomitization event that obliterated the original precursor microporosity.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)