ABSTRACT: Upper Triassic Tidal-Flat Carbonates of the Boundary Lake Member, Northeastern British Columbia, Canada

EMOND, DIANE, Esso Resources Canada Ltd., Calgary, Alberta, Canada

The Boundary Lake field is located along the British Columbia/Alberta border, approximately 750 km northwest of Calgary. Hydrocarbons are produced from the Upper Triassic Boundary Lake member, a carbonate unit within the Charlie Lake Formation. The Boundary Lake member is underlain by bedded to massive anhydrites and overlain unconformably by siltstones of the Charlie Lake Formation.

The Boundary Lake member is an erosional remnant of a tidal-flat succession. Internally, it is composed of three upward-shoaling cycles of sedimentation. A relative drop in sea level terminated carbonate deposition. At this time, the Boundary Lake carbonate was subaerially exposed and eroded.

Five facies have been recognized in the Boundary Lake member: (1) bivalve carbonate facies, (2) laminated carbonate facies, (3) pelletal carbonate facies, (4) stromatolitic carbonate facies, and (5) mollusk-oolite grainstone facies.

Depositional facies and early dolomitization are the two main controls on reservoir quality. The Boundary Lake member has an average porosity of 20% and an average permeability of 30 md. Reservoir continuity is primarily controlled by facies distribution and faulting, which is believed to have occurred after Boundary Lake deposition, but prior to deposition of the Charlie Lake siltstones. Faulting was reactivated during the Cretaceous.

Three-dimensional modeling of the Boundary Lake member has been helpful in understanding variations in reservoir quality on a facies basis and thus improving on waterflood performance.

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