Open File Report 1988-01

Open File Report 1988-01

OFR 1988-01

The Geology of the Mid Mannville Subgroup in the West-Central Lloydminster Heavy Oil Trend, Alberta

Author(s) Benns, G.W. O'Connell, S.C. Date 1988-01-01

The mid Mannville sequence in west-central Lloydminster, Alberta, was deposited in a shallow semi-enclosed, brackish embayment on the western side of the Wainwright Ridge. The development of the sequence in this area was controlled by; the topography of the sub-Cretaceous unconformity; eustatic sea-level changes; and the regional sediment supply.

Three major lithofacies were developed in the west central Lloydminster area.

1. A mudstone/sandstone lithofacies deposited in a tidally influenced, brackish, lagoonal/estuarine setting. This makes up the RL and GP units and also occurs at the base of the Lloydminster and Sparky units.

2. Well-sorted wave-dominated coarsening-upward sandstone sheets deposited on a marine shoreface.. These sheet sandstones are present in the upper part of the Lloydminster and Sparky units.

3. Poorly sorted, fining-upward, feldspathic sandstone channels with associated overbank and coal swamp deposits which were formed in an upper estuarine, tidally influenced fluvial setting. These channels occur in the GP and Sparky units.

The mid Mannville sequence in west central Lloydminster differs from the mid Mannville in east-central and south Lloydminster, which was deposited on the eastern side of the Wainwright Ridge. The brackish lithofacies that predominate west of the Ridge are not as extensively developed to the east and south. The GP unit in particular entirely loses its marine character in west-central Lloydminster. Lower shoreface marine sediments are common in south Lloydminster, but are absent in the west.

The Viking-Kinsella field is the only field developed in west-central Lloydminster. It is one of the few Lloydminster fields in Alberta whose origin is not directly related to the structure of the sub-Cretaceous unconformity. It is a result of the incision of the Sparky B reservoir unit by both mid and upper Mannville fluvial/estuarine channel systems. Recently a new pool was discovered in west-central Lloydminster within an anticlinal structure formed by drape over a positive feature on the sub-Cretaceous unconformity surface.

O'Connell, S.C. and Benns, G.W. (1988): The geology of the mid Mannville subgroup in the west-central Lloydminster heavy oil trend, Alberta; Alberta Research Council, ARC/AGS Open File Report 1988-01, 85 p.