Internal Stratigraphy of the Lower Cretaceous McMurray Formation, MacKay River Area, Alberta Oil Sands

Douglas J. Cant¹, Mark Savage², and Ketema Amare^2
1 Doug Cant Geological Consulting, Redwood Meadows, AB
² Petro-Canada, Calgary, AB

MacKay River, Petro-Canada's first commercial SAGD development has a minimum of 56 MM m³ OBIP. The initial SAGD production is from 25 horizontal well pairs.

In the MacKay area, the middle McMurray section consists of estuarine channel sands and interbedded mudstones (IHS). However, more than 90% of the preserved middle McMurray is composed of 30 m-thick successions, either of almost pure sand or sand with less than 10% interbedded mudstones. These estuarine deposits occur in at least three cross-cutting incised channel fills, all incising from the top of the unit. This can be verified by cross-correlation. It is also implied by the lack of variance shown in dip directions of IHS beds over relatively wide areas, implying no freely meandering systems existed, only lateral migration across valleys.

The sandiest channel fills are not genetically related to the muddier successions lateral to them. Due to limited accommodation space and later truncation, almost all the valleys appear to incise down from virtually the same stratigraphic surface. Age relations can be determined only by mapping the different lithologic units to determine cross-cutting relationships. To the north of the MacKay development, the sandy channels are removed by a later, incised valley dominated by shaley fill that acts as an updip seal. To the south of the MacKay development, resource quality sands continue.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005