Evidence for Submarine Channels in the Lower Carboniferous Banff Formation, North-Eastern British Columbia: A New High Impact Exploration Play?

Warren Walsh¹, Brent Miller², and Richard Brandley^3
1 British Columbia Ministry of Energy and Mines, Victoria, BC
² Petro-Canada Oil and Gas, Calgary, AB
³ Rock Research Inc, Calgary, AB

The Lower Carboniferous Banff Formation in North-Eastern British Columbia comprises shale, silt and carbonate mudstones deposited in a deep water slope environment; seismic data typically confirms the deposition of the Banff Formation in large west dipping clinoforms towards the Prophet Trough. Regionally, evidence suggests that the middle Banff slope was incised by submarine channels that transported sediment downslope to the west, depositing coarse crinoidal grainstone and carbonate mudstone.

In the plains area of NE BC (94-H) discrete clean units identified on geophysical logs up to 8 meters thick are present within the upper slope deposits. Here, depositional fabric is difficult to determine due to poor sample returns but good reservoir potential is inferred by a history of gas blowouts and local drilling problems through this unit. Further to the west (94-G) units of 50 - 75 metres of clean fine grained carbonate mudstone lie disconformably on dark grey and black shale, however, modern 3D seismic indicates locally incised channels which have not been drilled through. These units grade westward into stacked units 25 to 75 metres thick of carbonate mudstone and shale which are occasionally interstratified with units of coarse crinoidal grainstone several metres thick.

These deposits are interpreted from east to west as: small submarine channels and tributaries in the plains moving towards large submarine channels and finally submarine fans interstratified with distal channel facies. This series is similar to those identified in west-central Alberta (Brandley and Villéger, 2004) where dolomitization of the coarse crinoidal carbonates has created reservoirs that produce up to 25 MMCf/d with cumulative production of 4 to 30 Bcf.

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