Warren, Marian1, Andrew Lowe1, Murray Gilhooly1
(1) EnCana Corporation, Calgary, AB
ABSTRACT: A High-impact Gas Discovery in a Maturing Basin (Western Canada)
EnCana’s 2001 gas discovery at Ferrier, Alberta in the lower Mississippian Banff Formation was a significant new pool discovery in a long-active, competitive part of a maturing basin. Subsequent development of the pool has proven >70 Bcf equivalent gas + condensate, at gross production rates of up to 100 mmcfe/day. The gas is produced from dolomitized crinoidal grainstone reservoir, with up to 30% porosity and several hundred mD to several Darcies permeability.
Most drilling east of the foothills in western Canada pursues stratigraphic plays. Earlier drilling in the Ferrier area focussed on subcrop plays in younger Mississippian carbonates, and on overlying Mesozoic clastic plays. A few deepened wells encountered dolomite porosity in the Banff formation, significantly down-dip from its subcrop edge, culminating in local development of three 20-30 Bcf pools in the 1990s. Further exploration drilling encountered only wet porosity or tight limestone.
EnCana’s discovery, the largest pool in this new play, was significantly down-dip from known wet porous trends and was the result of a more regional, interdisciplinary exploration approach. Our strategy focussed on defining regional stratigraphic, structural and diagenetic fairways, in order to locate 3-D seismic surveys to best image the Banff porosity. Conventional amplitude and AVO analysis, coupled with a regional sequence stratigraphic model, have been critical in distinguishing Banff Formation shales from reservoir, and thus dramatically reducing the initially high reservoir risk on this play. We continue to adjust our exploration approach as our understanding of play risk, reserve distribution and play fairway evolves.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.