Bulletin of Canadian Petroleum Geology, Vol.52, No.1, 23-38, 2004
Exploration potential of the Falher G shoreface conglomerate trend: evidence from outcrop
The lower Cretaceous Father Member shoreface conglomerate trends are the most prolific natural gas reservoirs of the Alberta and British Columbia Deep Basin. Individual pools can be in excess of 100BCF with discovery wells yielding AOFs of more than 100 MMCFD. Since the 1980s, five conglomerate shoreface trends (Fathers A, B, C, D and F) have been successfully drilled and mapped in the subsurface through observations of cores, cuttings, and well logs. Subsequent to their initial discovery and drilling in the subsurface each trend has been correlated to an outcrop equivalent in the Rocky Mountain Front Ranges of northeastern British Columbia. Until recently, no other Father conglomerate shorelines have been recognized. South (paleolandward) of the Father A-F trends, an older shoreface conglomerate fairway, designated the Father G, has been discovered through outcrop observations at Holtslander Ridge near Belcourt Creek, British Columbia, 110 km southeast of the southernmost described Father shoreface conglomerate outcrop. This trend, which is oriented oblique to younger trends, can be extrapolated into the subsurface plains at the Narraway Field, Alberta, approximately 35 km south of the nearest (Father F) shoreline conglomerate reservoir fairway. Detailed analyses of measured sections, gamma log profiles, and photo mosaics show that the Father G is a prograding shoreface facies association of clast-supported and sand matrix chert pebble conglomerate 8 to 12 m thick. The outcrop is approximately 5.0 km in length, along a north-south-trending depositional dip exposure that grades basinward from clast B supported conglomerate to pebbly sandstone. The Father G shoreface outcrop contains several internal ravinement surface that dip at 5-10degrees to the NNW (320degrees). Analysis of locally available coal exploration core limits the paleoshoreline width of the Father G conglomeratic shoreface trend to less than 5.0 km, with a paleoshoreline orientation of 285degrees/105degrees. Extrapolation of this trend into the subsurface may yield a new and significant shoreface conglomerate reservoir.