Abstract: Deep Basin Reservoir and Exploration Analogue: Elmworth, Western Canada

D. P. Robinson, R. D. Sadownyk, G. M. Staples

The giant Elmworth gas field straddles the Alberta/British Columbia border along the eastern front of the Rocky Mountains in the Western Canada Sedimentary basin. Since its discovery in 1976 over 300 pools have delineated 4.5 TCF (127 × 10₆ cu m) of natural gas reserves over an area of 100 miles (160 km) long by 30 miles (48 km) wide.

In the deeper parts of the Deep basin, the entire sedimentary section is gas saturated. Updip porous and permeable time equivalent rocks are regionally water bearing. Trapping is believed to be stratigraphically and/or diagenetically controlled. Deep basin gas is internally sourced by Cretaceous coals resulting in sweet dry gas.

For this study, the reservoir characteristics for three Albian aged horizons, the Cadotte, Falher B, and Falher F, are compared. The producing reservoirs are all high permeability conglomerates deposited on high energy northward prograding shorelines. Factors controlling reservoir quality are grain size, sorting, mineralogy, compaction and diagenesis. The encasing deposits are low permeability fine grained shoreface sandstones and coastal plain shales and coals. Pressure regimes which vary from subnormal to overpressured, are also important, impacting both reserve volumes and wellhead deliverability. The key to encountering favourable reservoir conditions is to focus on high energy foreshore conglomerates.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994