Elm Coulee Field: from Update from "the Tight Reservoirs Analog"

Pramudito, Aris ^1
1 Geology and Geological Engineering, Colorado School of Mines, Golden, CO.

The Elm Coulee Field covers an area of 530 square miles (1,370 km2) and has recently become one of the 20 largest oil fields in the United States. The field, discovered in 2000, produces from the middle Bakken reservoir with current production yields of nearly 50,000 BOPD.

The Bakken Formation is informally divided into upper, middle, and lower member. The lower Bakken is not present in the field. The middle Bakken reservoir consists primarily of dolostone with silt-sized quartz and feldspar that have been sourced from erosion of older formations (Three Forks and Nisku formations) to the south-southwest of the area. The upper Bakken is organically rich and is the hydrocarbon source.

The middle Bakken ranges in thickness from 8 ft to 20 ft (2.5 m - 6 m) and has an average porosity of 8% - 10% and an average permeability of 0.05 md. The vertical depth of the middle Bakken in the Elm Coulee Field ranges from 8,500 ft - 11,500 ft (2,590 m - 3,505 m). The Bakken is slightly overpressured with an average pressure gradient of 0.53 psi/ft. The production limit is well-defined by the net pay thickness map created in this study.

Productivity of the field is controlled by overpressuring within the Bakken.Middle Bakken reservoir geometry is suitable for the horizontal drilling application and this is the key success of the Bakken plays in the Williston Basin. Elm Coulee Field is the analog of how a tight middle Bakken reservoir can be very productive by drilling horizontal wells and applying multi-stages fracture stimulation. The field can be used as an analog for other fields in the rockies based on the reservoir geometry and heterogeneity.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009