Elm Coulee Field, Middle Bakken Member (Lower Miss./Upper Dev.), Richland County, Montana

Walker, William B.², Alfred R. Powell², Richard A. Rollins², Ronald V. Shaffer² (1) Headington Oil Co, LP, Denver, CO (2) Headington Oil Co., LP, Denver,

Elm Coulee Field produces from the middle dolomite member of the Bakken Formation. Approximately 270 horizontal development wells have been drilled since the field’s initial horizontal producer was drilled in late 2000 by LYCO Energy. Horizontal drilling and large fracture treatment stimulations are keys to developing economically viable reserves from this field.

EURs per well range up to 1,250,000 BO, averaging 500,000 BO per well. The field is expected to produce over 200 MMBO from an area of over 400 square miles. Exploratory drilling activity may expand the limits of the field dramatically.

The field is a stratigraphic trap developed in the Middle Member Bakken with an uncertain contribution of production from the overlying Upper Shale Member of the Bakken. The Middle Bakken is considered the principal reservoir and is primarily dolomite, variably silty with scattered pyrite and anhydrite, and increasingly argillaceous toward its base. The reservoir appears to have developed diagenetically within a large, complex carbonate bar/bank accumulation which extends over 130 miles, ranging from 6 to 15 miles in width and up to 35 feet thick (thinner to SE). This complex stretches from northwestern Richland County, MT to southwestern Dunn County, ND, parallel to and basinward of the southwestern margin/shoreline of the member’s depositional basin. Structurally, the Bakken pay section dips about 2,000 feet from NW to SE Richland County. The reservoir is slightly overpressured (0.50 fpg) and consists of 8-14 feet of 8-12% porosity and low permeability (0.05 to 0.10 md). Local variations in these reservoir properties, occasional increased natural fracture development within the reservoir and variations in completion techniques likely collectively play an important role in the range of well productivity within the field.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana