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Mississippian/Devonian Bakken (Middle Member Dolomite) Horizontal Drilling Play - Williston Basin - Richland County, Montana

Telfer, Matthew J.1, Russell A. Wheeler2
1 Kodiak Resources, Inc, Austin, TX
2 Border to Border Exploration, LLC, Austin, TX

Since 1980, 36 vertical wells with typical EUR’s of 122,000 BOPW were completed in Richland County. In 1989, Meridian Oil drilled horizontally in the Upper Bakken Shale with an IP of 8 BOPD, recovering 8,545 BO. Between 2000 and 2002, Lyco Energy completed 20 horizontal wells in the Middle Member Dolomite with IPs up to 440 BOPD. Headington, drilling in 2002 with different completion practices, had IPs of up to 955 BOPD.

The Middle Member Dolomite is up to 16 feet thick, usually has less than 10% porosity and reported maximum permeability of just .2 md. The coarsening upwards sequence suggests deposition in a shallowing sea with increasing wave and current activity. Winnowed carbonate grains and mud were deposited in offshore bars. The amalgamated reservoir-quality bar deposits are twelve miles wide by sixty miles long. Cores and electric log response indicate the dolomite is highly fractured, more so towards the flank of the Poplar Dome. Open fractures trend northeast-southwest. The Bakken is slightly over-pressured and the hydrocarbon is characterized as “black oil”, with a 500 GOR. The reservoir has a solution-gas drive. Simple, preliminary estimates of 400,000 BOE recoverable per 640-acres, yield a 288 MMBOE resource, potentially one of the largest fields in Montana.

Hydraulic fracture treatments have multiple breakdowns, indicating numerous areas of horizontal wellbore are treated in a “progressive” heel to toe manner. Eventually the area might be conducive to secondary recovery methods such as fire-floods. Early consideration should be given to well configurations and spacing patterns.