John McCaslin
Exploration Editor
Horizontal drilling in the Mississippian Bakken formation of the Williston basin has established a new play for the industry.
Recent estimates of ultimate recoverable reserves from the current Bakken fairway in North Dakota are as high as several hundred million bbl of oil. The number of successful completions in this play are above 30 at this point. Interest is now moving out into the area up to 35 miles north of the fairway.
HIGH SUCCESS RATES
Petroleum Information in its latest Petroleum Frontiers issue, Williston Basin Bakken Shale: learning curve on the horizontal, notes that horizontal drilling of the Bakken began in late 1987 by Meridian Oil Co..
By mid-December of that year, the first horizontal well in the basin was completed successfully at 33-11 MOI. One year later, the company reported a dozen other producers. This was an unbroken roll of success at 100%.
Though the play has been dominated by independents, several majors have also gotten into the act. Conoco drilled a marginally successful well in May 1988, and completed a second one in 1989. Oryx, Texaco, and Chevron are also drilling horizontal wells in the Bakken play, according to the PI publication.
Meridian holds a net half million acres, about 65% of which ( in terms of fee minerals) it owns outright as part of the old railroad land grant from the federal government. This ownership applies to every other section over a large portion of the existing fairway.
WILL BRING NEW CONCEPTS
Continued exploratory success in the Bakken play opens a new period of history in the Williston basin.
The Bakken shale continuously underlies a large portion of the Williston basin. This formation has been known since the late 1950's as a hydrocarbon reservoir of local significance. And, since at least the early 1970's, the Bakken has been known as a source rock of primary importance in the basin.
Where it produces, the Bakken is fractured. Such fracturing often involves immediately over and underlying units, which Are otherwise of very low matrix reservoir quality and good sealing capability.
Petroleum Frontiers points out that geochemical analyses imply that, in North Dakota alone, the formation has generated about 90 to 100 billion bbl of oil, and that it continues in the midst of hydrocarbon generation.
A significant portion of the total oil generated thus far (estimates vary) still remains within the Bakken. Reservoirs in the formation are mainly gas-solution driven. Williston watchers will need a copy of this Petroleum Information publication. Bakken hunting is in its infancy.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.
