A glance at the Birdbear, an oil-bearing formation geologists say could expand horizontal drilling in North Dakota.
What it is: The Birdbear is a thin oil formation _ only a few feet _ locked within muddy limestone and dolomite more than 2 miles underground.
Where it is: The formation, also called the Nisku, is found in the central part of the Williston Basin in North Dakota and extends into Montana and Canada.
Drilling status: About 50 horizontal wells are aimed at the Birdbear in southwestern North Dakota. The formation there is nearly identical to a Birdbear formation Bottineau County, about 250 miles away in north central North Dakota and just beyond the Bakken and on the far fringe of the state's existing oil patch.
Outlook: Most oilmen are having too much success with the rich Bakken and the Three Forks-Sanish formations above the Birdbear to busy themselves with it for now.