Drilling fever in the Rocky Mountains these days isn't entirely focused on natural gas. Along the eastern edge of the Rockies-in western North Dakota, eastern Montana and the southern parts of the Canadian provinces of Saskatchewan and Manitoba-more and more wells are being spudded throughout the 202,000-square-mile Williston Basin. The target: oil. The 143,000-square-mile U.S. portion of this huge sedimentary basin-whose hydrocarbon accumulations are largely attributable to structural traps produced by the folding and faulting of rock during the formation of the Rockies-isn't exactly unfamiliar hole-punching country to the industry. In the 1950s, the U.S. portion of the basin witnessed a boom in oil drilling as the result of the Beaver Lodge Field discovery by Amerada Oil Co. on the Nesson Anticline in North Dakota and the finds of the Richey and Southwest Richey fields by Shell Oil Co. in eastern Montana. By the early 1960s, further exploration of the Williston in Montana and North Dakota yielded the discovery of some 25 large fields, each with oil reserves greater than 15 million barrels. More than a decade later, the 1979-81 industry boom arrived and the Williston saw annual oil production in Montana hit a peak of around 32 million barrels in 1982, and in North Dakota a high of more than 50 million barrels in 1983. Then came $9 oil in 1986 and the economics of drilling up the Williston in Montana and North Dakota skidded. So, too, did oil-production levels. That, however, was a few yesterdays ago. Today, the Williston Basin-Oil and Gas Investor's first cover story (August 1981)-is undergoing a renaissance. For more on this, see the August issue of Oil and Gas Investor. For a subscription, call 713-260-6441.