Texaco wildcatters atop a windswept hill here in northern Kansas are searching for what could be the biggest oil strike since the vast North Sea reserve was discovered more than a decade ago.

Tight-lipped company officials have little to say about the test well being drilled on the dairy farm of Noel Poersch, about 150 miles northwest of Kansas City. But Texaco's decision to spend millions of dollars to probe for oil in a region never before thought to contain important petroleum deposits has touched off a scramble for leases to mineral rights from here to Duluth, Minn.

The sudden burst of interest focuses on what geologists call the "Midcontinent gravity high," a deep, banana-shaped rift with abnormally strong gravity stretching from the western tip of Lake Superior southwest across Wisconsin, Minnesota, Iowa and Nebraska to north central Kansas.

First outlined by geologists more than 25 years ago, the region has been defined with increasing clarity over the years. It is believed to be a vast reservoir formed where the continent began to split apart eons ago and filled with billion-year-old sediments that could turn out to contain petroleum.

In most respects, the gravity high resembles a similar formation underlying the North Sea that has yielded billions in oil and natural gas revenue, chiefly to Great Britain and Norway. Such a find in the northern Midwest could aid America's efforts at energy independence, and at much lower financial and environmental risk than offshore discoveries.

"We could pretty well tell the Arabs to go . . . jump," said Poersch, who, like most farmers in this depressed agricultural region, could see his financial situation radically altered if the "Noel Poersch Lease No. 1" well strikes oil.

Although no other drilling is under way in the region and a world petroleum glut has sharply depressed energy prices, a significant strike by Texaco would touch off an oil rush all the same.

Key to spurring the activity has been a series of optimistic assessments of the rift formation based on intensive seismological surveys across the region. The surveys, carried out on an east-west line across the lower end of the formation in northern Kansas, indicate that the rift is filled with sediments rather than ancient lava, as previously believed. These sediments could bear petroleum, as they have in the North Sea formation.

Writing in the authoritative Oil and Gas Journal in August, analysts Carol Kindle Lee and S. Duff Kerr reviewed the data and concluded: "Since the size and extent of the production may well be of giant proportion, the Midcontinent rift system represents a major prospective onshore North American hydrocarbon oil province."

At the same time, knowledgeable experts caution that nothing is certain about what the gravity high contains. Sidney Kaufman, professor of geophysical sciences at Cornell University and executive director of the consortium that carried out the seismic surveys, put it this way:

"Part of our work shows sedimentary layering, not lava. The rock appears to be layered rocks, and that means there could be hydrocarbons there. But sedimentary rock is only one factor. You also need a source for the hydrocarbons, porousness in the rock, and some kind of a seal so that the hydrocarbons do not simply rise to the surface . . . . It is always speculative until you get the oil in the tank."

Although Texaco has had little to say, it is known that contract geologists for the company have stopped the drilling more than half a dozen times to obtain core samples as a means of checking geologic data. The frequency with which this costly procedure has been ordered is seen as an important sign of Texaco's hopes for the well.

When an oil company the size of Texaco starts drilling an area everyone else in the business has virtually written off as fruitless, people in the industry take notice.

According to Henry Bethard, a public affairs spokesman for Exxon USA, it is not unheard of for domestic oil prospectors to decide, based on new information and theories, that a site previously thought barren of oil may prove fruitful.

"Usually these new theories don't pan out, but if they do, then every company will get out their maps and start trying to lease the oil-drilling rights," Bethard said.

He said he found it interesting that Texaco is drilling in the area, but cautioned that "any well out in an area where you haven't had production is a real long shot. Exxon drills about 1,000 wells a year. One single well won't draw much interest unless they find something."

Wall Street, too, is taking a wait-and-see attitude, according to Todd L. Bergman, a vice president in the oil research division at the brokerage house Goldman, Sachs & Co. "Maybe it's something, but I don't think people have been focusing on this," he said. "They may have something decent. I would say good luck to them, but I'd be skeptical."

Meanwhile, "lease hounds" are scouring for cheap rights to drill all across the northern heartland. Officials of Washington County, Kan., where the Texaco wildcat rig is located, say they believe that the company has negotiated leases to about 100,000 acres in the farming region. Poersch said many of his neighbors have signed leases.

The Texaco rig has proven a popular attraction in the sparsely populated area of corn, soybean and hog farms. On weekends, families from miles around drive up the hill to look at the 148-foot tower atop its 28-foot steel base.

"They never say a thing," said Tommy Dickson, 50, the "tool pusher" who runs the rig. "They just look at it silently, sometimes hours at a time."