Canadian shale oil hunters are embarking on the pursuit of rich deposits believed to have migrated north from the United States and become trapped by dense rock beneath the plains of Saskatchewan eons before the border existed.

The formerly elusive target — known as the Torquay in Canada and part of the Three Forks formation in the United States — emerged to prominence by playing a starring role in a C$2.1 billion (US$ 1.9 billion) trio of recent corporate transactions.

Participants in the hunt, and Saskatchewan energy department officials who are urging on the companies, describe the Torquay as the next oil-bearing geological zone down from the renowned Bakken, which has helped to lift U.S. production to its highest levels since the 1970s.

Both layers occur extensively across Saskatchewan’s 51,480-square-kilometer (19,800-square-mile) share of the 250,000-square-kilometer (96,500-square-mile) Williston Basin, which mostly underlies North Dakota and parts of Montana and South Dakota.

“Most oil found in Saskatchewan migrated from the United States portion of the Williston Basin, where source rocks are at greater depths,” says a technical newsletter circulated to geologists and engineers by the Saskatchewan Ministry of Energy and Resources. “It is likely that oil migrated into structural and stratigraphic traps” that caught gradual northbound flows over extended periods between the Paleozoic era 540 to 250 million years ago and the Cretaceous 145 to 66 million years before the present.

The Canadian Torquay deposits, at depths in the 2,100-meter (6,890-feet) area, are moderately shallower than their Three Forks counterparts in the United States. The oil-rich layers are also thinner, in horizontal bands just three to 5.5 meters (10-18 feet) thick. But Saskatchewan adaptations of U.S. shale drilling and production methods have worked well enough to make even the skinny deposits of light, premium-grade oil captured by Canadian shale well worth pursuing.

“There is huge potential…in the underexplored hinterlands of southeastern Saskatchewan and southwestern Manitoba, particularly with the increased drilling that is taking place for deeper targets and the advent of horizontal well technology,” said Petrel Robertson Consulting Ltd., a geology and engineering firm in Calgary.

Exploration-minded, independent publicly-traded companies based in Calgary — which are bigger and stronger than mostly privately-owned Saskatchewan firms — are voting with their treasuries that the petroleum geologists and engineers are right.

Legacy Oil & Gas Inc., a celebrated master of adapting shale production methods to Canada, laid out about C$588 million (US$540 million) in shares, cash and debt assumption to buy Highrock Energy Ltd. from its private owners. In announcing the transaction, Legacy vowed to start later this year on drilling at more than 100 locations identified on Highrock properties in Saskatchewan that include multiple Torquay sites as well as other, more familiar targets such as the Bakken.

Vermilion Energy, a Calgary-based international firm with extensive assets in France, paid C$427 million (US$393 million) to break into the Saskatchewan shale oil scene with a takeover of privately-owned Elkhorn Resources and its extensive portfolio of undeveloped drilling rights.

In the biggest Saskatchewan takeover, Calgary-based Crescent Point Energy Corp., a veteran of Bakken drilling in both the United States and Canada, bought privately-held CanEra Energy for C$1.1 billion (US$1 billion). The acquisition includes 680 square kilometers (260 square miles) of Torquay rights and raised Crescent Point’s disclosed number of identified drilling locations for the emerging Canadian shale production target to more than 480.

At Crescent Point’s inaugural Torquay field development, Flat Lake in southeastern Saskatchewan, the company reports taking production from zero to 5,100 boe/d, chiefly oil, in just the past 12 months.

By Canadian light oil exploration standards, Crescent Point rates Torquay drilling as a low-risk, low-cost, high-reward affair. Typical wells into the emerging priority target cost C$3.35 million (US$3.1 million), find up to 275,000 bbl of oil each, pay a 300% annual rate of return and cover their capital costs in seven months, the Calgary firm has told its shareholders.

Shale drilling for premium quality light oil, while still in early phases in southern Saskatchewan, already overshadows the prairie province’s traditional mainstay of heavy crude, which often fetches only deeply discounted prices from refineries.

Of C$98.6 million in sales of leases to provincially owned mineral rights so far this year the government reports northern heavy oil targets drew only C$2.3 million (US$2.1 million). So far in 2014 industry paid C$42.8 million (US$39.4 million) for prospects in the heart of Torquay-Bakken country in the Weyburn-Estevan region of southeastern Saskatchewan.