Oil companies looking for the next big find are wading into the Powder River Basin of Wyoming, where pipelines are not congested and land is cheaper than in Texas' Permian Basin, the world's fastest-growing oil-producing region.

A series of largely undisclosed land deals is fueling interest in its conventional and shale formations, according to people familiar with the transactions who requested anonymity this week to discuss the confidential deals. U.S. crude prices have risen 48% over the last year, also spurring deals.

Rebellion Energy LLC, an Oklahoma firm backed by private equity firm NGP Partners, this month paid more than $100 million, or $5,200 an acre, for 19,000 acres from Liberty Resources LLC, five sources familiar with the transaction said. Vermilion Energy Inc. (NYSE: VET), recently snapped up 55,000 acres from Massif Oil & Gas LLC for $150 million, sources familiar with the deal said. Navigation Powder River LLC last week paid about $10 million for 3,000 acres, a person close to the deal said.

Rebellion, NGP Partners and Vermilion did not respond to requests for comment on Aug. 28. Massif declined to confirm details of the transaction.

"There are a lot of similarities between where the Powder River is today and where the Permian Basin was just a few years ago," said Edward Geiser, managing partner at Juniper Capital Advisors, the financial backer of Navigation.

U.S. shale drillers turned the Permian Basin in West Texas and southeastern New Mexico into the most active and productive U.S. oil field after they figured out how to exploit its multiple stacked layers of oil-soaked rock.

But the surging activity there has clogged pipelines, soaked up available labor and left the region to face at least a year of slower growth. Its higher land costs, challenges for getting pipeline access and water constraints have prompted private equity investors to seek areas with higher returns.

Anschutz Exploration Corp. is hearing from buyers interested in its land, and sold 5,000 acres this month, said President Joe DeDominic in an interview. He declined to identify the purchaser or the sale price.

Helping kick off the dealmaking flurry are moves by larger oil producers to expand in lower cost areas. In March, Apollo Global Management's Northwoods Operating LLC paid $500 million for SM Energy Co.'s (NYSE: SM) assets, including 112,000 acres.

At about $4,500 an acre, the sale is well below the $70,000 an acre that Concho Resources Inc. (NYSE: CXO) paid for prime Permian land this spring with its $9.5 billion acquisition of RSP Permian.

"You look at the numbers and compared to the Permian, it's extremely favorable," Anschutz's DeDominic said.

More land may be coming on the market. Wold Energy Partners, a Denver-based oil producer with 147,000 acres in Powder River and nearby Green River Basins, has sold several thousand acres this year in the Powder River Basin, CEO Jack Wold said, and has hired investment banks to continue sales.

Denver-based Evolution Midstream LLC, which operates pipelines in the Powder River, said all the rising activity has it committed to building a new gas processing plant.

Producers are "trying to unlock different pay zones, and that has translated into a renaissance of activity," said Evolution CEO Raj Basi.

Powder River will not soon replace the Permian as the largest and fastest growing field, but over time it can produce 250,000 bbl/d to 400,000 bbl/d, said Bob Fryklund, chief upstream strategist with IHS Markit.

Production in the basin was 107,552 bbl/d in June, according to state data, more than double what the basin produced in 2010.

Onshore