There's been a land grab going on in the Niobrara oil play in Wyoming and Colorado, and some observers think it may be time to sell.

On Tuesday IHS Herold released findings from a special report suggesting that private exploration and production companies operating there might want to consider selling their assets, as prices have become pretty rich in those parts.

It's already happening. In February, China's Cnooc Ltd. (NYSE:CEO) picked up properties there from Chesapeake Energy Corp. (NYSE:CHK) as part of a joint venture for $570 million in cash, or what worked out to be about $5,000 per acre. Last month, Marathon Oil Corp. (NYSE:MRO) agreed to sell 30% of its interest in the Niobrara to Marubeni Denver Julesburg LLC, a unit of Japanese trading giant Marubeni Corp. (XETRA:MARA.DE), for $270 million. That same month, Slawson Exploration Co., founded and owned by Donald Slawson, said it had hired Meagher Energy Advisors to sell its assets in the area, along with others.

The Niobrara play is a vast, potentially promising U.S. oil formation extending from Wyoming and Colorado into Nebraska and Kansas.

With improved fracking technology, experts estimate that the Niobrara can generate about 10 million to 20 million barrels of oil per square mile -- well worth the effort if oil stays above $100 per barrel.

IHS says the play is still relatively unproven, however, and those who have any doubts and want to capitalize on the acquisition mania there may want to think about getting out.

"It's like a gold rush. People think the technology is going to catch up, and if they can't get in there now, they might not be able to in the future," says Sven Del Pozzo, a senior analyst who prepared the report for IHS Herold. "But this play is early stage. It's not like the Bakken or the Eagle Ford, where we know the technology works. In most cases, this play doesn't work. Companies that go in early and spend a lot of money up front will get burned."

Del Pozzo says the Chinese and Japanese are making "reckless" investments there before they've had a chance to prove up and thus boosting the acreage values, which he thinks should be selling at around $500 to $1,000 an acre. "There's execution risk, financing risk and geologic risk, and the reserves might not even be there," he says. "I'm not condemning the entire play. But the hot spots need to be delineated and found, and they haven't been yet."

The heavyweights in the area are Chesapeake, which has 700,000 acres, EOG Resources Inc. (NYSE:EOG), which has 300,000 acres, and Noble Energy Inc. (NYSE:NBL), which has 800,000 acres (it added properties in the area when it bought almost all of the Rocky Mountain assets of Suncor Energy Inc. (NYSE:SU) in January 2010 for $494 million).

There are plenty of smaller companies that operate in the area that might be interested buyers -- or sellers. There's Helis Oil & Gas Co. LLC of New Orleans and Texas American Resources Co. of Austin, Texas -- whose CEO David Honeycutt recently said the more you know about the basin, "the more you like it."

There are plenty of private equity-backed companies there that might be ready to sell. One is Wapiti Oil & Gas LLC, an affiliate of Quantum Energy Partners-backed Wapiti Energy LLC, which picked up development projects there in August as part of a $130 million property package from Delta Petroleum Corp. (NASDAQ:DPTR) Another is Laramie Energy II, owned by EnCap Investments LP, which has 110,000 acres in the area.

In his study, Del Pozzo notes other private companies with positions in the area, including Simray Production Co., Paladin Energy Ltd. (ASX:PDN.AX), Lario Oil & Gas Co., Diversified Operating Corp., Cirque Resources LP, Julander Energy Co., Bonanza Creek Energy Co., North Finn LLC, Foundation Energy Co., Breck Operating Corp. and Rosewood Resources Inc. "They should sell the acreage now, in the early stage, before everyone finds out what the truth is," he says.