Continental Resources Inc. shares jumped nearly 15% Tuesday after shale pioneer and billionaire Harold Hamm offered to take private the shale oil and gas company he founded for about $4 billion.

Continental CLR, +14.18% earlier Tuesday said that Hamm and family offered to take the company private for $70 a share, a premium of about 9% over Monday’s closing price and a 21% premium over the average share price this year.

The stock was headed for its highest close since Sept. 17, 2014, when it closed at $75.82.

The family already owns about 83% of the Oklahoma City-based company. The offer is not binding and the board will evaluate it.

That could leave the door open for competing bids from peers, analysts at Truist said in a note Tuesday.

The company is worth “at least our $95/share price target,” the analysts said.

It will be “worth watching” what a potential outside bidder would offer for the company, although in a letter to employees Hamm assured that there’d be little change to compensation and operations, which “somewhat lowers the expectation of a winning outside bid,” the analysts said.

In the same letter, Hamm, who founded the company in 1967, said that there’s lack of support for public oil and gas companies and that a private model would allow for more flexibility especially around exploration.

A non-binding offer “has room for negotiation,” analysts at Siebert Williams Shank said in their note. The analysts, who have a $80 price target on the stock, said they expect the shares to trade around the $70 take-private offer.

Hamm, the U.S.’s richest oilman and 63rd richest American, according to Forbes, and his family have owned more than 70% since the company went public in 2007.

They increased their stakes through downturns and more recently through buybacks, analysts at Cowen said in their note.

Hamm stepped down as Continental’s chief executive in 2019, but remained as chairman.