HOUSTON, June 25 (Reuters) - Private equity firm Kimmeridge, through its subsidiary Kimmeridge Texas Gas, has acquired a 90% stake in proposed U.S. liquefied natural gas export project Commonwealth LNG, it said on Tuesday.

The investment will allow the project to move ahead, the companies said. The sum paid for the controlling interest was not disclosed.

Kimmeridge appointed former BP Americas head David Lawler as CEO of Kimmeridge Texas Gas, effective immediately.

"We are excited to take a controlling interest in Commonwealth LNG as we integrate our business....and look forward to the completion of a best-in-class LNG export facility in Louisiana," said Ben Dell, managing partner of Kimmeridge and director at KTG.

Commonwealth LNG has been trying to develop a 9.5 million metric tons per annum (mtpa) LNG export facility in Cameron, Louisiana, and has been unable to reach a financial decision as it has not yet received an export license from the Department of Energy to sell the superchilled gas to non-FTA countries.

The plant has been awaiting an export permit for over a year and Commonwealth Executive Chairman Paul Varello said on Tuesday the delay has cost the company about $500 million.

Varello announced his retirement on Tuesday at an LNG construction conference in Houston.

Kimmeridge said the acquisition was a move to ensure that a final investment decision on the LNG project is made by the end of the second quarter next year.

Commonwealth LNG Chief Executive Officer Farhad Ahrabi, who joined the company in 2022 following a seven-year tenure at Cameron LNG, will continue in his current role under Kimmeridge ownership, Commonwealth said. (Reporting by Curtis Williams in Houston; Editing by Leslie Adler and David Gregorio)