China National Offshore Oil Company Limited (CNOOC Ltd.) announced Monday it has agreed to pay 1.08 billion U.S. dollars for a 33.3-percent stake in the U.S.-based Chesapeake Energy Corp.'s 600,000 oil and natural gas leasehold acres in the Eagle Ford shale project.

CNOOC International Ltd., a wholly-owned subsidiary of Hong Kong-listed CNOOC Ltd., China's largest offshore oil and gas producer, would make the purchase and the price was subject to adjustment at transaction, CNOOC Ltd. said in a statement released Monday on its website.

Closing of the transaction was anticipated before the end of the year.

In addition, CNOOC Ltd. agreed to fund 75 percent of Chesapeake's share of drilling and completion costs until another 1.08 billion U.S. dollars has been paid, which Chesapeake expected to occur by the end of 2012, the statement said.

The companies planned to develop unproved resource potential of up to 4 billion barrels of oil equivalent over the next "several decades," the statement said.

As operator of the project, Chesapeake would conduct all leasing, drilling, completion, operations and marketing activities for the project, based in south Texas.

According to the agreement, CNOOC Ltd. would also have an option to acquire a 33.3-percent share of any additional acreage acquired by Chesapeake in the area and also an option to take a 33.3-percent interest in midstream infrastructure related to production, the statement said.

Fu Chengyu, CNOOC Ltd. chairman, said in the statement that as one of the world's largest independent oil and gas companies, CNOOC Ltd. had the will and ability to establish itself in this field by cooperating with a leading company such as Chesapeake.

"This transaction will provide the capital necessary to accelerate drilling of this large domestic oil and natural gas resource, resulting in a reduction of our country's oil imports over time, the creation of thousands of high-paying jobs in the U.S.," the statement cited Aubrey K. McClendon, chief executive officer of Chesapeake, as saying.

Headquartered in Oklahoma City, Chesapeake Energy Corporation is the second-largest producer of natural gas and an active driller of new wells in the U.S.