United States energy firm, Chevron, is selling its stake in two Nigerian shallow water oil blocks, the company said the latest oil major seeking to dispose of assets in Africa’s biggest oil producer.

The two blocks OML 83 and OML 85 hold an estimated 200 million barrels of oil and an unknown amount of natural gas but there has been no production yet, two industry sources said Chevron did not give details of reserves.

“As part of a continuous process of portfolio evaluation and business prioritisation, Chevron Nigeria Limited … has put forward its interests in two oil mining leases for auction,” a company spokesman said.

“The assets are located in the shallow waters.”

Chevron owns a 40 percent stake in 13 shallow water blocks with Nigeria’s state oil firm NNPC and also has several deep offshore assets. Its 2012 net daily production in Nigeria averaged 238,000 barrels of crude oil and 165 million cubic feet of natural gas.

Several oil majors have sold assets onshore or in the shallow waters of the Niger Delta over the past few years.

Nigeria suffers from widespread oil theft and at times difficult relationships with local communities onshore, driving up the costs of operating there, while a long-delayed energy bill is stuck in parliament, adding to industry uncertainty.

Joint owners Royal Dutch Shell, Italy’s Eni and France’s Total have sold several blocks.

Buyers of these included UK-listed firms Heritage Oil and Eland Oil. Chinese-owned Addax has said it is interested in buying more Nigerian assets.

Chevron’s blocks are at the exploratory stage, unlike Shell’s already producing fields, which will make valuations less straightforward, one banking source said.

U.S. firm ConocoPhillips is also planning to sell its Nigerian businesses to Oando Energy for about $1.79 billion, the company said in December.

Oil majors, which are looking more towards deepwater offshore, say they can’t invest in large new projects until the oil bill is passed.