Turkmenistan, holder of the world’s fourth-largest gas reserves, is seeking bids from foreign producers to develop untapped Caspian Sea deposits as Europe, Russia and China compete for supplies.

The government is discussing investment in offshore blocks directly with several international producers, Acting Energy Minister Bairamgeldy Nedirov said last week in Abu Dhabi, declining to name the companies. KazMunaiGaz National, Kazakhstan’s state oil company, said it may bid.

“Russian and Asian companies are most likely to show an interest in new offshore acreage, along with some Western independents,” Julian Lee, senior energy analyst at the London-based Center For Global Energy Studies, said in an e-mail. “Offshore blocks will be of less interest than onshore opportunities, which remain off-limits to foreign investors.”

Turkmenistan, where foreign investment was held back until the 2006 death of isolationist President-for-Life Saparmurat Niyazov, ships gas to Russia and Iran and opened a pipeline to China last year. The European Union, seeking less reliance on Russia, wants Turkmen gas for the proposed Nabucco pipeline, although plans to build a link across the Caspian Sea have been frustrated by unresolved marine borders.

International oil companies such as Chevron, BP and Royal Dutch Shell have sought access to the country’s inland gas resources, while spurning less explored offshore deposits. Only China National Petroleum Corp. has succeeded in signing an onshore production-sharing agreement in 2007 to develop the Bagtyyarlyk area near the Uzbek border.

BASF’s Wintershall unit, operator of two offshore blocks, has informed the Turkmen authorities that it’s going to surrender the project because “the exploration potential is too low,” Stefan Leunig, a spokesman for the company said Thursday. Dubai-based Dragon Oil, developing the Cheleken area, missed a 15 percent production growth target last year, the London-listed explorer said Jan. 22.

Turkmenistan has five offshore production-sharing agreements with foreign producers in its part of the Caspian, including Itera and Malaysia’s state-owned Petroliam Nasional.

Turkmenistan now offers only service contracts to its onshore reserves, which include South Yolotan-Osman, one of the world’s largest untapped gas deposits.

KazMunaiGaz is studying the offshore blocks and may bid, chief executive Kairgeldy Kabyldin said in Abu Dhabi. Kazakhstan’s sector of the Caspian Sea is home to the Kashagan development, its biggest oil deposit by reserves. “Over the next five years Turkmenistan will be offering more offshore fields because they can’t tap them on their own,” said Alexei Kokin, an oil analyst at Metropol. “They are a little late on offshore compared with Kazakhstan.”

CNPC and South Korea’s LG International won service contracts for as much as $9.7 billion for South Yolotan in December. They got no stake in the field’s reserves or output.

U.S. and European oil companies such as Exxon Mobil and BP have yet to agree to a major investment in Turkmenistan. Chevron is interested in onshore projects as a partner, not a service contractor, said Douglas Uchikura, head of the company’s operations in the Central Asian country.