Undersea oil and gas off Cambodia's southern coast continue to drive the buzz surrounding the country's potential hydrocarbon windfall.

But inland petroleum reserves are beginning to also attract the attention of prospectors, as well as environmentalists concerned over the impact of drilling wells in some of Cambodia's most sensitive eco-systems.

Oil and gas exploration in the Tonle Sap basin, a vast swath of Cambodia surrounding the country's great lake, is in its infancy, with only one company - Medco Energi Global of Indonesia - confirmed as having been licensed for exploration.

Medco's international director, Grant Bowler, confirmed his company has the go ahead to explore in the Tonle Sap in a partnership with the Cambodian National Petroleum Authority, but declined to comment further.

But as energy majors from China, Australia and other countries line up for their shot at striking it rich in Cambodia's unproven inland petroleum fields, some warn of the need for extraordinarily strict policies for companies operating around the lake, which is home to a number of threatened bird and animal species, as well as the source of most of the country's fish.

“The government is just beginning to lease to the companies. [The environment] is not a big concern so far.”

– Neou Bonheur, Ministry of Environment

"Any single environmental violation - one fish dead - and you lose your license," said an independent oil expert familiar with Cambodia's fragile ecology, adding that drilling for oil and gas in the Tonle Sap should be based on "the most stringent environmental regulations of any basin in the world."

Others also said they were worried and would be watching progress in this area of Cambodia's energy sector very warily.

"We are concerned about it. Our mission is to coordinate the management, the conservation and then the development of the Tonle Sap Basin," said Sok Keang, deputy secretary general of the Tonle Sap Basin Authority, which was created last year by the Council of Ministers to study the area's "management, conservation and development."

Very little is known about the potential for oil and gas in the Tonle Sap Basin, which is bigger than the lake itself, making it likely that exploration will also take place on shore as well as under the water.

"The government is just beginning to lease to the companies. [The environment] is not a big concern so far," Neou Bonheur, deputy director of the Ministry of Environment, told the Post, adding that environmental impact studies would be conducted before each stage of exploration.

Two studies - for Medco and PGS, a global oil services company that focuses on geophysical services such as seismic data - have already been completed by the Bangkok-based company International Environmental Management (IEM), said the business's president and CEO Ron Livingston.

Studies from 2007 and this year showed that "none of the seismic lines are in protected areas," and that the vibrations that would be caused by seismic surveys are minimal.

IEM expects to conduct additional environmental studies for other oil companies in Cambodia, where it has worked in the sector since 1992, Livingston said.