At least 10 billion barrels of potential oil in place is thought to lie in the Horse Hill shale license area in the south of the country, a British group said.

U.K. Oil and Gas Ltd. said an independent assessment from oil services company Schlumberger found a mean 10.9 billion barrels of oil in pace in a 55 square-mile area of the Horse Hill basin.

U.K. Oil and Gas Chairman Stephen Sanderson said the independent analysis predicts "significant" oil volumes and gives further support for development plans.

The company early this year said the reserves at Horse Hill are in shale beds that are fractured naturally, meaning extraction may be carried out using conventional techniques.

The discovery at Horse Hill comes as the country contemplates the future of North Sea oil fields. Operating expenses in the North Sea are up 8 percent while revenues for oil companies working in the region are at their lowest levels since 1998.

Sanderson said the company expected to recover as much as 15 percent of the oil in Horse Hill, which he said would translate to the 2030 equivalent of 30 percent of the nation's oil demand.

Schlumberger, the world's largest oilfield services provider, is acting as the sole adviser to UKOG on the Horse Hill prospect. In a separate statement, the services company said it was acquiring oilfield equipment maker Cameron International Corp. in a $14.9 billion deal.

Schlumberger Chairman Paal Kibsgaard said the acquisition reflects the need to transform amid the upheaval in the exploration and production sector, which is depressed in the weak crude oil market.

The British shale oil and natural gas sector is in its infancy. Advocacy groups expressed alarm over the discovery at Horse Hill, saying UKOG will face stiff opposition from environmentalists concerned about shale development in the country.