The Jurassic shales of southern England's Weald basin could hold between 2.2 billion and 8.5 billion barrels of oil resource but no gas, the UK government said Friday in a new report.
The Department of Energy and Climate Change also launched a consultation on plans to simplify underground access for shale and deep geothermal projects.
The new report, compiled by the publicly funded British Geological Survey, found no shale gas potential in the Weald basin but gave 4.4 billion barrels as a "reasonable central estimate" of shale oil resources.
It gave no estimate of recoverable reserves, which it said would need more drilling.
Oil saturation levels in the Weald basin shales are "low when compared to shale oil producing areas in North America," the report said.
"However as there are shallower conventional oil fields in the Weald basin this would suggest that there are optimum conditions for oil generation in some areas within the basin," it added.
The latest report follows a similar study last year of the Bowland-Hodder shales in northern England, which gave a central estimate for gas resources of 37.6 trillion cubic metres (1,329 trillion cubic feet).
The government is promoting UK shale as a way of offsetting declining offshore production, including through tax incentives, but has faced protests from environmentalists.
The actual level of potential production remains unclear as operators continue to test drilling techniques.
Campaign group Greenpeace condemned the government's latest efforts to provide easier underground access for shale drillers.
"Stripping away people's property rights while trying to kick off a Klondike-style shale oil rush in the Home Counties is a highly toxic policy mix," said Greenpeace UK energy campaigner Lawrence Carter. "Dangling larger bribes in front of communities won't quell their deep concerns about fracking," he added.
The government proposes to simplify current rules on gaining permission for shale activity, introducing instead a "clear notification system" and a "voluntary community payment" of GBP20,000 ($34,000) per lateral well, DECC said.
Current rules "are costly, time consuming and disproportionate for new methods of underground drilling," it said.
The UK's nascent onshore shale industry is being mostly led by smaller companies. BP and Shell have both said they do not plan to get involved.
France's Total however has bought into shale licences held by smaller operators, as has UK energy company Centrica.
