A British company tapping into inland shale oil basins said oil was flowing to the surface at a natural rate fast enough to yield obvious commercial potential.

U.K. Oil & Gas Investments said oil was moving to the surface freely from the Kimmeridge reserve area of the Horse Hill shale basin at more than 900 barrels per day.

Executive Chairman Stephen Sanderson said the latest test results provide "unequivocal proof" that oil can be pulled from the Horse Hill shale at commercial rates.

"This result is therefore very significant for the company and the Weald basin of the United Kingdom," the company said in a statement. "The Kimmeridge play has moved from science project into the zone of commercial reality."

Preliminary estimates made by the company last year put the entire Horse Hill reserve total as high as 100 billion barrels of oil. Sanderson said the company expected to recover as much as 15 percent of the oil, which he said would translate to the 2030 equivalent of 30 percent of the nation's oil demand.

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

The future of British energy is uncertain given the downturn in the global oil sector and maturation of fields in the North Sea. Oil & Gas U.K., the industry's lobbying group, said the North Sea oil sector is in for a long period of decline, with less than $1.4 billion in new spending expected in 2016.

Total British oil and liquids production increased 12.8 percent because of new production and fewer shutdowns attributed to maintenance activity. Nevertheless, the country remained a net importer of petroleum products.