Horse Hill Development (HHD), a London-based consortium, discovered an oil pay zone at the Horse Hill-1 well in southern England Friday.
The well encountered a conventional Upper Jurassic Portland Sandstone reservoir at a depth of 1,791 feet.
Preliminary estimates place reserves at 3.1 million barrels of gross in place hydrocarbon volume in the upper Portland sandstone reservoir.
The oil bearing interval measures 102 feet and has an average porosity of over 16 percent with average oil saturation estimated at 36 percent.
HHD estimates a further gross unrisked in place prospective hydrocarbon volume of 16.8 million barrels of oil in a separate lower sand area of the Portland interval in an untested fault block to the south of Horse-1.
Further analysis is being conducted to establish recoverable volumes at the discovery.
The well is being deepened to the Triassic to target a potential gas reservoir.
The target is expected to be reached in the next two weeks.
Horse Hill-1 is located on the northern side of the Weald Basin near Gatwick Airport on the border between Surrey and Sussex in onshore licence PEDL 137.
HHD holds a 65 percent operating stake in the PEDL 137 and the adjacent PEDL 246.
The consortium is comprised of UK-based companies Alba Mineral Resources, Regency Mines, Solo Oil, Stellar Resources, Doriemus, Angus Energy and UK Oil & Gas Investments.
Denver-based Magellan Petroleum Corporation has a 35 percent interest in Horse Hill-1.