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Portland Oil discovery, Horse Hill-1, Weald Basin UK

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Oilfield Technology,

UKOG has announced that, following preliminary evaluation of the electric logs, the Horse Hill-1 well has discovered an oil accumulation in the conventional Upper Jurassic Portland Sandstone at a top reservoir depth of 1791 ft TVD.

A preliminary most likely estimate of 3.1 million bbls of gross in place hydrocarbon volume has been calculated within the upper Portland, with a further gross unrisked in place prospective hydrocarbon volume of 16.8 million bbls of oil in a separate lower sand in the Portland interval located in an untested fault block to the south. As previously announced, the well is being deepened to the Triassic where an additional target, believed to have potential for gas, is expected to be reached in the next two weeks.

The Portland Sandstone was previously reported on 16 October 2014 to have oil shows in cuttings and elevated gas readings whilst drilling and these indications have been confirmed by independent petrophysical analysis of the electric logs acquired in the well during the last week.  Further analysis is continuing to establish the recoverable volume of oil that has been discovered.

David Lenigas, the Company's Chairman, commented:

"We are very pleased with the results so far from this well. The presence of a larger, unappraised, Portland feature creates considerable further upside.  We are now looking forward to drilling the Triassic, which is a new and untested exploration target in the area and which, if successful, may contain appreciable volumes of gas."

UKOG interest in Horse Hill

The Horse Hill-1 well is located on the northern side of the Weald Basin near Gatwick Airport. UKOG owns a 20% direct interest in Horse Hill Developments Ltd and an additional 2.4% interest in HHDL by virtue of its 6% ownership in Angus Energy Limited. Angus Energy owns 40% of HHDL. HHDL is a special purpose company that owns a 65% participating interest and operatorship of onshore licences PEDL 137 and the adjacent licence PEDL 246 in the UK Weald Basin. The participants in the Horse Hill-1 well are HHDL with a 65% working interest and Magellan Petroleum Corporation with a 35% interest. UKOG's net attributable interest in PEDL 137 and 246 is therefore 14.56%.

Additional analysis:

The upper Portland Sandstone reservoir, which produces at the nearby Brockham oil field, was also intersected by the Collendean Farm-1 exploration approximately 790 m north of the Horse Hill-1 well.  Using the solely available 2D seismic data and the well results, the operator has mapped an area of closure of approximately 3.8 km2 where the Portland Sandstone is above the observed oil down to at a depth of 1901 ft TVD. The presence of two wells within the same mapped structural closure significantly increases the confidence in a commercial discovery and there is every indication that the Portland reservoir can be developed as a commercial oil field.

The gross oil bearing upper Portland Sandstone interval in Horse Hill-1 measures 102 ft, has an average porosity of over 16% and average oil saturation is estimated as 36%.  Based on regional and local trends, confirmed by wells at Brockham, these reservoir parameters indicate a high likelihood of production at commercial rates.  The equivalent interval in the Collendean Farm-1 well, drilled by Esso in 1964, shows similar reservoir characteristics over a 97 ft gross interval.  The gross oil column contained within the Horse Hill-Collendean Farm structure is in excess of 140 ft.

The lower Portland Sandstone reservoir, which is seen to be water wet in Horse Hill-1 and Collendean Farm-1, lies above the oil down to in an untested fault block to the south of the Horse Hill-1 well and is interpreted to contain an unrisked most likely in place gross oil volume of 16.8 million bbls.

The Corallian Sandstone and Great Oolite targets in the Horse Hill-1 well are not seen on electric logging to contain moveable hydrocarbons, however, further evaluation of several thick Kimmeridgian-age limestones, which had hydrocarbon shows and elevated mud gas readings whilst drilling, may provide additional oil potential within the well.

Adapted from a press release by David Bizley

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