The well was completed on 5 November 2014, reaching a total depth of 8,770 ft (2,673 metres), and encountering several hydrocarbon-bearing horizons. Having initially acquired a 5 per cent interest in the Project, following subsequent acquisitions Alba now has a 15% shareholding in Horse Hill Developments Limited ("HHDL").
HHDL is a special purpose company that owns a 65% participating interest and is the operator of the licence area, comprising Production and Exploration Development Licences (PEDL) 137 and 246 ("Horse Hill or the "Licence Area"). The remaining 35% participating interest in the Licence Area is held by Magellan Petroleum Corporation (NASDAQ: MPET). As such, Alba owns an effective economic interest of 9.75% in the Horse Hill Project.
On 11 May 2015 Alba announced that the calculated estimates by Xodus Group (“Exodus”), an independent international energy consultancy based in the UK, showed that the Upper Portland Sandstone conventional reservoir contains a "Best Estimate" (P50) gross oil initially in place (“OIIP”) of 21.0 million barrels ("mmbbls") entirely within PEDL137 and incorporating both the HH-1 and CF-1 wells. Alba had initially announced a gross OIIP of 3.1 mmbbls (P50) in the Upper Portland Sandstone on 24 October 2014, which was then upgraded to 8.2 mmbbls (P50) on 17 December 2014.
In August 2015, Schlumberger provided HHDL with an independent report of the estimated oil in place contained within the licence area. The calculated gross OIIP at Horse Hill was 10,993 mmbbls, and is composed of 8,262 mmbbls within tight limestones and shales of the Kimmeridge Clay Formation, and 2,731 mmbbls associated with the shales of the Oxford Clay and Lias Formations.
In Q1 2016 work a flow test was carried out from the HH-1 Upper Portland conventional oil pool and the Upper and Lower Kimmeridge limestones in order to assess the recoverable volume of oil. The final total aggregate stable dry oil flow rate from two Kimmeridge limestones plus the overlying Portland sandstone was recorded at 1688 bopd. Over the 30-90 hour flow periods from each of the three zones, no clear indication of any reservoir pressure depletion was observed. The final Portland test of 323 bopd, over an 8.5 hour period is the highest stable dry oil flow rate from any onshore UK Portland well. The stable, natural dry-oil flow rate of 464 bopd from the Lower Kimmeridge Limestone is the first ever flow from this rock unit in the Weald Basin and onshore UK. Based on the analysis of published reports from all significant UK onshore discovery wells, the 901 bopd from the Upper Kimmeridge zone is likely the highest stable natural dry oil flow rate from a single reservoir in any UK onshore new field wildcat discovery well.
High quality Brent Crude was produced: light, sweet oil (40 degrees API in Kimmeridge, 35-37 degrees API in Portland), with 1,940 barrels delivered to the Esso Fawley refinery. Preliminary analysis confirms that the Lower and Upper Kimmeridge Limestone units are naturally fractured reservoirs with high deliverability. There is a strong possibility for further optimisation and increased flow rates from all three zones in future development and production wells, particularly through the use of horizontal wells.
The most recent Xodus calculation (February 2017) for Portland sandstone P50 Oil in Place (OIP) is 32 million barrels, a 53% increase on previous calculations. The base case Portland initial oil rate was estimated at 350 barrels of oil per day per well. Ultimate recovery could be increased by a further 8-14% of OIP via implementation of a water re-injection scheme.
Regulatory consents are now awaited for the start of long-term production testing at Horse Hill, with the aim of moving towards a declaration of commerciality and stable long-term production from the Portland and Kimmeridge by the end of 2018.
Horse Hill 1 Well Site during drilling (Summer 2014)
Licence Map of Weald Basin Showing PEDL 137 / PEDL 246 Horse Hill Licence Area