(ShareCast News) - UK Oil & Gas Investments (UKOG) revealed on Monday that operations were finally starting at the Horse Hill site, with the extended flow test being conducted over three separate zones within the HH-1 discovery well by Horse Hill Developments Limited (HHDL).The AIM-traded energy form owns a 30% interest in Horse Hill Developments Ltd, and a 1.02% interest in HHDL via its 6% holding in Angus Energy Limited. UKOG described HHDL as a special purpose company that owns a 65% interest and operatorship of licences PEDL137 and PEDL246 in the UK Weald Basin.It said the extended flow test was designed to test both the oil-bearing Upper Portland sandstone, and two Kimmeridge limestoned beneath the Portland."We look forward to safe and successful operations, and the project moving forward", said UKOG executive chairman Stephen Sanderson.The HH-1 discovery well, which was drilled at the end of 2014, is located within exploration licence PEDL137 on the northern side of the Weald Basin near London Gatwick Airport.