Successful onshore UK wells are relatively rare, so the Horse Hill discovery, located in onshore UK block PEDL 246 in the Weald Basin, about 50 km south of London, has created quite a stir. The well was drilled in late 2014, but testing has only recently been completed, and has proved Horse Hill to have considerable potential. In March 2016, the Horse Hill Development Ltd (HHDL) partners reported successful testing a 31.4m zone in the Late Jurassic Portland Sandstone, with 37° API oil flowing to surface at 323 bopd. The partners had previously reported successful testing from a 26.8m zone in the Late Jurassic Upper Kimmeridge Limestone and from the Late Jurassic Lower Kimmeridge Limestone, with 40° API oil recovered from both.
Log analysis of Horse Hill 1 had identified 156m net pay with potentially 277 MMbpkm2 oil originally in place (OOIP) within the Kimmeridge clay, mostly in three reservoir sections comprising interbedded argillaceous limestone and mudstone. A further untested play is the Jurassic Oxford Clay and Middle Lias Formations, and the resource is believed to extend beyond HHDL’s licenses, suggesting that the whole Weald Basin holds considerable potential. However, significant appraisal drilling will be required to satisfactorily evaluate the resource, with EOR techniques likely to feature. HHDL maintains that fracking will not be necessary but the experience of analogous plays in the US and Russia suggests that this cannot be ruled out. Since the area is relatively well populated and also part of the London ‘Green Belt’, any suggestion of fracking is likely to be very contentious.
These figures are in addition to conventional resources of 21 MMb OOIP (P50) within the Upper Jurassic Portland Sandstone, which the operator believes can be mapped across to the adjacent Collendean Farm structure 1.5 km to the north-west, which was drilled unsuccessfully by Esso in 1964.
PEDL 137 covers 99 km2 over block TQ/24b, and was awarded in October 2004 as part of the 12th Landward Licensing Round. Equity partners are Horse Hill Developments Ltd with 65% and Magellan Petroleum Corp with 35%.