Abstract The Schiehallion subsea development comprises two fields, Schiehallion and Loyal, which are located approximately 200 km to the west of the Shetland Islands in the UK Continental Shelf. The Schiehallion and Loyal fields were discovered in late 1993 and 1994, respectively, with a combined oil-in-place of more than 2.3 Bbbl. The fields are developed under waterflood and were on production from 1998 to 2013. After an extended shut-in, the fields were brought back on line in 2017, through new floating production facilities. Most of the production to date has been from the Paleocene Vaila Formation deep-water turbidite, in the T31 and T34 reservoir intervals. The ongoing Quad 204 redevelopment drilling programme commenced in April 2015, has drilled and completed 21 wells to date, and is expected to continue for several more years. The campaign includes new producer–injector pairs and stand-alone wells to support existing well stock, targeting stacked turbidite reservoir intervals, including the youngest T35–T34 interval, the main T31 interval and the previously under-developed T28–T25 fairway. In addition to an active drilling programme, a 4D seismic survey was acquired and processed in 2018, and its interpretation is key to unlocking further potential sources of value in this mature field.

Abstract The Solan Field is a Jurassic reservoired oil accumulation located in Block 205/26a in the East Solan Basin, West of Shetland. The field was discovered in 1991 by the 205/26a-4 well which encountered oil in the Kimmeridgian to Early Volgian age Solan Sandstone and appraised between 1992 and 2009 by four wells and four sidetracks. Premier Oil farmed into Licence P.164 in 2011 and became operator. The reservoir, which is up to 100 ft thick, is a basin-floor turbidite sequence and is informally subdivided into a thick and good quality Upper Solan sandstone unit and a thinner, poorer quality, Lower Solan sandstone unit, separated by the laterally extensive Middle Solan unit. Whilst the reservoir sandstones are relatively clean (texturally and compositionally mature) and laterally extensive, sub-seismic structural and stratigraphic complexity resulted in a challenging field development. The field development to date comprises four subsea wells (two oil producers and two water injectors) tied back to a small jacket and topsides with an innovative subsea oil storage tank. Oil export is via shuttle tanker. First oil was achieved in April 2016. The field oil in place volume is in the range of 55–85 MMbbl.