Footwall uplift and erosion during Jurassic rifting: Scott and Telford fields, Outer Moray Firth, UK Central North Sea

Abstract

As producing fields enter late life, successful mitigation of subsurface risk is critical in order to justify continued infill well drilling. Despite penetrations by more than 100 wells and the availability of modern 3D seismic across the Scott and Telford fields (Outer Moray Firth, UK Central North Sea), reservoir absence has led to repeated development well failures. A new model now attributes reservoir attenuation to Late Jurassic footwall uplift and erosion. The 2015 Scott J40 well encountered a reduced Upper Jurassic reservoir section of Lower Scott sands, with Upper Scott and Piper sands absent. Reinterpretation ascribed reservoir truncation to the effect of Late Jurassic footwall uplift and erosion rather than fault cut-out as previously interpreted. The failed 2016 Telford F6 well was shown to have drilled a thick Kimmeridge Clay hanging-wall section north of the Telford Fault, rather than the southern footwall section targeted. Planning for the Scott J43 and four subsequent wells implemented lessons learned from these failures and mitigated reservoir risk while optimizing reserves. The Scott and Piper sand distributions are likely to reflect early growth folding before the main Mid-Kimmeridgian–Early Tithonian phase of NE–SW extensional faulting and footwall uplift, which saw the Piper and Scott reservoirs eroded at footwall crests and locally reworked as deep-water Claymore sands. Later Mid-Tithonian–Early Berriasian east–west faulting during the opening of the Witch Ground Graben saw major crestal synsedimentary erosion at Telford and continued erosion at the western crest of Scott Block 1b, while the footwall to the east was partially downfaulted.