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Durham University

Department of Earth Sciences

Profile

Publication details for Prof Ken McCaffrey

McCaffrey, K.J.W. , Holdsworth, R.E. , Pless, J. , Franklin, B.S.G. & Hardman, K (2020). Basement reservoir plumbing: Fracture aperture, length and topology analysis of the Lewisian Complex, NW Scotland. Journal of the Geological Society

Author(s) from Durham

Abstract

Upfaulted ridges of Neoarchean crystalline basement rocks formed in the Faeroe-Shetland basin as a consequence of Mesozoic rift processes and are an active target for oil exploration. We carried out a comprehensive fault and fracture attribute study on the extensive exposures of geologically equivalent crystalline basement rocks onshore in NW Scotland (Lewisian Gneiss Complex) as an analogue for the offshore oil and gas reservoirs of the uplifted Rona Ridge basement high. Our analysis shows a power-law distribution for fracture sizes (aperture and length), with random to clustered spacing, and high connectivity indices. Regional variations between the Scottish mainland and the Outer Hebrides are recognised that compare directly with variations observed along the Rona Ridge in the Faeroe-Shetland basin. Here we develop a model for the scaling properties of the fracture systems in which variations in the aperture attributes are a function of the depth of erosion beneath the top basement unconformity. More generally, the combination of size, spatial, and connectivity attributes we found in these basement highs demonstrates that they can form highly effective, well plumbed reservoir systems in their own right.