The search for a gas source near to Apache's Forties Field in the North Sea was motivated by the prediction of an ever-increasing fuel gas shortfall as the field oil rate declined. The Central North Sea is well known for a large number of shallow gas hazards in the Pleistocene section that have historically caused blowouts during exploration and development. These gas accumulations typically show up as small bright anomalies on seismic data. In 2009, a large gas anomaly was identified to the east of Forties, and the Aviat Field was discovered in 2010 when exploration well 22/7-5 was drilled.The Aviat Field reservoir is interpreted to be a subaqueous glacial outwash fan, consisting of silt-grade, rock flour material, deposited in front of a grounded ice sheet in some 400 m of water. Aviat sits on an overcompacted silty mudstone that was deformed by this ice sheet – the Crenulate Marker. The distribution of this horizon implies that the Early Pleistocene ice sheet covered at least the northern half of the UK North Sea.Although the Aviat reservoir is thin (2–9 m thick), the well tests, pressure profiles and geophysical response demonstrate that the reservoir is well connected, extensive (over 35 km2) with high deliverability (up to 18 MMscfd achieved). Aviat was sanctioned in 2014 for development as a fuel gas supply for the Forties Field, with first gas achieved in July 2016.

Ice sheets repeatedly advanced into the central North Sea, south of ~60°N, from 2.53 Ma ago onward moving over slippery beds with low slung profiles.

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The Forties Field, the largest oilfield in the UK North Sea, has been a prolific producer since its initial development. With an initial plateau rate of 500 000 bopd the field had produced some 2500 mmbo and the field rate had declined to 41 000 bopd by 2003 when the operatorship changed from BP to Apache. From 2004 to 2012, over 100 bypassed pay targets were drilled with a success rate of 75%, establishing a late life plateau of 50 000–60 000 bopd.The Forties reservoir is provided by Paleocene turbidites of the Forties Sandstone Member of the Sele Formation, deposited in a channelized proximal area of the Forties Fan. In this paper, the reservoir architecture is described, and bypassed pay examples are discussed in the context of the reservoir architecture and the production history. Bypassed pay is shown to occur in both the high net to gross channel axes and the heterogeneous wing deposits. Oil is trapped by subseismic channel architecture and subtle faulting. The occurrence of bypassed pay at a particular location is also shown to be dependent on the continually evolving pattern of injection and production within the field.