The Victory gas field, West of Shetland

Abstract

The Victory gas field is located 48 km northwest of the Shetland Isles, in UKCS Block 207/la. The structure was first drilled in 1977, the discovery well 207/1-3 encountering 224 ft (68 m) of gas-charged Lower Cretaceous sandstone at a subsea depth of 4144 ft (1263 m). No gas-liquid contact was recorded in the well. Five wells have been drilled on the Victory trend to date with the most recent, 207/la-5, being drilled in 1996. The Victory Field was originally mapped with 2D seismic data as a structural high associated with a rotated fault block. In 1996, 3D seismic data were acquired over the area as part of a Shelloperated group-shoot and the improvements in resolution and data quality have prompted a re-evaluation of the field. The 3D seismic data have demonstrated that the Rona Ridge and the linked West Shetland Basin in this area have undergone a complex geological history with multiple phases of Cretaceous tectonism. The structural elements that affect trap configuration and reservoir sand distribution are related to faulting which follows both a NE-SW Caledonian trend and an offsetting NW to SE fault trend. The reservoir is of Early Cretaceous (Late Aptian-Late Albian) age and comprises shallow to marginal marine sandstones and conglomerates overlying Precambrian basement. Reservoir quality is consistently high. Geochemical analyses of both gas and oils encountered within the Victory field area have been undertaken and tied both to basin-scale modelling of the petroleum system and structural mapping at a field-scale. These studies demonstrate the complex, multi-phase charge and alteration history of the trapped hydrocarbons of the Victory Field.

Thermal history and oil charge on the UK Atlantic margin

“…This appears to be a mixture of a degraded and a fresh oil, respresented by the complex mixture and the well-defined n-alkanes, respectively. Other published organic geochemical data for oils from the West of Shetland region also show evidence for mixture from two sources, believed to be Kimmeridgian (late Jurassic) and mid-Jurassic (Scotchman et al 1998;Goodchild et al 1999).…”

“…Models for oil charge in the West of Shetland region include (1) temporary residence in Mesozoic reservoirs followed by remigration into the Paleocene ('motel' model of Lamers & Carmichael 1999); (2) overpressure build-up in Cretaceous sandbodies followed by hydraulic fracturing and leakage into the Paleocene (Iliffe et al 1999); and (3) direct migration into the Paleocene due to overpressure retardation of hydrocarbon generation (Carr & Scotchman 2003). Evidence from organic geochemistry (Scotchman et al 1998;Holmes et al 1999;Goodchild et al 1999), basin modelling (Jowitt et al 1999) and fluid inclusion petrography (Parnell et al 1998) indicates that more than one oil generation is present.…”

An overview of the Upper Palaeozoic–Mesozoic stratigraphy of the NE Atlantic region

“…The Cretaceous succession was deposited in a synrift setting (Dean et al 1999). The Lower Cretaceous sequence is largely confined within the various basins and sub-basins, with the thickest accumulations juxtaposed against the footwall of the adjacent basement/intrabasinal high (Dean et al 1999;Grant et al 1999;Goodchild et al 1999;Lamers & Carmichael 1999;Ritchie et al 2011bRitchie et al , 2013 (Fig, 14a, d). The Upper Cretaceous sequence is more widely developed and by the end of the Cretaceous period most of the major basement highs, including the Rona High, had been isolated or drowned (Dean et al 1999;Stoker & Ziska 2011).…”

“…The Upper Cretaceous sequence is more widely developed and by the end of the Cretaceous period most of the major basement highs, including the Rona High, had been isolated or drowned (Dean et al 1999;Stoker & Ziska 2011). In the Faroe -Shetland region, an angular unconformity separates folded and eroded Turonian and older strata from Coniacian -Maastrichtian rocks in the West Shetland, North Rona, East Solan and West Solan basins, as well as the Foula Sub-basin (Booth et al 1993;Dean et al 1999;Goodchild et al 1999;Grant et al 1999;Stoker 2016). In other West Shetland Shelf basins, much of the Cenomanian -Turonian section is absent, and the unconformity essentially separates Upper and Lower Cretaceous (Fig.…”

Evolution of hydrocarbon migration style in a fractured reservoir deduced from fluid inclusion data, Clair Field, west of Shetland, UK

“…Cross-section indicating the main geological features in the region around the Clair Field and a fluid flow model demonstrating features of hydrocarbon migration and diagenetic histories during Tertiary times (geology adapted fromMeadows et al, 1987;Hitchen and Ritchie, 1987;Goodchild et al, 1999).…”