The Arran Field contains gas-condensate accumulated within the Paleocene Forties Sandstone Member of the Sele Formation. It is located along the margin of the medial Forties turbidite depositional system, on the eastern flank of the Central Graben's Eastern Trough. The field comprises a low-relief southern extension (Arran South) from a high-relief northern closure (Arran North) around a salt diapir. The eastern margin of the field represents the pinch-out of the Forties Sandstone Member against the Jaeren High. As part of the field development planning, a comprehensive re-evaluation of subsurface data was undertaken. A thorough understanding of the reservoir distribution and turbidite architectures was vital to ensure that the appropriate elements were captured within the reservoir model. This was achieved through a thorough integration and multidisciplinary interpretation of all available data including seismic, core, petrophysical and analogue data. These data indicate that the best quality Forties Sandstone Member reservoir consists of stacked, elongate, amalgamated and non-amalgamated fairway sandstone bodies. These thick-bedded and sand-dominated reservoir units pass laterally into, and are extensively interbedded with, linked debrites, heterolithic low-density turbidite lobe fringe deposits, slumps, and debris flows, along with hemipelagic and turbiditic shales. A seismic shale volume (Vshale), derived from inverted pre-SDM data, together with reflection seismic data, were used to identify and map intra-reservoir depositional lobe geometries. These show large-scale, lobe-like depositional bodies which migrated laterally over time and onlapped on to the Jaeren High to the east. Within these, smaller-scale elongated lobe bodies, generally derived from the NW, are interpreted from layer-parallel extractions of the seismic Vshale volume. Possible slump units were also identified, predominantly derived from the edges of the Arran North salt diapir, suggesting that the basin floor topography was mobile during deposition. The seismic Vshale volume was used to condition the static facies model, utilizing probability relationships between the seismic data and core facies at the wells, providing a soft linkage between the data and models developed. Core, analogue data and facies interpretations from the seismic data were utilized to ensure that appropriate reservoir body geometries and spatial relationships were maintained in the static model and allowed key reservoir heterogeneities to be captured. This integrated approach also supported analysis of reservoir uncertainties, with specific focus on the vertical and lateral reservoir connectivity within this lobe-dominated reservoir.

Compared with the prolific success of the Triassic play in the East Irish Sea Basin (EISB) the lack of hydrocarbon discovery in neighbouring Permo-Triassic basins of the Irish Sea has been an enigma. However, recent exploration of the Peel, Solway and Central Irish Sea basins has provided new insights into the geology of these basins and the controls upon hydrocarbon prospectivity in the Irish Sea area. Regional seismic interpretation suggests that 12 of the 15 exploration wells drilled in the basins adjacent to the EISB tested valid structural closures at top Triassic reservoir level. Re-evaluation of the Irish Sea petrolemn system reveals that, although effective reservoirs occur in the Lower-Middle Triassic Ormskirk Sandstone Formation, and evaporites in the Middle-Upper Triassic Mercia Mudstone Group provide a regional top seal, the major factor controlling hydrocarbon prospectivity is the limited presence of effective source rocks in the underlying Carboniferous section. A further control upon prospectivity is the timing of hydrocarbon migration, from those areas where Carboniferous source rocks were deposited and preserved. The Namurian basinal marine oil-and gas-prone shales, which form the principal source of hydrocarbons for the Triassic play in the EISB, are restricted to an east-west fairway extending from the EISB into the Kish Bank Basin. Rocks of this age are absent from the Peel and Solway basins as a result of Variscan uplift and erosion. However, palaeogeographical reconstructions based on well and outcrop data suggest that, even if preserved, the depositional environment was not conducive to the formation of marine oiland gas-prone source rocks. Well and seismic data suggest that rocks of Namurian age were not deposited in the Central

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