Tertiary Deep-Marine Reservoirs of the North Sea Region

Discovery of the Arbroath, Montrose and Forties fields initiated intensive exploration of the Tertiary deep-marine play in the North Sea region. Subsequent discoveries demonstrated the success of this play and the geological diversity of the depositional systems. The play is now mature and in many areas the remaining exploration potential is likely to be dominated by small, subtle traps with a major component of stratigraphic trapping. Economically marginal discoveries need an in-depth understanding of subsurface uncertainty to mitigate risk with limited appraisal wells. Mature fields require detailed geological understanding in the search for the remaining oil. This volume focuses on the regional depositional setting of these deep-marine systems, providing a stratigraphic and palaeogeographical context for exploration, and development case histories that outline the challenges of producing from these reservoirs. The fields are arranged around the production life cycle, describing the changing needs of geological models as the flow of static and dynamic data refines geological understanding and defines the nature of new opportunities as fields mature.
Arran Field: a complex heterolithic reservoir on the margins of the Forties Fan System Available to Purchase
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Published:January 01, 2015
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CitationJamie Collins, Steve Kenyon-Roberts, Brian Cullen, Jason White, Nathalie Bordas-Le Floch, John Downey, 2015. "Arran Field: a complex heterolithic reservoir on the margins of the Forties Fan System", Tertiary Deep-Marine Reservoirs of the North Sea Region, T. McKie, P. T. S. Rose, A. J. Hartley, D. W. Jones, T. L. Armstrong
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Abstract
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.
- Atlantic Ocean
- Central Graben
- cores
- correlation
- data integration
- depositional environment
- development
- distribution
- drill stem tests
- formation evaluation
- geometry
- geophysical methods
- heterogeneity
- lithofacies
- natural analogs
- North Atlantic
- North Sea
- oil and gas fields
- outcrops
- physical properties
- probability
- reservoir properties
- reservoir rocks
- seismic methods
- statistical analysis
- stratigraphy
- structural analysis
- theoretical models
- well-logging
- Sele Formation
- Jaeren High
- static models
- Forties Sandstone Member
- Arran Field