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.
Termination geometries and reservoir properties of the Forties Sandstone pinch-out, East Central Graben, UK North Sea
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Published:January 01, 2015
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CiteCitation
Akio Nagatomo, Stuart Archer, 2015. "Termination geometries and reservoir properties of the Forties Sandstone pinch-out, East Central Graben, UK North Sea", 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
As hydrocarbon-prone basins mature through time, stratigraphic traps become increasingly important as hosts for yet-to-find reserves. Explorationists strive to reduce the uncertainty in reservoir distribution and quality, but considerable complications exist in the evaluation of stratigraphic traps owing to the inextricable links between stratigraphy, trap definition and their subsequent risking. This study quantifies the relationships that exist between reservoir geometries and the rates of reservoir property degradation in a turbidite sandstone pinch-out zone. The investigation focuses on the Paleocene Forties Sandstone Member of the Everest and Arran fields of the East Central Graben of the UK North Sea. We utilized standard seismic interpretation techniques and integrated stratigraphic and petrophysical analysis of wireline log data to map deep-water turbidite sandstone terminations and develop a predictive model for reservoir property changes close to the feather edge. The Forties Sandstone Member thins systematically up on to a palaeoramp on the eastern basin margin of the Central Graben. Results reveal that the net reservoir sandstones pinch out after the turbidite flows had traversed 5 km across the palaeoramp. The gross interval is predicted to completely terminate 6.4 km up the palaeoramp. The reservoir properties decrease in concert with the thinning trend in the wedge zone as a function of the interaction of palaeotopography and the hydraulics of the decelerating flows. The inclination of the counter-regional slope is considered to be a key controlling factor that determines the rate of thinning and thus the termination position of the sandstones and their concomitant reservoir property decline. The results of this study demonstrate that characterization of pinch-outs into distinct zones based on a palaeotopographic template can be of utility in stratigraphic and combination trap definition. This work also has wider implications for prospect risking, volumetric analysis, the population of properties and geological modelling of stratigraphic traps.
- Atlantic Ocean
- case studies
- Cenozoic
- Central Graben
- clastic rocks
- correlation
- Ekofisk Formation
- Europe
- geometry
- geophysical methods
- geophysical profiles
- geophysical surveys
- isochrons
- mapping
- North Atlantic
- North Sea
- oil and gas fields
- paleocurrents
- paleorelief
- petroleum
- petroleum exploration
- physical properties
- quantitative geomorphology
- ramps
- reflection methods
- regional
- reservoir properties
- reservoir rocks
- sandstone
- sedimentary rocks
- seismic methods
- seismic profiles
- stratigraphic traps
- stratigraphic wedges
- stratigraphy
- surveys
- Tertiary
- thickness
- traps
- turbidite
- United Kingdom
- well-logging
- Western Europe
- Everest Field
- Sele Formation
- Jaeren High
- Forties Sandstone Member
- Arran Field