Aileen E McLeod¹, John R Underhill¹, Sarah J Davies², Nancye H Dawers³

(1) The University of Edinburgh, Edinburgh, United Kingdom
(2) The University of Leicester, Leicester, United Kingdom
(3) Tulane University, New Orleans, LA

ABSTRACT: Exploration for Subtle Stratigraphic Traps in Extensional Basins: Insights from the Northern North Sea Hydrocarbon Province

Successful exploration for subtle stratigraphic traps in extensional settings requires a rigorous understanding of the facies mosaic and depositional architecture of syn-rift strata. Syn-rift sedimentation patterns are a record of the complex interactions between the rates of sediment supply and accommodation generation; hence, for the basin dynamics to be understood both these variables must be constrained.

We present structural, stratigraphic and sedimentological observations from a 2500 km2 area of the Late Jurassic northern North Sea rift. The subsurface dataset (comprising 3D seismic and wells) encompasses a number of major fault arrays of >100 km length with maximum displacements >2 km. Seismic stratigraphic techniques and fault scaling relationships are employed to constrain the temporal and spatial growth of the fault populations. From this, the generation of accommodation space due to tectonic subsidence can be quantified. These results are integrated with facies interpretations (based on observations from core samples), and the mapping of seismic stratigraphic sequences to constrain sedimentation patterns in the basin.

We demonstrate that fault displacement patterns controlled the loci of syn-rift deposition throughout the rift event. Sediment routeways in the basin were also strongly influenced by fault activity. In particular, channel migration into hangingwalls, axial sediment flux, and basin partitioning by footwall highs are observed. Two potentially significant subtle stratigraphic trap types are defined in the study area. (1) An early syn-rift play that exploits stacked fluvial sandbodies in small, fault-bounded depocentres. (2) A late syn-rift marginal marine and detached turbidite system sourced from the erosion of uplifted footwalls.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado