Detailed mapping of marine erosional surfaces and the geometry of clinoforms on seismic data: a tool to identify the thickest reservoir sand

Abstract

ABSTRACTDeltaic sediments of the Billund and Bastrup sands were deposited in a ramp setting in the storm‐dominated North Sea during the early Miocene. A marked relief in the hinterland and the relatively high precipitation resulted in a high sediment supply to the sea and progradation of major delta‐coastal plains south of the present‐day Norway. The focus of this study is on the forced regressive wedge system tracts of the two delta complexes, which show remarkably well‐developed marine erosional surfaces associated with sand‐rich packages characterised by steeply dipping clinoforms (up to 10°). The well‐developed clinoformal packages indicate that deposition occurred in water depths of 60–100 m even under a sea‐level fall. The sand‐rich delta lobes also demonstrate that it was a high‐energy environment and that wave‐generated re‐suspension at the delta front effectively re‐sorted the sediments and sand‐rich systems became separated from mud‐dominated portions of the delta complexes. The evolution of the above occurred in a basin that has been exposed by inversion tectonism. The sediment supply was consequently high. During deposition, eustatic sea‐level changes strongly controlled the evolution of sequences. The results found in this study may be applicable for mapping reservoir sands in ramp settings and in rift basins especially when looking for reservoir rocks in the basinal setting or when carrying out detailed reservoir mapping in already existing hydrocarbon fields.