Applications of High Resolution Sequence Stratigraphy in North Sea Syn-Rift Reservoir Correlation and Development: ABSTRACT

Abstract

Tectonically active basins may host a spectrum of sequence stratigraphic expressions previously considered to be spatially mutually exclusive. In low accommodation areas with high sediment supply, fourth order eustatic cyclicity results in high frequency sequence sets while within rapidly subsiding areas, time-equivalent Type-2 sequences are expressed by highly asymmetrical coarsening upward successions, resembling large parasequences. In the shallow marine Fulmar Formation, of the U.K. North Sea Central Graben a sequence boundary and overlying lowstand deposits, which illustrate the effects of laterally variable subsidence rate and intrabasinal topography on the expression of a eustatic sea-level fall, lie between the Glosense and Serratum (J54a and J54b) maximum flooding surfaces. The syn-rift physiography comprises major tilted fault blocks, with the Central Graben dipping parallel to the major faults, simulating a ramp setting. Where the throw of the faults were greatest (SE), the structure acted as a local shelf-slope break. Adjacent to the basin margin, incised valley were cut at fluvial input points (structural transfer zones) and laterally, interfluvial sequence boundaries developed. During early lowstand, sand bypassed the footwall shelf and was deposited as lowstand fan sediments within the deepest part of the hangingwall, with the fault zone acting as a local shelf slopemore » break. Within the shallower water areas of the hangingwall a localised ramp geometry existed parallel to the fault zone. Forced regression deposits developed here were coeval but not physically related to the deep water lowstand turbidite fan deposits.« less