Hydrothermal vents and seismic anomalies: implications for the petroleum system NE of Shetland

The influence of igneous intrusions and their associated vent complexes on hydrocarbon migration is poorly understood, yet may be significant in the exploration of petroleum basins located on passive margins. A regional review of the northeasternmost frontier sector of the UK Continental Shelf (UKCS) encompassing the southern extent of the More Basin has revealed evidence of extensive vent formation during the Late Paleocene. Anomalous seismic amplitude events that have not been previously described in this area are identified above and clearly related to several of the vent complexes, and a number of scenarios are postulated to explain their presence. Integrating existing geological studies and regional seismic interpretation with a new 3D seismic dataset reveals a close relationship between sills, vents and seismic anomalies which may be related to the presence of gas/fluid. Recognition of the vent complexes as potential fluid conduits long after initial formation may be important in focusing migration to younger stratigraphic levels. Important observations are made regarding a link to possible hydrocarbon migration mechanisms within the study area and the associated implications for hydrocarbon exploration and risking within this petroleum basin are investigated.