Seepage Slick Calibration of Seal Bypass Systems and Vice Versa

Dedicated: Fluids & Flow - This paper presents an overview of calibrated subsurface plumbing systems in a salt diapir/minibasin setting (West Africa) based on the integration of 3D seismic data and sea surface satellite imagery. Salt structures on the middle slope serve a dual purpose as trap and leak-forming features, with traps focused on the down-dip side of overhanging diapirs and leaks located on the updip sides and flanks where strata are deformed and inclined with vertical relief exceeding two kilometres. Associated subsurface leakage phenomena include gas and gas hydrate accumulations, seal bypass systems including pockmarks, pipes and faults, depending on the structural configuration of the aquifers and aquitards defining the stratigraphically concordant parts of the plumbing system. Our analysis suggests that seismically defined seal bypass systems (pipes, pockmarks, BSRs) can be linked to seepage slicks of various degrees of confidence ranging from 99% confidence to no observed slicks, which may be explained by discontinuous seep activity or by pure gas seeps. Interpreted seepage slicks of moderate confidence may variously be underlain by well defined seal bypass systems, pockmarks with no discernible fluid migration paths, or have no bottom or sub-bottom expression at all.