Structural geometry, evolution, and subseismic-scale deformation in traps adjacent to salt walls/welds: Observations from Green Canyon, Gulf of Mexico

Well and seismic data are used to constrain the geometry of traps formed in folds adjacent to salt walls/welds in two deep water subsalt oil fields (Fields A and B) in the northern Gulf of Mexico, USA. The fields are combined structural-stratigraphic traps associated with minibasin-scale folds formed at the basin margin. Field A is adjacent to a megaflap fold with an overturned limb that changes abruptly from a thin to a thick sequence of Paleogene strata along trend. The lateral change in fold geometry occurs at an outward bend in the trend of the salt-sediment interface. Field B is a minibasin-scale fold without an associated megaflap and developed along a more linear salt-sediment interface. Middle to Lower Miocene reservoir sandstones in both fields are moderately dipping-to-overturned and pinch-out stratigraphically prior to intersecting the salt-sediment interface. Trap scale folding and variations in megaflap characteristics are interpreted as primary controls on subseismic deformation, comprising primarily of deformation bands (DBs) observed in core and image logs. Spatial distributions, orientations, and frequencies of DBs are documented from well data in Fields A and B and placed into the trap-scale context to consider their origin. One DB set trends parallel to the strike of the folds in both Field A and Field B and formed in response to bed-parallel shortening. The second set of DBs trends at a high angle to the fold strike and formed to accommodate a change in Field A fold geometry. Flow measurements, along with petrophysical characterization, are used to estimate the impact of DBs on subsurface fluid flow, which is then compared to observed flow measured during well-tests. Despite the high density of DBs throughout the fields, they only impact reservoir flow where both sets are present at a distinct change in Field A megaflap and reservoir geometry. •Seismic and well data are used to characterize subsalt oil fields in Green Canyon area of the northern Gulf of Mexico, USA.•3D characterization of the salt-sediment interface shows along-strike changes from an overturned thick to thin megaflap.•Sub-seismic deformation bands are characterized from new high-resolution wellbore images and whole core.•Changes in deformation band frequency and orientations are related to the trap-scale changes in fold geometry.•Production data and modeling indicates that deformation bands influence permeability only in specific structural positions.