The 3D Geometry and Distribution of Sub-seismic Scale Halokinetic Unconformities: Implications for Salt Minibasin Evolution and Associated Reservoir Architecture

Abstract

Salt is recognised to laterally seal potential reservoir rocks adjacent to the flanks of salt walls. Halokinetic uplift and erosion of the flanks, coupled with salt withdrawal from, and subsidence of, the intervening areas, produces salt ‘minibasins’ with a sedimentary fill typically characterised by complex unconformities at sub-seismic scale. These relationships have received comparatively little attention at this scale, as they cannot be analysed from seismics alone, and therefore require the creation of models to aid interpretation of higher resolution sub-seismic components. I present an investigation in to the 3D geometry and distribution of well-exposed, salt-related unconformities from the Salt Anticline Region of Utah, USA, at sub-seismic scale, with the intention to follow this work up with further observations looking into the larger scale regional differences present, after creating 3D models from previous fieldwork using detailed terrestrial photogrammetry. These demonstrate that salt-induced unconformities are strongly 3D in geometry and restricted spatially, especially in relation to the ends of salt walls and zones of salt-wall overlap. This study has wider implications for the evolution of halokinetically controlled basins, and interpretation of their fill at sub-seismic scales. I apply these models to the Melville Basin of the Southwestern Approaches, UK, where a recent evaluation of newly reprocessed seismic data has recognised a sedimentary fill partly influenced by halokinesis. This work provides insight into the likely sub-seismic scale geometry of the basin’s fill adjacent to salt walls, as well as surrounding salt wall terminations, as part of a reappraisal of the area’s hydrocarbon prospectivity,

AAPG Datapages/Search and Discovery Article #90351 © 2019 AAPG Foundation 2019 Grants-in-Aid Projects