Abstract

The Rimthan Arch, situated between the Arabian carbonate platform and the Gotnia intrashelf basin, represents a world class hydrocarbon province in Saudi Arabia. Middle to Upper Jurassic shallow-water depositional sequences are associated with productive hydrocarbon fields in which challenges exist in defining exploration targets, mainly stratigraphic trap plays. An attempt is made to investigate the basin depositional architecture on the flank of the Arch and also to model the stratigraphic trap potential of the youngest Arab third-order sequence. The basin architecture, stratal geometries, and impact of tectonics are explored using 3D seismic and well data. Seismic chronostratigraphy, seismic stratigraphy, seismic attribute, and log-based reservoir heterogeneity techniques are applied as an integrated approach to interpret the sequences from basin to reservoir scale. The study identifies two second-order sequences, SEQ 1 and SEQ 2, to frame a 3D geologic model and to examine basin development through time. Results derived from the integrated study indicate that although initial basin subsidence began later in SEQ 1 north of the Arch, it increased appreciably during SEQ 2. The Dhruma J20 maximum flooding surface, Lower Fadhili, and Hanifa provide clues in tracking major basin changes. Seismic stratigraphy applications highlight reflection terminations and prograding stratal geometries throughout the stratigraphic section to demonstrate tectonoeustatic influences. Tectonics impact SEQ 2 more intensely than SEQ 1 and may influence the migration of hydrocarbons across juxtaposed lithologies. A complex association between shallow marine tidal and ramp carbonates, and deeper basin halite beds, is linked to the subsiding Gotnia Basin. Log-facies analysis of the Arab third-order sequence demonstrates reservoir and seal trends, including the stratigraphic entrapment potential along a carbonate ramp profile. Seismic attributes support reservoir-depositional trends and salt-bed geometries. The integrated approach provides a targeted workflow to investigate the complex depositional systems and their stratigraphic trapping potential on the Arch.

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