--> --> Potential Stratigraphic-Diagenetic Traps in the Upper Jurassic Massive Dolomitized Formations, Northeastern Saudi Arabia: Insights From Integrated Geologic and Forward Diagenetic Modeling

2018 AAPG International Conference and Exhibition

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Potential Stratigraphic-Diagenetic Traps in the Upper Jurassic Massive Dolomitized Formations, Northeastern Saudi Arabia: Insights From Integrated Geologic and Forward Diagenetic Modeling

Abstract

Stratigraphically discordant massive dolomite bodies have long been documented and studied on the Upper Jurassic formations in northeastern Saudi Arabia. Severe dolomitization associated with solution collapse of regional anhydrite seals has been observed. Recent studies shed light on the potential of stratigraphic-diagenetic traps within this heavily dolomitized area. This study integrates geological and forward diagenetic modeling focusing on the following aspects: (1) detailed 3D geologic modeling to delineate the spatial distribution of the massive dolomite, (2) property modeling to predict the reservoir quality, (3) integrated the geological and forward diagenetic modeling to investigate the dolomitization mechanisms and their impacts on reservoir quality, and (4) prediction of reservoir fairways and the potential exploration opportunities in the vicinity of the dolomite fronts. Preliminary modeling results indicate that (1) the massive dolomite is heterogeneously distributed and developed mainly in the northeastern part of the study area, with a southward decrease in dolomite; (2) partial dolomitization improves, but over-dolomitization reduces reservoir quality; (3) two episodes of dolomitization are likely, supported by cores, thin-sections, geochemistry and seismic data; and (4) the dolomitization fronts are characterized by partial dolomitization and leaching, resulting in potential exploration opportunities for stratigraphic-diagenetic traps. Of the two episodes of dolomitization, one is driven by the tectonic compression and developed adjacent to the Gotnia salt basin, whereas another is related to late hydrothermal dolomitization overprinting the early dolomite. The hydrothermal dolomitization may be related to structural characteristics and fracture systems.