AAPG Middle East Region Geoscience Technology Workshop

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An Updated Stratigraphic Framework for the Palaeozoic Haima Supergroup of North Oman

Abstract

The siliciclastic successions of the Haima Supergroup (Cambrian to Silurian in age) encompass a number of significant hydrocarbon-bearing intervals in Oman (including the Amin, Miqrat and Barik reservoirs), the regionally important earliest Silurian source rock, and potentially a previously unrecognised source rock in the Middle Ordovician. A robust biochronostratigraphic framework is essential to understand this important stratigraphic interval. Over 1000 palynological samples were analysed from 95 holes, and these new data were integrated with pre-existing biostratigraphic data in a comprehensive review study. The findings were used to update and enhance the existing palynological zonation schemes and biochronostratigraphic framework. This updated stratigraphic framework was then used to correlate wells on a field and regional scale (together with electric logs and seismic data) to review and revise the lithostratigraphic tops in the PDO database. The updated stratigraphic framework added a number of enhancements to the existing framework, including 1) the subdivision of the Al Bashair Formation into lower and upper units, 2) the identification of new palynomorph events, including a priapulid worm teeth event from the lower Al Bashair unit (a taxon previously recorded only from the mid-Cambrian of Canada), 3) an additional Maximum Flooding Surface in the Middle Ghudun Member, 4) the recognition of an intra-Saih Nihayda shale unit, 5) the identification of a Middle Ordovician (Darriwilian) source rock and 6) the addition of new palynology biozones, and a restructuring and renaming of the existing Palynology biozone scheme.