A. Baniasada,*, V. Sachsea, R. Littkea and B. Soleimanyb

a Institute of Geology and Geochemistry of Petroleum and Coal, Energy and Mineral Resources Group, RWTH Aachen University, Aachen, Germany.

b Exploration Directorate, National Iranian Oil Company, Tehran, Iran.

* Corresponding author, email: alireza.baniasad@emr.rwth-aachen.de

This study presents a 3D numerical model of a study area in the NW part of the Persian Gulf, offshore SW Iran. The purpose is to investigate the burial and thermal history of the region from the Cretaceous to the present day, and to investigate the location of hydrocarbon generating kitchens and the relative timing of hydrocarbon generation/migration versus trap formation. The study area covers about 20,000 km2 and incorporates part of the intra-shelf Garau-Gotnia Basin and the adjacent Surmeh-Hith carbonate platform. A conceptual model was developed based on the interpretation of 2700 km of 2D seismic lines, and depth and thickness maps were created tied to data from 20 wells. The thermal model was calibrated using bottom-hole temperature and vitrinite reflectance data from ten wells, taking into account the main phases of erosion/non-deposition and the variable temporal and spatial heat flow histories. Estimates of eroded thicknesses and the determination of heat-flow values were performed by burial and thermal history reconstruction at various well and pseudo-well locations. Burial, temperature and maturation histories are presented for four of these locations. Detailed modelling results for Neocomian and Albian source rock successions are provided for six locations in the intra-shelf basin and the adjacent carbonate platform. Changes in sediment supply and depocentre migration through time were analyzed based on isopach maps representing four stratigraphic intervals between the Tithonian and the Recent. Backstripping at various locations indicates variable tectonic subsidence and emergence at different time periods.
The modelling results suggest that the convergence between the Eurasian and Arabian Plates which resulted in the Zagros orogeny has significantly influenced the burial and thermal evolution of the region. Burial depths are greatest in the study area in the Binak Trough and Northern Depression. These depocentres host the main kitchen areas for hydrocarbon generation, and the organic-rich Neocomian and Albian source rock successions have been buried sufficiently deeply to be thermally mature. Early oil window maturities for these successions were reached between the Late Cretaceous (90 Ma) and the early Miocene (18 Ma) at different locations, and hydrocarbon generation may continue at the present-day.

Key words: Basin modelling, SW Iran, maturation history, burial history, Persian Gulf, Cretaceous, source rocks, Gotnia Basin, Kazhdumi Formation, Garau Formation.

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