Role of Regional Structural Elements in the Hydrocarbon Prospectivity of Bahrain Offshore Blocks

Subramanian R. Iyer*, Cheruku B. Reddy, and Ravi K. Pathak
Bapco, Bahrain
*[email protected]

Bahrain Island and its offshore exploration blocks are located in the northern Gulf infra-Cambrian Hormuz Salt Basin, a prolific petroleum habitat hosting the major oil fields of the Arabian Plate. The fields are located on the rising flanks of the Qatar Arch to the east and En Nala Anticline (Ghawar-Berri high) to the west, separated by a syncline from which the hydrocarbons were sourced. Exploratory efforts in Bahrain offshore acreages were concentrated on drilling low-relief structural prospects, which gave hydrocarbon indications. Regional lineaments play a dominant role in the generation-migration-entrapment cycle. This presentation will show a conceptual regional structural elements model that integrates all the available data. The objective was to focus exploratory efforts on identifying fault-bounded traps as the dominant structural play in the offshore area. An integrated review of regional geology, seismic, gravity and satellite image data has brought out three dominant regional lineament trends corresponding to the NW-trending Najd strike-slip system, NE-SW Wadi Al Batin-Dibba trend and NS/NNW basement trend. These trends were reactivated during various phases in the tectonic evolution of the basin. The NE trend was active during Jurassic and the NW trend was dominant during Cretaceous. The oldest, NS-NNW basement trend was reactivated during the Late Cretaceous to Early Tertiary compressional phase resulting in the present-day structures. The predominant structural grain in the area is NS and associated with wrench tectonics analogous to the Abu Dhabi model (Marzouk an Abd El Sattar, 1995). A review of prospectivity of the offshore blocks, based on the present structural model, has brought-out many potential fault-closure traps. Finer scale mapping and fault-seal analysis are vital to establish trap integrity. The role of these trends in determining preferred flow directions in the reservoirs of the Awali field in Bahrain requires further investigation.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain