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Into the Deep - Geological Evolution Insights in the NE Gulf of Aden

Harker, Stuart D.1; Burrows, Adrian J.1; McGeer, Paul 1
1 Exploration, Circle Oil PLC, Finchampstead, United Kingdom.

Rifting that separated the Arabian and African plates in the Gulf of Aden began in the Early Tertiary, creating a young oceanic basin. However, the geological evolution of the area has a complex and much longer history, starting with the deposition of the Late Pre-Cambrian Huqf sediments onto crystalline basement. Offshore southwest Oman there is a major unconformity at the top Huqf with most of the Palaeozoic and early Mesozoic absent. This deeply eroded surface was onlapped by Jurassic, then Cretaceous sediments, until in the Late Cretaceous, a collision, caused by the rapid motion of the Indian plate, resulted in the obduction of the Masirah ophiolite. The ophiolite was uplifted, then eroded and redeposited, into the nearby accommodation space. The Early Tertiary commenced with rifting, forming series of horsts and grabens. Hadramaut sediments onlapped and infilled the resulting surface, in places resting on the Early Cretaceous where it was exposed by local erosion. Later Oligo-Miocene rifting was followed by widespread deposition of the Fars carbonates and evaporites as the current Gulf of Aden developed. The oldest underlying ocean floor crust is dated at approximately 30my.

These insights are the result of an exploration effort by Circle Oil Oman Offshore in Block 52, a 91,000 sq km permit which ranges over 150km offshore in water depths up to 3500m. An interpretation involving the use of over 16,000 line km of 2D seismic, together with available gravity and magnetics data has been integrated with data from onshore Oman. Unfortunately the three shallow-water wells on the block were all drilled on basement highs and shed little light on the evolution of the structure and stratigraphy of the deeper water areas as seen on seismic. A working petroleum system in the area is evidenced by marine oil seeps and the recent discovery in the adjacent Block 56 onshore. Reservoirs and sealing units are present in Mesozoic and Tertiary units of Block 52, and potential for both structural and stratigraphic traps has been identified.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009