The Myth of the Flat and Monotonous Mesozoic Epeiric Carbonate Platforms in the Middle East

Henk J. Droste
Shell Technology Oman, Muscat, Oman

Epeiric carbonate platforms covered the Middle East during the Mesozoic and host some of the most prolific hydrocarbon reservoirs in the world. These platforms are described as “very extensive areas of negligible topography”. Depositional profiles on these platforms are assumed to be very gentle (<1 degree), without a clear slope break and with broad facies belts and gradual facies transitions.
High-resolution seismic data from Oman shows, however, that in the Lower Cretaceous, the epeiric platforms have an internally highly differentiated topography with water depths of several tens up to 100 m deep. Depositional profiles show a clear break in slope and slopes show dips ranging from 0.5 to more than 30 degrees. Consequently, intra-platform facies are highly variable and may change at short distances.
There are no modern analogues for epeiric carbonate platforms and the models for these systems are based entirely on well and outcrop data which failed to capture the km scale stratal geometries now recognized on seismic. Also these geometries could not be resolved with biostratigraphic dating as the progradation of these systems was relatively rapid and took place over short geologic intervals. Furthermore, the ‘flat epeiric platform paradigm' in geologists minds too often led to overcorrelation of 1-dimensional data, which in turn results in a flat-topography model and hence a self-fulfilling prophecy of the flat-epeiric platform myth.
This new depositional model for epeiric basins has important implications for the prediction of reservoir architecture and reservoir heterogeneities, as well as for stratigraphic trapping potential.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece