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Abstract: Integrated Reservoir Study - M/T Structure Offshore Abu Dhabi

G. Cartier, J. Tachet Des Combes, T. H. Hassan, S. R. Azer

A multidisciplinary approach involving geology, geophysics, petrophysics and reservoir engineering is used to assess the oil-bearing Thamama reservoirs in the Offshore Abu Dhabi M/T Structure. The structural definition is hampered by subtle variations of the seismic velocities created by shallow high velocity channel fills. Improved time to depth conversion was achieved through detailed velocity studies and layer caking. As defined at the Thamama level, the M/T structure is a gentle low relief feature with closure of about 125 feet.

The Lower Cretaceous Thamama Group comprises the producing zones and consists of a succession which was deposited over an extensive carbonate ramp platform. Seven depositional environments and fifteen associated lithofacies range from slope or basin edge, gradually passing to fore shoal, algal shoal, and rudistid backshoal of the inner ramp. Three third order sequences, their associated systems tracts, sequence boundaries and shallowing upwards parasequences are recognised. Based on geological and petrophysical data, a rock type scheme was developed as a basis for detailed reservoir layering and simulation studies.

The main diagenetic processes which adversely affect porosity are circumgranular, ferroan and non-ferroan calcite and saddle dolomite cementation, while leaching is the primary porosity-enhancing process. Conventional and special core analyses indicate that specific poroperm, petrophysical and engineering parameters can be assigned to various rock types. The integration of all disciplines will optimise future appraisal drilling and lead to a more efficient development strategy of this field.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France