The Marmul field lies in the Dhofar province of the Sultanate of Oman. The heavy oil accumulation was discovered in 1956 by Dhofar Cities Services who drilled five wells, but the field was not considered commercial and operations were abandoned. Petroleum Development Oman acquired the concession in 1969. Producible oils occur in Paleozoic clastics overlain unconformably by a Cretaceous sealing shale. Initial appraisal showed the complex nature of the reservoir distribution to be due to its glacial/periglacial environment of deposition, and a simple geologic model was conceived. Seismic impedance contrast at the seal's unconformity surface was then used as a predictive tool to differentiate glacial waste zones (tillites) from periglacial reservoirs and as support to the co tinuing appraisal and development drilling. The glacial/periglacial geologic model was progressively refined by further development drilling. The appraisal effort based on geologic and seismic impedance models was then deliberately pursued toward possible additional younger stacked reservoirs stratigraphically trapped at the periphery of the field. These reservoirs were proved by drilling to be separate from the main field and oil bearing. The unraveling of the field's complex trapping mechanisms, and the buildup of the geologic models needed for primary development and secondary recovery schemes, could only be achieved through an integrated and dedicated approach by geologists and geophysicists.

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