Online Journal for E&P Geoscientists

Abd El-Aziz, Ahmed M.^*1; Van Alebeek, Hans ²; Van Steenwinkel, Mia ³; Brandenburg, Aly ¹
(1) New Opportunities, Petroleum Development Oman, Muscat, Oman. (2) Oil North Exploration, Petroleum Development Oman, Muscat, Oman. (3) OmanGeoconsultants, Muscat, Oman.

The prospectivity of the Tuwaiq Formation in North Oman has been recognized for a long time and is verified by several hydrocarbon shows (both oil and gas) and production tests.

The play in Oman comprises the Tuwaiq shallow water carbonate grainstones as a reservoir, but unlike in the Kingdom of Saudi Arabia where the Tuwaiq is sealed unconformably by the Hanifa Formation, in North Oman the Tuwaiq reservoir is sealed unconformably by the overlying Jurassic Aphanitic Limestone or other units of Kahmah Group (Mia Van Steenwinkel 2010). The Aphanitic Limestone forms a low quality very brittle seal, explaining some of the mixed exploration results in the past. The charge is provided by Huqf source rocks via faults and fractures and possibly laterally from Tuwaiq source rocks that may be present within the oil window towards the west.

Recent geological work along with the well data highlighted that the Tuwaiq Formation pinches out to the east suggesting that not only structural traps may exist in this play but also potentially stratigraphic traps.

The merging of several different seismic surveys to create a Megacell, allows the presence of overlying Habshan clinoforms to be delineated but it has also resulted in the addition of some artificial features which will be illustrated. There is, however, a good correlation between reservoir quality and acoustic impedance. Seismic mapping and 3D seismic attribute extractions have been used to delineate the distribution of the better reservoir facies and to delineate the edge of potential pinch out traps.