Mapping the Upper Shu’aiba in Northern Oman: How to Get the Best Out of Difficult Seismic Data and Specifically How to Pick the Formation Top and Identify the Presence of Good Reservoir?

Christophe Gonguet*, Kees De Leeuw, and Gordon Coy
PDO
*[email protected]

The Upper Shu’aiba stratigraphic play is being pursued in the northern part of Petroleum Development Oman’s (PDO) Block 6 (Petroleum Development Oman). To date, three fields have been discovered and our understanding of the play and its seismic expression has progressed significantly. The area is mostly covered by 3-D data of poor to medium quality, characterised by the pervasive presence of inter-bed multiples. Furthermore, when good reservoir subcrops the Nahr Umr regional shale, there is no impedance contrast and the expected Top Shu’aiba hard-kick will actually be Base Reservoir. The Bab Basin is a shallow basin with limited accommodation space showing progradation of low-angle clinoforms, alternating clean carbonate and argillaceous units. The targeted reservoir units generally consist in proximal, high-energy shoal/build-up facies. A regional high-resolution sequence stratigraphic model shows progradational infill of the basin from its respective margins. The combined seismic response of successive inclined units may cause a tuning effect. In these cases some weak clinoform geometries may be seen on vertical sections and tuning bands appear on amplitude maps in spectral decomposition seismic volumes. The seismic approach is coupled with building and updating the sequence based Petrel^TM 3-D geological model. This integration has become an essential part of our exploration process. Finally, we increase the value of the seismic data from re-processing (multiple attenuation and velocity picking) and sparse-spike inversion. Also our current acquisition of new higher fold 3-D data and better sampling of the near-surface should contribute to improved imaging of the reservoir units.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain