Online Journal for E&P Geoscientists

Elghorori, Ahmed ^*3; Paton, Gaynor ¹; van Kleef, Frank ²
(1) ffA, Aberdeen, United Kingdom. (2) Dubai Petroleum, Dubai, United Arab Emirates. (3) ffA, London, United Kingdom.

The delineation of structural and stratigraphic features in carbonate environments can be greatly enhanced by the application of seismic analysis. This investigation focuses on the application of specific carbonate and fault workflows to delineate the stratigraphic framework and structural fabric of a complex carbonate reservoir in the Persian Gulf. The study looks at enhancing subsurface visualization of the geology by using volume combinations of multiple attributes.

At the Lower Cretaceous Thamama level in a field offshore UAE, fault interpretation using conventional techniques has proven difficult and the potential for reservoir compartmentalization is high due to changes in fault geometry and orientation. Multiple seismic analysis techniques, targeting the delineation of varying fault expressions, were applied in the vicinity of a key well location to objectively analyse the subtle fault expressions. Edge attributes and curvature based attributes were used in combination and two perpendicular trends of faulting were identified.

Rudist reefal accumulations of the Middle Cretaceous Mishrif Formation have proven successful oil reservoirs in the Middle East. A good understanding of the seismic geomorphology of these features, especially subtle stratigraphic plays and areas of low relief faulting, is crucial. In this study bedform analysis techniques were applied and combined with Instantaneous Frequency data to identify pinchouts and clinoforms. These features were then extracted as geobodies to better understand their extents and the potential for untapped up-dip reserves. Frequency decomposition was undertaken and the examination of magnitude volumes generated at discrete frequencies provided clarity on geological features that were otherwise hidden in the reflectivity data. RGB Blending of frequency response volumes around the Lower Cretaceous Thamama complex allowed us to see thinning of sedimentary units and also highlighted, with exceptional detail, subtle and previously unseen faulting.

Advances in seismic analysis technology have enabled the development of workflows to combine multiple attributes in a single volume, giving us an easier approach to transforming geophysical information into geological interpretation. In this study various techniques were used including mathematical combinations, volumetric colour blending, and volumetric opacity blending.