3-D Seismic Evidence of Tertiary - Cretaceous Karsts & Collapse Disturbances from Offshore Oil Field in Abu Dhabi and Outcrop Analogs from Jebel Hafit, United Arab Emirates

Abstract

Tertiary to Cretaceous age karsts and collapse disturbances were observed from recent 3D seismic interpretation of an offshore Abu Dhabi oil-field. The seismic evidence of karst features was investigated using full-stack, spectral whitened, and discontinuity volumes. In addition, circular features were detected at specific sequence boundaries after examining curvature maps, disturbed amplitudes, velocity effects, and attenuation attributes. Several karsts and collapse disturbances tend to be associated with anhydrite beds overlaying thick carbonate intervals and seem to be limited to the Tertiary stratigraphic column; other karsts were observed to be limited to Cretaceous dolomite and limestone reservoir intervals. The Tertiary age karsts were observed to cause seismic image and amplitude disturbance at various depths, whereas the Cretaceous age karsts tend to be limited in radius and depth and have more limited effect on seismic response.In the attempt to better understand the limit of some karsts and collapse disturbances, well data (wireline log, conventional core, and thin-section) were investigated within the karst areas and integrated with 3D seismic data. 3D seismic based geometries and attributes were analyzed to evaluate the possibility of detecting the damage-zone limit versus velocity effect with depth due to fill material. Another effect investigated is that of fracture-fault zone distribution relative to karst localization.Analogue karst features of a similar age-range (Tertiary and younger) to the seismic examples occur within Jebel Hafit in the onshore UAE, where solution effects, debris fill, mineralization, and collapse effects can be observed and compared with the offshore examples. Here, structural discontinuities also enhance the karstic features.

A New Method of Surface Wave Analysis and OBC Signal Enhancement in Shallow Water Environment of the Arabian Gulf using Time-Frequency-Wavenumber Polarization Analysis

“…The area for this seismic 4C study is one giant carbonate offshore oilfield near Abu Dhabi, U.A.E, which is a part of Arabian platform that was the passive northern margin of Gondwana during the Triassic to Jurassic and early Cretaceous (El-Awawdeh et al, 2008). Arabian Gulf and its coastal areas contain predominantly carbonate sediments (including reservoirs) that were folded during Neogene tectonic phase, which was a result of the Arabian plate subducting under Eurasian plate (El-Awawdeh et al, 2008).…”

“…Arabian Gulf and its coastal areas contain predominantly carbonate sediments (including reservoirs) that were folded during Neogene tectonic phase, which was a result of the Arabian plate subducting under Eurasian plate (El-Awawdeh et al, 2008). They are the world's largest source of crude oil, where about 800 offshore oil and gas platforms and 25 major oil terminals are established in this region.…”

Fracture Characterization by Integrating Seismic-Derived Attributes including Anisotropy and Diffraction Imaging with Borehole Fracture Data in an Offshore Carbonate Field, United Arab Emirates

“…In this paper, we present a case study of fracture characterization by integrating borehole data with a variety of seismic attributes in a giant carbonate oilfield located in the offshore of Abu Dhabi (Edwards et al, 2006;El-Awawdeh et al, 2008;Zhang et al, 2010;Sultan et al, 2011). The region contains predominantly carbonate sediments that were folded during the Neogene tectonic phase.…”