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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Velocity
Analysis: Focusing 3-D data from Offshore Abu Dhabi
1 AGRI, KACST, PO Box 6086, Riyadh, 11442, Saudi Arabia, phone:
+966-1-4813323, fax: +966-1-4813523, [email protected]
2ADMA-OPCO, PO BOX 303, Abu Dhabi, United Arab Emirates
The 3-D data set from offshore Abu Dhabi has suffered from shallow velocity
anomalies concentrated in center of the
surveyed region and above the critical reservoirs area. Previous processing results, that mainly ignored such anomalies,
produced images that lacked reflection signatures in that middle critical region. Even those processing methods that have
tried to predict the anomaly, but are based on prestack depth migration concept, have failed to focus the image at the
center. Thus, we use the inherent stability features of representing the image and all processes prior in the TAU instead of
the depth domain to estimate the interval
velocity
model for this 3-D data set. The process is based on prestack 3-D
migration
velocity
analysis and thus honors the complex inhomogeniety up shallow in that region. The final estimated
interval
velocity
model in the TAU domain provided low residuals in the imaged sections from different offsets and agreed
well with the four wells located in the area. This
velocity
model also encompassed all the main features of the region like the
low
velocity
zone up shallow and the major fault present in the middle of the region. Using the
velocity
model we applied 3 -
D prestack TAU migration to the full data as opposed to subsets of the data as done in the
velocity
development stage. As a
result of using the TAU domain, we managed focus the image far better than in previous attempts. Using the new images,
we managed to identify the location of the major sealing fault, and recognize major structures in the central zone.