A Feasibility Study for a 3-D, 4-C
Seabed Seismic
Survey in the Arabian Gulf
By
Costas G. Macrides1, Paul A. Ras2, Martin Widmaier3
(1) Saudi ARAMCO, Dhahran, P.O. Box 2407, Saudi Arabia (2) Saudi Aramco, Dhahran, Saudi Arabia (3) PGS Geophysical, Lysaker, P.O. Box 354, Norway
We present a feasibility study, designed to investigate whether 3-D seabed,
multi-component (4-C) seismic
recording over the Zuluf field would lead to an
improved structural and stratigraphic
interpretation
. A primary objective of the
study was to determine which of the potential benefits of 4-C recording could
materialize into tangible benefits for the case of the Zuluf field.
Surface seismic
datasets consisting of towed streamer and OBC (2-C)
data
from
a neighboring field were analyzed and compared. Multi-component VSP
data
was
also used both to evaluate the amount of shear wave energy generated by mode
conversion and to predict the achievable bandwidth and vertical resolution.
Earth models built from the P and S logs were used to model P and S offset
reflectivity and create realistic elastic synthetics.
We have been able to predict those aspects of the proposed 4-C survey that
would provide additional new insight and those aspects that are less likely to
succeed. For instance, whereas the use of S-waves for imaging low P-impedance
contrasts does not seem promising for the main producer to date, the Khafji Main
sand, converted S-waves are expected to bring improved imaging for the overlying
Khafji and Safaniya stringer sands where most of the remaining reserves are
located. There is also scope for S-wave data
to provide additional constraints
on the
interpretation
through the use of Vp/Vs analysis. Combined
interpretation
of the two
data
volumes (PP and PS) could provide both a reservoir quality
indicator and a means for lithology and fluid discrimination