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