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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
1 Exploration Technical Services, Saudi Aramco, P.O. Box 2407 Dhahran, 31311, Saudi Arabia, phone:
+966-3-873-1288, [email protected]
2 Exploration Technical Services Department, Saudi Aramco, P.O. Box 6684, Dhahran, 31311, Saudi Arabia
3 Northern Fields Reservoir Characterization Department, Saudi Aramco, Dhahran, 31311, Saudi Arabia
In 2002 Saudi Aramco conducted its first ever 3D, 4-Component ocean bottom cable (OBC) seismic survey in the Arabian
Gulf. The main objective was the delineation of the Cretaceous fluvial stringer sands of the target reservoir overlying the
massive main sands of the Zuluf field. A pre-survey modeling study based on Vp and Vs logs indicated that the use of
converted waves holds promise of improved structural
and stratigraphic imaging of the target reservoir which is typically
characterized by weak acoustic impedance contrasts.
Commensurate with the objectives of the experiment, the 100 Km2 survey was acquired with an in-line swath shooting geometry employing two seabed receiver cables, with a symmetric split spread deployment of the 4-C sensors. There were six sail lines per swath with a single boat dual source flip-flop configuration.
The data was processed through dual source summation, horizontal component rotation and PP/PS pre-stack time migration. Post-stack enhancement in the form of non-stationary Gabor deconvolution proved particularly beneficial in view of the low frequency content of the acquired converted wave data.
Well-to-seismic calibration for both PP and PS data at five wells greatly aided in the interpretation of the data. In the end,
five key horizons were interpreted and correlated between the PP and PS sections
. Joint analysis of the interpreted
horizons, using both amplitude and interval time information, enabled us to map the lateral variations of Vp/Vs ratio within
the survey area. Although it was not possible to resolve individual sand stringers, these
maps
of the Vp/Vs ratio allowed us
to estimate the overall net pay zones of the sand-shale sequences of the target reservoir.