--> --> Abstract: Impact of 3D and Avo Technology to Exploration Efforts in Deepwater Nigeria, by D. Ghosh, M. Blum, S. Adesanya, and H. Tijhof; #90933 (1998).
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Abstract: Impact of 3D and Avo Technology to Exploration Efforts in Deepwater Nigeria

Ghosh, Deva; Michael Blum; Sola Adesanya and Henk Tijhof - Shell Nigeria E&P Co. Ltd.

SNEPCO on behalf of a consortium consisting of ELF, AGIP, ESSO and SNEPCO acquired a large 3D survey of 3500 sq.km in water depths ranging up to 1500m, in OPL 212 and 219 in deep offshore Nigeria. The early application of state of the art 3D technology has played a major role in enhancing SNEPCO and partners? position in this frontier area giving sufficient lead time to drill the first well in less than two years.

GEOPHYSICAL ISSUES: Several ideas have been implemented in acquisition and processing yielding high technical standards in a cost effective manner without jeopardizing either quality or turnaround. This includes 3D Previous HitDMONext Hit for imaging and infilling, wavefield reconstruction for multiple elimination and constrained phase/true amplitude preservation.

PROSPECT EVALUATION: The early availability of 3D seismic has had a major impact on the geological evaluation, including:

i) the emergence of a turbidite depositional fan system

ii) prospect identification,

iii)choice of drilling location and well planning.

In particular the following technology were applied:

a). Voxel-Geo 3D Visualization for amplitude and AvO anomaly detection.

b). Mapping: high quality image of 3D dataset allowed for detailed reservoir characterization.

c). Shallow hazards investigation from 3D image of seabottom.

d). Pressure/depth prediction: close spatial velocity grid allowed for accurate T-Z Previous HitcorrectionTop and velocity inversion.

3D AvO & INVERSION: Long 6km cable in AvO played a strong role not only in hydrocarbon porefill prediction but also in ranking and classifying leads and prospects. The 3D prestack migrated data allowed for accurate AvO prediction & resulted in the discovery well, Bonga. This was further followed up by static and dynamic modeling and inversion studies. Prediction from inversion studies was confirmed by subsequent appraisal wells.

CONCLUSION: Incorporation of 3D early in the exploration effort in deepwater led to valuable lead times that gave SNEPCO a competitive edge. 3D data allowed completion of a full geological and geophysical evaluation of the acreage leading to the successful drilling of Bonga-I in OPL 212.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil