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Kelsch, Kenneth1,
Fola Soetan1, Eugenia
Rojas2, Rex Hanson1, Jim Magill3;.(1) ChevronTexaco,
Chevron Nigeria Limited (CNL) acquired a four component (4C) ocean bottom cable (OBC) seismic survey over the Malu Field, Nigeria in 2002. Gas accumulations in several reservoirs produced large gas clouds coupled with large fault shadows affect the seismic image to define the subsurface. The survey was processed to provide both compressional (PP) and converted shear wave (PS) datasets. The project team, composed of CNL develop-ment/structural geologists and geophysicists, strongly supported by ChevronTexaco’s Exploration Technology Company (ETC) staff conducted a technical review of this data leading to a detailed work program:
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Review contractor processing techniques & impact on interpretation
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Test & apply ChevronTexaco’s proprietary prestack processing
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Create velocity models & depth uncertainty estimates
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Identify & analyze amplitude & attribute anomalies
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Create amplitude / attribute models from key wells
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Complete integrated 4C interpretation of PP / PS data images & attributes
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Update maps, field development plan and confirm prospects for infill drilling
Gas
accumulations within the Malu oil field create large mis-ties using PP data volume alone. The effect of large
gas accumulations is eliminated using the converted shear wave (PS) volume and
improves the well to seismic ties. Interpretation of this new data and application
of key work processes are helping to rejuvenate a field that proved difficult
for past interpreters, contributed to a 17 year production high in 2004 and
provided 3-5 additional infill drill opportunities for 2005-06.