APPLICATIONS OF SEISMIC EXPLORATION TECHNIQUES IN IMAGING COMPLEX GEOLOGY OFFSHORE TRINIDAD: A CASE HISTORY
ALLISON DUPIGNY
Trinidad and Tobago Petroleum Company Ltd,
Santa Flora, Trinidad & Tobago
DOUGLAS ELROD
TGS Geophysical Co. Houston, U.S.A.
ROLF RANGO
TGS Geophysical Co. Houston, U.S.A.
ERIC A. WILLIAMS
Trinidad and Tobago Oil Co. Ltd, Pointe-a- Pierre,
Trinidad & Tobago
In August 1989, a 2019 km speculative seismic data survey was acquired offshore Trinidad In support of an upcoming
government lease sale. The areas covered are known as Blocks 89-2, 89 -3, 89 -4, and 89 -5.
Despite previous seismic surveys, there were still several geological uncertainties in these Blocks which had to
be resolved. The geologic objectives of the 1989 survey included:
1. The acquisition of data in what appeared to be 'no data' areas, which may have been indicative of basement;
2. The proper imaging of steel dips in both shallow and deep horizons
3. The imaging of faulting types and trends;
4. Imaging into the Mesozoic - in particular the Cretaceous where the source rock is known to exist; and
5. To delineate reservoir facies using sequence stratigraphy To accomplish these objectives, the following general
specifications were employed:
ACQUISITION - High volume-131, 281cc (8026 cu. in), wide- 58.5m, high pressure 29300 atm (2000 psi), tuned air
gun array
- Long hydrophone cable (3600m) with a large number of channels
PROCESSING
(144), plus short group offset (25m)
- High Fold (7200%)
- Short near offset (1 67m)
- Longer recording times (8 to 10 sec)
- Dip Move Out (DM0)
- Same high nominal fold as in the acquisition (7200%)
- F/K filtering
- Steep Dip Migration
- Retention of very low frequencies addition stringent quality control was maintained throughout the acquisition
and processing phases with the aid of a microcomputer based system.
The net result of these quality control measures is a data set of improved quality which made it possible for the
original objectives to be achieved.
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