Abstract: Integration of 3D Seismic Technologies to Predict Pliocene Gas Sands: Post Appraisal of the El Diablo-1 Discovery, Trinidad

Sharp, J. and Pish, T. - Amoco Trinidad Oil Company;Bailey, J. - Amoco Egypt Oil Company

The combined use of several 3D technologies such as 3D coherency, 3D AVO, and 3D depth migration led to the El Diablo discovery. These technologies provided the exploration team with a set of powerful tools to better understand predrill risk and to accurately predict prospect resources.

El Diablo-1 is located in the Columbus Basin of Trinidad, approximately 40 miles northeast of Galeota Point in 206 feet of water. The well was drilled to a total depth of 12,400 feet MD, discovering over 300 BCF of gas from five separate Pliocene age sand reservoirs. El Diablo-1 encountered 320 feet of gas pay sand in the primary T-sand objective with an average porosity of 25%, an average water saturation of 18% and a 500 foot gas column. Additional gas pays were identified in the F sand "series" and T-1 sand.

El Diablo-1 has the distinction of being the first prospect in Trinidad where 3D coherency and 3D AVO were used in conjunction to successfully predict a gas accumulation. Associated with this successful exploration process are a number of exploration technology calibrations useful for future prospect RISK evaluations:

- Gas sands in parts of the Columbus Basin are identifiable as bright spots along the recognizable contact events interpreted as gas/water contacts.

- Gas sands show Positive AVO (increased amplitude with offset) and strong coherency signatures.

- Both AVO and Coherency signatures mimic structure.

- Downthrown fault traps are a viable play concept in the Columbus Basin of Trinidad.

- Gas Column heights can be predicted from fault seal analysis and seismic amplitudes.

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