Marcus B. Patterson1, Frits Blom2, Chris M. Griffith1, Brian J. Tepper1, Daniel Truempy1
(1) Shell International Exploration and Production Inc, Houston, TX
(2) Shell International Exploration and Production, Rijswijk
ABSTRACT: Sweet Music in the Columbus Basin: From Mozart to Haydn, and Then?
Shell and AGIP used a regional 2D seismic data set for their pre-bid evaluation of the Trinidad deepwater and defined three large structural closures against shale diapirs in Block 25(a). Prospect Mozart, a large structure characterized by a shallow, structurally conformable amplitude, illustrated the presence of turbidite channel and fan sands covering an area of 70 km2. Early volume expectations were based on a number of such reservoir intervals stacked vertically.
Newly acquired 3D data could not confirm the exploration value of Mozart. The other truncation traps with high volume potential could not be drilled in this untested basin because of dramatic and uncertain pressure forecasts. Consequently, Haydn a structurally simple prospect downdip from Mozart was selected. The prospect displayed excellent, structurally conformable amplitude anomalies, and channelized turbidite reservoirs draping over a small 4-way dip closure.
Haydn-1 encountered light gas in thin-bedded levees of Pleistocene turbidite channels. The gas becomes isotopically heavier with depth. The better-developed channel sands leaked up-dip following a late structural tilt. The Haydn test proved that turbidites were transported into the deepwater basin during the Pleistocene and also proved that thermogenic charge existed. It failed to prove whether substantial oil charge exists in the area.
Analysis of the well results and subsequent seabed coring suggest that a deeper oil charge is present in the deepwater Columbus Basin at depths not penetrated by Haydn. Future plans focus on testing the deeper stratigraphy, the results of which may prove whether there is sweet music in this basin.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado