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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: The Subsalt Tahiti Field Discovery, Green Canyon 640:
Opening Another Deepwater Frontier
By
Deepwater Exploration/Projects Business Unit
Chevron North America Exploration and
Production Company
Houston, Texas
The Tahiti Discovery, announced in April 2002, represents not only a major oil discovery in the deepwater Gulf of Mexico, but also opens an exciting new deepwater exploration frontier in ultra-deep, subsalt reservoirs. The Lower Miocene reservoirs in Tahiti Field are expected be the deepest producing reservoirs in the Gulf of Mexico when first oil arrives through the pipeline in 2008.
The Tahiti Green Canyon 640 #1 well,
located in 4,100 feet of water, targeted the hydrocarbon-bearing
Lower Miocene section in the emerging Mississippi Fan Fold belt
trend, located in south-central Green Canyon (Figure 1). The
prospect was located more than 35 miles from the nearest stratigraphic
penetration of this interval, and the trend proved to be at
a significantly lesser depth than was predicted.
The closure tested by the discovery well is a
three-way structural
nose, trapped against a
salt feeder/weld
system
, buried beneath an
11,000-foot-thick salt canopy. This
trap
type
was considered to be much higher risk than
the salt-cored, four-way anticlines previously
targeted in the fold belt trend and is very
difficult to image on conventional seismic
data. Significant stratigraphic risks were also recognized, as
pre-drill data were limited.
Figure 1. Location Map of the Tahiti field, GC 640.
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The Tahiti discovery well, spudded in December 2001, successfully
confirmed the structural
and stratigraphic concepts, encountering
more than 400 feet of net oil pay, primarily in three main
Miocene turbidite sheet sands at depths ranging from 24,000 to
27,000 feet. Reservoirs penetrated by the well have unusually high
quality sands for this depth. Subsequent sidetracking of the
discovery and appraisal drilling have confirmed significant
hydrocarbon columns of high-quality crude, with excellent
reservoir parameters and lateral connectivity (Figure 2).
Additional appraisal wells and well tests have resulted in
announced recoverable resources of 400 to 500 MMBOE for
Tahiti Field.
Future exploratory success for subsalt, ultra-deep reservoirs will need to mirror the successful integration of 3D prestack-depth migration imaging, regional analysis, basin modeling, and prospect scale mapping applied at Tahiti Field. Application of “lessons learned” will be critical, as additional data becomes available in this exciting, but challenging new deepwater frontier.
Figure 2. The Rig Cajun Express Conducts the Tahiti GC 640 Well Test in August 2004.
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