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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Hoover: A Significant Oil Discovery in the Western Gulf of Mexico Deepwater
By
1Exxon Exploration Company
2BP Exploration
The Hoover field discovery represents
the largest of a string of recent successes
in the sand-rich, Plio-Pleistocene, Diana field intraslope basin of the western
Gulf of Mexico. Hoover is located 160 miles south of Galveston and 120 miles
offshore in 4800' of
water
. The discovery is an amplitude-supported, oil and gas
discovery
located in Alaminos Canyon
Blocks 25 and 26; an anticlinal closure in
the central portion of the Diana basin.
Hoover contains reserves in excess of 100
MBOE in two zones. The first is a shallow,
Pleistocene gas sand. The second,
and most prolific, is a Pliocene oil zone
with very good reservoir
quality
. Both
zones have significant amplitude expression
with apparent flat events related to
hydrocarbon/
water
contacts.
The discovery well, the Exxon/BP AC 25
#1 ,(Figure 1) drilled in early 1997, found
47' of gross gas pay in the Pleistocene and
97' of gross oil pay in the lower portion of
the Upper Pliocene. The discovery well
found the hydrocarbon/
water
contact in
both zones and confirmed the amplitude
based areal extent for each accumulation.
Although high
quality
reservoir was predicted,
the Pliocene reservoir
quality
exceeded expectations. The reservoir has
average porosity in excess of 30% and
average permeability over 1000 md.
The Hoover discovery is in stark contrast
to the largely unsuccessful Rockefeller
prospect, five miles west. Although an
anticlinal closure like Hoover. Rockefeller
had no thermogenic hydrocarbons. In late
1995, Exxon drilled the Exxon EB 992 #1
and #1 ST which found full saturation biogenic
gas in only one of four objectives.
The remainder were
water
sands with low
saturations of biogenic gas.
A detailed vertical and lateral migration analysis of the entire Diana intraslope basin was undertaken to insure Hoover and the surrounding prospects had adequate migration to warrant investment. The study found Rockefeller to be heavily dependent upon a single fault for vertical migration from the Early Tertiary source. Hoover, however, had several prospective vertical migration conduits within its lateral migration drainage basin. In addition, all the closures along this migration pathway had amplitudes to their structural spill points. This analysis was provided the critical technical justification to proceed with exploration at Hoover.
The presence of thermogenic hydrocarbons in the Hoover's Pliocene reservoir confirmed our current model for vertical and lateral migration of hydrocarbons in the Diana intraslope basin. It also lowers the source risk of other closures within the same migration system.
With these latest discovery volumes, the Exxon/BP partnership should be able to fully exploit Hoover, the sizable Diana reserves discovered in 1990, and surrounding satellite discoveries and prospects.
End_Page 17---------------
Figure 1. Cover photo from discovery well in Alaminos Canyon Block 25. The cores has 33% porosity and 1540 md permeability.
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