Regional-Scale Tectonostratigraphic Evolution and Petroleum System of the Tano
Basin,
Ghana
Smith, Nat1,
Gabor Tari2, Thomas Manu3, Nii Adzei-Akpor3,
David
Valasek2 (1)
CGG, Houston, TX (2) Vanco Energy Company, Houston,
TX (3) Ghana National Petroleum Corporation, Tema,
Ghana
Located offshore
Ghana and
Ivory Coast, the Tano
Basin extends 300 km by 100 km oriented in an
east-west direction. On the
Ghana side of the basin a regional transect
has been extracted from 3-D surveys and supplemented by recently acquired
deepwater 2-D seismic sections. This 160 km transect extends from near shore to
water depths of 3,500 meters and is interpreted to highlight the basin history
in a regional context.
A wide range of reservoir, source, and trap style possibilities
are present in the
Tano
Basin. Syn-rift Aptian and Albian continental to
shallow marine facies are the reservoir intervals in
the North Tano Development Area on the shelf. In
deeper water the reservoir for WT1X and 2X discoveries are post-rift Upper
Cretaceous turbidites. The most significant source
rocks in the basin are Albian syn-rift
lacustrine shales, which
locally are 4,000 meters thick. Other potential source rocks include Cenomanian and Turonian marine shales and the Devonian Takoradi
Shale. Structural trap styles in the Tano-Ivory
Coast basin include rotated fault blocks
below the break-up unconformity and faulted or ponded
channel systems above the unconformity. Producible stratigraphic
traps have been encountered in Maastrichtian and Campanian deepwater fans.
The Tano
Basin hydrocarbon system is evidenced by
numerous onshore seeps, tested flow rates of up to 7,000 BOPD and 20 MMCFGPD
offshore
Ghana, and established fields
offshore
Ivory Coast. The proven hydrocarbon potential of the
basin, limited drilling, and the range of untested structural and stratigraphic plays indicates that continued exploration of
the
Tano
Basin is clearly warranted.