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.