Abstract:
Scientific ocean drilling has been conducted for more three decades. The Ocean Drilling Program (ODP) and its predecessor program the Deep Sea Drilling Project (DSDP) conducted activities with a riserless ship. Extensive pre-drill reviews are performed for safety reasons and to prevent pollution. Even with these reviews, with the drilling of the first DSDP Leg and continuing with the current program minor hydrocarbon shows have been encountered. These shows suggest the presence of a petroleum system. Potentially as important as the identification of a petroleum system, which could be accomplished through other means, drilling has provided access to samples of potential hydrocarbon source rocks. Such samples are well constrained stratigraphically and free from organic drilling fluid contamination. ODP Leg 159 was drilled along the continental margins of Cote d'Ivoire and Ghana. Four drilling sites were included in the Leg. These sites recovered sediments from the Pleistocene to the Albian. Shipboard studies, including organic carbon and pyrolysis, revealed the presence of a number of organic-rich zones within both the Cretaceous and Tertiary sections. These intervals also display elevated hydrocarbon generation potentials. Both oil- and gas-prone intervals are present. A shore-based study has focused on Site 959. These studies provided an opportunity to expand upon the original dataset. Detailed characterization (biomarker and isotope analysis) of the bitumen fraction, provided information on the geochemical character of these zones, which may, in turn, be used to more definitively establish the origins of oils within the deepwater portions of the Niger Delta.