Prof Akande Samuel O's research grant

Lead Researcher

Title Prof
Firstname Samuel
Middlename O
Surname Akande
Phone 07039123724

Research Grant Details

Research Topic Hydrocarbon Source Rock evaluation in the Cretaceous to Neogene Basins of Southern Nigeria and Implications for the Niger Delta Petroleum Systems
Benefit to Oil and Gas Increased potential of hydrocarbon discoveries in the Nigeria inland basin. Attractive package for investors and technical partners. Identification of reserves for hydrocarbon mapping within the Dahomey and Niger Delta basins on-going.
Research Duration 2
University University of Ilorin
Abstract The current extended study of petroleum source rocks of the Dahomey and Anambra Basins focused on further assessment of the generation and expulsion potentials of the source rocks on the south and north sides of the Eastern Dahomey Basin on one hand and completing the previous work on the extended traverse on the south side of the Anambra Basin fringe of the Niger Delta within the lignite basin of southern Nigeria. The methods employed for the research include continued Literature survey, Fieldwork and Laboratory analysis. Data gathering for the Dahomey Basin transect extended offshore to the X and BB wells in deepwater Dahomey Basin through a southern traverse where the Orimedu-1, Ise-2 and Epiya-1 wells were investigated and a northern traverse where coreholes from Araromi-Obu, Ajegunle, Erekiti-Luwoye and Igbotu were also investigated. Previous studies in the southern Anambra Basin lignite belt was extended into the Nnewi areas where outcropping lignite and coaly shale facies were investigated. Laboratory work include biostratigraphy (foraminifera biostratigraphy and palynology), organic petrology and geochemical investigations with detailed characterization of generatable and expelled oil and gas of selected samples by hydrous pyrolysis experiments, biomarkers and stable carbon isotopes. From the ongoing biostratigraphic and geochemical data accumulated, preliminary volumetric calculations of generatable hydrocarbons of the proven source rock units in the Dahomey Basin were compiled and some interpretations have emerged as follows. At least six planktonic biozones comprising Rotalipora greenhornesis, Praeglobotruncana Helvetica, Marginotruncana pseudolinneiana, Globotruncana renzi, Globotruncana calcarata and Globotruncana Aegytiaca-Abathomphalus mayaroensis zones were observed from the base to the top of the sections. The first three planktonic biozones define the Cenomanian – Turonian stratigraphy of the southern traverse whereas the last two biozones define the Campanian – Maastrichtian stratigraphic levels. Palynological data set reaffirm biozones of Cenomanian – Coniacian and Campanian – Maastrichtian groups. This defined stratigraphic records combined with geochemical data indicate that the Cenomanian – Coniacian transgressive sequences in the Eastern Dahomey Basin contain marine shales with Type II oil-prone kerogen contrary to the previous suppositions. These shales are good to excellent source rocks related to the worldwide Oceanic Anoxic Event -2 (OAE2) and therefore represent an integral element of the petroleum system of the regionally extensive coastal basins in the West African Gulf of Guinea. Burial history construction suggests that the burial temperatures of the Cenomanian – Coniacian successions reached maturity levels since the Santonian age compared with the overlying Campanian- Maasttrichtian successions which are not sufficiently buried to reach maturity especially on the northside of the Dahomey Basin. An on-going reserve estimation of hydrocarbons generated at this interval suggest that the thickness of mature Cenomanian – Coniacian source rocks in the Eastern Dahomey Basin (which could be over 400m) should have generated about 750million barrels of oil over the entire area of the basin. The stratigraphic limitation of this play horizon is currently being tested by Yinka Folawiyo petroleum in the Aje Field (OPL 309, now converted to OML 113) and LekOil (with Afren Plc as the Technical partner ) in the recent discoveries of the OPL 310. Our research is proving the efficiency of the thermally mature source rock at this interval accompanied with excellent reservoirs and seals on the south side of the coastal, shallow water and deepwater offshore the Dahomey Basin. Geochemical characteristics of the Campanian – Maastrichtian shales of the Araromi Formation in the Dahomey Basin indicate a dominantly gas prone assemblage for the adjacent sediments to the tarsands. Furthermore, the VRovalues suggests immaturity with respect to hydrocarbon generation and hence the heavy oil was not generated from the immature adjacent sediments but most likely from the deeper Cenomanian – Coniacian source rocks of the Afowo Formation. Sequential hydrous pyrolysis and stable carbon isotope data presented in this study show that the organic- rich intervals of coal especially the lignite and shale successions within the paralic Ogwashi-Asaba Formation of the Anambra Basin or Agbada Formation (subsurface equivalent) in the Niger Delta at maturity can be responsible for Niger Delta oils having mixed terrigenous and marine characteristics. The lignite and coaly shale perhaps represent components of similar candidate source rocks responsible for the oils of mixed origin across the Niger Delta. Identification of the two groups of candidate source rocks (terrestrial and marine hydrocarbon contributors) at this interval could stratigraphically limit source horizons in burial models without invoking deeper Cretaceous source contribution.

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