Source rock maturity evaluation in the coastal swamp Depobelt, Western Niger Delta Basin

Abstract

Hydrocarbon generating potential and maturity status on eleven non-composited shale samples retrieved from 1390 – 3466m (4560 – 11370ft) depth interval of the KB-1 well located in the Coastal Swamp depobelt in the Niger Delta Basin using conventional Rock-Eval techniques has been done in this study to expand knowledge on the source rock status of the Niger Delta Basin. A range of 0.09 – 1.16wt % (av. 0.78wt %) recorded for Total Organic Carbon (TOC), indicate fair to good potential source rock. The production index (PI), genetic potential (GP) and hydrogenindex (HI), ranges from 0.05 – 0.2 (av. 0.12), 0.2 – 0.51 (mg/g) (av. 0.31mg/g) and 21 – 44 (mgHC/gTOC)(av. 27mgHC/gTOC)respectively. Calculated vitrinite reflectance and Tmaxrange from 0.45 – 0.53 (0.50) and 408 – 430°C (av. 419°C), indicates immature source sediments. HI calibration constrained with S2/S3 indicates a dominance of type IV non-source organic matter. Cross plots of HI vs OI refined and confirmed type IV kerogen as dominant species. A flat PI trend withno decrease of increase with depth is unusual and difficult to explain, but may be probably due to the effect of impregnation by migrated hydrocarbons from older sequences which may have masked the expected trend for the well. Maturity indices from this study, thus far shows that the sediments of the Agbada Formation in the section of the well and in this aspect of the Coastal Swamp Depobelt though have potential to generate hydrocarbon, containspent and immature organic matterthat cannotgenerate any form of hydrocarbon.

Keywords: Coastal Depo Belt, Calculated vitrinite, Hydrogen Index, Niger Delta, Source Rock Maturity