Hydrocarbon generative potential of cretaceous sediments of Kanadi-1 well, Bornu basin, Nigeria

Abstract

The hydrocarbon potential and paleodepositional environment of Cretaceous sediments from the Borno Basin, Nigeria, were assessed by Rock-eval pyrolysis and biomarker geochemistry. The Total Organic Carbon (TOC), soluble organic matter (SOM) and genetic potential (GP) values ranged from 0.52 – 0.82wt%, 455.64 – 1003.04 ppm and 0.23 – 0.63 mg/g, respectively. These values suggested that the sediments were moderately rich in organic matter. The Hydrogen Index (HI) values (19 – 85 mgHC/gTOC) and cross plots of Hydrogen Index (HI) versus Oxygen Index (OI), classified the sediments as types 111 and IV organic matter which had potential o to generate mainly gas. The T and Production Index (PI) values ranged from 339 – 436ºC and 0.08 – 0.32 max while the Production Index (PI) ranged from 0.08 – 0.32, respectively, suggesting low maturity. Biomarker data revealed the presence of C₂₇ to C₂₉ steranes and oleanane which indicated organic matter from mixed sources with  more terrigenous contribution. The dominance of C₂₉  over C₂₈ and C₂₇ also supported higher terrigenous input. , Various thermal maturity parameters computed from the terpanes and steranes distributions in the sediments indicated low thermal maturity. The C₃₅ /C₃₁ – C₃₅ Homohopane index and Pr/Ph values ranged from 0.06-0.24    and 0.23 – 2.52 respectively. These values suggested organic matter deposited under anoxic to suboxic conditions. The results of this study showed that the sediments had potential to generate mainly gas at appropriate thermal maturity.

Keywords: Bornu Basin, Biomarkers, Hydrocarbon Potential, Paleodepositional Environment