Organic Matter Quantity, Quality and Maturity Studies of the Paleocene Ewekoro Formation, Southwestern Nigeria

Abstract

Organic matter quantity, quality and maturity studies was carried out on the Paleocene Ewekoro Formation to assess its source rock potentiality using organic geochemical and petrographic techniques. Organic richness assessment based on Total Organic Carbon content (TOC), Genetic Potential, Soluble Organic Matter (SOM), hydrocarbons generated before pyrolysis (S₁) and residual petroleum potential (S₂) indicates that the carbonate facies of the Paleocene Ewekoro Formation are organic matter lean and has very poor hydrocarbon generation potential. Type of Organic Matter evaluation using hydrogen and oxygen indices, plot of HI against T_max and S₂/ S₃ ratio shows that they are predominantly kerogen type IV and some type III; of terrestrial organic matter, a characteristic of oxic depositional milieu.  Maturity studies presents their status as immature or over mature with low level of convertibility to hydrocarbons. S₂-TOC cross-plot indicates that the organic matter is composed mainly of ‘dead’ organic carbon with no potential for hydrocarbon generation.

Keywords: Organic matter, kerogen, source rock, hydrocarbon