Hydrocarbon Potential of Some Afowo Shale Deposits in Part of South Western Nigeria

Abstract

Six (6) core samples were collected at different depths from a borehole at a locality in part of Southwestern Nigeria at depth range of 92 – 112fts, 151 – 161fts, 210 – 220ft, 240 – 250ft, 250 – 260ft, 300 – 310ft. respectively and were subjected to Total Organic Content (TOC). Three samples with high TOC were equally subjected to Rock Eval Pyrolysis to evaluate the petroleum generative potential, organic richness, organic matter quality, origin of organic matter and thermal maturity of the rock.

The Rock-Eval Pyrolysis result showed total organic carbon content range of between 2.12 and 2.94wt% indicating organic –rich rock; hydrogen index (HI) ranged from 15 – 43 indicating increasing hydrocarbon potential with depth ; oxygen Index (OI) ranged from 121 – 177; Productive Index (PI) ranged from 0.19 – 0.26 with increase in depth and at depth 151-161ft it decreases indicating immature rock. S₁ + S₂ ranged from 0.59 - 1.37 indicating good hydrocarbon potential and Tmax range from 343⁰C to 427⁰C indicating thermal immaturity of the samples.

Hydrocarbon generative potential of the rock can be said to be poor. HI Vs OI plot indicates organic matter that belongs to Kerogen Type III and Type IV, which indicate gas prone source rock. The organic matter from the plots can also be deduced to be of terrestrial origin.

Key words- Hydrocarbon, Vitrinite, Kerogen, Shale and Rock-Eval-Pyrolysis.