Petroleum Potential of Gombe Formation, Kolmani River-1 Well Gongola Basin, NE Nigeria

Abstract

Gombe Formation is one of the promising potential source-rock of petroleum in the Gongola basin based on its appreciable amount of organic matter. The present study is therefore aimed at evaluating the hydrocarbon potential of Gombe Formation. Ditch-cutting samples were collected from the depth of 731.5 m to 1554.5 m from Gombe Formation that penetrated the Kolmani River-1 well. The source-rock potential was evaluated based on kerogen analysis and soluble organic matter content using Fourier Transform- Infra red spectroscopic (FT-IR) and Gas chromatography-Mass spectrometric (GC-MS) techniques respectively. There is presence of peak at 900-1000 cm-1 which is due to CH2 rocking vibration in long chain aliphatic substances, which is characteristic of liptinite macerals indicating good potential source-rock for oil and gas. The n-alkane ranges from C11-C33 maximizing at nC16 which suggests that the organic matter are majorly derived from marine organic matter. The Pr/Ph (1.49-1.92) shows that the organic matter was deposited under sub-oxic condition. The distribution of hopanes, homohopanes (C27-C29) steranes, (C0-C4) alkylated naphthalenes and (C0-C3) alkylated phenanthrenes indicate the presence of angiosperm, gymnosperm, algae, marine and bacteria input to the organic matter contained in the samples. Also the plot of DBT/P vs. Pr/Ph classifies the samples into zone 3 (i.e. marine shale and other lacustrine). Various maturity parameters computed from saturate biomarker and polycyclic aromatic hydrocarbon distributions shows that the samples are low mature with the moderately mature zone at the bottom (>1408.2 m) of Gombe Formation. In conclusion, the kerogen was probably derived from type II/III organic matter capable of generating both oil and gas and the moderately mature zone lies at the bottom of the Formation. Key words: Lacustrine, Gombe formation, Maturity, Hydrocarbon, Kerogen