Petroleum Prospectivity of Cretaceous Formations in the Gongola Basin, Upper Benue Trough, Nigeria: An Organic Geochemical Perspective on a Migrated Oil Controversy

Abstract

Organic geochemical studies of Cretaceous formations in the Gongola Basin, northern Nigeria, show TOC values that are generally higher than the minimum (0.5 wt %) required for hydrocarbon generation. Data from Rock‐Eval pyrolysis and biomarker studies indicate the presence of both terrestrial and marine derived Types II and III organic matter, which is immature in the Gombe Formation and of marginal maturity in the Yolde Formation. Immature Type III to IV OM is present in the Pindiga Formation; and Type III OM, with a maturity that corresponds to the conventional onset (or perhaps peak) of oil generation occurs in the Bima Formation. However, Bima Formation samples from the 4710 – 4770 ft (1435.6 – 1453.9 m) depth interval within well Nasara‐1 indicate Type I OM of perhaps lacustrine origin (H31R/H30 ratio generally ≤0.25). Although the Nasara‐1 well was reported to be dry, geochemical parameters (high TOCs, S1, S2 and Hls, low Tmax compared to adjacent samples, a bimodal S2 peak on the Rock‐Eval pyrogram, a dominance of fluorinite macerals), together with generally low H3IR/H30 biomarker ratios within the 4710–4770 ft (1435.6–1453.9 m) interval, suggest the presence of migrated oil, perhaps sourced by lacustrine shales in the Albian Bima Formation located at as‐yet unpenetrated depths. The presence of the migrated oil in the Bima Formation and its possible lacustrine origin suggest that the petroleum system in the Gongola Basin is similar to that of the Termit, Doba and Doseo Basins of the Chad Republic, where economic oil reserves have been encountered.

Geochemical characterisation of Early Cretaceous lacustrine sediments of Bima Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Organic matter input, preservation, paleoenvironment and palaeoclimatic conditions

“…In the Gongola Sub-basin ( Fig. 1), three exploratory wells were drilled and an estimated reserve of 33 billion cubic feet of gas was found from Kolmani River e 1 well, confirming the presence of a petroleum system in the basin (Abubakar et al, 2008;Abubakar, 2014;Sarki Yandoka et al, 2015). There is no reported drilled well or core in the Yola Sub-basin and thus, there is no subsurface data from the Bima Formation in the study area (Fig.…”

“…Mohammed et al, 1999) and the Termit Basin of Chad (e.g. Genik, 1993) and may have generated hydrocarbons in the adjacent Gongola Sub-basin (Abubakar et al, 2008;Abubakar, 2014).…”

“…Biomarker concentration ratios can be used to describe organic matter type, source input and paleoenvironmental conditions of sedimentary rocks (Sun et al, 2014;Farhaduzzaman et al, 2012;Hakimi et al, 2011;Abubakar et al, 2008;Korkmaz and Kara Gülbay, 2007;Peters et al, 2005;Holba et al, 2003;Abdullah, 1999). The distributions of nealkanes, acyclic isoprenoids, tricyclic terpanes, hopanes and steranes were performed on m/z 85, m/z 191, and m/z 217, respectively from GCeMS fragmentation and determined based on the retention time and comparison with published work (e.g.…”

“…1), which host good petroleum systems in the Muglad Basin of Sudan and in the Termit Basin of Niger and Chad Republics (Mohammed et al, 1999;Obaje et al, 2004;Abubakar et al, 2008). The Bima Formation was deposited in continental environments under widely varying conditions: alluvial, braided river and lacustrine (Carter et al, 1963;Guiraud, 1990;Sarki Yandoka et al, 2014).…”

Geochemistry of Upper Miocene–Lower Pliocene source rocks in the Hellenic Fold and Thrust Belt, Zakynthos Island, Ionian Sea, western Greece

“…Rock-Eval pyrolysis is the most widely used method for screening the petroleum generative potential and thermal maturity of sedimentary rocks (Espitali e et al, 1986;Peters, 1986;B ehar et al, 2001). Recently published works have employed pyrolysis methods to provide insight on the hydrocarbon prospectivity in sedimentary basins (Abubakar et al, 2008;Maravelis and Zelilidis, 2010;Alizadeh et al, 2012;Korkmaz et al, 2013;Opera et al, 2013;Pantopoulos and Zelilidis, 2014).…”