Source rock geochemistry of shale samples from Ege-1 and Ege-2 wells, Niger Delta, Nigeria
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ORIGINAL PAPER-EXPLORATION GEOLOGY
Source rock geochemistry of shale samples from Ege‑1 and Ege‑2 wells, Niger Delta, Nigeria S. L. Fadiya1 · S. A. Adekola1 · B. M. Oyebamiji2 · O. T. Akinsanpe1 Received: 19 August 2020 / Accepted: 2 November 2020 © The Author(s) 2020
Abstract Selected shale samples within the middle Miocene Agbada Formation of Ege-1 and Ege-2 wells, Niger Delta Basin, Nigeria, were evaluated using total organic carbon content (TOC) and Rock–Eval pyrolysis examination with the aim of determining their hydrocarbon potential. The results obtained reveal TOC values varying from 1.64 to 2.77 wt% with an average value of 2.29 wt% for Ege-1 well, while Ege-2 well TOC values ranged from 1.27 to 3.28 wt% (average of 2.27 wt%) values which both fall above the minimum threshold (0.5%) for hydrocarbon generation potential in the Niger Delta. Rock–Eval pyrolysis data revealed that the shale source rock samples from Ege-1 well are characterized by Type II–Type III kerogens which are thermally mature to generate oil or gas/oil. The Ege-2 well pyrolysis result showed that some of the ditch cutting samples are comprised of Type II (oil prone) and Type III (gas-prone kerogen) which are thermally immature to marginal maturity (Tmax 346–439 °C). This study concludes that the shale intercalations between reservoir sands of the Agbada Formation are good source rocks in early maturity and also must have contributed to the vast petroleum reserve in the Niger Delta Basin because of the subsidence of the basin. Keywords Agbada Formation · Niger Delta · Hydrocarbon potential · Total organic carbon · Rock–Eval
Introduction The geochemistry of sedimentary rocks is vital to deduce factors that control sediment characteristics during and after their deposition and also to describe the relationship between specific units of both clastic and carbonate strata (Nagarajan et al. 2007; Madhavaraju and Lee 2009). The significance of geochemistry in describing the origin of sedimentary rocks, paleo-weathering conditions as well as tectonic evolutions of sedimentary basins is recognized in many studies (Cullers et al. 1988; Nagarajan et al. 2007; Frimmel 2009). Organic geochemical analyses are unique in determining the hydrocarbon potential of sedimentary rocks as well as playing a pivotal role in the continued development of oil and gas exploration and production (Philp 2014). These analyses
* S. L. Fadiya [email protected]; [email protected] 1
Department of Geology, Obafemi Awolowo University, Ile‑Ife, Nigeria
Department of Geology, University of Lagos, Lagos, Nigeria
2
have been a significant tool in determining the hydrocarbon prospectivity of the Niger Delta. The Niger Delta is located on the western coast of Africa between Latitudes 3°50′ and 6°50′ North and Longitudes 3°25′ and 8°50′ (Fig. 1; Akinsanpe and Benjamin 2018). The delta is one of the world’s largest complexes and a prolific hydrocarbon province with estimated hydrocarbon reserves of about 36.2 billion barrels (EIA 2008). The origin of th
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