Abstract
Organic geochemical studies and fossil molecules distribution results have been employed in characterizing subsurface sediments from some sections of Anambra Basin, southeastern Nigeria. The total organic carbon (TOC) and soluble organic matter (SOM) are in the range of 1.61 to 69.51 wt% and 250.1 to 4095.2 ppm, respectively, implying that the source rocks are moderately to fairly rich in organic matter. Based on data of the paper, the organic matter is interpreted as Type III (gas prone) with little oil. The geochemical fossils and chemical compositions suggest immature to marginally mature status for the sediments, with methyl phenanthrene index (MPI-1) and methyl dibenzothiopene ratio (MDR) showing ranges of 0.14–0.76 and 0.99–4.21, respectively. The abundance of 1,2,5-TMN (Trimethyl naphthalene) in the sediments suggests a significant land plant contribution to the organic matter. The pristane/phytane ratio values of 7.2–8.9 also point to terrestrial organic input under oxic conditions. However, the presence of C27 to C29 steranes and diasteranes indicates mixed sources—marine and terrigenous—with prospects to generate both oil and gas.
Highlights
The Anambra Basin is a late Cretaceous–Paleocene delta complex located in the southern Benue Trough (Figure 1)
Initial efforts were unrewarding and this led to the neglect of this basin in favour of the Niger Delta, where hydrocarbon reserves have been reportedly put at 40 billion barrels of oil and about 170 trillion standard cubic feet of gas [2,3,4]
Borehole samples from Enugu 1325 and 1331 wells were obtained from Nigerian Geological Survey Agency (NGSA), Kaduna and used in this study
Summary
The Anambra Basin is a late Cretaceous–Paleocene delta complex located in the southern Benue Trough (Figure 1). The third phase, credited for the formation of the petroliferous Niger Delta, commenced in the Late Eocene as a result of a major earth movement that structurally inverted the Abakaliki region, displacing the depositional axis further to the south of the Anambra basin [12]. Specific references to the organic richness, quality, and thermal maturity in the Mamu Formation and Nkporo shales have been reported by Unomah and Ekweozor [16], Akaegbobi [1], and Ekweozor [17]. Iheanacho [18] investigated aspects of hydrocarbon source potential of the organic rich shales belonging to some parts of the Anambra basin He indicated the source rocks as shales and coals, which present good prospects in terms of economic viability as typified by the quantity and quality of organic matter they contain.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
