The Search for Petroleum in the Benue Trough: The Challenges and Strategies.  Paper Presented at the University of Jos PTDF Chair Seminar.

19th April, 2012

by 

Dr. M. E. Offodile FNMGS, FNAH

The Benue through is the, 150km, width, stretch of an elongated sedimentary basin that extends from the southeast, bordering the Niger Delta in the south south, to the northeast of the country a distance of about 1000km. The Benue trough is in filled by Cretaceous to Tertiary sedimentary rocks, running from the Abakakliki area, below the present confluence of the Rivers Niger and Benue to the northeast.  The sedimentary sequence extends from the coastal basin of the Niger Delta and has been described by Reyment(1965) "AS THE LONG ARM"  of the Nigerian coastal Basin.  The concept of a continuous linear sedimentary sequence extending from the Nigerian Coastal basin to the Upper Benue area is confirmed, according to Cratchley and Jones, (1965), by:

1] The continuity of the palaeontological zonatian with the coastal marine formatios

2] The series of long narrow folds with ENE-WSW trend linked with the south western folds of the Abakiliki sedimentary area

3] The narrow lead-zinc mineralization belt running from Abakiliki areas in the southeast to the north east of the basin. 

The Benue trough is vaguely subdivided geographical, for stratigraphic correlation only, into the Upper, or northeast region, Middle Benue region, or Lafia - Muri area, and Lower or south Benue valley, (Offodile 1975).  The Lower Benue region is separated into the Abakiliki and Anamba subbasins. Similarly, the Upper Benue area is also further subdivided into the Gongola, Duku-Kerri, Ashaka and Yola subbasins.  The region covering the trough is drained by the RIvers Niger in the Lower basin, the Rivers Benue and Gongola in the Middle and Upper areas of the basin, respectively.  The middle Benue trough is separated from the Upper Benue by the basement high in the Bashar, Amar and Zurak area described as the Zambuk ridge and from the Lower Benue by another Basement high in the Makurdi - Gboko region.  The lower Benue is contiguous with the Anambra basin which is further separated from the Niger Delta by the Onitsha high.

Work on the Benue Trough was preceded by the pioneering efforts of Falconer (1911), schematic report in connection with lead zinc exploration by McConnel (1949) Farrington (1952), routine geological mapping by Shell BP. (1957) and Esso Exploration Inc. 1967 of the sedimentary areas south of rivers Niger and Benue.  Other accounts include that by Cratchley and Jones (1965) Wright J.B. (1975 and 1968) Burke; Dessauvagie and Whiteman 1972 Offodile (1976, 1984 and 2004) Benkhelil 1982, Peters (1978) Wright (1981) Benkhelil (1989) etc.   Offodile (1976) concentrated on the Middle Benue area, where it was possible to establish not only the geology of the area which, before then, was only scantily known, but also established the stratigraphic and paleogeographic connection with the Upper and Lower Benue sections of the trough with the Tethys.  All other authors, carried out much of their research on the Lower and Upper Benue, which were, not only more easily accessible, but also had more extensive surface exposures and outcrops of the underlying rock formations.

The indicators for the existence of petroleum or hydrocarbon has been analysed.  The identified source rocks are mature and compare with those of the southwest of the trough and the Anambra basin.  The reservoir rocks and possible oil traps have also been identified.  The much talked about igneous activity and the possibility of the accumulated hydrocarbon being dissipated should not discourage the search programme.  The structures arising from the tectonics of the trough and the development of pre depositional intra tradonic sub basins within the trough, and in filled by thick sequence of sediments,  are thought to be reasonably conserved and most probably shielded from the effect of the igneous activity, which deserve more detailed study.  Hydrocarbon exploration requires sufficient, consistent and sustainable funding  for more regional exploration programme.

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