Is the search for oil in the North-East a fool’s errand? By Ikenna Okonkwo

President Buhari recently ordered (if that is the right word) the Nigerian National Petroleum Company (NNPC) to intensify its search for hydrocarbons in the Nigerian sector of the Chad basin (North-Eastern Nigeria).

The reaction as usual was renewed skepticism over a search that is in its third decade and with each passing year looks more and more like a fool’s errand.  I remember watching, in 2011 the then Minister of Petroleum, Diezani Allision-Madueke talk excitedly (on NTA) about exploration efforts in the Nigerian sector of the Chad basin. She confidently assured that chances of discovering commercial reserves of hydrocarbons are very good and production should start in three years (i.e.2014).

That nothing has come till date could be blamed on the security situation it must be admitted or maybe it is more than that.

A lot of the conversation about the question of oil in the Nigerian sector of the Chad Basin has been colored by considerations of the Northern part of Nigeria wanting its own local source of petrodollars which then deteriorates into the many arguments about marginalization and the ordering of the Nigeria federation. I would like to look at the question from the facts that actually matter: The Geology as no amount of regional sentiment or wishful thinking or executive ordering can alter the geologic factors that lead to hydrocarbon accumulations of commercial quantity in some places.

A Clarification of Locale

One of the arguments for the geology favoring the presence of hydrocarbon reserves in the Nigerian sector of the Chad basin is the presence of proven reserves in Niger Republic and Chad within the Chad basin in those countries. If the Geology is the same (as the argument goes) if they have oil, then we should expect same.

The reality is that Chad basin is an extensive Pleistocene age (less than 3 million years old) veneer of sediments that cover much older Late Cretaceous age (around 105-65 million years ago) series of related but isolated basins. These basins formed around the time when the African continent separated from the South American continents leading to the formation of Atlantic Ocean. They include the Benue Trough in Nigeria, the Termit Basin in Niger, the Doba and Doseo basins in Southern Chad and other basins in Cameroon and Central African Republic. The oil discoveries made by Niger and Chad are from the Cretaceous rocks of the Termit, Doba and Doseo basins respectively. Point is when we talk about oil exploration in the Nigeria part of the Chad basin we are actually talking about exploration in the Northern part of the Benue Trough (sometimes called the Bornu Basin) beneath the sediments of the Chad basin.

The Elements of Hydrocarbon Accumulation

With that clarification in mind the next question to answer is if we should expect oil in the Benue Trough as has been found in the other basins beneath the Chad basin.

Oil exploration basically involves the evaluation of the geology of an area to establish seven key elements required for hydrocarbon production and accumulation: Source, Maturation, Reservoir, Seal, Trap, Timing, and Migration.

The Source Rock is an organic rich rock which contains remains of dead (usually) marine organisms which weren’t properly decomposed leading to preservation of their organic chemicals. These organics when subjected to increased temperatures (due to burial) are converted into simpler hydrocarbon constituents of petroleum by a process known as Maturation.

A Reservoir Rock is a porous and permeable rock that can allow for the accumulation of generated hydrocarbon. Its permeability also means it allows the flow fluid hydrocarbons within the reservoir and most importantly to the wells drilled to exploit them.

For a reservoir to serve as a tank allowing hydrocarbons generated from a source rock to accumulate in large quantities and not flow elsewhere and be lost the reservoir unit must be Sealed by another unit with low permeability. The reservoir rock and the seal rock also have to be configured either structurally (faults, folds etc) or stratigraphically in order to form a Trap.

The most important element in all of this is the Timing. The reservoir, trap and seal have to be in place at the time when the source rock releases the matured hydrocarbons through a process called Migration. If maturation and migration takes place before the reservoir, seal and trapping configuration are in place the oil generated will be lost.

Are Elements in Place in the Nigerian sector of the Chad Basin?

The presence of good candidates for source, reservoir and seal rocks have been established in outcropping and subsurface sections of the Northern Benue trough. The basin also has numerous structures that could serve as traps for accumulated hydrocarbons (faults, anticline structures etc.). The real question mark is on the issue of timing; the formation of the trapping structures in the Benue Trough took place at the end of the Cretaceous period after the source, reservoir and sealing units had been created. The question is if maturation and migration took place before that time. Another important question is the effect of the intense volcanism and magmatism that took place in the Northern Benue trough from 7 to 2 million years ago. This volcanism created the extensive Biu Plateau in Borno state. Volcanic activity usually has the effect of providing the extra heat that “overcooks” already mature source rocks or destroys already accumulated hydrocarbons. You don’t get that kind of volcanism in the Termit, Doba and Doseo basins.

A Fool’s Errand?

It is the task of the geologists of oil exploration companies to determine if the elements are present in prospect. From the late 70s into the early 90s extensive surface geological exploration was carried out by a group of largely french geologists sponsored by Total (then Elf-Aquitaine). Shell, ExxonMobil, Agip, Chevron and Total began drilling operations in the Benue trough in 1994. Apart from non-commercial gas discoveries in one well by Chevron most of the attempts turned out to be unsuccessful. There are stories that these companies only carried out drilling in those areas to appease the late Sani Abacha and reportedly as a prerequisite for accessing oil blocks in the Niger Delta. The international oil companies abandoned efforts at the beginning of the millennium only to be replaced by NNPC who apparently have carried on exploration till date.

In summary the geology of the Nigerian sector of the Chad Basin doesn’t offer much in terms of prospectivity. The fact that the international oil companies haven’t shown interest should be a pointer to this. That the NNPC is spearheading the efforts (unlike in the Niger Delta or even, more recently, in the Benin Basin) seem to point to political motivation rather than geological. At a time of low oil prices and limited resources the continual investment of huge amounts of money in place that offers not very promising chance of success looks like a futile exercise and a fool’s errand.