By Toyin Akinosho
People often say that the Niger Delta basin is a mature basin, an oil rich province in the waning days of its productive life. Ebi Omatsola disagrees. “The Niger Delta is a mid- life basin”, he argues.
“Only 2% of Niger Delta wells have reached deeper than 15,000feet(4572metres) Total Depth”, laments Omatsola, managing director of Conoil Producing, the Nigerian independent. “70% of the wells in the basin have not gone deeper than 9,000feet(2743metres) True Vertical Depth. This is something like scratching the surface”, he told a monthly technical meeting of the Petroleum Club recently. Operators, he said, are afraid of taking risks. “Once we run into a shale sequence which gives us a heart attack, we run away”, he told the club, an assembly of owners as well as ranking managers of E&P companies.
“Rent A Depth”
Omatsola says that policies should be introduced that allow government let companies rent a depth. “If you are holding on to an acreage and you can’t go deeper than a certain depth,can I take it over?”, he asked. “So long as I can show that I can, I should be offered the deeper parts of the acreage below which you can’t go and I should have obligations to drill a certain number of wells, for a certain number of years, before I give it up”. He said that companies “keep talking about incentives”, to do what should ordinarily be in their own interest.
The Niger Delta basin has 37Billion (proven) barrels of oil left, after 47Billion have been produced in 55 years, but oil companies can still find more than twice these remaining reserves, if only they can breach their comfort zones and drill deeper.
There have been several, sporadic attempts in the past. In the mid- 90s, Shell attempted a deep drilling campaign, with mixed results. A decade after, ExxonMobil and TOTAL jointly spud a well, targeted to drill deeper than 15,000feet, but pressure problems forced them to stop, even though they were using a High Temperature, High Pressure rig.
As I write this, Agip is drilling a deep well, Ogbainbiri Deep, to appraise and develop the deep sands earlier encountered in Ogbaibiri 2, which is currently producing at shallower depths.
“You’d never find new oil if you’re stuck with the same idea”, warned Omatsola, a 71 year old former Chief Geologist at Shell Nigeria. “Here’s a basin that has productive zones as deep as 20,000feet(6,096 metres),” and that doesn’t have to reach “the lower part of the Agbada(the oil prone, sandy shale sequence in the basin) or Akata, (the massive shale, high pressure sequence)”.
He should know. Conoil, which he heads, is currently drilling a well, Ango-2, with targets at deeper than 16,000feet(4,877 metres) for commercial sized oil pool. Earlier in the year, Conoil flowed 4,000BOPD of light (340 API)oil in two reservoirs inAngo 1Stk 3, in Oil Mining Lease(OML) 59, at depths between 15,400ft and 15,550ft True Vertical Depth (TVD). “The reservoirs are ponded against a shale ridge”, Omatsola says of the play concept. “It’s the deepest productive zone in the Niger Delta”.
The word ‘productive’ is instructive. Agip has a number of wells that have reached deeper than 16,000feet, but are not producing.
The Ango 1Stk 3 results have provided Omatsola more ammunition to campaign for deep drilling in the Niger Delta. Showing a number of slides of seismic lines indicating strong seismic events at great depths (around 6secs),he told the Petroleum Club that “the Coastal Swamp belt is the most productive depobelt” of the five extensional depobeltsin the onshore terrain of the Niger Delta. “Here, there’s 16,000 feet of untested sequence”.
Omatsola admitted that there were challenges to overcome, in getting everyone on board his “go-deeper” campaign. “You must understand basin modeling”, he told his audience. For this “the geoscientist (geologist and geophysicist) is the key”.
Companies need to embark more on High Resolution deep seismic imaging, which pictures the subsurface clearly as deep as eight (8)seconds (seismic time), equivalent to about 23,000feet(7,010metres)-after time depth conversion.
“We must close the skill gap in the industry and have earth scientists who can tell Schlumberger what they want and not just receive what Schlumberger claims it has to offer”.
And then the industry has to have the tools of deep drilling. “There are only three rigs in the country with the capacity and two of them are owned by Depthsize”. The rigs he was talking about, he said, “must have depth capacity of up to 35,000feet(10,668metres), rated to at least 15,000psi (pounds per square inch) choke/kill/ manifold pressure. Such rigs must be over 3,000HP (Horse Power), absolutely” .
Nigeria, he concluded, must be ready to tap into and develop the potential upside of the Niger Delta Basin.