Nigeria: Shell moves to enhance oil recovery
The Royal Dutch Shell is introducing a technology that would help recover oil from almost foreclosed oil fields in onshore and shallow waters of the Niger Delta.
The technology referred to as ‘low contrast pay’ if well implemented may help to recover as much as 30 per cent of the country’s hydrocarbon base.
Shell’s Global Principal Technical Expert in Complex Formation Evaluation, Mr Chike Nwosu, disclosed these while delivering a paper entitled ‘Sleeping giants – Unraveling low contrast pay opportunities’ at the March monthly technical meeting of the Nigerian Association of Petroleum Explorationists (NAPE). He said the terminology, ‘Low contrast pay’, encompasses a wide range of reservoirs, where the identification and quantification of hydrocarbon pay is typically challenging, as the conventional petroleum engineering tools do not provide sufficient contrast between hydrocarbon pay and non-pay.
In a chat with our correspondent, Nwosu said when oil companies do appraisal drilling, especially the major, they look for big sands, which are expected to hold large reserves that are considered commercial for such big companies. But he noted that in search of such big sands, there are thin sands that are associated with the big sands, which also hold some oil but are not considered commercial and are ignored by the majors. Such sands if tapped could yield as much as 30 per cent of the oil reserves, which he advised could be harnessed by the small players such as the indigenous oil companies.
He said: “When we do appraisal of development drilling, what we are looking for are big sands because this big sands contain large hydrocarbons and over time what we found in the Niger Delta and the deepwater is that the initial exploration efforts were big cat discovery and these were large thick sands with a lot of hydrocarbon inside them. We have matured these assets over time and that means we have drilled the wells and produced a lot out of them and a number of them are now producing more water than oil.
“What we have missed are opportunities in thinner sands. This thinner sands is a kind of survey we carried out and not able to pick up these thinner sands very clearly but this thinner sands can be very big if you combine them together. They can be very continuous laterally. They can go as far as several kilometres and they also contain hydrocarbons. And the hydrocarbons there are typically about when you see a big sand associated with another thin sand, you can have almost 30 per cent of what you have in the big sands in those thin sands.
“Therefore, think about what we have left out by missing out those thin sands. We have left out about 30 per cent of our hydrocarbon base in Nigeria. Hydrocarbon base is about 36 billion barrels, which means we are leaving about 10-12 billion barrels and that is a huge amount to leave behind. The big companies are concentrating on tapping the big cats and are looking out for big cat discoveries. Those thin sands are not that important to them, though they are becoming a little more important as their mature fields start watering out.
“But the smaller indigenous companies that are coming into play on onshore and in shallow waters, those are substantial opportunities. So, when you think about Shell and ExxonMobil whom their production targets are in millions of barrels of oil per day, may be these are not the kind of things they will want to look at but when you look at indigenous companies that make 60,000-100,000 barrels per day, it is a substantial revenue coming in to them. Those are the opportunities that I’m trying to make people identify, go back, take a look at them, learn how they will produce and afterwards start producing them. The paper I presented are techniques by which they can identify them, quantify them and produce them.”
During the presentation of the paper, Nwosu noted that one of the more important, and volumetrically most significant, occurrences of Low Contrast Pay is in thinly bedded laminations of sand and shale, with thicknesses below the resolution of conventional logging tools.
He said a review of these thin-bedded pay opportunities, identified in both onshore/shallow waters and deep water settings in Nigeria, indicate that the volumes in place are under-estimated using conventional techniques (tools and evaluation methods), and proper evaluation (advanced tools and interpretation methods) would result in an increase of between 10 to 25 per cent in the calculated hydrocarbon volumes in these reservoirs.
The presentation also reviewed the depositional processes that control the distribution of clays in siliciclastics, the complexity of identification and quantification of hydrocarbon resources in these thin-beds, the modern logging tools that aid proper identification and, combined with established and novel evaluation techniques, which provide more accurate quantification of in-place volumes.
https://www.thenationonlineng.net/2011/index.php/business/energy/41792-shell-moves-to-enhance-oil-recovery.html