Gulf states seeking to prolong the lives of ageing oilfields face a shortage of the gas needed to pump into wells to maintain crude output. And the problem is rapidly worsening. The UAE last year was injecting 1.7 billion cubic feet per day (cfd) of gas into oilfields to maintain production levels.
The need for gas to use this way could rise by as much as 8 per cent a year for the next decade, said Fereidun Fesharaki, the vice chairman of the consultancy FACTS Global Energy. By 2020, demand could reach 4.2 billion cfd, approaching the nation's total current gas output from onshore fields. If Abu Dhabi, the nation's main producer, had not pledged most of its offshore gas output to supply Asian customers under long-term contracts for liquefied natural gas, that might not be so serious. But Mr Fesharaki said the UAE, along with Saudi Arabia, Kuwait and Oman, was "out of gas". If it used all the gas it would need to maintain oil production, it would fall short of gas for power generation and industry.
Gas injection is one of the most common techniques used in enhanced oil recovery (EOR), the umbrella term for methods of revitalising older oilfields. When a reservoir is first tapped into, the natural pressure exerted on the oil by the gas lying above it pushes oil into the well. As crude and some gas is drawn out of the reservoir, the remaining gas expands and the reservoir pressure drops. Eventually the oil stops flowing unless the reservoir is repressurised.
Gas injection works well for most Middle East oil reservoirs, typically increasing their recovery factor to between 60 and 80 per cent of the initial oil in place, from about half that without EOR. But for large fields, the amount of gas needed is enormous. Saudi Arabia, the region's biggest oil producer, is injecting more than 3 billion cfd of gas and could more than triple that by 2015, according to FACTS.
Iran, which uses the largest gas volumes in the region to pump its sticky crude, last year started the world's largest EOR project at its Aghajari oilfield, into which it plans to inject 3.6 billion cfd of gas. Even though the country sits on the world's second-biggest gas reserves, some engineers believe current gas development plans are "insufficient for the actual re-injection needs", said Mr Fesharaki.
"They indicate Iran's oil reservoirs may need up to 20 billion cfd of gas in the next decade." Unsurprisingly, then, Gulf oil producers are investigating other types of gas for EOR projects. Nitrogen and carbon dioxide are the main candidates. Both have been tried elsewhere with various degrees of success but they have not caught on widely because they are usually more expensive than natural gas. An exception was Mexico, which in 2000 decided to use nitrogen to revive the flagging output from its biggest oilfield Cantarell. Mexico was short of natural gas as it had neglected its development.
At first the intervention was successful but Cantarell's production peaked only four years later and has been in steep decline since 2006. Would natural gas have worked better? Possibly, petroleum engineers suggest, because it is more soluble in oil than nitrogen and therefore better at coaxing oil to flow by thinning it. Nitrogen has the advantage of being produced from air and separation plants can be built near oilfields.
Carbon dioxide, which is much more soluble in oil, has the disadvantage of usually having to be collected from an industrial source and piped to sometimes distant oilfields at considerable cost. That is not a viable proposition in most places although it could become so if tight caps on global carbon emissions are agreed to. The UAE is planning to develop nitrogen and carbon dioxide injection facilities at a major onshore oilfield.
Saudi Arabia is considering carbon dioxide to maintain output from Ghawar, the world's biggest oilfield, with a 40 million cfd pilot project set to start in 2013. Both countries hope to benefit from an elusive international agreement on carbon capture and storage that might enable them to recoup some of their costs. In the end, it may be gas shortages that turn them into carbon storage pioneers because they are short of other gas-injection options.
tcarlisle@thenational.ae
