The other process, still in use, is to cut a window in an old well's steel casing and then drill horizontally into the oil zone.
Most analysts expect oil prices to be softer in the first quarter as the euro-zone crisis dominates the news and unseasonably warm winter weather keeps oil demand weak.
For decades geologists have discovered bountiful oil and gas onshore in the Wilcox zone.
So far this year, oil producers' imports from the euro zone are up by a quarter on 2003: imports from America are up by just 8%.
ECONOMIST: What might oil producers do with all that extra cash?
However, in September the leaders of both nations signed a deal, mediated by the African Union, to resume oil sales and set up a demilitarised buffer zone.
However, special factors are largely to blame: first America's boom and then rising oil prices lifted the proportion of trade with countries outside the zone.
Euro-zone exports to Asia, central and eastern Europe and oil-exporting countries have been growing apace.
In addition to restarting oil exports from South Sudan, the two presidents agreed on a demilitarized zone and principles of border demarcation.
In addition to a deal to restart oil exports from South Sudan, the two presidents agreed on a demilitarized zone and principles of border demarcation.
At a meeting in September the buffer zone was agreed and South Sudan said it would resume the production of oil, but the deal was not implemented.
The central bank now has reason to reverse course because the underlying causes of inflation (oil, commodity and food prices) are easing and the economic outlook for the euro zone has deteriorated.
According to the commission's report, in 2000-05 oil exporters spent a bigger share of each extra dollar of export revenues on imports from the euro zone than they did in 1973-81.
Euro zone economic data released Tuesday showed producer price inflation rose sharply in August, mainly due to higher oil prices.
And because the bacteria use oxygen in the water as they digest oil, scientists are concerned that process could cause an oxygen-depleted area underwater a "dead zone" that could choke off a variety of undersea life.
With the euro zone in recession and growth flagging in America and China, the world's three largest consumers of oil are buying less of it than expected in early 2012.
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