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Bacteria, Underground Fires to Unlock Oil Reserves

Could microbes, underground fires, or sonic vibrations help open up untapped oil resources?

These unlikely candidates are among a variety of techniques that could help squeeze more oil out of developed reservoirs, oil engineers say.

The technology is not new, but has been made increasingly viable by the scramble for incremental supply on the crude market.

Today's $40 per barrel oil price helps lend economic sense to many projects that seemed ridiculous at the near $10 per barrel levels seen in the 1998/99 price crash.

Political desire for energy security has spurred the drive to squeeze every last drop from maturing fields in North America and the North Sea. With more than half the oil in these accumulations often left in the ground, new technology could extend their life significantly.

While oil firms are looking at improving their understanding of oil accumulations, and at injecting vast quantities of gas into wells to push out the crude, academic reservoir engineers are taking things a step further, proposing to set fire to heavier oils to get them to flow, and to enlist helpful bacteria to ease the flow of the oil.

Oil firms have improved average North Sea reservoir recovery factors by about five percentage points over the last 10-15 years, to about 47 percent of oil initially in place, helped by the development of horizontal drilling techniques, estimates David Hughes, principal reservoir engineer at Reservoir Management Limited in Aberdeen, Scotland.

He adds that perhaps another five percentage points could be gained by Improved Oil Recovery projects, using time-lapse seismic data libraries to gain a better understanding of the way oil drains from a reservoir, and thus directing infill well drilling.

FOURTH DIMENSION

BP researchers reckon this "4D" seismic data has gained the company almost 100 million barrels of additional recoverable oil, mostly in the North Sea, at yields in excess of application cost.

But even these computer-intensive technologies will struggle to get average recovery factors much over 50 percent.

"One way of looking at it is that you are still leaving half of the oil in the ground when you abandon a field," Hughes says.

Higher recovery calls for more radical innovation: known to researchers as Enhanced Oil Recovery, a subset of IOR.

These techniques concentrate on processes inside the reservoir -- injecting gases, chemicals, heating the oil, vibrating it with sound, or unleashing oil-eating bacteria.

No one really knows how much EOR could contribute to world oil production, especially considering the early stage of development of many of the technologies involved.

North Sea EOR projects include extension of reservoir life at BP 's Magnus field, where deepwater hydrocarbon gas from other fields will be reinjected into Magnus to increase recovery by some 50 million barrels.

Combining gas injection with commitments to reduce greenhouse gas emissions could help develop another EOR possibility: injecting carbon dioxide into mature fields, although a recent UK government study found this uneconomical under present conditions.

BACTERIA AND BURNING OIL

Technology could also help develop oil accumulations once thought unworkable.

Analysts estimate the world holds about four to five trillion barrels of heavy oil that is too thick to flow in the reservoir. Recovery of just 20 percent of this would equal current estimates of the world's conventional reserves.

North Sea heavy oil alone amounts to a substantial 10 billion barrels.

"It is not that we are running out of oil, we are just running out of technology to get it out," said Malcolm Greaves, whose work at the University of Bath in England has concentrated on injecting air into oilfields to start a combustion process that burns some of the heaviest fractions of the oil, allowing the rest to flow out through nearby horizontal collection wells.

A pilot study with oil firm Petrobank will try out the technique in Canada's massive Athabasca tar sands next year.

"Some have called it radically revolutionary. If the pilot in Canada takes off then that will be it," Greaves says.

If setting fire to the reservoir wasn't enough, what about using bacteria to help?

"Microbial EOR is the sort of "Cinderella" technology. It is very cheap and it promises a lot, but it is not very well understood," Hughes said.

Researchers say Norway's Statoil reckons it will get around 32 million incremental barrels from its Norne field through encouraging the growth of naturally occurring bacteria that feed on oil and produce detergent-like chemicals that make it flow more easily.

The UK government and major oil companies have shown interest in Statoil's approach, and are hoping to set up their own pilot scheme.

All this may only scratch the surface of today's 80 million barrel per day world oil market. Analysts estimate EOR oil production at only around 1.2 million bpd, although there is little data from India, China and the former Soviet Union.

But it may have a larger role to play in the future as the conventional opportunities available to Western firms shrink.

"There is not a lot of interest in EOR from operators yet, although there is a lot of interest in IOR -- infill wells, time-lapse seismic and improved drilling techniques," Hughes said. "But there is a lot of interest from the academic sector, which tends to be as much as a decade ahead."

"Since floor oil prices have risen so much, that might just start to make some of these projects economic."

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