Deep sea giants hold clues to fossil fuels (8/9/2008)

As fuel prices continue to rise, researchers have shown how giant channels on the ocean floor could point the way to finding new oil and gas reserves.

The research, led by Ian Kane of the University of Leeds, examined how these channels, similar to rivers, but deep underwater, build up to scar the ocean floor. And he discovered that their formation follows a very different pattern to that of rivers on land.

"River channels have been studied for centuries," he said. "Many schoolchildren learn how rivers meander and form ox-bow lakes, but these processes are still very poorly understood when it comes to submarine channels. These channels are built by currents carrying large volumes of sediment – and seem to be far more stable and far less likely to meander or form ox-bow lakes than those on land."

The findings, published by the Geological Society of America, have significant implications for helping the oil and gas companies get the most out of the ground.

"The sands and gravels deposited by these sub-sea giants, have in many cases trapped valuable accumulations of fossil fuels," said Kane. These fields are already being tapped by deep-water production rigs off Brazil, West Africa, the Nile Delta, Mexico and Indonesia – but knowing where to drill is an inexact science.

As Kane explained: "What the companies have to do is make estimations using very limited data. Anything that can give them a clearer picture of where to find the oil and gas will be very valuable."

Compared to river systems these underwater channels are difficult to study, even using remote-sensing techniques. So Kane, whose work is part-funded by a consortium of oil companies, used the world-leading Sorby Environmental Fluid Dynamics Laboratory at the University of Leeds to model the creation of these submarine channels.

The results show that flows within these channels may deposit sediment on both the inner and outer bends. This is different to river channels where deposition occurs primarily at the inner bend, leading to continuous meander expansion and the formation of ox-bow lakes. This explains why submarine channels generally lack these features and may remain stable over long time periods.

The spin-off for the oil companies is clear. "An individual production well may cost over £50m, so understanding and predicting the distribution of the different rock types that hold these hydrocarbons is critical for optimising well type and location, and therefore producing more of the oil," said Kane.

"In most oilfields they don't manage to recover all the oil and gas. In some cases most is actually left in the ground. From both an economic and an environmental point of view it makes sense to get as much as you can out.

"Understanding the differences between submarine channels and rivers will enable improved geological models, and enhanced oil production from these giants of the deep."

Note: This story has been adapted from a news release issued by the University of Leeds

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