[Editors] MIT studies undersea channels to aid oil recovery

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT studies undersea channels for oil recovery
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For Immediate Release
MONDAY, MAY 22, 2006
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

--PHOTO AVAILABLE--

CAMBRIDGE, Mass.--Work in an MIT lab may help energy companies 
withdraw millions of additional barrels of oil from beneath the sea 
floor.

Typically, companies recover only 30 percent to 40 percent of the oil 
in a given reservoir. Since a single reservoir may contain a billion 
barrels total, increasing that "recovery efficiency" by even a single 
percentage point would mean a lot of additional oil.

Toward that end, Assistant Professor David Mohrig of earth, 
atmospheric and planetary sciences and Carlos Pirmez, a research 
geologist from Shell International Exploration and Production Inc., 
have been examining one type of geological formation of interest to 
industry -- channels filled with highly permeable and porous 
sedimentary deposits that extend deep below the sea floor.

These structures form when sediment-laden currents flow off the 
continental shelf and into channels on the deep-ocean floor, dropping 
sand, silt and clay as they go. Over many thousands to millions of 
years, the channels can become filled with porous sandstone covered 
by impermeable mud -- a perfect trap for oil and gas that seep up 
from below.

Over the past 20 years, energy companies have withdrawn significant 
amounts of oil from such buried channels. But they could extract even 
more if they understood the channels' internal structure.

"If we could understand how they develop, then we would also 
understand a great deal about what they're composed of -- the 
distribution of clay, silt, sand and even gravel that they're built 
out of," Mohrig said. With a better understanding of porosity and 
permeability within a channel, companies could more accurately 
determine how much oil is present, where it is located and how 
quickly it can be withdrawn.

Researchers have been re-creating the formation of submarine channels 
in Mohrig's Morphodynamics Laboratory using a 5-meter-square sand 
table.

The experiments have yielded results that the collaborators call 
"counterintuitive." On a map, the sinuous submarine channels look 
like meandering surface rivers. However, they exhibit behaviors that 
are markedly different and -- to us surface-dwellers -- totally 
unexpected.

The behaviors stem from differences in density. Water in a river is 
about a thousand times denser than the fluid it flows through -- air. 
As a result, a flow tends to remain confined to its riverbed, 
escaping over the banks only rarely. In contrast, the current running 
through a submarine channel may be only 10 percent denser than the 
seawater around it. Thus, the current can spill out of its channel 
more easily and frequently than a river might.

That difference explains several unexpected findings. For example, at 
times the bottom of the current sloshes almost all the way up the 
edge of the channel and then back down again. And at bends, the 
current may go straight, pouring up and over the bank and dropping 
its sediment outside the channel -- an outcome with important 
implications for energy companies as they plan to drill.

Because of their close and continuing involvement in the scientific 
investigation, the Shell researchers are prepared to put the research 
findings to practical use. "The experiments that David is doing have 
never really been done before, so we're learning new things about how 
channels are put together," Pirmez said. "We're getting new ideas, 
new concepts that may change the way we think about the subsurface."

The result should be improved predictions, reduced uncertainty and 
more efficient recovery from these oil-rich submarine formations.

This research was supported by Shell International Exploration and 
Production Inc. through the MIT Department of Earth, Atmospheric and 
Planetary Sciences.

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Elizabeth A. Thomson
Assistant Director, Science & Engineering News
Massachusetts Institute of Technology
News Office, Room 11-400
77 Massachusetts Ave.
Cambridge, MA  02139-4307
617-258-5402 (ph); 617-258-8762 (fax)
<thomson at mit.edu>

<http://web.mit.edu/newsoffice/www>
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