Part 1: Introduction
Give or take 100 miles south of Louisiana and Texas, the
broad continental shelf of the Gulf of Mexico becomes steeper.
Instead of falling smoothly to the 3600 meter depths found
at the center of the basin, the slope heaves and twists across most of its
northern edge. These mounds, ridges, and valleys formed over geologic time
from the upheavals of a vast salt deposit buried over 100 million years
ago.
Until very recently, the Gulf Slope lay well beyond the
normal sphere of human activity.
Rich fisheries and active marine transport in the region
mostly take place closer to shore and the animals living on the lightless
muddy bottom interested only a few specialists. |
An oil platform in the gulf. |
Offshore oil and gas drilling began in the Gulf of Mexico,
but technology did not support production facilities in the 500 meter depths
of the slope. This began to change in the early 1980's when the quest for
oil drew scientists, engineers, and managers into a strange and previously
unimagined realm.
The Gulf of Mexico has an unusual abundance of oil reservoirs--the
deeply buried layers of sand and other porous materials that hold oil--and
the reservoirs of the Gulf are unusually leaky. The movement of salt layers
that buckles the seafloor into ridges also cracks the layers of sedimentary
rock that trap the oil in the reservoirs. Pressure in the oil reservoirs
forces oil up through these faults until it vents through the seafloor into
the sea. An indication of this pressure is the enormous force that drives
oil and gas up the 'risers' (pipes leading from a reservoir up to a oil
platform) when oil well drillers tap into a reservoir. Drilling often releases
so much pressure that engineers have to burn off the excess to maintain
pressure at safe levels. |
