Offshore drilling platforms
re-create the land on the water. Using the same rigs
as on land, the platforms are able to stabilize the
equipment in turbulent seas. There are two types of
offshore drilling rigs: those that can be moved from
place to place, and ones that are permanently
placed. Moveable rigs are often used for exploratory
purposes but once large deposits of oil or gas are
found, a permanent platform is built. Artificial
platforms can take many forms depending on the
characteristics of the well to be drilled. The subsea drilling template connects the underwater
well site to the drilling platform on the surface of
the water. It is placed over the well site, usually
lowered into the exact position required using
satellite and GPS technology. A relatively shallow
hole is then dug in which the drilling template is
cemented into place. The drilling template, which is secured
to the sea floor and attached to the drilling
platform above with cables, allows for accurate
drilling to take place. However, it allows for the movement
of the platform above, which will inevitably be
affected by shifting wind and water currents.
The first offshore drilling rigs
from the 1860s were designed to operate in very
shallow water with four legged towers not unlike the
ones used today. However, deeper excavations were
impossible because the platforms could not go into
open seas without capsizing. After the Second World
War, the first offshore well platform was developed,
and was erected completely out of sight from land in
the Gulf of Mexico in 1947. This was a fixed
platform drilling rig, which was imbedded in the sea
floor with permanent foundations. Building and
recovery of these types of platforms were expensive.
A mobile self-elevating drilling platform was
needed. In the early 1950s, R.G. Le Tourneau
invented the modern offshore drilling platforms,
which can be floated out to the drill site, and then
converted into a stable structure by opening lattice
tripod support legs down to the sea floor. In 1956,
Zapata Off Shore Company of Houston, Texas bought LeTourneu’s drilling platforms and sent them off of
Texas and then in the Gulf of Mexico.
The most extensive of today's
natural gas and oil drilling platforms, while not
altogether ocean cities, are ocean
"villages." There is a North Sea oil ocean platform
with 97.7 metres by 67.1 metres deck area capable of
providing housing for 900 workers. The facilities
for this platform include an onboard desalination
plant to provide fresh water, as well as a waste
treatment plant, kitchens, bakery, mess hall, and an
assortment of cranes and hoists, and helicopter
landing pad.
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