Offshore drilling began in 1896 off the coast of California when an oil rig was constructed on a pier extending into the Pacific Ocean. Early offshore rigs were barges that were sunk into shallow coastal waters and marshes near shore, with drilling equipment placed on the deck. The first steel offshore platform was built in 1947 in the Gulf of Mexico. There are several types of offshore drilling rigs and platforms used today including semi-submersibles, fixed platforms, jack-up rigs, drill ships, and floating production units. Each type is suited for different water depths and designed for stability, mobility, and long-term oil and gas production.

1. Offshore Technology
Offshore Rigs & Platforms
Ibrahim Al-Jabberi

2. Introduction
History of Offshore Drilling
 First well drilled offshore :
 1896 off the coast of southern California, as enterprising businessmen pursued
California’s prolific Summerland oilfield all the way to the beach, the lure of
offshore production enticed Henry L. Williams and his associates to build a pier
300 feet out into the Pacific – and mount a standard cable-tool rig on it.
 Early Barges and Platforms:
 Seismic surveys in the 1930’s showed hydrocarbon formations in the
marshlands, bayous and shallow bays next to the Gulf of Mexico.
 Oil companies dredged a 4’-8’ deep channel in marshes and bays then towed in a
barge.
 They sunk the barge and secured it using wooden pilings, then erected a rig on
the deck above the waterline.

3. History of Offshore Drilling
 The first steel platform was built in 1947 and installed in the Gulf of Mexico
at a water depth of 20’.
 1948 Naval architects and engineers designed a system consisting of a barge
with several steel beams, or posts attached to its deck
 Drilling Equipment was installed on the deck
 When the rig arrived on location the lower part (barge hull) was allowed to fill
with water in order to sink the rig to the sea floor.

4. Drilling Rigs
• A drilling rig is a machine which creates holes in the ground for Oil & Natural Gas.
• The term can refer to a land-based rig, a marine-based structure commonly called an
'offshore rig' or a structure that drills oil wells called an 'oil rig'. The term correctly
refers to the equipment that drills oil wells or extracts mineral samples, including the
rig derrick (which looks like a metal frame tower).
• Sometimes a drilling rig is also used to complete (prepare for production) an oil
well. However, the rig itself is not involved with the extraction of the oil, its primary
function is to make a hole in the ground so that the oil can be produced.

5. There are many types and designs of drilling rigs, depending on their purpose and
improvements.
 Semi Submersible

6. • This floating drilling unit has pontoons and columns that, when flooded with
seawater, cause the pontoons to submerge to a predetermined depth. Although it is
moved by wave action, it sits low with a large part of its structure under water. This,
combined with eight huge mooring anchors, make it a very stable installation and
the preferred choice for exploring the North Sea and the new wells west of Scotland.

7.  Fixed Platform Rig

8. This immobile structure can be built from concrete or steel and rests on the seabed.
When oil or gas is located a platform may be constructed to drill further wells at that
site and also to produce the hydrocarbon. Although some platforms can be small,
most are massive compared to the other types of installations.

9.  Jack Up Rig
This is a mobile drilling rig,
different to the semi
submersible. Instead of
floating over its drilling
location the Jack up has long
leg structures, which it
lowers to and into the seabed
raising the rig out of the
water. The obvious
limitation with this type of
installation is the depth of
water it can operate in. The
maximum being five
hundred feet.

10.  Drill Ship

11. As the name suggests this is a ship
shaped drilling vessel.
Unlike the semi-submersible and the
Jack up, it does not require
tugboats to tow it to location.
Although they are not as stable as
semi submersibles they also drill in
very deep waters

12.  Flotels
This is usually a converted semi-submersible. It is attached to a platform by a long
gangway to provide extra accommodation. This, along with the usual leisure and
catering facilities, is their only task. They do have a marine crew in charge of
stabilizing the installation.

13. Platform Types
• An oil platform is a large
structure used to house
workers and machinery
needed to drill and then
produce oil and natural gas
in the ocean. Depending on
the circumstances, the
platform may be attached to
the ocean floor, consist of
an artificial island, or be
floating.

14.  Fixed Platforms
• Built on concrete and/or steel legs
anchored directly onto the seabed,
supporting a deck with space for
drilling rigs, production facilities
and crew quarters. Such platforms
are, by virtue of their immobility,
designed for very long term use (for
instance the Hibernia platform).
• Various types of structure are used,
steel jacket, concrete caisson,
floating steel and even floating
concrete. Steel jackets are vertical
sections made of tubular steel
members, and are usually piled into
the seabed.

15.  Compliant Towers
• These platforms consist of slender
flexible towers and a pile foundation
supporting a conventional deck for
drilling and production operations.
• Compliant towers are designed to
sustain significant lateral deflections
and forces, and are typically used in
water depths ranging from 1,200 to
3,000 feet (370 to 910 m).

16.  Semi-submersible Platforms
These platforms have hulls of sufficient buoyancy to cause the structure to float, but of
weight sufficient to keep the structure upright. Semi-submersible platforms can be
moved from place to place; can be ballasted up or down by altering the amount of
flooding in buoyancy tanks; they are generally anchored by combinations of chain,
wire rope or polyester rope, or both. Semi-submersibles can be used in water depths
from 200 to 10,000 feet (60 to 3,000 m).

17.  Jack-up Platforms
are platforms that can be jacked up above the sea, by dint of legs than can be
lowered like jacks. These platforms, used in relatively low depths, are designed to
move from place to place, and then anchor themselves by deploying the jack-like
legs.

18. • References
1. American Oil & Gas Historical Society 2007:Offshore Petroleum History, viewed 09
June 2015,<www.aoghs.org/offshore-history/offshore-oil-history>
2. Offshore Magazine Volume 75, Issue 5: Vessels, Rigs & Surface Systems, viewed
09/06/2015,<www.offshore-mag.com/currentissue>
3. Energy Information Administration Natural Gas 1998 : Offshore Oil and Gas
Recovery Technology, viewed 09/06/2015,
<www.eia.gov/pub/oil_gas/natural_gas/analysis_publications>