useful for offshore structure designer.

1. INTRODUCTION TO OFFSHORE STRUCTUREINTRODUCTION TO OFFSHORE STRUCTURE

2. Searching for oil over water using seismology

3. ANATOMY OF OIL RIG

4. MAJOR SYSTEMS OF LAND OIL RIG
Power system
electrical generators
large diesel engines
Mechanical system
hoisting system
turntable
Rotating equipment

5.  Hoisting System: The hoisting
system is used to raise and lower
pipe in and out of the hole and
to support the drill string to
control the weight on the drill bit
during drilling. It also acts as an
elaborate pulley to lift the
travelling block and remove the
drill pipe.

6.  Rotating equipment - used for rotary drilling
swivel - large handle that holds the weight of the
drill string; allows the string to rotate and makes a
pressure-tight seal on the hole
drill string - consists of drill pipe (connected sections
of about 30 feet (10 meters) and drill collars (larger
diameter, heavier pipe that fits around the drill pipe
and places weight on the drill bit)
turntable or rotary table - drives the rotating motion
using power from electric motors

7.  drill bit(s) - end of the drill that actually cuts up the rock;
comes in many shapes and materials (tungsten carbide
steel, diamond) that are specialized for various drilling
tasks and rock
Casing - large-diameter concrete pipe that lines the drill
hole, prevents the hole from collapsing, and allows drilling
mud to circulate

8.  Drilling mud:
used to stabilize the excess pressure created due to fluid in the
formation
used to cool drill bit
remove rock chips
 Derrick - support structure that holds the drilling apparatus; tall enough
to allow new sections of drill pipe to be added to the drilling apparatus
as drilling progresses
 Blowout preventer - high-pressure valves (located under the land rig or on the
sea floor) that seal the high-pressure drill lines and relieve pressure when
necessary to prevent a blowout (uncontrolled gush of gas or oil to the
surface, often associated with fire)

9. DRILLING PLATFORMS
Types of offshore drilling platforms:
Movable drilling rig-(MODU-mobile offshore drilling
unit)
exploration purposes
Eg, drilling barge, jack-up barges, ,submersibles ,semi-
submersibles ,FPSO (floating, production, storage
and offloading systems), drill ships
Permanent drilling rig-
extraction and production
Eg, jacket platform, gravity platform

10. Complaint platform:
tension leg platform
guy towers
articulated towers

12. Questions
1.Petroleum and natural gas deposits are found in -------- rocks in
sea bed.
2.Oil and gas are made up of --------.
3.When was 1st
offshore drilling began and where.
4Name one active location where many platforms exist
5.What is derrick?
6.List some functions of drilling mud.
7.Write few movable drilling platform names and draw free sketch
of one

13. GRAVITY PLATFORM:Hibernia oil platform

14. GRAVITY PLATFORMS
 The Hibernia Gravity Base Structure is the world's
largest offshore oil platform

17.  Caisson: void spaces used as storage compartment for
crude oil or filled
with permanant Fe ore ballast
importance:
to provide buoyancy during
construction/towing and later serve as oil storage space
 Skirts:
improve foundation stability
act erosion resistance feature
provides transverse resistance to platform sliding

18. Troll A platform
(condeep )

19. GRAVITY PLATFORM
GBS: gravity based structure-concrete, steel
Condeep (concrete deep water structure) :gravity base structure for oil platforms developed
and fabricated by Norwegian Contractors in Stavanger, Norway .
The Condeep is used for a series of production platforms introduced for crude oil and natural gas
production in the North Sea and Norwegian continental shelf
Design: production
: large reinforced concrete bottom mounted structure
:uses its weight to resist environmental loads. If it fails ,it fails severely
:generally built in soft soil like Gulf of Mexico
Depth : medium--- up to 350m

20. Advantages
 Support large deck loads
 Possible reuse
 Construction and testing may be completed before
floating and towing to site
Large field , long term production
 May have large storage capacity
 More tolerant to overloading and sea water exposure .

21. Disadvantages
 Cost increases exponentially with depth
 Foundation settlement (sea-bed profile increases due
to geological disturbances)
 Subject to seafloor scour
 May require more steel than steel jacket structure

22. Questions
1.Draw a neat sketch of one of gravity platform and mark the
parts
2.What are CONDEEP.
3.What are essential features of gravity platform.
4.Give one field example of gravity platform.
5.What is the key word of gravity platform.
6.What is a caisson.
7.What is the use of skirts.
8.Give essential features of gravity platforms.
9.What are exclusive advantage of gravity platform.
10.State few demerits.
11.Show in sketch possible failure modes of foundation of
gravity platforms

23. FIXED PLATFORM
 Two main components:
substructure
superstructure (topside)

24. JACKET PLATFORM

25. Sketch of jacket platform

26. 26

28.  Superstructure:
supported on jacket structure
consist of drilling equipment, production
equipment, gas turbine ,generating sets, gas flare
stations
it weighs up to 40,000 tonnes

29.  Substructure:
Jacket-tubular platform support structure
- It serves as guides for driving of piles –
called template structure
- It supports and protects well conductors,
pumps, risers etc
- Suitable for water depths:150-250m
- Soil condition: clay-penetrable- because
of piles

30.  Most common: steel jacket platform
Substructure and jacket is fabricated from
steel welded pipes and is pinned through to sea
floor with steel piles which are driven through pile
guides on outer members of jacket
The piles are thick steel pipes of 1 to 2m
diameter and can penetrate as much as 100m
into sea-bed
The jacket can weigh up to 20,000 tonnes

31. PARTS OF JACKET
PLATFORM
 Transition piece: connects topsides and jacket
structure
 Conductors: long hollow straight or curved
tubes that embed into sea- bed and through
which drilling for oil, gas or both is performed
 Risers: long slender tubes that carry the crude or
partially processed oil/gas to another location for
further processing either to a land based facility
or to another platform

32.  Boat landing, Barge bumper and riser guard:
-for berthing of supply vessels
-for smooth berthing to facilitate a reduced
vessel impact on the structure
Riser guard:Another protective structure that
protects the oil/gas carrying risers.
They are designed for accidental vessel impacts

33.  Launch truss:are provided on one side of jacket
to facilitate the loading out on to the barge
 Mud mat: bottom most framing of platform that
helps resist natural forces of nature towards
stability of platform before piles are driven
through legs

34. ADVANTAGES
Support large deck loads
Construction and testing may be
completed before floating and
towing to site
Large field , long term production
Piles result in good stability
Little effect from sea floor scour

35. DISADVANTAGES
 Cost increase exponentially with depth
 High initial and maintenance cost
 Not reusable
 Steel structure member subject to
corrosion
Corrosion severe near the SWL

36. Questions
1.List the purpose for building an offshore structure
2.What are the two main components of a fixed
platform
3.Describe important features of jacket platform
4.Draw a line diagram of jacket platform and mark
the parts
5.What do you understand by the term template
structure
6.What is the most suitable soil condition for a jacket
platform
7.What is the typical weight of a jacket platform in
tonnes
8.Write a brief note on flare boom

37. QUESTIONS
1.Give advantages of jacket platform.
2.Give some demerits of jacket platform
3.Generally top-sides are connected to jackets
by-----
4.Which component of the platform helps them
from skidding from barge
5.What do you understand by mud mats.
6.With neat sketches ,show installation steps of
jackets.
7.Jacket structure have high maintenance
cost .Why?