The document discusses various types of offshore structures used in oil and gas production, including both floating and fixed structures. It describes jack-up rigs, drillships, semi-submersibles, tension leg platforms, SPAR platforms, FPSOs, jacketed platforms, compliant towers, and concrete gravity structures. Each structure type is suited for different water depths, from shallow to deep water. The document also provides details on properties, uses and advantages of different offshore structure types.

1. SLBS ENGINEERING COLLEGE
NAME – DEEPAK SOLANKI
ROLL NO – 14ESLPE010
YEAR – IV YEAR
SUBMITTED TO
Dr. R.K. BAWA
(ACADEMIC DIRECTOR)

2. CONTENTS
1. INTRODUCTION
2. OFFSHORE MOBILE DRILLING UNITS
3. PRODUCTION STRUCTURE
4. FIXED PLATFORMS
5. FLOATING PLATFORMS

3. INTRODUCTION TO OFFSHORE STRUCTURES
& FIXED PRODUCTION PLATFORMS
3

4. OFFSHORE MOBILE DRILLING
UNITS
4
Broadly classified into two types:
1. Shallow water drilling
units:
 Self Elevating Jack-ups
 Drilling Barges
2. Deepwater drilling units:
 DrillShips
 Semi Submersibles

5. OFFSHORE PRODUCTION
STRUCTURES
5
Broadly classified into two types:
1. Fixed structures that extend to the sea-bed:
 Fixed Steel (Jacket) Structure
 Fixed Gravity based Structure
 Compliant towers
2. Floating Structures that float near the surface:
 Tension leg platforms
 SPAR
 Ship shaped vessel (FPSO)

6. STRUCTURES VS. DEPTHS
6

7. 7
FIXED
PRODUCTION
PLATFORMS

8. JACKETED PLATFORM
8
Space framed structure with
tubular members supported on
piled foundations.
 Used for moderate water
depths up to 400 M.
 Jackets provides protective
layer around the pipes.
Typical offshore structure will
have a deck structure containing
a Main Deck, a Cellar Deck, and a
Helideck.

9. JACKETED PLATFORM
9
 Underwater, the piles are
contained inside the legs of a
“jacket” structure which
serves as bracing for the piles
against lateral loads.
Natural period (usually 2.5
second) is kept below wave
period (14 to 20 seconds) to
avoid amplification of wave
loads.
95% of offshore platforms
around the world are Jacket
supported.

10. CLASSIFICATION OF JACK-UPS
10
Can be classified into two basic categories:
1.Independent leg jack-ups
2.Mat supported jack-ups

11. MAT SUPPORTED & INDEPENDENT LEG JACK-
UPS
11

12. PROPERTIES OF JACK-UP RIGS
12
Jack-ups can be either self-propelled, propulsion assisted, or
non-propelled.
The majority of jack-up rigs are non-propelled. The self
propelled unit although very flexible, requires a specially
trained crew of seamen as well as drilling team.
Jack-ups have been built with as 14 legs and as few as 3
legs. As the water depth increases and the environmental
criteria becomes more severe, we find that to use more than
4 legs is not only expensive but impractical.

13. SELECTION OF TYPE OF JACK-UP RIG
 When evaluating which type of jack-up to use, it is necessary to
consider the following:
1. Water depth and environmental criteria
2. Type and density of sea bed
3. Drilling depth requirement
4. Necessity to move during hurricane season
5. Capability to operate with minimum support
13

14. INDEPENDENT LEGS (SELF ELEVATING)
JACK-UPS: PROPERTIES
14
Consists of a triangular,
sometimes rectangular, shaped
box section barge fitted with three
(sometimes four) moveable legs
which enable the vessel to stand
on the sea bed.
Can work in water depths of
upto approx. 120 meters (400ft)
Transported in long sea passages
using submersible heavy lift ships.

15. COMPLIANT TOWER
Narrow, flexible framed
structures supported by piled
foundations.
Has no oil storage capacity.
Production is through
tensioned rigid risers and
export by flexible or catenary
steel pipe.
Used for moderate water
depths up to 600 M.
15

16. CONCRETE GRAVITY STRUCTURES
16
madeFixed-bottom structures
from concrete.
Used for moderate water depths
up to 300 M.
Part construction is made in a
dry dock adjacent to the sea. The
structure is built from bottom up,
like onshore structure.
At a certain point , dock is
flooded and the partially built
structure floats. It is towed to
deeper sheltered water where
remaining construction is
completed.
After towing to field, base is
filled with water to sink it on the
seabed.
Advantage- Less maintenance.

17. SUBMERSIBLE RIGS (DRILLING BARGES)
17
Submersibles are used mostly
for inland, shallow water drilling
up to 50 ft water depth. This
typically takes place in lakes,
swamps, rivers, and canals.
Drilling barges are large,
floating platforms, which must
be towed by tugboat from
location to location.