Offshore Drilling Introduction

Drilling Rigs
Drilling Systems
Drilling Rigs
Rotary Drilling
Drilling Team
Drilling Rigs
Rig Power System
Hoisting System
Circulating System . . .
2
Rotary Drilling - contd
The Rotary System
The Well Control System
Well-Monitoring System
Special Marine Equipment
Drilling Cost Analysis
Examples
3
Noble
Drillings
Cecil
Forbes
A Jack-Up
Rig
4
Sonats
George
Washington
A SemiSubmersible
Rig
Zapatas
Trader
A Drillship
TENSION LEG PLATFORM

8
Shells
Bullwinkle
Worlds tallest
offshore structure
1,353 water
depth
Production
began in 1989
45,000 b/d
80MM scf/d
9
Fig. 1.5
Classification of
rotary drilling rigs
10
Drilling Operations
Field Engineers, Drilling Foremen
A. Well planning prior to SPUD
B. Monitor drilling operations
C. After drilling, review drilling results and
recommend future improvements
- prepare report.
D. General duties.
What are the well requirements?

Objectives, safety, cost
11
Criteria for determining

depth limitation
Derrick
Drawworks
Mud Pumps
Drillstring
Mud System
Blowout Preventer
Power Plant
12
A Rotary Rig
Hoisting System
13
Projection of
Drilling Lines
on Rig Floor
E = efficiency = Ph/Pi = W/(n Ff ) or Ff = W/(nE) (1.7)
TOTAL
14
Load on Derrick
(considering friction in sheaves)
Derrick Load = Hook Load
+ Fast Line Load
Line Load
+ Dead
Fd = W + Ff + Fs
W
W
1 E En
Fd W
=
W
En
n
En
E = overall efficiency:
E = en
e.g., if individual sheave efficiency = 0.98 and n = 8, then E = 0.851
15
Example 1.2
A rig must hoist a load of 300,000 lbf. The drawworks
can provide an input power to the block and tackle
system as high as 500 hp. Eight lines are strung
between the crown block and traveling block.
Calculate
1. The static tension in the fast line
when upward
motion is impending,
2. the maximum hook horsepower
available,
16
Example 1.2, cont.

3. the maximum hoisting speed,
4. the actual derrick load,
5. the maximum equivalent derrick load,
and,
6. the derrick efficiency factor.
Assume that the rig floor is arranged as
shown in Fig. 1.17.
17
Solution
1. The power efficiency for n = 8 is given as 0.841 in
Table 1.2. The tension in the fast line is given by Eq. 1.7.
W
300,000
F
44,590 lb
E n 0.841* 8
( alternatively, E = 0.988 = 0.851 )
18
Solution
2. The maximum hook horsepower
available is
Ph = Epi = 0.841(500) = 420.5 hp.
19
Solution
3. The maximum hoisting speed is given by
Ph
vb
W
33,000 ft - lbf / min
420.5 hp
hp
300,000 lbf
= 46.3 ft / min
20
Solution to 3., cont.

To pull a 90-ft stand would require
90 ft
t
1.9 min.
46.3 ft / min
21
Solution
4. The actual derrick load is given by
Eq.1.8b:
1 E En
Fd
W
En
1 + 0.841 + 0.841(8)
=
(300,000)
0.841(8)
= 382,090 lbf.
22
Solution
5. The maximum equivalent load is given
by Eq.1.9:
n4
8 4
Fde
W
* 300,000
n
8
Fde 450,000 lbf
23
Solution
6. The derrick efficiency factor is:
Fd 382,090
Ed
Fde 450,000
E d 0.849 or 84.9%
24
Drillship
- moored
25
26
Heave
Surge
Sway
Roll
Pitch
Yaw
27
Vessel Motions
Motions restricted to the horizontal plane
SURGE: Translation fore and aft (X-axis)
SWAY: Translation port and starboard (Y-axis)
YAW: Rotation about the Z-axis (rotation about
the moonpool)
Motions that operate in vertical planes

HEAVE: Translation up and down (Z-axis)
ROLL: Rotation about the X-axis
PITCH: Rotation about the Y-axis
28
29
Wave Direction
Beam Waves
Head
Waves
Quartering Waves
30
31
32
Roll vs. Significant Wave Height
Significant Wave Height, ft

33
What is Significant Wave Height?

Significant wave height is the average height
of the 1/3 highest waves in a sample .
EXAMPLE The significant wave height in the
following sample is 24 ft.
7, 21, 19, 11, 18, 26, 13, 17, 25
[ Sign. WH = (21 + 26 + 25) / 3 = 24 ft ]
Avg. WH = (7, 21, 19, 11, 18, 26, 13, 17, 25) / 3 = 17.4 ft
34
Heave vs. Significant Wave Height
Significant Wave Height, ft

35
Heave vs. Wave Approach Angle
BOW
BEAM 36
Roll & Pitch vs. Wave Approach Angle
BOW
BEAM
37
Typical Vessel Motion Limits - Criteria

Operation
Wave Height
ft
Drilling Ahead
Running and
Setting Casing
Landing BOP and Riser
Transferring Equipment
Heave
ft
30
10
22
15
15
6
3
38
39
SEMI
SHIP
10% vs. 1.5 %

40
41
42
What is lt ?
43
Some Definitions
Freeboard
Draft
Width
44
45
G = center of gravity.
B = center of buoyancy
G is
above B!
46
NOTE:
B has moved!
GZ =
righting
arm
47
48
Dynamic Stability - for certification
49
Dynamic Stability
For adequate stability, the area under the
righting moment curve to the second
intercept or to the down-flooding angle,
whichever is less, must be a given amount
in excess of the area under the wind
heeling moment curve to the same limiting
angle. The excess of this area must be at
least 40% for shiplike vessels and 30% for
column-stabilized units (see Fig. above).
50
Free Surface Effects
CG moves!
51
Tall, narrow tank is more stable ...
52
Effect of Fluid Level in Tank
53
54
Moment Arm (only)
Effect of Partitions in Tank
55
The Vessel - Classification

Three classification societies are particularly
important to offshore drilling. These societies are:
56

Offshore Drilling Introduction

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Drilling Rigs

Rig Power System

Rotary Drilling - contd

The Rotary System

The Well Control System

Special Marine Equipment

Drilling Cost Analysis

TENSION LEG PLATFORM

What are the well requirements?

Criteria for determining

E = efficiency = Ph/Pi = W/(n Ff ) or Ff = W/(nE) (1.7)

e.g., if individual sheave efficiency = 0.98 and n = 8, then E = 0.851

Example 1.2, cont.

Ph = Epi = 0.841(500) = 420.5 hp.

Solution to 3., cont.

Motions that operate in vertical planes

Roll vs. Significant Wave Height

Significant Wave Height, ft

What is Significant Wave Height?

Heave vs. Significant Wave Height

Significant Wave Height, ft

Heave vs. Wave Approach Angle

Roll & Pitch vs. Wave Approach Angle

Typical Vessel Motion Limits - Criteria

10% vs. 1.5 %

Dynamic Stability - for certification

Free Surface Effects

Tall, narrow tank is more stable ...

Effect of Fluid Level in Tank

Moment Arm (only)

Effect of Partitions in Tank

The Vessel - Classification

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