3 3 DS rig WH pandadesign

Network of Excellence in Training

Drillstring Design
Rig Sizing
Wellhead Systems
Plug and Abandon
© COPYRIGHT 2001, NExT. All Rights Reserved


DS Design, Rig Sizing WH and P&A
•

Course Contents
1.
2.
3.
4.
5.
6.
7.
8.
9.

2

Objectives
Functions of drillstring components
Grades and strength properties of drillpipe
Drillcollar weight and neutral point
Drillstring design methods incl. MOP
Drillstring damage and inspection

Rig sizing considerations
Wellhead components
Plug and Abandon considerations
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DS Design, Rig Sizing WH and P&A
• Objectives
At the end of this lecture YOU will be able to:
•List drillstring components and describe functions
•Define grades and strength properties
•Calculate drillcollar weight for required WOB
•Design drillstring in vertical wells
•Describe drillstring damage and inspection methods
•Perform rig sizing calculations
•List wellhead functions and components
•Describe P&A considerations
3

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Network of Excellence in Training

Drillstring Design

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Drillstring Design
• Functions of Drillstring
The drill string is the mechanical linkage connecting the
drillbit on bottom to the rotary drive system on the
surface.
The drillstring serves the following functions :

D
P

1. Transmits rotation to the drillbit
2. Exerts weight on the bit
3. Guides and controls the trajectory of the bit,

DC WOB

4. Allows fluid circulation
WOB
5

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Drillstring Design
Functions of Drillstring

Basic components of drillstring:
1. Drillpipe
2. Drillcollars

Accessories include :
– Heavy-walled drillpipe
– Stabilisers
– Reamers
– Directional control equipment
6

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Components
The Kelly/Top Drive
 

7

Strictly speaking, Kelly/
Topdrive are not
components of the drill
string. However, the Kelly/
top drive provide the
essential requirement for
rock breakage (drilling)namely rotation.  

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Components
The Kelly
The Kelly is the rotating link between the rotary table and
the drill string.
• Transmits rotation and weight-on-bit to the drillbit
•

Supports the weight of the drillstring

•

Connects the swivel to the uppermost length of
drillpipe

•

Conveys the drilling fluid from the swivel into the
drill string

The Kelly comes in lengths ranging from 40 to 54 ft
with cross sections such as hexagonal (most common),
square or triangular.
8

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Components
Kelly cock
The Kelly is usually provided with two safety
valves, one at the top and one at the bottom, called
Kelly cock.

The Kelly cock is used to close the
inside of the drillstring in the event of a
kick.
The lower
manually.

9

Kelly

cock

operates

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Components

Top Drive
The top drive is basically a combined rotary table and kelly.
It is powered by a separate motor and transmits rotation to the drill
string directly without the need for a rotary table. The top drive
functions in the same way as the kelly.

Advantages over the kelly system:
1. Circulating while back reaming
2. Circulating while running in hole or pulling out of hole in
stands
3. The kelly system can only do this in singles; ie 30 ft.
1
0

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Drill Pipe Grades
The grade of drill pipe describes the minimum yield
strength of the pipe.
In most drillstring designs, the pipe grade is increased
for extra strength rather than increasing the pipe
weight.

1
1

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Drill Pipe Grades
Minimum Yield
Stress
(psi)

GRADE
Letter

D

1
2

Alternate Designation

D-55

 

55,000

E

E-75

75,000

X

X-95

95,000

G

G-105

105,000

S

S-135

135,000

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Drill Pipe Classification
Drill pipe is classified to account for the degree of wear
API RP7G - DP Classes
New:

No wear, has never been used

Premium:

Uniform wear and a minimum wall thickness of
80% of new pipe.

Class 2:

Drill pipe with a minimum wall thickness of
70% with all the wear on one side so long as
the cross sectional area is the premium

class.
Class 3:
1
3

Drill pipe with a minimum wall thickness of
55% with all the wear
on one side.
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Drill Pipe
Tooljoints
A drillpipe joint is an assembly of three components:
• drillpipe with plain-ends and
• one tooljoint at each end (Pin & Box)
All API tooljoints have a minimum yield strength of 120,000

psi regardless of the grade of the drillpipe they are used on
(E, X, G, S) .
API sets tooljoint torsional strength at 80% of the tube
torsional strength : this is the torsional strength ratio of 0.8. 
Make up torque is determined by pin ID or box OD. The
make up torque is 60% of the tool joint torsional capacity.

1
4

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Drillstring Connections
Thread Styles and Forms
a)

NC

b)

REG
FH

0.038”
V-038R

0.025”

V-040
V-050

Styles

Forms
c)

SST

0.057”

SST (PINS)
V-038R
(BOXES)

d)

e)

IF
XH
PAC
OH
SH
DSL
H-90

f) WEDGE

THREAD

1
5

0.015”
V-065

0.025”

H-90

WEDGE
THREAD

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Drillstring Connections
NC (Numbered Connection)
The most common thread style in drillpipe
The thread has a V-shaped form and is identified by the pitch
diameter , measured at a point 5/8 inches from the shoulder ; the
gauge point, multiplied by 10.
The size of a rotary shouldered connection is fixed by
its gauge point pitch diameter.

5/8”

GAUGE POINT PITCH DIAMETER

1
6

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Drillstring Connections
If the pitch diameter is 5.0417 in  This is an NC50 connection
Multiply 5.0417 by 10 → 50.417
Choose first two digits → 50
Hence NC 50
There are 17 NC’s in use : NC-10 (1 1/16”) through NC-77 (7 3/4”) 
NC-23 and above use the V-38R thread form.
Typical sizes: NC 50 for tool joints with 6 1/2” OD for 5” pipe and NC
38 for 4 3/4” tool joints and 31/2” pipe.

1
7

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Drill Collars
DRILL COLLAR SELECTION

First section of the drillstring to be designed.
The length and size of the collars will affect the grade, weight
and dimensions of the drill pipe to be used.
Predominant component of the BHA.
Both slick and spiral drill collars are used .
In areas where differential sticking is a possibility spiral drill collars
and spiral HWDP should be used in order to minimise contact area
with the formation.

1
8

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Drill Collars
HOLE SECTION
(ins)

1
9

RECOMMENDED DC OD
(ins)
Spiral or

36

9½ + 8

26

9½ + 8

17½

9½ + 8

16

9½ + 8

12¼

8

8½

6¼

6

4¾
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Slick

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HWDP
HEAVY-WALLED DRILLPIPE (HWDP) 
Has the same OD as a standard drill
pipe but with much reduced inside
diameter ( usually 3”) and has an
extra tool joint.
It is used between standard drill pipe
and drill collars to provide a smooth
transition between the section
module of the drillstring
components. 

Slick

2
0

or Spiral

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BHA Design
STANDARD BHA CONFIGURATIONS

All wells whether vertical or deviated require careful design of

the BHA to control the direction of the well in order to
achieve the target objectives.
The main means by which directional control is maintained on a
well is by the effective positioning of stabilisers within the
BHA.

2
1

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Stabilizers & Roller Reamers
Types

2
2

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BHA Design
Types of Rotary BHAs

2
3

•

Pendulum assembly

•

Packed assembly

•

Rotary Build assembly

•

Steerable assembly

•

Mud Motor and bent-sub assembly

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BHA Types
1.
SLICK

2.
PENDULUM

3.
BUILD

4.
PACKED II

5.
PACKED III

6.
PACKED IV

STAB
STAB

DRILL
COLLAR

DRILL
COLLAR

STAB

DRILL
COLLAR

STAB

STAB
DRILL
COLLAR

SHOCK
SUB

2
4

DRILL
COLLAR

SHOCK
SUB

DRILL
COLLAR

SHOCK
SUB

PONY

STAB

DRILL
COLLAR

STAB

DRILL
COLLAR

STAB
DRILL
COLLAR
FULL
GAUGE
STAB

DRILL
COLLAR
FULL
GAUGE
STAB

SHOCK
SUB

DRILL
COLLAR

PONY

FULL
GAUGE
STAB

STAB

STAB

SHOCK
SUB

SHOCK
SUB

PONY
STAB

STAB

STAB
DRILL
COLLAR

FULL
GAUGE
STAB
DRILL
COLLAR

DRILL
COLLAR

STAB

DRILL

COLLAR
DRILL
COLLAR

DRILL
COLLAR

DRILL
COLLAR

7.
PACKED V

STAB

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BHA Design
Drillcollar as Weight
1. Drill collars provide weight on bit as they can be run in
compression while keeping the drill pipe in tension
2. Drill collars have a significantly greater stiffness when
compared to drill pipe
3. Drill pipe tend to buckle in compression
4. Repeated buckling will lead to early drill pipe failure
5. Fatigue failure of pipe can be eliminated by maintaining a
constant tension in the drill pipe

2
5

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