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Transcript of Automated Mon
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USMS
CI?E36L3
Aj t oinaeti
Monitorin6of CYciic Loading o n
Oilfield Drillstring
M.P . VW?,,
University College London;
T
PlcCann University College London;
MH
Fatel . U.niv.ersiby College London;
..............?..... .
G.J.
Lyons University College London;
A.D. Watkins
University Co:lege London;
mm~qqgm _QFPEIROLHNINzNEmS
This manuscript was provided to the Society of Petroleum Engineers for
distribution and possible publication in an SPE Journal. The Contents of this
paper (1) are subject to correctionby the author(s) and (2) have not undergone
SPE peer review for technical accuracy. Thus, SPE makes no claim about the
contents of the work. Permission to copyor use is restricted to an abstract of
not more then 300 words. Write SPE Book Order Dept.r Library Technician,
P.O.
Box 833836, Richardson TX 75083-3836 U.S.A.
Telex 163245 SPEUT,
Facsimile 214/952-9435
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. .
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UNSOLICITED
296 Y
MAR41994
AUTOMATED MONITORING OF CYCLIC
LOADING ON OILFIELD DRILL STRINGS
M. A. VAZ, T. McCANN* , M. H. PATEL, G. J. LYONS & A.D. WATKINS
Santa Fe Laboratory for Offshore Engineering, Department of Mechanical Engineerin
University College London, Tornngton Place, London WCIE 7JE, UK
ABSTRACT
Demands
for
cost reduction in offshore hydrocarbon field developments
have driven drilling technology research in two areas. The first of these is
concerned with. using highly deviated drilling to access larger reservoir
voiumes from fewer platforms whereas the second aims at employing drill
pipes more efficiently
i.e. close to
their
fatigue
Iimits.
This
paper presents
the results of a work programme carried out at University College
London
aimed at producing hardware and software for automated monitoring of
cyclic loading of oilfield drill pipes.
The system consists of an automated
drill pipe tagging local monitoring and system analysis package to predict
measure and analyse cyclic loading in drill strings. Although no economic
analysis
has
been carried
out it is believed that drilling companies may be
able to reduce
operating risks
and maintenance costs significantly by
utilising such a system. The results achieved in
preliminary tests are
shown
to be promising and indicate that a working drill floor based system should
deliver substantial benefits in the long term.
Key words: Drill pipe tagging cyclic loading drill strings pipe deployment
fatigue damage cycle counting.
BPPTechnicalServicesLtd
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1. INTRODUCTION
Exploration and production of hydrocarbons particularly in the North Sea is
increasingly dependent on advances in drilling technology to achieve large
horizontal well deviations, greater drilling depths, and more efficient
drilling rates and bit utilisation.
A technique for automated in-service
monitoring of drill pipe deployment and service loading would improve
drill pipe utilisation and avoid costly down-hole failures. Such in-service
monitoring needs to be completely automated so as to run essentially
independently of the drilling crew and to use robust sensors, computers, and
software. lnformat.ion ~om the rn-onitoring system may either be used by
drilling engineers on a day-to-day basis or be archived for record purposes
for review and analysis at a later date.
The identification of drill pipe deployment in bore holes and an estimate of
the cyclic loading history to which a pipe segment is subjected offers
substantial operational advantages in four areas
1)
2
3
4
It permits identification of the precise location of each drill pipe
.,
section in the hole at all times.
This identification combined with a drill string analysis allows the
cyclic loading history of each drill pipe section to be identified and
monitored.
The cydlc loading histories can be used in a fatigue damage analysis to
identify the expended and remaining service life of each drill pipe
section.
Unique identification of each drill pipe segment will improve
inventory control as well as drill pipe maintenance and
refurbishment.
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The basic system requirements are to read and identify each section uniquely
as the pipe is run into the hole and to combine information to give each
pipe a life history within computer software. The monitoring system will
allow the drill pipe deployment to be precisely known and recorded.
Furthermore, the identification and removal of sections that may have
..----
expended most _of their service lives will reduce the risk of down-hole
failures and significantly improve their utilisation. This paper presents the
results of a work programme concerned with development and testing of a
prototype system for the automated in-service monitoring of drill pipe
deployment incorporating analysis techniques for pe service loading and
fatigue damage. The paper has been divided into two distinct sections - the
first describes development of the necessary hardware including
investigation into various methods of identifying and tagging drill pipe
segments. This has led to the choice of a passive coded semi-conductor cMp
inserted into the drill pipe which can be interrogated by a non-contacting
. ..
- -.
read head to provide unique identification numbers.
The second part
concerns the implementation of drill string analysis techniques to
determine the service loading that each drill pipe section is subjected to.
These service loadings can then be used to compute the fatigue life
expended by each drill pipe section as its operational life progresses.
2. SYSTEM HARDWARE
2.1 The Drilling Environment
For a drill pipe identification system tags or labels would have to withstand
an extremely severe down-hole environment. This includes high
temperatures and pressures, abrasion, excessive vibration, and impact loads.
Down-hole temperatures increase with depth, and typically range between
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100C and 150C at the bottom of a deep well. The drilling fluid imposes a
considerable pressure.
The design environment for. the drill pipe was defined as follows
Physical
Chemical
Temperature
Pressure
Rough handling and impact loads from tongs, elevators,
cranes, tuggers, and kickback or jarring if the pipe gets stuck
down-hole. Strong abrasive forces from side contact and
returning mud. High frequency vibrations.
Drilling muds can be sea water, oil, or high chloride
polymer based.
-40C to 200C although it would be preferable if even
higher temperatures could be sustained.
15000 to 20000 psi at the bottom of a deep well.
Further points to be considered are thah
1
Wear at the tool joint during its life may reduce its diameter by 10 to 15
mm (most wear occurring at the box connection), F@ure 1.
2
During pipe joint refurbishment, layers of steel are laid down at
temperatures around 600C and any mark or tag would probably be
destroyed.
3
Drill pipes can magnetise during drilling because of the rotation in the
earths magnetic field.
The magnetism is removed during another
part of the refurbishing program when the pipes are passed through a
degaussing coil.
.
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2.2 Hardware Alternatives
Viability studies were carried
out on five possible systems for identification
of drill pipe segments as they are tripped into and out of the hole. The main
features of each of these alternatives are described below
a) Manuak This is impractical as it would require an operator on the drill
floor to key in each sections code. Locating the marking where it is easily
readable yet protected from wear seems to be impracticable.
b) Optical: The
lines (barcode).
code might comprise a series of thick and thin contrasting
Using a light (possibly laser) detector a sensor could image
an identifying barcode. However, if the barcode should be obscured owing
to wear or maskkg by opaque fluids the sensor may fail to read the code.
c) Electrical conductivity A barcode with alternately spaced conductive and
insulating stripscould be inserted into the pipe or embedded in the surface.
A measurement of the sequential resistances across the set of strips could
then be combined to yield a unique identification code.
would have to be in surface contact with the drill pipe.
The sensor probe
d) Ultrasonic: A barcode plug composed of layers of materials with different
densities and thicknesses could be scanned using ultrasound. The
ultrasonic probe could scan through the coded plug and the beam reflected
from the layers of the plug would take different amounts of time to return
to the receiver, hence a unique code could be identified. However, to obtain
the desired resolution it would be necessary to grind a lens with its focus on
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the surface of the barcode plug and the reader would have to be kept at a
precise distance from the drill pipe.
e) RF Oscillation These devices are
generator can be fitted into a small
stable and inexpensive. A frequency
package and detected from a remote
position. Such systems contain a small coil which is exated by a second coil
forming the sensor (or read head). As the sensor sweeps the tag an induced
current powers the system and the identifying frequency is obtained. An
oscillator can be inserted into a 2 mm diameter cylinder and so it is possible
to form a cylindrical amplifier of 3 or 4 mm diameter.
Owing to the problems with obscuration and likely damage for close contact
reading methods a) to d) these are considered unsuitable. The RF oscillator
may be successful y deployed as discussed in the following.
2.3 A
Suitable Tag
An improvement on the simple single frequency RF oscillator is
commercially available from a number of sources (e.g. Hughes Technology).
These are known as Radio Frequency Identification Device (RFID).
Although this technology already exists some modifications would be
needed for operation down-hole.
These tags consist of a microchip, and a coil wrapped around a ferrite rod.
The microchip contains a memory section, which stores a unique
. .
. .
identification code, and further sections to process and transmit this code.
The coil acts both as power supply (through electromagnetic induction) and
aerial to transmit the code back t; the receiver. fiese tags &e a-vailable in a
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variety of shapes and sizes. Laboratory tests have been performed with these
but further operational trials down-hole have yet to be carried out.
The tag should be located in a hole as shown in Figure 2. Investigations
were carried out at UCL to determine if the tags could be read when bonded
within a large volume of steel.
The Hughes TX1200 slug tag was used to
establish the relationship between depth of embedment in the steel with
read dMance. The relationship appeared to be almost linear with reasonable
read distances being obtained for quite deep holes (the deepest hole tested
was 17 mm giving 10.5 mm of protective cover). It is envisaged that the
system utilises a tag scanner that surrounds the whole pipe. This is a set up
which has successfully been tested by Hughes and should allow the tag to be
read at the Klghest drilling rotation rate.
2.4 Location of Drill Floor Equipment
As a consequence of detailed
semisubmersible Santa Fe Rig
and reader has evolved. The
investigations (in particular on the drilling
135) a system of separate antenna, scanner,
scanner and reader should be housed in an
explosion-proof box and placed either in the doghouse or to the side on the
drill floor. Theantenna (or read head) can be located on the diverter packer
insert which has a large rubber annulus with an internal diameter of 10 in
(25.4 cm) and an external diameter of about 26 in (66.0 cm) located at the top
of the casing with a considerable clearance tlom the underside of the drill
floor. The antenna being embedded in a solid block of impermeable plastic
formed into an annulus with a radius to match the packer insert. The
diverter packer ring is sandwiched between two steel plates to which the
antenna unit is bolted using a quick release system (see Figure 3). Hence, as
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the packer is removed from the hole the antenna could be disconnected and
placed in a protective housing beside the well opening.
2.5 Deployment Issues
Some issues that still have to be evaluated d~ing implementation of the
system within a specific drilling programme include
Temperature effects
.
.
.
Although the tag microchip can withstand 300C and the copper in the coil
.
could survive a temperature of 200C, the coil insulating material, and
connection solder need to be chosen to accommodate these temperatures. A
suitable compound for sealing the tags in the holes is Dow Corning RTV
1345, a proven material used for MWD equipment.
Intrinsic safety
The tag reader may need to be certified intrinsically safe for location under
the drill floor. However, provided only the antenna was installed on the
drill floor, (with the other electronics located in the doghouse or logging
cabin) this intrinsic safety requirement could be satisfied.
Magnetisation and demagnetisation
Tests need to be carried out to confirm that magnetic fields induced on the
tag by degaussing during pipe refurbishment do not have any adverse
effects.
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Pipe refurbishment
The temperature changes and mechanical shocks imposed
during refurbishment need to be evaluated to determine if
on the pipe
the tags can
reliably survive these. If the tags cannot survive such treatment then tag
replacement would have to become part of the refurbishment process.
3. SYSTEM SOFTWARE
3.1 Loading and Fatigue
In directional drilling most drill pipes fail owing to the accumulation of
fatigue damage. A typical drill string failure in deep wells may cost tens of
thousands of pounds, therefore it is necessary to minimise such occurrences
(Joosten, Shute and Ferguson).
-Fatigue damage is known to originate in
dog-legs (kick-off points), caused by the rotation of bent pipes under high
tensile forces, although cyclic loading ind_ucedby vibration also plays a part.
Furthermore, dynamic stresses arise, for instance, from setting slips
(Vreeland2) or when the drilling vessel is subjected to sea-wave induced
motions (Hansford and Lubinskis). In fact, an accurate understanding of the
cyclic loading mechanism in drill strings has still to be developed. Here
Hansford and Lubinskisd method has been adopted to estimate the
accumulation of fatigue damage in gradual and long dog-legs.
The
following parameters, assumed constant over a 30 ft hole segment, are
considered to influence drill pipe life rotary speed, rate of penetration, drill
pipe outside diameter, tensile force, dog-leg severity, mud and formation
specification (corrosive or not), density of mud and grade of steel.
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A drill pipe may fail under repeated cycles of relatively low stress levels
owing to the growth of internal cracks that can be initiated from local
fabrication or at stress concentration sites.
Such fatigue damages are
quantified from experimental S-N curves which are plots of stress range S
against number of cycles to failure N.
The l?almgren-Miner cumulative
fatigue damage rule quantifies the fatigue damage caused by a number of
cycles at low stress ranges. This linear damage law assumes that the total
fatigue damage results from the summation of the fractions (or percentages)
of life expended in each stress cycle.
When the total accumulated fatigue
damage approaches unity (or 100 ) the drill pipe section should be removed
from service to avoid unexpected failure.
It is further assumed that the averages of the rotary speed, rate of
penetration, inclination and weight on bit (and tensile force) are known. In
conventional -oil rig: these parameters are recorded in the drilling sheet
while in modern rigs measurement while drilling (MWD) systems provide
these data on demand.
3.2 Simulation
.
This section presents a software system that works with the drill pipe
tagging hardware to count pipe cyclic loading and resultant accumulated
fatigue damage. In_ order to illustrate the software and computational
procedures involved, an example simulation of the operation of the
software is presented below.
.
Ideally the-software will operate with the tagging system hardware on a real
time basis and with the minimum of human interference.
Sensors
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monitoring mud pumps, rotary speed, weight on bit and bit trajectory will
send signals to the computer - it will interpret thk data and activate the
corresponding modes.
The software simulation presented here is designed to be used for drilling
programme design or with the tagging system for on-site monitoring or
post-drilling analysis. It permits cyclic loading to be calculated every time a
drill pipe section is used or a few times a day using drilling sheet or MWD
data.
There are two basic steps in the simulation.
(1)
Data Preparation - The first step is to generate a file containing the
geometric and material properties of the pipes with the tag numbers
and accumulated fatigue darnage of every drill pipe section. Here it is
assumed that APF approved drill pipes made of Grade E steel are used
with outside (inside) diameters equal to 3.5 (2.992), 4.5 (3.953) and
5 (4.408). The initial fatigue damage is taken to be nil. The initial
hole geometry is generated by subdividing the well into vertical,
curved and straight inclined portions. A geometry file contains
inclinations and curvatures of every 30 ft (9.14 m) so as to define the
hole profile. Next, the sequence of tag numbers, corresponding to a
trip in, is produced. The generation of the pipe sequence is simplified
in the example simulation the tag number of the upper most pipe is
entered and alinearly decreasing distribution is used.
(2)
Drilling - When thk mode is selected, the initial geometry and pipe
sequence are read. Every time a new pipe section is used, its
respective tag number is read and the averages of rotary speed, rate of
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penetration, weight on bit, and bit inclination are read in. The
curvature of the new hole segment, the cyclic loading, and fatigue
damage are calculated, and files updated. If drilling continues a new
tag number is read and the process repeats. This part of the program
is outlined in the flow chart of Figure 4.
3.3 Examples
Examples I and 2 below illustrate the importance of a dog-leg control
programme to minimise fatigue damage.
The two hole profiles of Figure 5
have sligthly different profiles but they reach the same final target zone.
Well number 1 has a dog-leg 600 ft long and severity of 2,50 deg/100 ft while
the dog-leg in well number 2 has half the severity but double the length.
Both drill string arrangements 1 and 2, pictured in Figures 6a and 6b,
comprise ten drill. collars_ with outside (inside) diameters of 7 (1.5) and
distributed dry weight of 125 lbf /ft. Mud is assumed corrosive and its
density is 12.0 1~/gal. Five pipes are used in each drilling session with the
drilling parameters shown in Table 1.
session
IROP (ft/hr) RPM (rpm)
WOB (lbf) Inclination (deg)
I
100
100
30000
15
; 50
100
25000 15
Table 1- Drilling
Sessions
Example 1- The drill string arrangement 1 (Figure 6a) is run into holes 1 and
2, Drill pipes 351 to 355 and 356 to 360 were respectively tripped in sessions
a and b. Table 2 presents the accumulated fatigue damage, after the
trip
in, for the affected drill pipes. The average fatigue damage, calculated over
the drill pipe sections fatigued, is 3.1 and 6.5 for arrangement 1 in holes 1
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and 2, respectively. In longer and less severe dog-legs more drill pipes are
damaged but the fatigue damage is more evenly distributed between the
affected drill pipes and the rate of accumulation for an individual segment
is lower.
Hole 1
Hole2
Tag numbers
Fatigue ( )
Tag numbers
Fatigue ( )
292
0.3
297 0-6
293
0.6
298 1-3
294
0.9
299
1.9
295
1.2
300
2.6
296
1.5
301 3.3
297
2.1
302 5.0
298 2.7 303 6.7
299 -- 3.3
304
8.5
300 3.9
305
10.3
301 to 311
4.5 306
12.2
312
4.2 307
11-7
313
3.9 308
11.1
314
3.6 309
10.5
315
3.3
310 9.9
--
316 3.0
311
9.3
317
2.4 312
7.5
318
1.8 313
5.7
319
1.2 314
3.9
320
0.6
315
2.0
Table 2- AccumulatedFatigueDamage
in
TwoHoleProfiles
Example 2- A heavier drill string arrangement 2 (Figure 6b) is run into well
number 2. In drilling sessions a and b the drill pipes 591 to 600 were
tripped in.
Table 3 summarises the results.
The average fatigue damage
using arrangement 2 in hole 2 is
7.7~0
per affected pipe. The fatigue damage
is more severe owing to the higher @al forces in arrangement 2.
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Hole 2 / Arrangement 2
Tag numbers
Fatigue ( ) Tag numbers Fatigue ( )
537 0.8 547 13.8
538
1.5
548 13.1
539
2.4
549 12.4
540
3.2 550 11.6
541
4.0
551
10.9
542 6.0
552 8.8
543 8.0
553
6.7
544 10.1
554 4.5
545
123 555
2.3
546
14.5
.-
Table 3- AccumulatedFatigueDamagein Heavier Drill String
3.4 Extensions
Whilst the software developed to date adequately demonstrates the salient
features required for the major aspects of drill string fatigue there are several
software enhancements that could be readily made to this. These are listed
below.
1
Incorporate a wider range of drill pipes in the pipe file.
2) Define hole profiles by three-dimensional curves (hence the dog-leg
severities should consider the overall hole change).
3) Read tag numbers and drilling parameters from files.
4)
Calculate the footage drilled by each pipe, so that this may be
associated with pipe wear.
5)
Record inspections and repairs in the pipe data file.
6) Consider contact and friction forces when calculating axial forces.
7
Develop methodology to calculate fatigue for dog-leg severities
exceeding 10 deg/100 ft
becomes more common.
as drilling with short radii of curvature
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4. CONCLUSIONS
The foregoing describes the hardware and software development for
automated monitoring of cyclic loading and accumulated fatigue damage on
oilfield drill strings. The hardware is capable of uniquely identifying drill
pipe joints whilst they are being tripped in and out of the hole - the
associated software then estimates the cyclic loading and both the expended
and remaining service lives of the pipe segments. Some further system
detail work remains to be done although the details of this are to some
extent dependent on the drilling sites on which the system will be deployed.
Following such deployments, assessments of the reliability and accuracy of
resultant fatigue damage estimates will be made.
..
ACKNOWLEDGEMENTS
This work was carried out with the support of the
facilities of the Santa Fe
Laboratory for Offshore Engineering, University College London and
assistance from Santa Fe Drilling Co (North Sea) Ltd, and Hughes
Technology Ltd. The first author acknowledges the support of the Brazilian
Council of Research (CNPq) for ~is work.
REFERENCES
1
2
Joosten, M. W., Shute, J. and Ferguson, R. A., New
Study Shows How to
Predict Accumulated Drill Pipe Fatigue
World 011, (Oct. 1985), 65-70.
Vreeland, T., Jr., -
Dynamic Stresses in Long Drill Pipe
Strings, The
Petroleum Engineer, (May 1961), B58-B60.
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3 Hans ford, ]. E. and Lubinski, A., Effects of Drilling Vessel Pitch or Roll on
Kelly and Drill Pipe Fatigue Journal of Petroleum Technology, (Jan.
1964), 77-86.
4 Hansford, J. E. and Lubinski, A., Cumulative Fatigue Damage of Drill
Pipe in Dog-Legs Journal of Petroleum Technology, (March 1966), 359-
. .. . . .
--- -
363. - - -
5 American Petroleum Institute, Recommended Practice for Drill Stem
Design and Operating Limits (API RP 7G), (Aug. 1, 1990).
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vortexoccurs in
tldsregion
\
~xcess
vewearcccu
in thisregion
pipeB
11~
II
II
II
II
II
\
II
\ll
\l
,/
\; ;/
1-l
11
II
II
I
II
I
II
SPE28648
17
pinjointpipeB
box joint pipeA
PipeA
~lgure 1- FlowDiagram around Tool Joints
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Holeperpendicular to
m
Holeperpendictdar to
35 deg weld
pipe axis
Q
d
.,
II
1[
l?@Ire 2-
Hole in Weld
,.
/
Metal
Top Plate
CircularAntenna
Packer Insert
Figure 3- PackerInsertShowingPropusedAntennaPosition
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SpL28648
INITIAL GEOMETRY
READ initial
IDENTIFY
geometry file
*pm
IDENTIFY pipes k dog-legs and
CALCULATE drill string weight below
1
each drill pipe
STAKTDRILLING
tag number
+
STOP DRILLING
INPUT ROP, RPM,
n
WRITE
WOB and - - > ri]ing
INCLINATION
parameters
~
CALCLJLATE UPDATEWRITE pipe
fatigue
UPDATE drill
CHECK curvature
I
below each pipe
19
~@re 4- FlowChart of Simulation
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Well No 1
tn I
. . .
. . .
. . .
. . .
. . .
. . .
. ..
. . .
. . .
40 vertical segments
-----
I l-::.i
1[
...
..
:::
,/
,,
,/
,/
= ;;{
o
u-
:::
h
:::
:::
:::
:::
:::
:::
:::
,,,
::.
,::
:,:
:::
:::
:::
Initial
. . . . . . . . .
position
Figure 5- HoleProfiles
1.
Drill pipes
(3D=4.5
::;
360 to 351 IQ=3.g5e
:.
.; Drill pipe 350
E&
0 drill collars ~==1~5.
Initial
---------
Well No 2
El
95 straight
inclined segments
inclination
15.0 de rees
:,:
j
~Drill pipes oo ~
5.
j ; 600 to 591 ID=4-m8
j { Drill pipe 590
::
1
1
: ,
: :,
: ;;
: :
: ; 190
pipes~DD==45408-
1
::1
:::
: :,
::1
;;:
:::
::,
::,
:
X
OD= 4.5-
; 50 pipes ID = 3.95fy
:
,, t
::
:
~ Drill pipe 351
:;
Drill String Arrangement 1
Drill String Arrangement 2
Figure 6a
Figure 6b