I N N OVAT I N G W H I L E D R I L L I N G
High-strength, thin-wall, all-steel drill pipe may
provide solution for ultra-extended-reach wells
By Lou Elliott and Vincent Buchoud, VAM Following the successful development TECHNICAL DRIVERS
Drilling; Tony Krepp, K & M Technology of 165 ksi material (VM-165 grade), one
From a modeling perspective, this article
operator has selected high-strength
IN PLANNING FOR ultra-extend- thin-wall 165 ksi drill pipe as the best
will focus on the 10 5/8-in. hole section,
ed-reach (uER) wells, projected torque & from approximately 36,760 ft to 48,000 ft
solution for their uER well development.
drag (T&D) loads exceed the capabilities (11,200 m to 14,630 m) MD. The drill pipe
This article will discuss the key perfor-
of existing high-strength drill pipe. As design and selection is critical for wells
mance drivers that enabled the operator
operators continue to evaluate uER well of this magnitude. Detailed planning
to select this all-steel alternative and the
options, they have been forced to con- shows that non-conventional solutions
methodology used for specifying the final
sider using non-steel drill pipe materials are necessary for the final hole sections
acceptance criteria of this material.
(such as aluminum, titanium, composite to TD.
or other) for reduced surface loads. While
these materials have been used for some BACKGROUND Both all-steel and alternative-material
drillstring materials were considered.
time in a variety of applications, many Due to the operator’s environmental and
Use of existing drill pipe involves surface
drilling engineers are reluctant to pursue commercial considerations, this new
torque loads that cannot be managed
complicated and high-value developments shallow-water field (6 m/20 ft) will take
without developing new top drive equip-
with what they perceive as lesser known advantage of existing infrastructure in
ment and new tool joint technologies.
or less understood technologies. order to be developed. The projected
Surface torque loads are up to 100,000
wells are significantly beyond current
An alternative approach (and/or comple- ft-lbs. Tension loads when picking up
industry experience so are considered
mentary approach) is to use new ultra- from TD are also a constraint for the
high-strength material, which will bridge uppermost drill pipe.
the gap between existing steel grades Detailed planning has identified the nec-
Because of the TVD of these wells,
and alternative solutions. The signifi- essary technical solutions for drilling,
“combined loads” (combined torque, ten-
cantly improved strength-to-weight ratio casing and completions operations. New
sion and pressure when drilling and/or
performance properties of this material technology solutions need to be devel-
backreaming) are a significant design
allows fit-for-purpose drill pipe to be oped for all phases of the wells. Of spe-
designed for this specific application. cific interest here is the rig’s equipment
and advanced drill pipe technology.
Figure 1 (left): Tension loads vs bit depth, for conventional S-135 material drill pipe. Pickup loads are unacceptable for design-range
FFs of 0.25 to 0.30 for S-135 6 5/8-in. drill pipe. Figure 2 (right): Torque loads (vs bit depth on left and TD-snapshot on right), for con-
ventional S-135 material drill pipe. For design-range FFs of 0.25 to 0.30, surface torque at TD is 80,000 to 100,000 ft-lbs. This exceeds
combined torque-tension load limit for 6 5/8-in. drill pipe.
42 March/April 2009 D R I L L I N G CONTRACTOR
I N N OVAT I N G W H I L E D R I L L I N G
Figure 3 (left); Tension loads vs bit depth for selected VM-165 material drill pipe (with thin-walled 5-in. and 5 7/8-in. tubes). Pickup
loads are now acceptable for design-range FFs for all pipes. Figure 4 (right): Torque loads (vs bit depth on left and TD-snapshot on
right) for selected VM-165 material drill pipe (with thin-walled 5-in. and 5 7/8-in. tubes). Surface torque at TD is slightly improved, while
pipe-loading margins are significantly improved.
DESIGN WORKFLOW 6. Combined loading of torque and ten- sion and combine-load scenarios. From
sion must be acceptable for the 90% this point, the expected torque loads are
The drillstring design for the 10 5/8-in.
limit of premium-grade pipe, when established.
hole section to TD is driven by:
drilling at TD.
This first-pass review established sur-
1. All materials must remain within reli-
7. Von Mises analysis must be acceptable face equipment requirements and pipe
able elastic behavior for the expected
at TD under full load. Design is based requirements for a standard solution.
formation temperature profile.
on temperature-corrected strengths.
Based on this, a 5-in. x 5 7/8-in. x 6 5/8-in.
2. Hydraulics to achieve necessary flow
8. Collapse strength must be ≥ 3,000 psi drillstring design was selected. This
rate at TD (for hole cleaning and BHA-
for premium-grade pipe. This allows combination was an effective compro-
operation reasons). The minimum
up to 4,000 ft of pipe to be empty on mise, taking into account drill pipe used
annular velocity is greater than 150 ft/
top (at 11.0 ppg mud weight, with 1.25 in the previous hole section.
min and preferably greater than 200
ft/min. Surface pressures are realisti- As Figures 1 and 2 show, solutions with
cally limited to under 6,700 psi (and 9. Burst strength must be such that the conventional S135 drill pipe are unac-
preferably under 5,500 psi for rig reli- pipe is able to withstand a pack-off ceptable for tension, torque and com-
ability reasons). of up to 2,500 psi when circulating at bined torque-tension loads.
maximum flow rate (or surface pres-
3. ECDs must be acceptable for realistic The next iterations involved making the
sure of 8,000 psi, whichever is great-
variations in rheology and flow rate. drillstring as light as possible (via use of
smaller drill pipe) for reduced loads on
4. Tension loads must be acceptable
the top-most pipe. By reducing the loads,
when pulling out of hole at TD. Surface DESIGN PROCESS this also allowed “smaller” tool joints to
tension load should not exceed the
The design process was highly itera- be used (which in turn further reduces
90% limit of premium-grade pipe. In
tive. The first-pass analysis assumed T&D).
this case, the design basis FF is up to
standard API dimensions and weights.
0.35, although most likely loads are At some point, the use of high-strength
Hydraulics (both pump pressures and
expected to be 0.25 to 0.30. drill pipe was investigated. The immedi-
ECDs) drives the hole size and pipe size
combination. ate benefit was improved overpull and
5. Torque when rotating at TD, for FF
combined-load capacity on the top-most
= 0.20 – 0.25. Torque loads must be
From this point, the T&D iterations pipe. A secondary benefit was the possi-
acceptable for connections, pipe body
commence. This resulted in a drillstring ble use of non-standard thin-walled drill
at FF = ≤ 0.25, and for peak varia-
designed firstly for managing the ten- pipe (for reduced pipe weight, as well as
tions at 0.3.
44 March/April 2009 D R I L L I N G CONTRACTOR
I N N OVAT I N G W H I L E D R I L L I N G
Tensile Tensile specimen UTS - Rm UTS - Rm Tail
Grade Rp0.2 (MPa) Rp0.2 (ksi)
specimen Form Size (mm) (MPa) (ksi) Cement
VM-165 cyl. 6,35 1220 177,0 1282 186,0 19,41
VM-150 cyl. 6,35 1138 165,1 1158 168,0 19,69
S135 cyl. 6,35 1035 150,1 1091 158,0 20,92
Table 1: VM-165 typical tensile properties.
KCV Experimental results 10 x 7,5 @-4°F (-20°C / -4°F)
Specimen 1 Specimen 2 Specimen 3 Average Average Min Ductility
(J) (J) (J) (J) (ft.lbs) (ft.lbs) (%)
S135 85 93 93 90,3 65,9 62,0 100
VM-150 98 95 103 98,7 71,9 69,3 100
VM-165 82 82 87 83,7 61,0 59,8 100
Table 2: Charpy V-notch energies reached with VM-165, compared with S135 API and VM-150 grade.
improved hydraulics performance). Thin- solution. To fulfill the lightweight drill performances in tension resistance and
walled tubes were eventually selected pipe component requirements, an alumi- in shock resistance. Yet this is not the
for both the 5-in. and 5 7/8-in. pipe. As num DP solution of 60-80 ksi aluminum case for VM-165 grade drill pipe.
Figures 3 and 4 show, an acceptable alloy is being pursued as the base case
solution is achieved via 165 ksi material option. This steel grade, when used in drill
drill pipe. It is acceptable for all loading pipe applications, associates ultra-high-
strength performance – 165 ksi minimum
situations. PIPE PERFORMANCE yield strength – with high-impact tough-
The drivers for the choice of the pipe ness – Charpy V-notch energies above
DESIGN CONSIDERATIONS body grade are: resistance to high ten- 44 ft-lbs at -4°C, for a 10 x 7.5 specimen.
The basic design philosophy was to sion, resistance to shock, resistance to It is this performance capability that
keep the entire drillstring as light as fatigue, and resistance to crack initia- makes 165 ksi drill pipe particularly
possible and to use higher-strength tool tion and propagation. Drillstring design well suited for highly demanding drilling
joints and pipe where required. Studies software calculations demonstrate that operations.
looked at both 150 ksi (V-150) and 165 a grade with minimum yield strength of
ksi (VM-165) strength material for steel 165 ksi offers the best performance and Severe drilling environments can intro-
components. Also, tools joints from 120, maximum safety margin. The VM-165 duce extreme mechanical loadings. Drill
130, 135, 140 and 145 ksi material were grade provides optimum strength prop- pipe for uERD and similar wells may
evaluated. The V-150 proved adequate erties, with no drawbacks. see high tensile loads, fatigue, shocks
but provided minimal allowance for tube and surface damage. The VM-165 grade
body wear and limited margin of safety; High-strength steels become usually addresses all these constraints.
therefore, VM-165 is being pursued as brittle under low service temperatures,
and it is very difficult to associate good High tensile loads
the base case with V-150 as a back-up
The VM-165 grade has a minimum yield
strength of 165 ksi and a minimum ulti-
mate tensile strength of 175 ksi. This
provides excellent ability to resist to
high tension loads. Typical values are
collected in Table 1 and compared with
those of VM-150 grade and a standard
Impact toughness measurements have
been conducted as per ASTM E23. The
VM-165 grade shows high impact tough-
ness performance, even at low tempera-
ture. Table 2 shows the performances
reached with VM-165 at -4°F in the
longitudinal direction, for 10 x 7.5 mm
The VM-165 still exhibits a fully ductile
behaviour at temperatures as low as
-35°C, as shown on the transition curve
Figure 5: Transition curve of the VM-165.
46 March/April 2009 D R I L L I N G CONTRACTOR
I N N OVAT I N G W H I L E D R I L L I N G
An alternative/complementary R= -1
approach to non-steel drill pipe UTS (ksi) Fatigue limit @ Fatigue limit @ Amplitude/UTS @
material is to use new ultra-high- 10^7 cycles (ksi) 10^6 cycles (ksi) 10^6 cycles (ksi)
strength material, which will P110 128 69,1 70,8 0,55
bridge the gap between existing S135 160 84,3 87,2 0,54
steel grades and alternative solu- VM-165 186 103,5 0,56
tions. Table 3: Comparison of fatigue limits of various high-strength low-alloy steels.
CTOD CTOD Kmax Kmax
(Figure 5). The ductile to brittle transi- Grade
(10^-3mm) (10^-3inch) (MPa.mm^0,5) (MPa.inch^0,5)
tion temperature is around -60°C.
S135 95,0 3,7 135,2 148,6
High resistance to fatigue
VM-150 99,0 3,9 136,1 149,6
Small-scale fatigue tests simulate the
resistance of the material when loads VM-165 111,0 4,4 149,6 164,4
are applied repeatedly, for example,
when the pipe rotates while remain-
ing within a dogleg. The fatigue limit of
VM-165 base material was evaluated,
with the use of round specimens submit-
ted to tension/compression loads (stress
ratio = -1), and a post treatment as per
The number of cycles to run-out was
set at 10 million. This data, compared
with the fatigue limit of other drill pipe
and OCTG casing grades, is compiled
in Table 3. The VM-165 grade shows the
highest fatigue limit.
Resistance to crack propagation
Fracture toughness and crack tip open- Figure 6: Fracture toughness and CTOD levels of the VM-165 compared with usual API
ing displacements (CTOD) have been and VM-150 grade.
measured on various steel grades as per
ASTM E399-06. The CTOD delta value C Si Mn P S Cr + Mo
gives the maximum acceptable notch
size that will not initiate a crack into Usual Chemistry
the material at a given temperature.
< 0.30 < 0.030 < 0.030 < 0.80
(content in wt. %)
The fracture toughness value gives
information on the ability of the material
< 0.35 < 0.40 < 1.00 < 0.020 < 0.005 < 2.00
to absorb the energy due to a sudden (content in wt. %)
shock. In both of these cases, when drill- Table 4: Specific chemistry for VM-165 grade, compared with common chemistry desig-
ing equipment is submitted to severe nated for API grades.
loads, these values are known to notice-
ably decrease with steel strength. • Very clean steel with limited amount of tensitic phase along the pipe’s length. To
impurities (P, S, …). avoid any thermally induced cracking, a
The results collected in Figure 6 show
• Optimum balance of alloying elements fine-tuning of the quench parameters is
that the VM-165 is in line with usual API
(C, Cr, Mo, …). necessary.
grades and doesn’t demonstrate a drop
of performance. Heat treatment Subsequently, tempering of the very hard
martensite under controlled conditions
Steel chemistry The heat treatment is divided into of temperature and time allows the steel
three phases, each specifically set up to to reach the required strength level
The chemistry chosen for VM-165 grade
ultimately reach an optimum strength/ while maintaining a processing tempera-
is a proprietary chemistry based on AISI
toughness compromise. First, austeniti- ture sufficiently high to keep dislocation
4130 material. It was developed more
zation aims at heating the steel above density to a minimum level.
than 10 years ago, initially for premium
AC3 point to recover a homogeneous and
casing applications. It is particularly
carbide-free austenite microstructure. Thanks to this optimized process con-
well suited for high-strength and high-
Then, through the use of carefully con- trol, the solution for ultra-high-strength
toughness performance. In particular,
trolled water-quenching, the material /high-toughness drill pipes applications
this grade offers:
reaches a complete through-wall mar- was developed, then industrialized in
48 March/April 2009 D R I L L I N G CONTRACTOR
I N N OVAT I N G W H I L E D R I L L I N G
Requirement Tool Joint Performances
Min Torque (kft.lbs) Torque (kft.lbs) OD (inch) ID (inch)
API - NC50 32.9 6-5/8 2-3/4
5” x 0.30”
Double Shoulder 30 48.3 6-5/8 3-3/4
High Strength Double Shoulder 54.3 6-5/8 3-3/4
API - 5-1/2 FH 37.4 7-1/4 3-1/2
5-7/8” x 0.32”
Double Shoulder 70 69.4 7-1/4 3-7/8
High Strength Double Shoulder 78.1 7-1/4 3-7/8
API - 6-5/8 FH 56.1 8-1/2 4-1/4
6-5/8” x 0.33”
Double Shoulder 110 99.6 8-1/2 5-1/4
High Strength Double Shoulder 112 8-1/2 5-1/4
Table 5: Torque requirements from calculation and performances of various connectors.
various combinations of outside diam- Drill pipe validation program of the drill pipe assemblies, with and
eter and wall thickness through the pro- without surface damages.
cessing of several heats of material. Regarding the geometry and grade • Shear, BOP and Iron Roughneck tests
requirements and choices, the chosen evaluate the suitability of the rig
Tool joint performance drill pipe assemblies for project are: equipment, and their ability to deal
The drivers for the choice of the con- • 5 in. x 0.30 in. pipe body in VM-165 with the specific products: shear rams
nectors are high torque capability with grade with 6 5/8 in. x 3 ¾ in. HSDS con- will be tested to shear the pipe body;
minimum OD and maximum ID in order nector. the Iron Roughneck will be tested
to reduce weight and achieve optimal • 5 7/8 in. x 0.32 in. pipe body in VM-165 through several hundreds of high
hydraulic performance. grade with 7 ¼ in. x 3 7/8 in. HSDS con- makeup and breakout torques.
nector. The last section deals with field tests.
Table 5 shows the torque performance • 6 5/8 in. x 0.33 in. pipe body in VM-165
by size of various types of connectors in Pipes will be run in real drilling opera-
grade with 8 ½ in. x 5 ¼ in. HSDS con- tions to confirm field use capability and
addition to the requirements of the drill- nector.
string design calculations for each of the field performance. Inspection procedures
three drill pipe sizes. An extensive qualification program has will be closely monitored.
been set up to demonstrate product
The first option is standard API con- performance. It includes the production KNOCK-ON EFFECTS
nector with 120 ksi yield strength. To of 400 5-in., 5 7/8-in. and 6 5/8-in. drill pipe
achieve the required torque within a Logically, when new technology is devel-
assemblies, as well as qualification tests oped in one area, it should be expected
usable size range is not achievable. to be performed during Q4 2008 and Q1 that there is likely to be knock-on
The second connector option is a 2009. effects in other areas. In this regard,
double-shoulder (DS) connection with The qualification tests are summarized the advancements of drill pipe technol-
a proprietary thread design to improve in Table 6. The first section deals with ogy are no different. On the positive
performance, and 120 ksi yield strength small-scale laboratory tests on the pipe and most importantly, it stretches the
tool joints. The torques increase by body, which confirm that the VM-165 technical limit beyond what is currently
approximately 80% on average, and grade is reached on the specific pipe thought possible. Technically speaking,
acceptable sizes are reached. However, sizes. The second section deals with if the VM165 is properly deployed, it will
acceptable torque performance cannot laboratory tests performed on full-scale allow access to previously unobtainable
be met for two of the three drill pipe drill pipe assemblies. The tests are hydrocarbon reserves. On the downside,
sizes. chosen to be representative of real use a leap forward with one technology
conditions. The results confirm that the requires the advancement of others.
The third connector option is based on
the same design as option 2, but the drill pipe assemblies meet all the field The development of high-strength,
material yield strength of the tool joint expectations. thinned-wall pipe has necessitated the
is enhanced to reach 135 ksi minimum. In particular: requirement to alter fundamental rig
This high-strength, double-shoulder design. To allow for safer and more effi-
(HSDS) connector meets both the • Tension and torque tests evaluate the cient running of drill pipe, more rig floor
torque and size requirements, for every performance of the weld when the drill space and pipe barn area was added.
drill pipe size. It was determined to pipe assembly is submitted to various Over 20,000 ft of drill pipe can stand
be the most suitable connector for the combinations of loads. back in the derrick, and another 20,000
project. • Fatigue and fatigue with slip marks in full stands can been picked up or laid
tests evaluate the fatigue performance down in the pipe barn.
50 March/April 2009 D R I L L I N G CONTRACTOR
I N N OVAT I N G W H I L E D R I L L I N G
5” x 0,30” Drill Pipe with 5-7/8” x 0,32” Drill Pipe 6-5/8” x 0,33” Drill Pipe
VM-165 Pipe body and with VM-165 Pipe body and with VM-165 Pipe body and
HSDS connector HSDS connector HSDS connector
Small Scale tests
Full scale tests
Fatigue Tests with Slip Marks
Iron Roughneck Tests
Stack Up Tests
Table 6: Qualification tests of drill pipe assemblies.
To allow for nearly 80 ft of drill pipe lic performance requirements with suf-
stretch when tripped off bottom, over Modeling strongly suggests that ficient safety margins. The 135k tool
20 ft was added to the height of the joints along with broadening connection
standard derrick. This will allow for the uERD project is technically performance makeup envelope will defi-
picking up and working pipe and cas- feasible but requires the develop- nitely add value.
ing of bottom. The BOP systems had to
be enhanced in order to increase their ment of the next generation in drill This means that having a connection
ability to shear drill pipe of up to 180 ksi with a wider make and break window
yield and to shear thick-walled pipe ADP pipe technology. will reduce fatigue of tool joints and
nearly 0.625-in. thick. Slips had to be surface running equipment. The leap
tested to confirm their ability to grip but from 150 to 165 ksi is monumental in
To a similar extent, changes in equip- improving the ability to reach extended
not crush or damage thin-walled pipe. ment run in the drillstring along with the
Slips had to be tested to confirm their targets, but, in actuality, with respect to
drill pipe like cross-over subs, mechani- chemistry and connection design, these
ability to grip and hold high-strength cal friction reduction devises, safety
tools joints (130-150 ksi) while making are simply enhancements to existing
valves, pipe in subs, kelly valves heavy technology.
and breaking. weight, drill collars and BHA acces-
In many cases, the development of the sories all had to be modified. Repair, To date, five sizes of VM-165 have been
165 ksi pipe means dramatically new maintenance and inspection are also successfully manufactured, and lab tests
equipment or significant modifications to undergoing more scrutiny and will likely have been conducted. All small-scale test
handle higher loads more safely. Several be changed. results either meet or exceed a strenu-
changes were in pipe-handling equip- ous purchase specification. The knock-
ment: CONCLUSIONS on effects have been significant but not
insurmountable, and, once combined
Modeling strongly suggests that the
• Top drive system capable of 150,000 with the 165, will allow drilling to push
uERD project is technically feasible but
ft-lbs and 120 rpm. well beyond the current drilling enve-
requires the development of the next
• Iron Roughneck capable of 150,000- lope. This project is evidence that even
generation in drill pipe technology.
200,000 ft-lbs makeup and breakout. with a tight time line – it started just two
• Bucking machine capable of makeup In every well design case, the VM165 years before projected spud – collabora-
and breakout of up to 150,000-200,000 triple taper design – 6 5/8-in. x 5 7/8-in. x tion works. Final proof will be in the
ft-lbs. 5-in. – with the high-strength tool joints execution.
satisfies the torque, tensile and hydrau-
52 March/April 2009 D R I L L I N G CONTRACTOR