5SF - WI3081 Ballot

API Ballot id# 5432
SC5 TGTGC
3081 – Guidelines for Evaluating Connection Performance in Multi-

Work Item
Fractured Horizontal Wells
Distribution-type
(Ballot, Comment-only
Ballot, Recirculation Ballot (voting and commenting)
(comment resolution),
Re-ballot, etc.)
API Standard TR 5SF [proposed identifier]
Impacted Documents RP 5C5
Revision Key NAThis is a first edition with no Track Changes for its initial ballot.
Work Item Charge: Develop a testing protocol to evaluate premium connections for use in
non-standard applications. This includes both shale gas wells and scenarios like casing drilling
where low-cycle fatigue effects on premium connections need to be considered.
Ballot Rationale: Premium and semi-premium connections used in non-standard applications

such as shale wells are subjected to unique fatigue load combinations during installation and
well completion that are not addressed in the current industry premium connection evaluation
protocol (API 5C5). These unique loads include:
• Low-cycle fatigue as a result of rotating while bending;
• Pressure cycling during frac operations; and,
• Thermal shocking as cold frac fluids are injected downhole.
Many users and manufacturers support a distinct protocol required for non-standard
applications separate from API 5C5 because the load conditions are considerably different.
Premium connections evaluated for shale application may not require the rigor of an API 5C5
CAL IV test program; however, they still need to be evaluated against a prescriptive and severe
test matrix to ensure sealability and structural integrity.
This protocol will strive to create a representative and efficient and effective evaluation
methodology (testing, and potentially analysis) that manufacturers and users can refer to when
designing connections for non-standard applications.
NOTE See the ballot email notification for additional information regarding this ballot.
This document is not an API Standard; it is under consideration within an API technical committee but has not received all approvals
required to become an API Standard. It shall not be reproduced or circulated or quoted, in whole or in part, outside of API committee
activities except with the approval of the Chairman of the committee having jurisdiction and staff of the API Standards Dept. Copyright
API. All rights reserved.
Guidelines for Evaluating

Connection Performance in
Multi-Fractured Horizontal Wells
API TECHNICAL REPORT 5SF

FIRST EDITION, XXXX 20XX
The Special Notes, Foreword, and Contents will be generated by API

during the page proofing stage before publication.
Introduction
The well designs and completion strategies associated with hydraulic fracturing have a unique set of
challenges. During well construction, the long lateral sections of extended-reach wells may require the
production or intermediate casing to be rotated and pushed through build sections of relatively high
curvature (greater than 10° per 100 feet or 30 meters); furthermore, some operators rotate the casing during
cementing to improve cement placement quality. This rotation can subject the connections in the build
section to a high number of rotating-bending load cycles, and the high stresses associated with these cycles
could lead to localized yielding of the material, loss of sealability, or potential structural failure. The hydraulic
fracturing process itself subjects the tubular to rapid increases in pressure at high-magnitudes;
consequently, wells with a high number of stimulation stages will be subjected to cyclic pressure-loading.
Given these considerations, connections used in hydraulically fractured wells can be subjected to significant
cyclic-loading before the well is produced, and this loading may have an impact on the overall connection
sealing and structural capacity later in the service life of the well.
API 5C5 outlines a process for experimentally validating a connection performance envelope. While this
standard addresses both sealability and structural integrity, the primary focus is validating the sealability
performance of a connection under various combinations of pressure, axial force, and temperature.
Although API 5C5 is applicable to a wide range of operating environments, the primary driver for the
enhancements under its 4th Edition was the increasing severity of loading present in offshore applications.
The primary focus of this standard is to evaluate connection performance under the structural loads that
typically occur in multi-fractured horizontal wells (MFHW). This standard may be used separately from API
5C5, if structural integrity is the sole concern, or in conjunction with API 5C5 to subject the connection to
structural loading before subsequent sealability evaluation.
This standard will provide a means to evaluate connection performance under a consistent method of
discrete test program elements developed to replicate the cyclic, rotating-bending loads of well construction
and the pressure cycling of multi-stage hydraulic fracturing. This standard will not follow a prescriptive
approach but rather allow the evaluator to customize a test program from the test program elements that
are most representative of the application of interest. While evaluators following the guidelines of this
standard should employ sound engineering judgment when devising test programs, it is ultimately the
responsibility of the end-user to determine the level of applicability of a given test program to the service
loads of interest.
Guidelines for Evaluating Connection Performance in

Multi-Fractured Horizontal Wells
1 Scope
This standard defines tests that may be used to determine the performance of threaded casing and tubing
connections for use in multi-fractured horizontal wells (MFHW). This standard defines experimental loading
conditions intended to simulate the various stages of MFHW construction and use—installation of tubulars,
stimulation of surrounding formation, and production of hydrocarbons. Dynamic effects from such factors
as thermal shock, vibration during running/rotating, and hydraulics are beyond the scope of this standard.
This standard does not address erosion or metallurgical impacts such as, for example, corrosion, hydrogen
embrittlement, and so forth. This standard also does not establish a standardized testing program or
acceptability criteria. Not all the test program elements (TPEs) presented in this standard may apply to all
MFHWs; consequently, this standard provides flexibility in tailoring a testing program for the specific,
anticipated field loads of a given well (or group of wells). End-users are ultimately responsible for
determining whether an evaluation program assembled from the TPEs presented in this standard is
appropriate for a given set of field conditions. This determination will likely be based on historical practice,
local regulatory requirements, and specific well conditions.
2 Normative References
The following referenced documents are indispensable for the application of this standard. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
API Recommended Practice 5C5, Procedures for Testing Casing and Tubing Connections, Fourth Edition
For a list of other documents associated with this standard, see the Bibliography.
3 Terms, Definitions, Symbols, and Abbreviations
3.1 Terms and Definitions
For the purposes of this standard, the following terms and definitions apply.
3.1.1
connection
A tubular connection product, either threaded and coupled (T&C) or integral, that is tested according to this
standard.
3.1.2
end-user
The entity who expects the connection to perform and typically an operating company that has operations
where the connection will be used in the field.
3.1.3
evaluator
The party creating and executing a test program following the guidelines of this standard.
4
NOTE In some instances, the evaluator will be one entity (e.g., a connection supplier selecting the TPEs and
executing tests in an internal lab); in some instances, the evaluator may be multiple entities (e.g., an end-user and/or
supplier selecting the TPEs and executing tests in a third-party lab).
3.1.4
load frame
A testing system that is designed to apply a load to the specimen.
3.1.5
multi-fractured horizontal wells (MFHW)
The target application of this standard wherein the target producing reservoir is drilled with an extended
reach or long horizontal section and fractured over the length of that horizontal section in multiple zones.
3.1.6
specimen
A representative sample of the candidate connection design prepared for testing.
NOTE 1 For threaded-and-coupled connection designs, a specimen consists of one coupling (centrally positioned)
with connection boxes machined on both ends made-up on either side to casing pups machined with connection pins.
NOTE 2 For integral connection designs, a specimen consists of one box-end connection made-up to one pin-end
connection.
3.1.7
supplier
The party that designs and/or manufactures the candidate connection tested according to this standard.
3.1.8
test program element (TPE)
A base component of the overall test program an evaluator can create from this standard.
NOTE Each TPE is a standalone program designed to simulate unique loading at a stage of the connection’s service
life in MFHW operation.
3.2 Abbreviations
CAL connection application level
MIYP minimum internal yield pressure
MFHW multi-fractured horizontal wells
PBYS pipe body yield strength
T&C threaded-and-coupled
TPE test program element
3.3 Symbols
D pin diameter of the pin end of the connection
r pin radius of the pin end of the connection
5
4 Creating a Representative Test Program
4.1 General Philosophy
This standard describes test procedures that can be used to evaluate connection performance properties
for connections used in MFHW. The well conditions for MFHW can vary widely. The various procedures for
each of the TPEs herein can be used to design an evaluation program for a specific application or a broad
spectrum of MFHW applications. Not all TPEs in this standard may be necessary for a particular application.
The evaluator following the guidelines of this standard is encouraged to use good engineering judgement
in determining what TPEs are necessary to determine the performance properties for a particular service
scenario. If uncertainty arises regarding the applicability of TPEs to a particular scenario, the evaluator
should consult with an end-user(s) to ensure that the test program is as representative of field conditions
as practical.
Although API 5C5 defined a CAL system with various levels of testing rigor, the onus of selecting the
appropriate CAL still fell on the end-user and not the API 5C5 standard. According to API 5C5, Fourth
Edition, Section 5 (part 5.1.1) states: “Users of this RP shall specify the CAL required based on the needs
for the particular service intended. Users of the connection should be familiar with the defined connection
test rigor, the performance limits, and limit loads.”
Because of the wide range of variables involed in MFHW design, the CAL system established in API 5C5
is not used in this standard. This philosophy encourages the evaluator to consult with an end-user(s) to
determine whether an appropriate combination of TPEs has been chosen to address anticipated service
scenarios. End-users should be familiar with the testing rigor inherent to the various TPEs in this standard
to determine how a given evaluation program applies to field performance.
Section 5 describes the various TPEs representative of the loading common to unconventional wells with
horizontal or highly deviated production strings.
4.2 Failure Modes
The primary foci of TPEs in 5.2, 5.3, 5.4, and 5.6 are structural integrity and liquid-tight sealability, not gas-
tight sealability; gas-tight sealability is the purview of production loads in 5.5. Consequently, the following
three failure modes are relevant to this standard.
a) Loss of structural integrity—This failure mode could include excessive deformation of the pin or box,
thread jumping or shearing, or excessive deformation of the tube body. Loss of structural integrity is
often (but not always) preceded by loss of liquid sealability. It is the responsibility of the evaluator to
monitor the deformation of the specimen through strain gauges or other means and, in potential
consultation with an end-user(s), to determine a threshold for loss of structural integrity. This monitoring
should encompass the behavior of not only the test specimen(s) itself but also all associated equipment
(e.g., end-caps). This monitoring is especially relevant if the selected TPEs and associated loads induce
near-yield cycling in the test specimen(s).
b) Loss of liquid sealability—For the purposes of MFHW design, liquid sealability is most relevant to the
containment of fluid during stimulation operations. Unlike gas sealability, there is rarely dispute over
whether a loss of liquid sealability has occurred; it is typically not a subtle event. While this standard
does not discourage the use of leak detection systems for this failure mode, it does not specify a
threshold over which liquid sealability loss has occurred. If such a threshold is desired, the evaluator
should consult with an end-user(s) to determine what threshold is most appropriate for a given
application.
c) Loss of gas sealability—For the purposes of MFHW design, gas sealability is most relevant to the
containment of gas-laden hydrocarbons during production; as such, it is typically the purview of
production loads in 5.5. Since loss of gas sealability can be a subtler event than loss of liquid sealability,
the definition of threshold leak rates is recommended. The evaluator is free to define these thresholds,
but the acceptance criteria presented in API 5C5 are recommended as a starting point.
6
This standard does not explicitly define acceptance criteria. The existence and definition of acceptance
criteria for loss of structural integrity and loss of liquid sealability are at the discretion of the evaluator, in
potential consultation with an end-user(s). The existence of acceptance criteria for loss of gas sealbility is
encouraged, but its definition is again left to the evaluator, with API 5C5 as the recommended starting point.
4.3 Specimen Geometry
4.3.1 General
This standard does not specify geometric tolerance combinations for connections; it is the responsibility of
the evaluator to understand the potential impact of thread and seal geometry variations on structural
integrity, liquid sealability, and gas sealability. Worst-case performance combinations should be identified
by the evaluator or supplier using analytical, computational, and/or experimental techniques. If TPEs related
to production loads are planned (see 5.5), then the geometry combinations presented in API 5C5 should
serve as the starting point; any deviations from these combinations should be justified via analytical,
computational and/or experimental techniques.
4.3.2 Specimen Notching
Several connection designs involve a seal that is associated with the engagement of the connection torque
shoulder. As this standard does not have sealability performance acceptance criteria, evaluators may
choose to leave the torque shoulder seal intact to assess the entire connection assembly performance
during a test program; however, if the evaluator is testing a premium connection design in their test program
and subjecting test specimens to internal pressure loads as part of this, they may want to consider disabling
the connection shoulder seal prior to that test. Grooving the connection shoulder can be done in the manner
described in API 5C5, Fourth Edition, Section 6 (part 6.6).
4.4 Test Load Calculation
This standard is not intended to prescribe the magnitude or combination of loads that may be applied to a
test specimen during its test program. The multiple load steps (as well as any necessary intermediate load
points to get safely between load steps) that make-up a test matrix are the responsibility of the evaluator
and should be generated with fundamental understanding of the connection performance, material
properties, and limitations therein.
If an evaluator chooses to develop a test matrix based on pipe body geometry and material properties
instead of connection load ratings, the evaluator may use nominal or actual values of these properties. The
final report shall note what methodology was used to generate the test matrix.
4.5 Quality Control
Connection manufacturing quality control procedures should be consistent with those outlined in API 5C5,
Fourth Edition, Section 4 (part 4.4).
4.6 Test Facility Safety
Test facility safety requirements shall be consistent with API 5C5, Fourth Edition, Section 4 (part 4.5).
4.7 Calibration and Accreditation Requirements
Test facility calibration and accreditation requirements shall be consistent with API 5C5, Fourth Edition,
Section 5 (part 5.4).
7
5 Test Program
5.1 Test Program Sequence and Test Program Elements
5.1.1 General
As stated in 4.1, test programs derived from this standard are composed of individual components referred
to as test program elements (TPEs), each of which focuses on the loading representative of a specific
process or stage in the well operation. Although this standard will allow evaluators to pick and choose what
TPEs are employed, it is recommended that evaluators follow a connection test load path representative of
field conditions as shown in the flow chart of Figure 1.
Test programs following the guidelines of this standard are application-driven, so there is no single way to
perform a test with respect to the TPEs that are selected; however, it is recommended that the sequence
of testing follows the load sequence of a typical operation: (1) connection make-up, (2) installation and
running, (3) stimulation, and (4) production. Figure 1 shows the recommended load sequence.
Figure 1―Recommended Load Sequence
The load sequence is significant in that much of the loading in MFHW applications may have a cumulative
impact on structural (and possibly sealing) performance. Therefore, it is important to be as representative
of field conditions during testing as possible, especially with respect to cyclic loading, since it can lead to
localized material yielding in connections.
Within each stage of the load sequence there are two sub-categories:
 Base TPEs: the TPEs required as part of that stage; and
 Supplementary TPEs: the TPEs that an evaluator can elect to include as part of the test program that
would enable the test to be as representative of field conditions as possible.
The TPEs that an evaluator chooses to include in their test program are designed to be customized.
Evaluators can skip entire stages of the load sequence if they do not feel that it is necessary to evaluate
the connection performance under those loads (e.g. installation loading). Figure 2 shows the base and
supplementary TPEs in the load sequence recommended by this standard. Annex A includes information
and examples of using base and supplementary TPEs to construct a test program.
8
Base TPEs Supplementary TPEs
Connection
Makeup
Connection Makeup
Section 5.2
Section 5.2
Galling Resistance
Testing
Section 5.2.2
Post-Makeup
Incremental Torque
Section 5.2.3
Tensile Load Capacity

Testing
Section 5.3.1
Rotating/Bending
Testing
Connection Running & Installation Loads
Section 5.3.2
Four-Point
Rotating/Bending
Section 5.3.2.1.1
Section 5.3
Resonant Fatigue
Rotating/Bending
Section 5.3.2.1.2
Combined Loading
Axial Load
Section 5.3.2.5.1
Combined Loading
Torque
Section 5.3.2.5.2
Combined Loading
Internal Pressure
Section 5.3.2.5.3
Figure 2―Base and Supplementary Test Program Elements in Sequence
9
Base TPEs Supplementary TPEs
Internal Pressure
Cycling
Stimulation Loads
Section 5.4.1
Section 5.4
Internal Pressure Cycling
w/ Dogleg Curvature
Section 5.4.1.5.1
Internal Pressure Cycling

w/ Axial Load
Section 5.4.1.5.2
Production Loads
Section 5.5
Test elements simulating production loads

as per API RP 5C5
RP 5C5 Limit Loads

Section 5.6
Torque to Failure
Section 5.6.1
Limit Loads
Section 5.6
Bend to Failure
Section 5.6.2
Bend with IP to Failure

Section 5.6.3
Fatigue to Failure
Section 5.6.4
Figure 2―Base and Supplementary Test Program Elements in Sequence (Continued)
10
5.1.2 Specimen Preparation
Specimens should be provided with ends prepared for welding or threading onto end-caps that will attach
the specimen to a load frame. The minimum specimen length should be consistent with of API 5C5, Fourth
Edition, Section 6 (part 6.3.1); however, any subsequent low- or high-cycle rotating/bending testing may
require the specimens to be longer than the minimum length specified in API 5C5.
If strain gauges are used to verify the pipe body stress during testing, a minimum of one strain gauge is
needed; however, it is recommended to prepare specimens with strain gauges as specified in API 5C5,
Fourth Edition, Section 5 (part 5.9.3.4), if rotating/bending testing or any other tests involving pipe body
curvature are selected by the evaluator.
5.2 Connection Make-up
5.2.1 Connection Make-up Guidelines
Connection make-up and break-outs should follow the procedures outlined in API 5C5, Fourth Edition,
Section 5 (part 5.6); however, connections may be made-up to any torque within the range of final make-
up torque specified by the connection supplier. The following aspects of connection make-up should be in
accordance with the connection supplier’s requirements:
a) make-up speed,
b) make-up position,
c) thread compound volume and application distribution (pin, box, or combination thereof), and
d) shoulder torque range (for shouldered connections).

Connection make-up should be monitored with a torque-turn monitoring system and, if included, the
evaluator should provide record of the following: make-up speed, mass and type of thread compound,
shoulder torque (if applicable), and final make-up torque for each connection.
5.2.2 Galling Resistance Testing
If galling resistance testing is to be included in the test program, the relevant test procedures for galling
resistance testing as described in API 5C5 should be referenced. Note that this standard does not require
the evaluator to follow the prescribed sequence and combinations for galling resistance tests in accordance
with API 5C5, but the evaluator can select any combination of galling resistance tests such as round-robin,
make-break testing or multiple make-break testing for any connection specimen. Results from galling
resistance testing should be documented.
5.2.3 Post-Make-up Incremental Torque
Connections may be subjected to incremental torque in the field beyond initial make-up due to casing
running or cementing activities. If incremental make-up torque is to be applied to a connection after final
make-up, it should occur separately from the original connection make-up. At a minimum, the tong or
bucking-unit backups gripping the coupling shall be released for 15 minutes before being re-applied to the
connection. Evaluators may scribe or otherwise mark the relative position of the pin and box of each
connection before incremental torque is applied as shown in Figure 3.
11
Figure 3―Connection Scribing Example
The evaluator can assign any maximum torque value at their discretion; however, the target maximum
incremental make-up torque should be defined by the connection supplier as the highest torque to which a
connection can be subjected without significant structural damage, such as:
a) ovalization of the pin and/or box,
b) evidence of pin nose yielding or deformation,
c) thread jump or shearing, and
d) loss of fluid sealability.

Drift testing after application of post-make-up incremental torque is recommended to detect if gross
deformation of the tube body or connection has occurred.
Incremental make-up torque should be applied to individual connections; however, if the evaluator decides
to float the two connections of a threaded and coupled specimen, this should be documented as part of the
test results. It is not a requirement of this TPE to be able to break-out a connection that has been subjected
to incremental make-up torque.
The incremental torque applied to a given connection should be recorded. If the relative position of pin and
box was recorded prior to incremental make-up, record any change in rotational position of the pin and box
in degrees using Equation 1 as shown in Figure 4.
360×∆r𝑃𝑃𝑃𝑃𝑃𝑃
∆𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑃𝑃𝑃𝑃𝑃𝑃 = (1)
πD𝑃𝑃𝑃𝑃𝑃𝑃
Figure 4―Example Connection Scribe Relative Position After Incremental Make-up Torque
5.2.4 Connection Make-up Reporting
A brief report should be written summarizing overall specimen performance. Any torque-turn curves that
were generated as part of this TPE should be included as an appendix to the report, as well as any relevant
photos showing the condition of the connection components before initial make-up and between any
subsequent make-ups in a galling resistance test.
12
5.3 Casing Running and Installation Loading
5.3.1 Tensile Load Capacity
5.3.1.1 General
Given that many MFHW incorporate extended-reach horizontal sections, evaluators may want to confirm
the maximum tensile load capacity of the connection. Connections near surface may see high tensile loads
during such operations as reciprocation during running, stimulation, or casing recovery.
This TPE consists of subjecting specimens to high axial load to simulate near-surface hanging load. If the
test program includes production load TPEs (see 5.5), then testing of tensile load capacity may be
incorporated there.
5.3.1.2 Test Set-up
This TPE will require specimens to be installed into a load frame capable of applying axial load to the
specimen. The specimens should have end-caps attached to both ends; however, the end-caps do not
need to have pressure sealing capability as internal fluid pressure is not part of this TPE.
The specimen should be instrumented with strain gauges to monitor strain. Information on the location and
orientation of the strain gauges is provided in 5.3.1.3. Test set-up calibration requirements should be
defined by the evaluator prior to the test program and consistent with industry good practice (e.g. API 5C5).
5.3.1.3 Test Matrix
The test matrix for tensile load capacity should incorporate a number of intermediate load steps to
understand connection behavior under increasing axial load. The number of steps between zero load and
maximum axial tensile load is at the discretion of the evaluator; however, it is recommended that at least
one intermediate step be incorporated in this TPE to demonstrate connection stability at various loads.
Table 1 shows an example of the tensile load capacity test matrix for an arbitrary T&C connection on 5-1/2
in., 17 ppf, P110 casing; for reference, the PBYS of the tube body for this example is 546,000 lb.
Table 1―Tensile Load Capacity Test Matrix Example

for 5-1/2 in., 17 ppf, P110 T&C Connection
Load Axial Load Duration

Step lb minutes
1 130,000 5
2 275,000 5
3 490,000 5
4 275,000 5
5 130,000 5
5.3.1.4 Reporting
Reporting of the tensile load capacity TPE will consist of a time-history plot and a table showing the recorded
loads at each load step. Supplementary observations of the test and specimen as a result of the test can
be included in the report as well as any relevant photos taken during the TPE.
13
5.3.2 Rotating/Bending Cyclic Testing
5.3.2.1 General
Connections that are run through a build section can be subjected to multiple rotating/bending cycles if the
string is rotated during either installation or well cementing activities. This cyclic loading can lead to crack
initiation and propagation at areas of high stress concentration (e.g., thread roots). In addition to creating
stress changes inside the connection, rotating/bending cycles may impact connection sealability later in the
service life.
The purpose of this section is to define fatigue testing to evaluate structural behaviour of the connection
under rotating/bending cyclic loading. For testing the performance of rotating/bending cyclic fatigue there
are two approaches: evaluating specific well conditions or defining an operating window for the connection
design.
The first approach is to test the connection under specific well conditions, which requires the following two
inputs: estimated number of rotating/bending cycles for the well operations of interest, and estimated dog-
leg severity experienced by the pipe during installation. The primary objective of this approach is to apply
fatigue loading representative of field conditions before proceeding to other TPEs in the test program. The
expectation is that the specified number of rotating/bending cycles will be applied without loss of structural
integrity or fluid sealability.
The second approach is to perform fatigue testing to failure. This test determines the limits of fatigue life of
the connection and results is a so-called “S-N curve” for the connection. This curve represents the maximum
number of cycles that can be experienced before failure for a given stress range. All rotating/bending cyclic
loading tests rely on material properties (among other things) and will therefore have a statistical nature in
their results. Consequently, the number of tested specimens should be carefully choosen to achieve reliable
results. As demonstrated in Figure 5, the purpose of this approach is to obtain an S-N curve that represents
the minimum number of cycles needed to produce failure in the connection within a certain level of statistical
confidence (typically 97.5 %).
As the two approaches are different in nature, a proper definition of the purpose of the test program shall
be performed by the evaluator beforehand. For instance, if the program is intended to simulate the well
conditions, the worst dog-leg severity expected in the well should be selected and checked for the intended
number of cycles. On the other hand, if the S-N curve approach is followed, then at least three dog-leg
severities representative of the application should be selected. Both approaches should account for the
additional mean, tensile stress anticipated in the string during the running operation through the bent
sections of the well.
The evaluator should acknowledge that the tests presented in this section are simplified representations of
the conditions observed in the field. None of the testing devices mentioned in this section replicate the exact
field conditions of MFHW, where bending, axial loads and torsion are performed simultaneously. Also, the
following elements are not included in the scope of this testing procedure:
 dynamic effects such as vibrations and interactions between the string and wellbore wall,
 effects of alternating applied torque while rotating,
 effects of potential casing wear on pipe and connections, and
 effects of corrosive and/or sour environments.
Fatigue tests parameters are defined in terms of applied maximum and minimum stresses observed in
cyclic loading, which are represented in Figure 6.
14
Figure 5―Example of S-N Curve
Key
σ min = minimum applied stress
σ max = maximum applied stress
Δσ = σ max – σ min = resultant stress range or alternating stress
σ m = (σ min + σ max )/ 2 = mean or average applied stress
σ a = stress amplitude (half of resultant stress range)
Figure 6―Schematic of Cyclic Loading
15
5.3.2.2 Test Set-up
5.3.2.2.1 General
Two typical set-ups for rotating/bending testing are briefly described below: four-point bending and resonant
fatigue. Although the four-point bending is typically used for large dog-leg severities and low number of
cycles, and resonant fatigue is normally used for small dog-leg severities and high number of cycles, both
test set-ups can be used to evaluate either condition.
5.3.2.2.2 Four-Point Bending
Some well trajectories may motivate an evaluator to consider dog-leg severities beyond the capabilities of
set-ups typically used for high-cyle rotating/bending testing. In such instances, use of an experimental set-
up tailored for four-point bending may be necessary to achieve the desired dog-leg severities.
Performing four-point bending testing will require a dedicated test frame capable of applying a prescribed
dog-leg curvature to the specimen while simultaneously rotating the specimen. This section will focus on
the four-point bending test apparatus to achieve the desired curvature.
For the four-point bending configuration, curvature is typically applied through contact points to the
specimen incorporating bearings or bushings to allow the specimen to rotate without significant friction or
wear. Note that the pipe body in contact with the four-point bend system may work harden over the span
of the test program if the contact points are narrow.
Specimen rotation is typically achieved using a motor connected to the specimen through a universal joint
or other flexible junction to allow the connection specimen to properly flex under curvature loading. Figure
7 shows a schematic of a typical low-cycle rotating/bending test system.
Figure 7―Example Four-Point Bending Test Apparatus Schematic
Figure 7 displays only one option of implementing a four-point bending test. Other options are permissible
as long as the set-up is capable of applying the desired magnitude of dog-leg severity while simultaneously
rotating the specimen.
Specimens tested in four-point bending frames shall be sufficiently long to allow for the specimen to fit
inside the test frame and have the contact points for the four-point bending system sufficiently far from the
connections in the middle of the specimen. Specimens that are later subjected to combined load testing
can be cut down to length to fit in the load frame. Furthermore, if there are concerns about localized material
hardening on specimens because of the rotating/bending test set-up, the hardened sections can be cut off
if the remaining length of the specimen exceeds the minimum length specified in API 5C5, Fourth Edition,
Section 6 (part 6.3.1). Figure 8 shows a schematic of specimen preparation for low-cycle rotating/bending
testing and potential locations of localized material hardening.
16
Figure 8―Four-Point Bending Specimen Contact Point Locations
Strain gauges are recommended to verify the pipe body stress and induced dog-leg curvature during testing.
It is recommended to prepare specimens with a ring of four biaxial strain gauges on both casing pups as
specified in API 5C5, Fourth Edition, Section 5 (part 5.9.3.4).
5.3.2.2.3 Resonant Fatigue
This machine uses a high-rate sinusoidal input to induce bending in the specimen. Since the resulting
bending frequency can be applied near the natural resonant frequency of the specimen, many cycles can
be applied in a relatively short time-frame. Although this method facilitates the execution of many cycles in
a reasonable period, the system is sensitive to small variations in the set-up of the machine.
A typical test set-up includes a specimen supported at two locations away from the connection. These
locations serve as the node points where specimen deflection is near zero in any direction. The connection
to be tested is usually at or very near the midpoint between two node points, where the maximum bending
deflection occurs. One end of the specimen is attached to the apparatus applying the sinusoidal input. The
alternating bending strain on both sides of the specimen connection should be monitored continuously
during testing as well as used for control. The sampling frequency of the data acquisition system should be
high enough to record the complete sinusoidal sample response. An example resonant high-cycle
rotating/bending test set-up is shown in Figure 9.
Specimen length plays an important role in the determination of the natural resonant frequency, and
therefore this length is defined by the laboratory based on their available test equipment. Specimens that
are later subjected to combined load testing can be cut down to length to fit in the load frame as required
by API 5C5, Fourth Edition, Section 6 (part 6.3.1).
Figure 9―Example of Resonant Fatigue Test Apparatus Schematic
17
5.3.2.3 Test Execution—Low-Cycle Rotating/Bending
Choice of rotating speed requires a balance between: (1) replicating field conditions as accurately as
practical and (2) achieving a reasonable test duration. Rotating speed may be increased relative to field
conditions to reduce the overall test duration; however, care should be taken to not exceed a safe roating
speed above which excessive vibrations or other dynamic loads may occur. It is worth noting that the types
of rotational operations envisioned by this standard encompass rotating while cementing or incidental
rotations required to run casing to its intended depth; rotations incurred during drilling with casing are not
covered by this standard.
The evaluator should establish both the curvature magnitude and number of rotations to which the
specimen will be tested. Several rotating/bending cycle test sequences can be performed at multiple dog-
leg curvatures (i.e., X number of rotations at one dog-leg curvature in Sequence 1, Y number of rotations
at another curvature in Sequence 2); however, a typical test under this TPE would consist of one test
sequence with a single dog-leg curvature. Table 2 shows an example test matrix for low-cycle
rotating/bending testing.
Table 2―Well Condition Test Matrix (Example)
Dog-leg Number Rotation

Test
Curvature of Speed
Sequence
deg/100 ft Rotations RPM
1 10 20,000 30
2 20 20,000 30
If the connection is to be tested under well conditions, it is expected to continue with sealability tests. In
cases where no data (previous testing or S-N curve) exists to confirm that the required number of cycles
can be safely achieved at the required dog-leg, some tests to failure at the required dog-leg (typically three
specimens) are recommended to generate confidence on the results.
If the program is intended to define an S-N curve, the specimens should be tested at high, medium, and
low stress ranges, and the evaluator should document the magnitude of these ranges as a percentage of
the nominal material yield stress. Due to the stochastic nature of the fatigue evaluation, a minimum of two
different specimens are recommended at each level of stress range, for a minimum total of six specimens;
however, the number of specimens is up to the evaluator.
The alternating bending stress range and mean stress should be tested at stresses that are representative
of the stress’s connections would experience in the field. Table 3 shows an example of a program with
three specimens (instead of the minimum of two) aiming to obtain an S-N curve either by reaching failure
or a significant number of cycles far larger than the number of cycles expected in the field.
Table 3―S-N Approach Test Matrix (Example)
Dog-leg
Test
Curvature Number of Cycles
Specimens
deg/100 ft
To failure or 10 million
1–3 8
cycles
4–6 10
cycles
7–9 12
cycles
18
5.3.2.4 Test Conclusion
Depending on the approach decided at the beginning of the program, the test concludes when either the
target number of cycles is reached or a loss of structural integrity or fluid sealability occurs.
If a loss of structural integrity or fluid sealability occurs, the specimen and especially the specific area around
the coupling should be investigated for cracks and other anomolies. Cracks can be detected by means of
non-destructive evaluations (magnetic particles, etc.). If the specimen broke, the nature of the fractured
cross section should be documented in the report
If the number of cycles was achieved without loss of structural integrity or fluid sealability, the specimen
may continue with subsequent TPEs. Review and record the position of the scribed line to check if the
connection position changed during the test program (i.e., did the connection make-up further or back-out).
In the event of incremental make-up, proceed with the remainder of the test program. However, if a
connection has backed out because of a rotating/bending test, the test specimen should be removed from
the test program. Restoring the connection to its original make-up position is not advisable as this will
artificially manipulate the outcome of subsequent tests to which the connection is subjected.
5.3.2.5 Reporting
The report for a rotating/bending TPE should contain at least the following data related to the test program:
a) type of approach followed (field condition or S-N curve determination);
b) type of equipment used for the test (resonant, four-point bending, other);
c) number of specimens tested, and number of tests performed per dog-leg severity or stress range;
d) dog-leg severities/stress ranges evaluated;
e) mean stress level(s) used, if applicable;
f) number of cycles achieved during the test;
g) reason for finishing the test (failure, completion of number of cycles, etc.);
h) results of crack evaluation (magnetic particles, etc), if applicable, including pictures;
i) if cracks were found, position (pipe body, pin and/or box, etc.) and pictures of the crack(s);
j) material test certificates or mechanical properties of each of the specimens tested;
k) graph of stress range or dog-leg applied vs number of cycles; and
l) evaluation of the scribed line.
If the position of the scribed line changed, the report shall include the change in position.
5.3.2.6 Rotating/Bending Testing Combined Loading Options
5.3.2.6.1 General
Connections that are run into MFHW may see combined loads beyond just rotating/bending loads because
of factors such as casing string weight, hydrostatic pressure, borehole friction, and tortuosity. Evaluators
may wish to include some or all the auxiliary loads in the following sections as part of the rotating/bending
TPE; however, care should be taken to understand the combined loading effects and their impact on the
overall stress condition in the pipe body and connections.
19
All of the following combined loading options—axial load, torque, and internal pressure—are optional test
elements and may not be applicable to all field conditions or operations. When the applicability is uncertain,
consultation between the evaluator and an end-user(s) is encouraged.
5.3.2.6.2 Applied Axial Load during Rotating/Bending Testing
Evaluators wanting to incorporate applied axial load during their rotating/bending TPE should ensure that
the frame or testing apparatus used to perform the rotating/bending TPE has capability to both apply and
react axial load. Axial load can be applied via a hydraulic cylinder or screw jack in line with the test specimen,
or via internal pressure by means of the capped-end pressure-effect, or other equivalent means. Note that
there may be limitations to the amount of axial load that can be applied depending on the rotating/bending
test set-up.
If axial compression is a part of the TPE, this may result in a helical buckle forming in the specimen under
certain conditions; as such, bracing and support should be designed to prevent out-of plane specimen
buckling as much as practically achievable. Axial load may also accelerate localized pipe body hardening
at the four-point bending contact points.
Axial load will affect the overall stress profile in the pipe body and connection(s) of the specimen. It is the
responsibility of the evaluator to understand the impact that the combined loading of axial load and
rotating/bending will have on the specimen, especially in localized areas of stress concentration inside the
connection(s). Axial load will also affect the overall specimen curvature so evaluators should measure the
curvature in accordance with 5.3.2.3 after axial load is applied and make corrections to the curvature as
needed prior to rotating the specimen.
5.3.2.6.3 Applied Torque during Rotating/Bending Testing
Evaluators wanting to incorporate applied torque during the rotating/bending TPE should ensure that the
test frame has sufficient torsional rigidity to react torsion loads on the specimen. Torque can be applied to
the specimen by connecting a hydraulic motor to the opposite end of the specimen from the motor driving
the rotation of the specimen. The opposing motor will create drag on the rotation and a resultant torque
load through the specimen. Specimen torque can be calculated from the output power of the drag motor.
Care should be taken to ensure that the combined effect of the driving and opposing hydraulic motor does
not affect the intended stress state of the connection during the evaluation causing rotations either in the
direction of make-up or break-out. To check the relative position of pin and box it is recommended to scribe
a line between pin and box and check after the test if the relative position has changed.
If applied torque is incorporated with applied axial compression, care should be taken to prevent out of
plane bending as this combination of loads can result in helical buckle formation.
5.3.2.6.4 Applied Internal Pressure during Rotating/Bending Testing
Evaluators wanting to incorporate applied internal pressure during their rotating/bending TPE should ensure
that the specimen end-caps can maintain liquid sealability up to the target pressure of the TPE. The
pressurizing medium should be water, testing with gas is not representative of field conditions.
The pump and pressure manifold applying the internal pressure can be connected to the specimen through
a series of valves at the specimen. Once target pressure is achieved it can be locked in by closing a valve
at the specimen. As it is a closed system with a non-compressible fluid as the pressure medium, loss of
specimen internal pressure will be characterized by liquid leaks coming from either the specimen or end-
caps. If the evaluator wishes to confirm the internal pressure after the rotating/bending test is complete, the
manifold can be reconnected and pressure measured; however, concession for some pressure drop should
be considered because of disconnecting and reconnecting the specimen to the pressure manifold.
20
Internal pressure will affect the overall stress profile in the pipe body and connection(s) of the specimen in
both the hoop and axial (because of the capped-end pressure-effect) directions. It is the responsibility of
the evaluator to understand the impact that the combined loading of internal pressure and rotating/bending
will have on the specimen, especially in localized areas of stress concentration inside the connection(s).
Axial load as a result of the capped-end pressure-effect will also affect the overall specimen curvature so
evaluators should measure the curvature in accordance with 5.3.2.3 after axial load is applied and make
corrections to the curvature as needed prior to rotating the specimen.
5.4 Stimulation Loading
5.4.1 General
The hydraulic fracturing process can subject casing to very high internal pressure at a rapid rate, which can
have a ballooning effect on the casing even when supported by cement. Modern MFHWs can repeat the
hydraulic fracturing process hundreds of times to prepare the well for production, and this cumulative
pressure cycling may have an impact on the structural integrity of the casing and connections. As such,
evaluators may choose to recreate this condition in the test program by subjecting specimens to several
pressure cycles with very rapid pressure increases to simulate the hydraulic fracturing process.
5.4.2 Internal Pressure Cycling
5.4.2.1 Principle
This TPE is designed to simulate the effect that the hydraulic fracturing process has on connections. The
specimen will be subjected to a number of pressure cycles at a frequency, magnitude, and duration
established by the evaluator. Applying a dog-leg curvature during stimulation loading is encouraged, and
including an axial load is an optional aspect of this TPE.
5.4.2.2 Test Set-up
Performing internal pressure cycling requires a high-pressure liquid pumping system connected to the
specimen by a high-pressure manifold. In order to achieve higher rates of pressure build-up, evaluators
can incorporate pressure accumulators and valving systems into the pressure manifold; however, the target
pressure rate is at the discretion of the evaluator. Although the pressurizing medium is liquid, it is
recommended that filler bars are installed in the specimen to reduce the amount of pressurized fluid in the
event of specimen catastrophic failure.
Test pressure-rated end-caps should be used for internal pressure cycling, either threaded or welded to the
specimen. Evaluators that want to eliminate the axial load because of the capped-end pressure-effect can
install the test assembly into a load frame to react the pressure-induced load. The reaction can be active in
which the load frame is controlled to match the axial tension load build-up because of pressure increase
with a corresponding axial compression load, or it can be passive in which the load frame is set to
displacement control and the frame prevents elongation of the specimen.
5.4.2.3 Specimen Preparation
Specimens subjected to the internal pressure cycling TPE do not need much modification from previous
TPEs. Strain gauges are not required for this TPE; however, it may be desired by the evaluator to monitor
hoop strain over the course of the test to check for any pipe body yielding because of the multiple pressure
cycles, and in this case strain gauges used in prior TPEs can be reconnected to monitor strain.
5.4.2.4 Test Matrix
The test matrix for the internal pressure cycling TPE is established by the evaluator. The target pressure
should be consistent with pressures used in hydraulic fracturing applications but should also consider the
21
maximum burst pressure of the specimen casing. The rate at which pressure is increased before a hold at
target pressure and the rate at which it is bled down after shall be established by the evaluator. Rates and
pressures do not need to be consistent throughout the entire test matrix, evaluators can choose to have
two or more sequences of pressure cycling in the test matrix at different pressure magnitudes, rates of
increase and decrease, and duration. Table 4 shows an example test matrix for internal pressure cycling
TPE over four cycles for an arbitrary T&C connection on 5-1/2 in., 17 ppf, P110 casing. For reference, the
MIYP of the tube body for this example is 10,640 psi. The hold times in Table 4 are only suggestive but are
representative of typical hold times when structural integrity is the primary concern. Lastly, the evaluator
may wish to perform the test at elevated temperature representative of certain reservoir conditions in MFHW
applications. The evaluator can set the test temperature to meet their requirements but note that sufficiently
elevated temperatures can affect MIYP and other material properties of the tube body. Figure 10 shows the
pressure profile over time of the example test matrix.
Table 4―Internal Pressure Cycling TPE Example Test Matrix
Pressure
Cycle Pressure Duration Temperature
Cycle Change
Point
psi ∆psi minutes °F
1.1 0 − 5 70
1.2 − 10,000 1 70
1
1.3 10,000 − 5 70
1.4 − -10,000 2 70
2.1 0 − 5 70
2.2 − 10,000 1 70
2
2.3 10,000 − 5 70
2.4 − -10,000 2 70
3.1 0 − 5 70
3.2 − 10,000 1 70
3
3.3 10,000 − 5 70
3.4 − -10,000 2 70
4.1 0 − 5 70
4.2 − 10,000 1 70
4
4.3 10,000 − 5 70
4.4 − -10,000 2 70
12,000
10,000
Pressure (psi)
8,000
6,000
4,000
2,000
0
0 10 20 30 40 50 60
Duration (minutes)
Figure 10―Pressure vs. Time Plot of Example Internal Pressure Cycling Test Matrix
22
5.4.2.5 Reporting
5.4.2.5.1 General
The report for the internal pressure cycling TPE should include the number of pressure cycles the specimen
was tested to, magnitude and rate of increase/decrease in pressure and duration at target pressure, and
test temperature. Supplementary observations of the test and specimen because of the test can be included
in the report as well as any relevant photos taken during the TPE.
5.4.2.5.2 Internal Pressure Cycling with Dog-leg Curvature
The most severe loading during stimulation often occurs in the build section, where the internal pressure of
stimulation combines with bending sresses due to dog-leg curvature. As such, the application of a constant
dog-leg curvature during stimulation loading is encouraged. In this circumstance, the evaluator can use a
four-point bend system similar to the set-up employed in API 5C5, Series B. The dog-leg curvature can be
locked in prior to testing by the evaluator. Care should be taken by the evaluator to pay attention to the
cumulative stress of internal pressure cycling and curvature on the maximum tensile fiber on the outside
curve of the specimen, as the combined load may approach or exceed the material yield strength for very
severe dog-leg curvatures.
5.4.2.5.3 Internal Pressure Cycling with Axial Load
Evaluators may want to assess internal pressure cycling performance of connections where axial load may
be present. Axial load can be applied by the load frame in one of two ways: actively by setting the target
load in the frame and then programming the load frame controller to compensate for the capped-end
pressure-effect axial tensile load in the specimen, or passively by targeting a displacement that results in
the desired target load. In either case, the target axial load (in either tension or compression) is established
by the evaluator.
If axial compression is selected by the evaluator, bracing should be installed around the specimen to
prevent the specimen from buckling during testing. Care should be taken by the evaluator to pay attention
to the cumulative stress of internal pressure cycling and axial load (especially compression), as the
combined load may approach or exceed the material yield strength for higher axial loads.
5.5 Production Loading
5.5.1 General
Production loads for MFHW cover a wide range of potential load combinations. API 5C5 has procedures to
assess connection sealability and structural performance through a series of complex test programs over
different connection application levels (CALs). This standard does not include separate test procedures
from API 5C5 for the evaluator to use when assessing production loading performance for connections in
MFHW; however, the test procedures are referenced as a guideline. This standard does not mandate the
performance criteria of connections as API 5C5 does; consequently, the evaluator, with optional input from
an end-user(s), should determine the appropriate combination of procedures to address anticipated
production loads.
Some of the connections that may be subjected to test programs created from this standard may have
already been tested to a CAL in API 5C5. Regardless of past connection performance, it is recommended
that production load TPEs are incorporated into an overall connection test program for MFHW as the
cumulative effects of the previous tests (casing running/installation, and stimulation loading) may have an
impact on production loading performance.
23
5.5.2 Principle
Production loading TPEs assess the performance of connections under combined pressure, axial load, and
temperature in conditions representative of MFHW operations. As stated previously, it is up to the evaluator
to create the TPEs from various test procedures from API 5C5, sealability tests (Series A, B, and C) using
the following high-level suggestions as a starting point:
a) If evaluators want to perform tests to assess alternating external and internal pressure in combination
with axial load and thermal cycle performance of the connection, they can create a TPE using the
procedures for API 5C5, TS-A tests.
b) If evaluators want to perform tests to assess internal pressure in combination with axial load, dog-leg
curvature, and thermal cycle performance of the connection they can create a TPE using the
procedures for API 5C5, TS-B tests.
c) If evaluators want to perform tests to assess thermal cycle performance of the connection in the
presence of internal pressure and axial tension, they can create a TPE using the procedures for API
5C5, TS-C tests.
5.5.3 Test Set-up
The test set-up for production load TPEs will vary depending on what production loads are considered.
Evaluators are advised to refer to API 5C5, Fourth Edition, Section 5 for the various test set-up requirements
and guidelines for each of the production load tests.
5.5.4 Specimen Preparation
Evaluators are recommended to refer to API 5C5, Fourth Edition, Section 6 for the guidelines and
requirements of specimen preparation for production load tests such as leak collection devices.
5.5.5 Test Matrix
Evaluators are recommended to refer to API 5C5, Fourth Edition, Section 7, for the guidelines and
requirements of test matrix development and calculation for production load tests. This standard does not
provide performance or acceptance criteria for production loads; it is up to the evaluator to define
acceptance criteria, whether from API 5C5 or from fit-for-purpose criteria based on the production load TPE
they have developed.
5.5.6 Reporting
Production load TPE reports do not need to be as comprehensive as the reporting requirements established
in API 5C5, Fourth Edition, Section 9; however, they should include all relevant TPE information to explain
the performance of the connection.
5.6 Limit Load Testing

5.6.1 General
Limit load testing is intended to apply loads to the connection up to failure. Failure is typically defined as
the inability of connection to seal or to maintain structural integrity, as described in 4.2.
According to the information in 4.2, this docuemnt does not specify acceptance criteria for limit loads tests.
In a typical scenario, loads are increased until a loss of sealability and/or structural integrity is obvious or
until the limits of the testing apparatus have been reached. The geometry selection for limit load testing is
in accordance with 4.3. For safety reasons, limit load pressure tests shall be conducted with a liquid
pressure medium.
A good reference for threaded connection limit load testing can be found in API 5C5. The three
recommended limit loads paths most relevant to this standard are:
24
 Limit Load Path 1—constant internal pressure with applied tension to failure,
 Limit Load Path 3—increasing tension to failure, and
 Limit Load Path 5—increasing internal pressure to failure.
Each of the limit load paths described in API 5C5 can be conducted with an applied constant dog-leg
curvature (bending moment) to the test sample during testing.
Beyond the scope of API 5C5, there are some (not all-inclusive) limit load tests that can be conducted to
help evaluate a connection for MFHW service, such as torque-, bending- or fatigue-to-failure.
5.6.2 Torque to Failure
The limit load should be determined by the following procedure.
a) Apply torque to the test sample in accordance with API 5C5. Consideration should be given to how the
make-up condition (pin-and-box, floating, etc.) reflects the intended field conditions.
b) Increase torque beyond the rated maximum recommended torque for that connection type. The limit
load can be evaluated as:
1) change in the torque-turn relationship of the connection, or
2) loss of drift according to the applicable drift specification.
Regarding loss of drift, conversations should be held with the manufacturer as to what constitutes a
significant change in the torque-turn relationship. This definition could depend on the specimen geometry
chosen in accordance with 4.3.
Regarding loss of drift, the torque beyond the rated maximum should be applied incrementally in increments
determined by the evaluator. After each increment of torque is applied, the sample should be drift tested.
Smaller increments will provide a more precise measure of the torque at which loss of drift occurs. As an
additional option, multiple drift sizes could be used so that a relationship between applied torque and
allowable drift can be developed. Such information could be useful to an end-user attempting to determine
the maximum diameter of tools that can be run through an over-torqued connection.
5.6.3 Bending to Failure
a) Use a specimen geometry with the worst-case performance as defined in 4.3
b) Test set-up is similar to that in 5.3.2.2.2, and leakage monitor could be incorporated via the appropriate
visual means as defined by API 5C5.
c) Apply increasing bending load to specimen failure. The limit load can be evaluated as:
1) loss of sealability in accordance with 4.2,
2) loss of structural integrity in accordance with 4.2, or
3) loss of drift according to the applicable drift specification (drift measured after the test specimen is
removed from the test frame to determine if a permanent buckle or deformation has occurred in
either the pipe body or connection).
Report the results of each test on a separate datasheet and include representative photos of the failure in
the connection test report.
25
5.6.4 Bending to Failure with Internal Pressure
a) Use a specimen geometry with the worst-case performance as defined in 4.3.
b) Bend the pipe using similar set-up as that in 5.3.2.2.2. The amount of bending load is defined by the
evaluator in potential consultation with an end-user(s).
c) While maintaining a constant bending load, apply increasing internal pressure to specimen failure as
defined in 4.2.
Report the results of each test on a separate datasheet and include representative photos of the failure in
the connection test report. The results of this limit load test could provide the end-user(s) with an estimate
of the maximum stimulation pressure that could be applied to a connection in an extreme dog-leg.
5.6.5 Fatigue to Failure
The limit load should be determined by fatiguing the sample until it reaches one of the failure modes
described in 4.2. The type of loading can be defined by (but not limited to) the following:
a) rotating/bending cyclic testing (see 5.3.2.2),

1) four-point bending (see 5.3.2.2.2),
2) resonant fatigue (see 5.3.2.2.3),
3) rotating/bending testing with combined load (see 5.3.2.6), or
b) internal pressure cycling (see 5.4.2).
Details of the test set-up, loads applied, and the number of cycles until failure shall be reported in the
connection test report.
26
Annex A
(informative)
Examples of Creating a Customized API 5SF Test Program
A.1 General
Evaluators using API 5SF are given the flexibility to create a test program that suits their specific needs.
Unlike other test protocols, there are no minimum number of connection test specimens, nor are there a
required series of TPEs that need to be included in any test program. Two example cases are included in
this section to demonstrate to prospective evaluators how a API 5SF program can be configured to assess
connection performance based on different objectives for the evaluation. The example programs
constructed from the various TPEs of API 5SF address two different user needs:
a) an operator with an extended reach well, and
b) a connection manufacturer creating a new semi-flush connection.
A.2 Example 1Operator with Extended Reach Well Design

An operator that has an extended reach well design involving significant dog-leg severity (DLS) in the build
section. The cementing program requires both rotation and reciprocation of the casing string to improve
cement quality. The extended reach horizontal section of the well has 80 fracture stages, and the operator
wants to use a monobore well design (i.e., same connection, casing, and casing weight run from surface
to toe). The operator is running cement through the production zone; however, they are concerned with
cement voids in the long horizontal section (if voids are present, fracture fluid may propagate along the
production string, subjecting intervals of the casing to high external pressure). The formation temperature
is 150 °C (302 °F), so material properties of the casing material may be affected.
The evaluator creating a test program should consider a range of TPEs to address various aspects of the
well design and the critical loads that, in succession, may impact the overall performance of the connection
in service. The number of connection test specimens should be sufficient to give the evaluator confidence
in connection performance in different locations in the well, or confidence in the repeatability of the test
results; however, economic considerations may prevent repetition of certain sequences in the test matrix.
The evaluator has decided to construct a test program for three connection test specimens. Each of the
specimens is subjected to a sequence of TPEs that address connection performance in different sections
of the well. Figure A.1 shows the sequence of testing for each connection test specimen.
Specimen 1 is the connection test specimen representing a connection near the wellhead that is not run
through the build section of the well and therefore does not require rotating bending testing; however, it
does see the stimulation and eventual production loads. Note that the evaluator has elected not to apply a
DLS to the production load TPE to be consistent with the well location of the targeted connection. After the
production load test, the evaluator removes the connection specimen from the test frame and torques it to
failure; first to a level to establish the torque threshold to maintain drift, and then further to structural failure
of the connection and/or pipe body.
Specimen 2 is a connection that is along the build section of the well; this connection sees many
rotating/bending cycles and remains in a bent configuration for its service life. After the rotating/bending
test of 50,000 rotations at a DLS of 15°/100 ft, the connection specimen is subjected to a modified API 5C5,
27
Series B test program at elevated temperature (target temperature 300 °F). After completing the production
load test, the connection specimen is held in the bent configuration and internally pressurized to failure.
Specimen 3 represents the connection in the production zone, which implies that it has been run through
the build section and is now in a straight configuration. It goes through essentially the same test matrix as
Specimen 2 with the exception that during the production load TPE the connection specimen is straight.
The evaluator chooses to not perform a limit load test on Specimen 3 having gathered enough
supplementary failure information about the connection design from the previous two specimens.
Specimen 1 Specimen 2 Specimen 3
Galling Resistance Test

Connection Makeup
3x MMU B-Side
Final Connection Makeup Final Connection Makeup Final Connection Makeup

A/B Min Torque A/B Min Torque A/B Min Torque
Incremental Torque
A/B 110% Max Torque
Casing Running Loads
Tensile Load Capacity

95% Connection Capacity
Low Cycle Rotate-Bend Low Cycle Rotate-Bend

50,000 Rotations @15° 50,000 Rotations @15°
Internal Pressure = 100 psi Internal Pressure = 100 psi
Axial Load = 0 kip Axial Load = 100 kip
Stimulation
Pressure Cycling Pressure Cycling Pressure Cycling

Loads
100 Cycles @ 15,000 psi 100 Cycles @ 15,000 psi 100 Cycles @ 15,000 psi
T(Specimen) = 70°F T(Specimen) = 300°F T(Specimen) = 300°F
Dogleg = 0°/100 ft Dogleg = 15°/100 ft Dogleg = 0°/100 ft
Production
RP 5C5 Series B Ambient RP 5C5 Series B Elevated RP 5C5 Series B Elevated

Loads
Q1-Q2 (3X) Q1-Q2 (3X) Q1-Q2 (3X)

T(Specimen) = 70°F T(Specimen) = 300°F T(Specimen) = 300°F
Dogleg = 0°/100 ft Dogleg = 15°/100 ft Dogleg = 0°/100 ft
Bending w/ Internal
Testing
Limit
Load
Torque to Failure Pressure to Failure

Dogleg = 15°/100 ft
Figure A.1―Example Test Program 1 (Extended Reach Well Operator)
28
A.3 Example 2Connection Manufacturer with a new Semi-Flush Connection

Design
The second test matrix example represents a connection manufacturer that has developed a new semi-
flush connection design and wants to assess the performance of this connection design in MFHW
applications. In this case, the manufacturer wants to understand the effects of combined rotating and
bending loading on connection performance, and they also want to know how many rotating-bending load
cycles the connection design can withstand before failure. As it is a preliminary assessment of connection
performance, the manufacturer does not want to invest too many specimens in the intial testing and has
settled on a two-specimen test matrix, as the design may change based on the outcome of the first few
tests. Figure A.2 shows the test matrix the evaluator developed to address the needs of the connection
manufacturer.
In this example, the evaluator subjected Specimen 1 to a galling resistance test in alignment with the
guidelines of API 5C5 (three make-break cycles), followed by a final make-up. The connection specimen
was installed in a four-point bending frame to perform a low-cycle rotating/bending test up to 40,000 cycles
at a prescribed DLS of 20°/100 ft. The connection specimen was held in the bent configuration and
pressurized to 15,000 psi 100 times before being installed in a load frame where an API 5C5, Series B
(elevated) test was performed. After all load frame based testing was completed, the connection specimen
was removed from the frame and torqued to failure.
The test program for Specimen 2 was created to give the connection manufacturer information about the
fatigue performance of the connection design. Consequently, it was subjected to the same low-cycle
rotating-bending TPE as Specimen 1 and then, after 40,000 cycles, was subjected to a high-cycle rotating-
bending test, where it was tested to the greater of 500,000 rotating/bending cycles or until failure. No
stimulation or production load testing was done on this connection specimen.
29
Specimen 1 Specimen 2
Galling Resistance Test

Connection
Makeup
3x MBG B-Side
Final Connection Makeup Final Connection Makeup

A/B Min Torque A/B Min Torque
Low Cycle Rotate-Bend Low Cycle Rotate-Bend

Casing Running Load
40,000 Rotations @20° 40,000 Rotations @20°

Internal Pressure = 0 psi Internal Pressure = 0 psi
Axial Load = 0 kip Axial Load = 0 kip
High Cycle Rotate-Bend

500,000 Rotations @5°
Or to Failure
Internal Pressure = 0 psi
Axial Load = 0 kip
Pressure Cycling
Stimulation
Load
100 Cycles @ 15,000 psi

T(Spec) = 300°F
Production
RP 5C5 Series B Elevated

Load
Q1-Q2 (3X)
T(Spec) = 300°F
Testing
Limit
Load
Torque to Failure
Figure A.2―Example Test Program 2 (Semi-Flush Connection Manufacturer)
30
Bibliography
[1] API Recommended Practice 5C5, Procedures for Testing Casing and Tubing Connections
[2] API Specification 5CRA, Corrosion-Resistant Alloy Seamless Tubes for Use as Casing, Tubing, and
Coupling Stock
[3] API Specification 5CT, Casing and Tubing
[4] API Specification 5L, Line Pipe
[5] API Technical Report 5C3, Calculating Performance Properties of Pipe Use as Casing or Tubing
[6] ASTM A370, Standard Test Methods and Definitions for Mechanical Testing of Steel Products
[7] ASTM E21, Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials
[8] ASTM E111, Standard Test Method for Young’s Modulus, Tangent Modulus, and Chord Modulus
31

5SF - WI3081 Ballot

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API Ballot id# 5432

3081 – Guidelines for Evaluating Connection Performance in Multi-

Ballot Rationale: Premium and semi-premium connections used in non-standard applications

• Low-cycle fatigue as a result of rotating while bending;

• Pressure cycling during frac operations; and,

• Thermal shocking as cold frac fluids are injected downhole.

Guidelines for Evaluating

API TECHNICAL REPORT 5SF

The Special Notes, Foreword, and Contents will be generated by API

Guidelines for Evaluating Connection Performance in

3 Terms, Definitions, Symbols, and Abbreviations

3.1 Terms and Definitions

CAL connection application level

MIYP minimum internal yield pressure

MFHW multi-fractured horizontal wells

PBYS pipe body yield strength

TPE test program element

D pin diameter of the pin end of the connection

r pin radius of the pin end of the connection

4 Creating a Representative Test Program

4.1 General Philosophy

4.2 Failure Modes

4.3 Specimen Geometry

4.3.2 Specimen Notching

4.4 Test Load Calculation

4.5 Quality Control

4.6 Test Facility Safety

4.7 Calibration and Accreditation Requirements

5.1 Test Program Sequence and Test Program Elements

Figure 1―Recommended Load Sequence

 Base TPEs: the TPEs required as part of that stage; and

Base TPEs Supplementary TPEs

Tensile Load Capacity

Figure 2―Base and Supplementary Test Program Elements in Sequence

Base TPEs Supplementary TPEs

Internal Pressure Cycling

Test elements simulating production loads

RP 5C5 Limit Loads

Bend with IP to Failure

Figure 2―Base and Supplementary Test Program Elements in Sequence (Continued)

5.1.2 Specimen Preparation

5.2 Connection Make-up

5.2.1 Connection Make-up Guidelines

d) shoulder torque range (for shouldered connections).

5.2.2 Galling Resistance Testing

5.2.3 Post-Make-up Incremental Torque

Figure 3―Connection Scribing Example

a) ovalization of the pin and/or box,

b) evidence of pin nose yielding or deformation,

c) thread jump or shearing, and

d) loss of fluid sealability.

5.2.4 Connection Make-up Reporting

5.3 Casing Running and Installation Loading

5.3.1 Tensile Load Capacity

5.3.1.2 Test Set-up

5.3.1.3 Test Matrix

Table 1―Tensile Load Capacity Test Matrix Example

Load Axial Load Duration

5.3.2 Rotating/Bending Cyclic Testing