The Effect of Axial Tension and Borehole Curvature on Torsion Limit of Drill String Threaded Connections

2021 ◽  
pp. 105555
Author(s):  
Feng Chen ◽  
Yonghao Huo ◽  
Haiyi Zhao ◽  
Qinfeng Di ◽  
Wenchang Wang ◽  
...  
Keyword(s):  
Drill String ◽  
Axial Tension ◽  
Threaded Connections

Fatigue of Drill String Connections

1995 ◽  
Vol 117 (2) ◽  
pp. 126-132 ◽  
Author(s):  
F. P. Brennan
Keyword(s):  
Aspect Ratio ◽  
Crack Growth ◽  
Empirical Model ◽  
Drill String ◽  
Full Scale ◽  
Growth Data ◽  
Service Environment ◽  
Threaded Connections ◽  
Bend Tests ◽  
Full Scale Tests

This paper reports full-scale tests on threaded connections used in drill strings. A concise background is given concerning the in-service environment and loading conditions on the connections. This details some of the reasons particular steels are used in preference to others. Crack growth data is given for ten full-scale axial and rotating bend tests. This is compared with predictions from a dedicated weight function fracture mechanics solution designed for threaded connections. Crack aspect ratio is considered with a view to development of an appropriate empirical model.

Fatigue Assessment of Drill Pipes

2017 ◽  
Author(s):  
P. J. Haagensen ◽  
T. I. Grøttum
Keyword(s):  
Failure Modes ◽  
Fatigue Behavior ◽  
Drill String ◽  
American Petroleum Institute ◽  
Directional Drilling ◽  
Fatigue Wear ◽  
Threaded Connections ◽  
Current Design ◽  
Drilling Operations ◽  
Drill Pipes

Fatigue failures during offshore drilling operations is still a very costly problem. The fatigue behavior of drill pipes is reviewed, and typical failure modes are identified. The effects of drill string curvature during directional drilling on pipe body stress and on the fatigue life is examined. Effects on applied mean stress from drill string weight are discussed. Interaction effects of degradation mechanisms such as fatigue, wear and corrosion are evaluated. Experimental background data and statistical evaluation that form the basis for the current design practice issued by American Petroleum Institute (API) and other guidance in codes and standards is reviewed. Results from several recent testing programs performed under rotating bending of pipes with threaded connections, and tests involving the pipe body under resonance conditions are presented. The tests were made with pipe sizes from 2 7/8 in. to 5 7/8 in. in Grade S-135 pipes. The results are compared with published test data and design guidance such as API Recommended Practice G7 [1]. Recommendations are given for research and testing to improve reliability and the safe operation of drill strings.

scholarly journals Helical post-buckling of a rod in a cylinder: with applications to drill-strings

2012 ◽  
Vol 468 (2142) ◽  
pp. 1591-1614 ◽  
Author(s):  
J. M. T. Thompson ◽  
M. Silveira ◽  
G. H. M. van der Heijden ◽  
M. Wiercigroch
Keyword(s):  
Petroleum Industry ◽  
Approximate Solutions ◽  
Drill String ◽  
Elastic Rod ◽  
Continuous Contact ◽  
Axial Tension ◽  
Cylindrical Casing ◽  
Post Buckling ◽  
Universal Graphs ◽  
Helical Buckling

The helical buckling and post-buckling of an elastic rod within a cylindrical casing arises in many disciplines, but is particularly important in the petroleum industry. Here, a drill-string, subjected to an end twisting moment combined with axial tension or compression, is particularly prone to buckling within its bore-hole—with potentially serious results. In this paper, we make a detailed theoretical study of this type of instability, deriving precise new results for the advanced post-buckling stage when the rod is in continuous contact with the cylinder. Results, including rigorous stability analyses and contact pressure assessments, are presented as equilibrium surfaces to facilitate comparisons with experimental results. Two approximate solutions give insight, universal graphs and parameters, for the practically relevant case of small angles, and highlight the existence of a critical cylinder diameter. Excellent agreement with experiments is achieved.

Analysis of the Motion of Deep-Water Drill Strings—Part 2: Forced Rolling Motion

1965 ◽  
Vol 87 (2) ◽  
pp. 145-149
Author(s):  
M. A. Frost ◽  
J. C. Wilhoit
Keyword(s):  
Equation Of Motion ◽  
Drill String ◽  
Ocean Floor ◽  
Rolling Motion ◽  
Combined Effects ◽  
Flexible Cable ◽  
Drag Forces ◽  
Point Of Entry ◽  
Axial Tension ◽  
Short Beam

An equation of motion for a drill string, considering elastic, dynamic, and drag forces, was derived in a previous paper and was applied to two types of beam behavior: A beam having constant axial tension and a perfectly flexible cable. A drill string was then considered as consisting of short beam sections at the top and bottom, joined by a perfectly flexible cable. The lateral deflection of the drill string was obtained by joining the beam and cable solutions subject to boundary conditions at each junction. In this paper, the drill string is considered built-in at the ocean floor and to be experiencing a harmonic change of slope at the ocean surface imposed by roll (or pitch) of the ship, the ship remaining stationary vertically above the point of entry at the ocean floor. Examples are discussed and results are compared with experimentally measured values. The combined effects of roll and displacement are obtained by superposition of the two solutions.

Friction Considerations in Rotary Shouldered Threaded Connections

2007 ◽  
Author(s):  
Catalin Teodoriu ◽  
Herschel McDonald ◽  
Charles Bollfrass
Keyword(s):  
Drill Pipe ◽  
Extreme Environments ◽  
Drill String ◽  
Directional Drilling ◽  
Frictional Properties ◽  
Threaded Connections ◽  
Safety Margins ◽  
Drill Pipes ◽  
Drilling Conditions ◽  
First Time

The new connection designs introduced by the drill pipe manufacturers (double shoulder connections, intelligent drill pipes or any new design for increased torque resistance) make the use of the Farr formula for calculating proper assembly torque more problematic. Additionally, severe drilling conditions like HPHT, directional drilling and extreme environments are affecting critical thread compound performance properties, which can make it impossible to attain the optimum makeup torque for the connection. The new drilling conditions are exposing the drill string components to higher loads and consequently reduce the safety margins. Since the makeup process is the only way to control and achieve the maximum tool joint loading capacity, it becomes important to understand the effect of friction on optimum makeup torque calculation. This paper presents a modified equation for optimum makeup torque calculation by using the latest research on thread compound frictional properties. Also, the thread compound lubrication mechanism will be explained. For the first time the thread turn load will be related to the optimum makeup torque. The paper will also explain why there is a need for a new API standard for determining thread compound frictional properties. The formula developed herein, based on experimental results, demonstrates that the newly introduced overall factor may differentiate between used and new connections.

Fatigue Life Prediction of Cold Rolled Rotary Shouldered Threaded Connections

2018 ◽  
Author(s):  
Fei Song ◽  
Michael Du ◽  
Ke Li
Keyword(s):  
Fatigue Life ◽  
Cold Rolling ◽  
Fatigue Resistance ◽  
Element Model ◽  
Drill String ◽  
Directional Drilling ◽  
Drilling Tool ◽  
Threaded Connection ◽  
Threaded Connections ◽  
Cold Rolled

The bottom hole assembly (BHA) of a modern drill string for directional drilling mainly comprises a drill bit, a rotary steerable system, and a measurement while drilling tool. The tools and subs used on a BHA are screwed together through rotary shouldered threaded connections. Each connection is made up with a pin and a box. These connections are the weakest links when the BHA undergoes a large number of revolutions in a curved well section. When the fatigue life of a connection is consumed during a drilling job, a twist-off would occur, which could result in an enormous amount of non-productive time and possibly loss of the bottom BHA section in the hole. Cold rolling has proven to be able to improve fatigue resistance of a threaded connection by pressing a rolling wheel against the thread root and generating a layer of compressive residual stress at the root. Understanding how cold rolling improves fatigue resistance of a threaded connection is important for optimization of the rolling parameters and prediction of the BHA service life in a given drilling condition. In this paper, a predictive method is presented for fatigue life of a cold rolled threaded connection. A finite element model was developed to simulate the cold rolling process. The resulting deformation and stress states at the root were carried over through makeup of the pin and the box as well as through cyclic bending of the connection. The fatigue life predictions were found to be in favorable agreement with the experimental measurements from full-scale fatigue tests at different bending moment levels applied.

Analysis of the Motion of Deep-Water Drill Strings—Part 1: Forced Lateral Motion

1965 ◽  
Vol 87 (2) ◽  
pp. 137-144 ◽  
Author(s):  
R. D. Graham ◽  
M. A. Frost ◽  
J. C. Wilhoit
Keyword(s):  
Equation Of Motion ◽  
Drill String ◽  
Subsequent Paper ◽  
Lateral Motion ◽  
Governing Equations ◽  
Flexible Cable ◽  
Drag Forces ◽  
Axial Tension ◽  
Short Beam ◽  
Variable Tension

An equation of motion for a drill string, considering elastic, dynamic, and drag forces, is derived. This equation is then applied to two types of drill-string behavior; i.e., a beam having constant axial tension and a perfectly flexible cable under variable tension. A drill string is then synthesized by subdivision into short beam sections at the top and bottom, joined by a flexible cable in the center. The lateral deflection of the drill string is obtained by joining the beam and cable solutions, subject to boundary conditions at each junction. The drill string is considered built-in at the ocean floor and is displaced harmonically at the surface by the ship. An example is discussed and results are compared with experimentally measured values. The effect of roll will be considered in a subsequent paper; as the governing equations have been linearized, these solutions may be superimposed.

Predicting the Risk of Twist-Off for Rotary Shouldered Threaded Connections With a Statistical Approach

2019 ◽  
Author(s):  
Haitao Zhang ◽  
Ke Li
Keyword(s):  
Tensile Strength ◽  
Fatigue Life ◽  
Material Properties ◽  
Statistical Approach ◽  
Failure Modes ◽  
Drill String ◽  
Statistical Prediction ◽  
Fatigue Properties ◽  
Threaded Connections ◽  
Reduction In Area

Abstract Fatigue is one of the most frequently encountered failure modes of rotary shouldered connections (RSC) used in drill strings. Once initiated, a fatigue crack tends to grow and ultimately lead to a twist-off, which is catastrophic and often results in lengthy non-producing time and expensive fishing operations. The complexity of the fatigue mechanism, the variabilities of material properties, and the nonlinear contact interactions of the pin and the box elements of an RSC pose a substantial challenge to accurately predicting the fatigue life of the RSC. This would require considerable conservatism to be exercised to prevent a twist-off, which causes premature retirement of drilling assets. Using a statistical approach to predict the risk of twist-off (ROTO) of each RSC on the drill string could be a more economically viable solution as it would enable quantified risk assessment and scientifically calculated tradeoffs between performance, cost, and risk of failures. In this study, a methodology for statistical prediction of the ROTO of rotary shouldered threaded connections was developed. First, static material properties, including yield strength, tensile strength, elongation, and reduction in area, were extracted from a wealth of available material certificates. Feature engineering was carried out to arrive at two independent properties, tensile strength and reduction in area. Fatigue properties were then generated with the retrieved static material data and earlier established correlations between static and fatigue properties. Afterwards, elasto-plastic finite element analyses were performed on RSCs made of the same material but with different properties to determine critical fatigue indicators, stress and strain states as respective functions of the tensile strength. Finally, Monte-Carlo simulations were conducted with respect to statistical distributions of the two independent material variables to predict the ROTO as a function of fatigue life. The predictions were found to be favorable agreement with the available full-scale fatigue test data of an API connection type.

Enhancing Trapezoidal Threads Using a Parametric Numerical Approach

2015 ◽  
Author(s):  
Timothy Galle ◽  
Wim De Waele ◽  
Patrick De Baets
Keyword(s):  
Internal Pressure ◽  
Load Distribution ◽  
Static Load ◽  
Numerical Approach ◽  
Gap Size ◽  
Performance Parameters ◽  
Taper Angle ◽  
Axial Tension ◽  
Threaded Connections ◽  
Geometric Changes

A parametric program designed for modeling tapered, trapezoidal threaded connections is used in combination with Abaqus to investigate the behavior of couplings subjected to static load combinations containing make-up, axial tension and internal pressure. Three criteria are defined and used to quantify the performance of the connection: load distribution, helical gap size between the threads and the amount of global plasticity. From these parameters, the load distribution provides valuable information about the effectiveness of the load bearing characteristics of the thread and can be used to detect possible overstressing of the connection. The helical gap size is used to estimate its tendency to provide a leak tight thread seal, while the global plasticity reflects the total amount of plastic deformation within the connection. During the investigation, the effects of taper angle, load flank angle, wall thickness, size of threads and initial thread clearance are considered. The presented modeling approach consists of three parts. First, the optimal make-up position for a trapezoidal threaded 4.5 inch TN80 connection is calculated using the plasticity criterion. Next, the results for the three performance parameters as a function of both axial tension and internal pressure are discussed. Finally, after investigating the various isolated effects induced by geometric changes, a newly defined, enhanced threaded geometry is suggested and compared with the standardized API-buttress thread.

Sectionalized Mechanical Models of Drilling Tool of Trenchless Directional Drilling

2012 ◽  
Vol 268-270 ◽  
pp. 1190-1193
Author(s):  
Hui Xia ◽  
Yi Hua Dou ◽  
Xin He Wang ◽  
Jiang Wen Xu
Keyword(s):  
Axial Compression ◽  
Working Conditions ◽  
Mechanical Analysis ◽  
Drill String ◽  
Drill Bit ◽  
Straight Section ◽  
Directional Drilling ◽  
Drilling Tool ◽  
Horizontal Section ◽  
Axial Tension

There are three working conditions namely drilling a guide hole, expanding the guide hole and pulling back pipeline in trenchless directional drilling. The position of drill string in the wellbore and loads exerted on the drill string varied in different working conditions. The models of buckling analysis of drill strings under compression, mechanical analysis of drill string under axial compression near drill bit in inclined straight section, mechanical analysis of drill string with multi-centralizers under axial compression near drill bit in inclined straight section, mechanical analysis of drill string near drill bit under axial compression in horizontal section, mechanical analysis of drill string near drill bit under axial tension in horizontal section, mechanical analysis of drill strings near drill bit under axial tension in inclined straight section and mechanical analysis of drill string in failed well are established based on the characteristic of loads and trajectories in each section. The establishment of sectionalized mechanical model of drilling tool is the fundament of further study of force analysis, deformation analysis and stress analysis.

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