Development of Titanium Drill Pipe for Short Radius Drilling

Many problems in a drilling operation can be caused by excessive contact forces between the drill pipe and the casing or hole wall. The contact force pipe and the casing or hole wall. The contact force is mainly controlled by the hole curvature, drill pipe stiffness, and the axial load on the drill pipe. pipe stiffness, and the axial load on the drill pipe. This paper discusses the relationship between the magnitude of the contact forces and the above three variables, as well as several other less significant variables. Introduction The lateral force with which the drill string interacts with the casing or open hole wall should be of vital concern in a drilling operation. Large lateral forces can result in excessive casing wear, excessive drill pipe and tool joint wear, and key seats in the hole wall. An understanding of the factors that control the lateral contact forces may allow preventative action to be taken before a problem develops. The problem of excessive contact force between the drill pipe and the hole wall has been recognized for many years. It was addressed in 1960 by Lubinski, but it has only been during the last few years that detailed computer modeling of the problem has been feasible. This paper presents the results of a finite element computer study of the variables that affect the magnitude of the contact forces under a variety of conditions. The parameters were chosen to represent conditions that may occur in realistic drilling operations. Finite Element Model During 1975 a consulting firm was contracted and directed by Amoco to write a dynamic triaxial finite element computer program for the analysis of bottom hole assemblies. This program can be used to analyze any multi-component drill string in a wellbore. The drill string can be divided into a maximum of 51 elements of uniform cross sectional geometry and uniform material. An iterative process of solving for deflections and forces is then performed until the drill string deflections converge within the boundary conditions of the borehole. The required input data is a description of the drill string, wellbore diameter, wellbore survey, drilling fluid density, and axial load (weight on bit). The computed data includes the forces and deflections for each node point. Further discussion of the program is included in the appendix. Two drill pipe models were investigated before one was chosen for the study. The first model represented a joint of drill pipe with five equal length finite elements and the tool joint as a single element with its length equal to the tool joint length. This model was unstable under certain combinations of axial load and hole curvatures. The second model represented a joint of drill pipe with two finite elements and the tool joint as a zero length element. The zero length element resulted in a single point of contact with the hole wall rather than a point of contact on each end of a short element. Both models gave the same results for the cases in which the first model would converge, thus the second model was used for the study. Figure 1 shows a diagram of the drill pipe configuration that was used for decreasing curvature and Figure 2 shows the increasing curvature configuration. Table 1 gives the drill pipe and tool joint dimensions that were used in the study. Cases were run for 3-1/2", 4-1/2", 5", 5-1/2", and 6-5/8" drill pipe, with 20", 13-3/8", 9-5/8", and 7" casing sizes. pipe, with 20", 13-3/8", 9-5/8", and 7" casing sizes. The 13-3/8", 9-5/8", and 7" casing sizes will give approximately the same results as 12-1/4", 8-3/4", and 6-1/4" open hole sizes. The effects of hole size, drill pipe size, axial load, hole curvature, length and orientation of the curve, and hole inclination were investigated. Unless otherwise noted, the drill pipe was positioned in the hole so that a tool joint would be at the center of the hole curvature. All the results presented in this paper were generated from a static (non-rotating) model. The results accurately represent the forces which develop while going in or out of the hole with the drill pipe. pipe.

Fatigue life of drill pipe is studied systematically based on reliability analysis. Calculation results show that bending and tensile stress in drill pipe body is significantly greater than that in the tool joint during drilling process. Drill pipe body’s fatigue strength is about 500MPa under the condition that the stress ratio is -1. The fatigue strength of tool joint is about 360MPa under the condition that the average tensile stress is 496MPa. The fatigue fracture position of drill pipe is concentrated on pipe body, and most fatigue cracks originate from pipe’s outer surface. Compared with material fatigue life, the fatigue life of whole drill pipe is significantly lower. Under the condition that the confidence level is 95% and deviation is 5%, drill pipe’s fatigue life distribution is normal distribution while the stress amplitude is 660MPa, 620MPa, 580MPa and 540MPa respectively. With the decreasing of stress amplitude, the peak of logarithmic fatigue life’ probability density distribution curve decreases gradually, and its dispersion increases gradually. Drill pipe’s fatigue life prediction equations whose reliability are 50%, 90%, 99% and 99.9% are calculated separately.

Both Saudi Aramco and Total Indonesia found benefits in selecting 4 in. drill pipe with streamlined double shoulder connections for the drilling of wells, for which the 3 1/2 in. drill pipe was unsuitable. Although dealing with different environments and applications, these benefits can be summarized in "successfully drilling longer slim holes with a drill string having enhanced torsional, tensile and hydraulic characteristics at a lower overall cost". For the Saudi Aramco QTF field, Extended Reach Drilling (ERD) was required with the objective to deliver pay zones located at measured depths of 18,000 ft (for the 1,500 HP rigs) and 25,000 ft (for the 2,000 HP rigs). These depths correspond to step outs ranging from 13,000 ft to 20,000 ft respectively from the drill site. For its Kalimantan field, Total was in a need of higher torsional capacity and also an improvement of the hydraulic characteristics of the drill string. Selecting a larger size of pipe was the retained option against an upgrade of the rig pump installation. The casing and drilling program remained unchanged with the drilling of a 6 in. hole after setting the 7 in. casing, adding a constraint for fishability of the string. In both cases, fishability and torque objectives made the selection of the appropriate connection essential. The selected double shouldered connection maintained a tool joint outside diameter similar to standard 3 1/2 in. drill pipe tool joints, that maintains fishing ability of the 4 in. pipe, in casing and open hole, despite the pipe size increase. The streamline connection design provides 22,000 ft-lb working torque, an outside diameter of 4–7/8 in. and an oversized internal bore that promotes hydraulic efficiency. Other important improvements include considerable gain in pipe resistance under buckling loads, increased available pressure at the bit, better telemetry for the MWD and LWD tools and improved hole cleaning and rate of penetration. Introduction Drilling deeper, slim hole wells has revealed limitations of 3 1/2 in. drill pipe traditionally used to drill the 6 to 6–1/4 in. hole sections. The level of torque that API rotary shoulder, as well as first generation double shoulder connections, can deliver does not match the new requirements for these deeper drilling programs. This increase in drill string length also puts an additional constraint on hydraulic performance. This encouraged drilling engineers to re-evaluate the drill string design requirements and select a new configuration of pipe that would respond to these new requirements. This paper addresses these pipe and connection design considerations and provides two case histories showing the benefits that were realized from using this new drill pipe design configuration. Over 1,400,000 ft of this pipe has been built to date and is in service all over the world. It is also important to mention that this new drill pipe arrangement can also be used for drilling upper hole sections eliminating the need for a string 5 in. drill pipe in many applications. Streamlined Double Shoulder Connections for 4 in. Drill Pipe There has been increasing requirements for drill pipe with improved hydraulic performance and mechanical properties to replace 3–1/2 in. drill pipe traditionally used in slim-hole drilling.

Drill string models are of two major types- Conventional and Periodic. Conventional drill string models are widely used due to their simplicity in manufacturing and dynamics analysis. Drill strings are affected mainly by torsional, lateral and axial vibrations. The dispersive or propagative nature of these vibrations can only be analyzed by using periodic drill string models. Drill pipe makes up the majority of the drill string. In reality, at each end of the drill pipe, tubular, larger-diameter portions called the tool joints are located. Since the dimensions of the tool joint are negligible when compared to the drill pipe, conventional drill string models assume drill strings to be uniform structures. The tool joints in drill strings introduce a geometrical periodicity in the structure.A periodic structural component is comprised of a repeating array of cells, which are themselves an assembly of elements. The elements may have differing material properties as well as geometric variations. The periodic structures act as mechanical filters for the wave propagation. A material or geometrical change in the structure causes a disruption to the continuous propagation of vibration waves.There are three types of waves propagating in rotating structures: torsional, flexural (bending) and longitudinal. Of these waves, torsional and longitudinal waves are dispersive while flexural waves are non- dispersive. The proportions of the waves which are dispersed vary according to the Wavenumber. The wavenumber is a property of the wave and depends on the structural, material and geometrical properties of the wave guide. Waveguide is the medium through which a wave travels. The wave number, and hence the dispersion and propagation characteristics of waves can be tuned by varying the material and geometrical periodicity in the drill strings.This paper presents the vibration propagation and attenuation characteristics in conventional and periodic drill string models. The periodic drill string model is developed such that it can be easily scaled to a real drilling rig model. The research also features a laboratory setting which comprises a mini drilling rig and actual drilling samples. These features ensure robustness of the dynamics analyzed for the periodic drill string model.The research findings are analyzed under zero and non- zero borehole drill string interactions. Vibration information is collected from upper and lower parts of the drill string models to compare the propagation and attenuation characteristics. Proximity sensors are used for the data acquisition which is then analyzed using frequency and power spectrum graphs. The time and frequency domain vibration propagation characteristics are investigated for both the conventional and periodic drill string models. Laboratory testing analyzes (1) introduction of stop and pass band regions in frequency spectra by periodic drill string models, and (2) vibration attenuation in torsional and lateral vibration modes. The tests confirm the introduction of stop bands in frequency spectra for the periodic drill strings, while they were absent and had an all pass-band for conventional drill string models.The research opens up a new method of passive control of drilling vibrations- by introducing tool joint designs which could be tuned to efficiently dampen out the harmful vibrations affecting the drilling rigs.

The paper is devoted to the results of the application of repair technology of drill pipes by surfacing. The analysis of the requirements for the tool joints after a recovery is made. Modeling of the stress state by finite elements is produced, bench testing is analytically explained. It is established that the destruction of the test samples on recovery did not occur, which confirms the feasibility of the previously proposed technology. Obtained bench tests data were used to develop the guidance manual for steel drill pipes with welded locks after repair in terms of restoration tool joints by surfacing method.

Abstract"Sour Service" refers to a well environment containing Hydrogen Sulfide (H2S), which is naturally associated with acid conditions. It is well known that H2S is hazardous to human health, living organisms, and more generally to the environment. It is for this reason that wells found with Sour Gas were often carefully plugged and abandoned in the past. H2S can also lead to catastrophic brittle failure of drillstring components: the physical phenomenon associated with Sour Service Environments and affecting steel based products under applied or residual stress is known as H2S embrittlement or more specifically as Sulfide Stress Cracking (SSC).With the increasing demand of gas worldwide, some highly sour oil and gas reservoirs are being explored, mainly in Russia, the Middle East, China and North America, and are now more and more associated with complex well profiles – such as deep reservoirs or extended reach wells. The use of high strength drill pipe is essential to achieve such drilling objectives; however it does represents significant technical challenges in terms of drill pipe integrity and operational safety with the current high strength grades available on the market, such as S-135 drill pipe. Because higher strength is generally detrimental to Sulfide Stress Cracking, innovative chemistries and new heat treatment processes are needed to push Sour Service material limits even further.A new high strength drill pipe family has been developed to specifically address those challenges: these new grades exhibit a minimum Yield Strength (120 ksi) higher than the current Sour Service grades available on the market as described by the current industry standards (95ksi or 105 ksi Specified Minimum Yield Strength). In order to guarantee the SSC resistance of these high strength materials, pipes and tool joints are tested as per the NACE standards. A first string of this high strength material is already being commercialized and used for the first time in offshore wells in the North Sea.

Abstract"Sour Service" refers to a well environment containing Hydrogen Sulfide (H2S), which is naturally associated with acid conditions. It is well known that H2S is hazardous to human health, living organisms, and more generally to the environment. It is for this reason that wells found with Sour Gas were often carefully plugged and abandoned in the past. H2S can also lead to catastrophic brittle failure of drillstring components: the physical phenomenon associated with Sour Service Environments and affecting steel based products under applied or residual stress is known as H2S embrittlement or more specifically as Sulfide Stress Cracking (SSC).With the increasing demand of gas worldwide, some highly sour oil and gas reservoirs are being explored, mainly in Russia, the Middle East, China and North America, and are now more and more associated with complex well profiles – such as deep reservoirs or extended reach wells. The use of high strength drill pipe is essential to achieve such drilling objectives; however it does represents significant technical challenges in terms of drill pipe integrity and operational safety with the current high strength grades available on the market, such as S-135 drill pipe. Because higher strength is generally detrimental to Sulfide Stress Cracking, innovative chemistries and new heat treatment processes are needed to push Sour Service material limits even further.A new high strength drill pipe family has been developed to specifically address those challenges: these new grades exhibit a minimum Yield Strength (120 ksi) higher than the current Sour Service grades available on the market as described by the current industry standards (95ksi or 105 ksi Specified Minimum Yield Strength). In order to guarantee the SSC resistance of these high strength materials, pipes and tool joints are tested as per the NACE standards. A first string of this high strength material is already being commercialized and used for the first time in offshore wells in the North Sea.

It is well known that the ball joint in a marine riser can cause fatigue damage in the drill pipe passing through. Previous investigators have assessed the damage done for a lower ball joint angle of 3–5 degrees (drilling) and 1–3 degrees (running casing). This paper extends that work to deep water operations in which an upper ball joint is also present. Also, it is shown, via finite element models, that tool joint bending stiffness can have a significant effect on fatigue life. Fatigue damage calculations, including this heretofore unconsidered effect, are presented for various ball joint angles and drill pipe tensions.

Industry advances continue to enable pursuit of more challenging drilling targets with complex well bore trajectories. Many of these targets are in costly deepwater and/or remote operating areas. Demand for a practical, field-proven drill pipe fatigue management system has grown as drill string failures due to fatigue contribute to a significant amount of non-productive time and cost. The response to this demand has been the development of an engineered approach that combines pipe section positioning and inspection scheduling based on estimated fatigue damage rather than rotating hours or footage drilled. Successful real-time field implementation with ongoing drilling programs demonstrates that the cumulative fatigue damage technique is a valuable and proven tool for risk mitigation and cost reduction. The cumulative fatigue damage technique and its implementation have been introduced in previous literature [1,3,8,10]. This method of monitoring fatigue damage due to rotary operations allows the pipe to be evaluated under real-time operating conditions along a specific section or the entire length of the drill pipe. Monitoring begins at spud and is performed on each joint of drill pipe as it traverses along the well path to total depth (TD). This not only allows a quantitative measure of the relative fatigue damage accumulated joint by joint for the drill pipe, but also provides the opportunity to manage logistics, forecast pipe inspections and position pipe sections to minimize cumulative drill string fatigue damage. The cumulative fatigue damage technique has been successfully applied in the field[1,10]. Hind casting, pre-drill planning and real-time analyses have been utilized for assessing drill string design as well as pipe management. The current case study further demonstrates the methodology introduced in the previous literature and illustrates the modeling and management of fatigue damage over a three well project. The subject operator originally anticipated that pipe inspection may be required before each well to mitigate costly historical drill pipe failures. However, the cost and logistical challenges of mid-program pipe inspection in remote operations could not be ignored. Described is the pipe management strategy employed to complete the drilling program without drill pipe failures and without the need for any mid-program inspections. In addition, the inspection results post TD of the third programmed well have been evaluated and correlated back to expected pipe damage, making this an excellent case study for the further deployment of this technology.

Harsh drilling conditions can exceed the capabilities of traditional drill string connections. As the petroleum industry moves toward more severe drilling applications - deepwater, extended reach, high-angle, short-radius and ultra-deep wells - new drill string connection designs are required to safely and efficiently achieve the drilling objectives of these projects. This paper describes three new rotary shoulder connections that provide significant operational advantages for extreme drilling applications. Introduction An advanced, high-performance tool joint design provides approximately 70% more working torque capacity than standard API connections. This new design is a second-generation, double-shoulder connection that is optimized for each drill pipe size. The connection's increased torsional strength allows for the use of a streamlined tool joint configuration. The connections can be configured with a smaller OD and larger ID compared to standard API connections without sacrificing torsional capacity. A second version of this connection incorporates a radial metal-to-metal internal pressure seal. This connection provides high torsional strength combined with gas-tight pressure sealing capability. Drill strings with the gas-tight connection can be used for drill stem testing (DST) operations, underbalanced drilling and high-pressure workover and completion operations. This eliminates the need for a separate work string saving time, money, rig space and set back capacity. This is a significant advantage in offshore operations where rig space and set back capacity are at a premium. A third development discussed in the paper is a new thread form that provides increased durability and improved fatigue life compared to standard API connections. This thread form has been successfully used on drill pipe pins and drill collar boxes. This paper discusses the engineering philosophy behind each of these new designs and details results of physical testing. Applications where the connections have been used are also presented. Design Configuration and Capabilities The eXtreme™ Torque (XT™) is a second-generation double-shoulder connection (see Figure 1). The XT design evolved from the design of the HI TORQUE (HT™) connection. Figure 2 depicts the make-up characteristics of XT and HT. Both connections spin up freely from the stab-in to hand-tight position. In the hand-tight position the primary external shoulder makes contact. As the connection is made-up from the hand-tight to power-tight position the box counterbore compresses and the pin base elongates elastically and the secondary torque stop engages. The secondary torque shoulder provides the increased torsional capacity compared to a standard API rotary shoulder connection. The external (primary) shoulder is the pressure seal for the connection just as on an API connection. Since the secondary shoulder functions solely as a torque stop and not a pressure seal, minor damage to the secondary shoulder can be tolerated without adversely effecting connection performance provided there is no protruding metal that will impede contact between the shoulder surfaces. Any protruding metal on the secondary shoulder must be removed with a file or abrasive paper. Use of thread protectors when the pipe is racked back in the derrick is not required or recommended.

For a horizontal well or an extended reach well, which is promising for well construction in . future, a well casing is subjected to local wear of wall thickness on its inside surface due to rotational contact with tool joint or drill pipe during drilling. Collapse strength of worn casing is analyzed as an unstable problem by the elastic-plastic finite-element method (FEM) and the decrease ratio of collapse strength due to casing wear is formulated by nonlinear programming using parameters of the wear shape. The elastic-plastic FEM is fully applicable as values calculated by the FEM program agree well with those of experiments. It was found that the decrease ratio of collapse strength of a worn casing is linearly proportional to the decrease ratio of wall thickness in both modes of plastic collapse and elastic collapse, and that the apical angle of the wear shape has a slight influence on collapse strength.

Sour service drill pipe product has long been in use with tool joints and tubes separately meeting criteria for sour service through IRP Volume 1 - Critical Sour Drilling to welding.1 The weld area of the final product is omitted for SSC testing. Though there are few reports of field failures of sour service drill pipe occurring in the weld area, in SSC laboratory tests, the weld area exhibits reduced resistance to cracking in H2S compared with drill pipe. Friction-type welds have several features which differ from arc welding type fabrication welds for which detailed qualification procedures are outlined in ANSI/NACE MR0175/ISO 15156.2 Friction-type welds present some unique challenges in obtaining SSC resistance. This paper will demonstrate that with an ongoing testing program, selection of appropriate testing stress levels and alloys, and strong end-user (customer) interaction, a set of production qualification criteria for SSC resistance of friction-type welds is possible. A Vickers hardness based production qualification procedure for friction-type welds which was developed and verified through SSC testing will be discussed. This SSC-resistant friction-type weld was developed for a very specific application: an intervention riser. End-user interaction was critical in developing testing procedures specific for the expected field environment conditions.

A comprehensive analysis on the longitudinal fracture in the tool joints of drill pipes

Fatigue is the most common known problem of drill pipes, since the combination of make-ups performed to connect the pipes and all the external loads, together with the threaded geometry of the connections, will stimulate the appearance of high stress points, cracks and finally promoting considerable economic losses. When threaded connections are used to connect the casing string, the fatigue resistance of the connection will affect the whole integrity of the string, and thus, in most cases, it is lower as the casing body. Generally, fatigue is classified as low-cycle fatigue and multi- or high-cycle fatigue. For Oil Country Tubular Goods (OCTG), a typical high cycle fatigue is represented by drill pipe fatigue in deviated wells. Unlike drill pipe, the casing may be exposed both to low-cycle as well as to high-cycle fatigue. Low-cycle fatigue is a common type of failure when the applied loads induce high stresses in the metallic material. The number of cycles may vary from as low as 10 up to 100. High-cycle fatigue requires a large number of cycles to failure. In order to avoid catastrophic failures, high-cycle fatigue resistance is usually considered to be sufficient if the number of cycles is above 106. The oil business has focused excessively on testing drilling risers and drill pipes under fatigue loads, but when it comes to casing and tubing the experimental approach may require different solutions. Drilling with casing opened the intensive testing of casing connections against fatigue resistance. Moreover, recent papers have shown intensive work on redesigning connections to withstand fatigue. New applications like rotating while running require a rethinking of testing strategy of Casing and Tubing. The following paper focuses on answering the question whether we test enough. The first part compares existing testing facilities, followed by an intensive discussion about the true loads of a casing or tubing connection. Using public testing data, the second part of the paper tries to identify how far the results provided by various types of testing machines can be compared with each other. For example, we found that low cycle fatigue results may not fully reflect the predictions based on extrapolations of high cycle fatigue results.

During the process of deep drilling with high temperature and high pressure, downhole drilling tools might be exposed to various corrosive mediums, such as water/oil-based drilling fluid systems, dissolved oxygen, H2S/CO2, halogen elements (Cl- and Br-), etc. Halogen elements existing in the drilling fluid are ions promoting corrosion of metals. This effect is mainly manifested in the forms of uniform corrosion, pitting corrosion, stress corrosion cracking, etc. of carbon steel. Quality of the drill pipe is determined by the DP body, joint and welding area of the drill pipe. Reasonable friction welding process and proper post weld heat treatment can make the mechanical property of weld joint satisfy related standards. If process of friction welding or post weld heat treatment is improper, the weld joint will be easily damaged and accidents of pricking, breaking, etc will be likely aroused. This paper carries out an evaluation experiment of chloride cracking on the DP body, joints and weld joints of the high-strength drill pipe (S135) and discusses corrosion of the high-strength drill pipe caused by chloride ions.