Do We Need an Intelligent Makeup Solution for Modern Rotary Shouldered Connections?

A new tightening method for the rotary shouldered connection (RSC) has been developed. In the developed method, the coefficients of friction between mating thread surfaces and between mating shoulder surfaces can be accurately and separately detected by sinultaneous loading of torque and compressive force to RSC. The tightening experiments have been achieved to verify the serviceability of the developed method. The 1/4 scale model of NC50 are used as the test model of RSC. The scatter band of axial force on RSC has been reduced within the error of ±10% under lubricated conditions by grease with MoS2. The reliability of the method is compared with Baryshnikov's method.

Introduction Drill pipe, and the connections used to join the pipe together, have had a long history of development and improvement. With the growing use of high tensile-strength pipe, the rotary shouldered connections used to join the lengths of drill pipe have become more critical. Fatigue-type failures of rotary-shouldered connections, or tool joints, have become a cause of much concern to operators and manufacturers. Most fatigue tests on tool joints have been made on the basis of bending moment applied vs number of cycles, rather than on the basis of stress vs cycles. A desire to learn more about the nature of stress in a tool joint due to bending caused a rather intensive experimental study to determine what actually happens to cause fatigue failure. It was known that a tool joint with insufficient make-up torque was subject to early fatigue failure. Therefore, the establishment of the relationship between make-up torque and allowable bending moment would enable a testing engineer to better correlate the results of various tests. The problem of calculating the stress in a tool joint due to an applied bending moment was complicated by: the effect of unknown stress concentrations; the applicability of the well known formula S = Mc/I; and the question of whether to use the combined cross section of the pin and box in calculating the moment of inertia I.

Vibrations are known as destructive loads and thus are leading to downhole fatigue failures, severe bottom hole assembly and bit wear and may cause wellbore instabilities. Downhole measurement of vibrations, however, can provide valuable information about downhole conditions and characteristics of the formations drilled. Uniaxial compressive strength is one of the representative characteristics of rock properties. It shows the capacity of a rock to withstand a certain amount of axial loads. Optimizing weight on bit and rotary speed of the drill string are the ways to continue drilling a hole - of course by exceeding uniaxial compressive strength of formations - and to keep rate of penetration in an optimal range during drilling operations. Therefore, it is expected that the axial vibrations change with variations of the uniaxial compressive strength of formations. Previous experiments with several layered concretes cubes proved that the drill string vibrations are related to the uniaxial compressive strength of concretes. To extend the study in this area, complex rock samples such as sandstone, dolomite and limestone were drilled with optimized ranges of weight on bit and rotary speed of drill string. Experimental drilling operations were conducted using a laboratory drilling rig (CDC miniRig) with a vibration sensor sub attached to the drill string. The uniaxial compressive strength of all samples was measured prior to the experiments. During all experiments, drilling parameters were recorded with a sampling rate of one second and the vibration data with a sampling frequency of 3200 Hz. Analysis of magnitude and higher order frequency moments of vibration data in combination with the mechanical specific energy demonstrated a change of the drill string's axial vibration measurements due to variations of uniaxial compressive strength. From that it is concluded that the formations can be recognized in real-time by incorporation of the vibration measurements. Introduction When talking about drill string vibrations, in most of the time downhole fatigue failure, severe bit wear and reduced rate of penetration come to the mind. Drill string vibrations are inevitable in the drilling operations and lots of researches have been investigated to manage the magnitude of vibrations by designing proper bottom hole assemblies (Macpherson et al., 1993; Chen et al., 2006). However, the vibrations can be utilized as a valuable tool to recognize formations drilled. In most of the cases, the vibrations are caused by bit and drill string interaction with the formations under certain drilling conditions. One of the dominant conditions is formation characteristics (mechanical and petrophysical properties). Uniaxial compressive strength (UCS) is one of the representative characteristic of the formation properties. It shows the capacity of a formation to withstand a certain amount of axial loads. Previous works show that the harder the formation, the bigger the magnitude of the vibrations and vice versa (Esmaeili et. al, 2012). Therefore monitoring vibrations in real-time can advance warning of formation changes. Myers et al. (2002) explained how the vibration data measured by an accelerometer are related to petrophysical properties of the formations in the Indian Ocean region. Al-Shuker et. al. (2011) presented changes in drilling dynamics driven by the bit's interaction with the formation can be a near instantaneous indicator of changes in formation characteristics. The key is real-time drilling dynamic measurement at the bit. Previous works (Esmaeili et al., 2012) presented a close relationship between the mechanical properties of layered concretes cubes and the measured vibrations. The study proved that the vibrations can be used as a tool to recognize the formation changes.

Introduction Divinyl benzene co-polymer beads, better known as plastic beads, have been used for reducing torque and drag in conventional drilling operations for 17 years. Over the last four years, they have also been utilized to reduce friction in horizontal wells when drill pipe is not sliding at a fast enough rate, or is not moving at all. Co-polymer beads have also gained recognition as a means of reducing friction in coiled tubing workovers. Friction is reduced by introducing co-polymer beads between the drill string and bore hole. Laboratory testing and field experience have developed methods for reducing friction through specific application techniques. Application of the beads can vary, from spotting small "pills" in specific sections of the bore hole to carrying a concentration of beads throughout the system using a bead recovery unit. Drill string drag is the incremental force required to move pipe up or down in the hole, and torque is the force required to rotate pipe. The magnitudes of torque and drag are related in any particular well, and high drag forces and excessive torque loads normally occur together. There are a number of causes for excessive torque and drag. They include:tight hole conditions;sloughing hole;key seats;differential sticking;cuttings buildup because of poor hole cleaning; andsliding well bore friction. With the exception of sliding friction, these causes are associated with problem conditions in the well bore. Although all of these conditions can occur in horizontal wells, the primary source of torque and drag in a horizontal well with good hole conditions is sliding friction. The ability to alleviate sliding friction using co-polymer beads has proven to be extremely beneficial in horizontal drilling and workover operations, including standard pipe and coiled tubing. Sliding Friction Normal contact force and the coefficient of friction between contact surfaces are the two factors that affect sliding well bore friction. Another factor, capillary attraction, must be considered in open hole situations. Capillarity is described as the relative attraction of the molecules of a liquid where it is in contact with a solid. The relative attraction of molecules leads to a force of adhesion between a solid and a liquid. The wallcake of a well bore will exert very strong capillary attraction forces on a drill string when it comes in close contact with the drill string. This is explained by the fact that the wallcake or mudcake is composed of very small particles of clay, barite, sand, or other matter, and these minute particles will have considerably more surface area exposed for wetting by liquid than would larger particles in the same section of mudcake. The smaller the particles, the more surface area exposed for liquid wetting, thus the greater the attractive capillary force exerted. The capillary attractive force could lead to the drill string adhering to the wallcake, creating torque and drag. The beads, having a larger particle size than the solids in the wallcake, reduce this adhesive force.

Torsional vibrations experienced by drill strings can be detrimental to drilling operations. With a goal of understanding torsional vibrations experienced by drill strings and determining means to attenuate undesired vibrations, the authors have studied the effect of adding a sinusoidal modulation to a constant rotation speed of a drill string. A combination of modeling, analysis, and experiments is used to explore the influence of this rotation input modulation on the system response. The drill string is modeled as a modified Jeffcott rotor, which is described by a system with three degrees of freedom. Considering the case of forward whirling of a rotor in continuous contact with a stator, the equations of motion are reduced to a single degree-of-freedom nonlinear oscillator describing the torsional motions. In order to understand the fast time scale and slow time scale components of the motion, the method of direct partitions of motions is used to determine an approximate response to the nonlinear oscillator. The obtained results of the analysis illustrate that with the sinusoidal modulation of the rotor drive speed, the equivalent torsion stiffness can be enhanced and the character of the friction force at the contact can be made smooth. The analyses helps bring forth the stabilizing influence of the added sinusoidal input to the rotor drive speed. Over the considered parameter ranges, the numerical results obtained with the full three degree-of-freedom model and the reduced single degree-of-freedom model are found to be in agreement with each other. Furthermore, the results from these models are found to compare well with those obtained by using the method of direct partition of motions. Experiments with a laboratory scale drill-string arrangement are to be carried out to validate the analytical and numerical findings and further explore the effectiveness of the drive speed modulation on the rotor dynamics. Introduction Slender rotating structures are used in many engineering applications. Drill strings are long rotating slender structures, which are used in drilling operations. A schematic of a rotary drill rig is shown in Fig. 1 (e.g., Liao, Balachandran, Karkoub, and Abdel-Magid, 2011). Drill strings experience different types of vibrations (axial, torsional, and lateral vibrations) that may lead to detrimental failures of a drilling system. Drill-string vibrations have attracted the attention of many researchers, and many models have been developed to understand them. Since drill strings have a large length-to-diameter ratio, typically, the first torsional natural frequency and first lateral natural frequency are close to each other. This frequency proximity and the nature of the system allows for coupling and energy transfer between the associated vibration modes. Here, as a step towards developing further understanding, a drill string is modeled as an extended planar Jeffcott rotor with gravity acting normal to the rotor. Due to the planar motions, no gyroscopic effects are considered. The extended model, which was earlier considered in the work of Vlajic, Liu, Karki, and Balachandran (2014), is shown in Fig. 2. The model is described with three degrees of freedom (DOF), namely, x and y to account for lateral motions, and theta to account for torsional motion. A large number of research efforts have focused on controlling drill-string vibrations by using different feedback control algorithms, which need measurements along the drill string. In this work, the authors propose a different control approach to mitigate whirling motions during continuous rotor-stator contact. This can be compared to a situation of a drill string being in continuous contact with the borehole. The approach is open loop in implementation and this approach is based on adding a high frequency input to the drive speed of the drill string. Given the open-loop nature, the method does not depend on any measurements along the drill string or rotary table, which could be attractive for a practical stand point. Although the current focus is on motions of a rotor with continuous stator contact, it is planned to study stick-slip and non-contact cases in the future. System Modeling, Studies, and Results As previously mentioned, the drill string is modelled as a Jeffcott rotor with three DOF. Proceeding along the lines of the group's prior work (Vlajic, Liu, Karki, and Balachandran, 2014), after some approximations for the continuous rotor-stator contact case, the 3 DOF system is reduced to a single second-order nonlinear differential equation governing the torsional motion. In Fig. 3, for a representative case with a constant drive speed, the torsional state histories obtained for the full model and the reduced model are plotted. It is noted that the final state of the motion is captured quite well. To further analyze the response during forward whirling, the reduced-order model was nondimensionalized and an approximate solution was obtained by using the method of direct partitions. This method allows one to separate slow scale motions from fast scale motions. As discussed, in the group's prior work, this method can be useful to examine whirling motions. The results obtained by directly integrating the full model as well as the reduced-order model have been compared with that obtained by using the method of direct partitions of motions. It is seen that the perturbation analyses is able to provide an approximate solution that compares well with the numerical results obtained through direct integrations. Next, this analysis is used to examine the influence of the addition of secondary frequency component. It is seen that the addition of the secondary frequency, a high-frequency one, helps smooth out the friction coefficient variation with respect to the relative speed at contact. This is found to have a beneficial effect on the motion and helps suppress large-amplitude torsional motions. Stability analysis was also conducted to examine this effect. Concluding Remarks A study has been conducted to examine the influence of sinusoidal modulation of rotor drive speed in a system, wherein the rotor experiences continuous stator contact. A single degree of-freedom reduced model is developed to study the torsion response and it is found that the addition of a high frequency input can be beneficial in attenuating rotor motions. This is believed to be useful for developing open-loop control schemes for attenuating forward whirling motions of drill strings. Results obtained from a lab scale experimental arrangement will be used to examine the effect of this drive speed modulation further and they will be reported in the conference presentation. Future studies could build on the current effort to examine cases of backward whirling. Acknowledgment: The authors would like to gratefully acknowledge the support received from the Qatar National Research Fund for NPRP Project 7-083-2-041, to pursue this collaborative work between the University of Maryland, College Park, MD, USA and Qatar University, Doha, Qatar.

Axial flux magnetic-geared double-rotor machines (AMGDRMs) are characterized as a potential core component of the power splitting system in hybrid electric vehicles (HEVs). Conventional AMGDRMs suffer from low mechanical strength due to high axial magnetic force. In this paper, an interior-modulating-rotor axial flux magnetic-geared double-rotor machine (IMR-AMGDRM) is proposed to solve this problem. An analytical model of the IMR-AMGDRM is proposed to predict the magnetic field distribution and electromagnetic performances. Since analytical model is based on 2-D geometry, a 2-D approximation of IMR-AMGDRM which has similar output performance to 3-D finite element analysis (FEA) is presented based on the permanent magnet (PM) magnetic energy equivalent principle. Utilizing subdomain method, the magnetic field distribution and electromagnetic performances are calculated. Finally, the accuracy of the proposed analytical model is validated by 3-D FEA.Index Terms—Analytical model, axial flux, magnetic-geared machine, double-rotor machine.I. IntroductionAxial flux magnetic-geared double-rotor machines (AMGDRMs), which enable high torque density, have been considered a promising candidate for power splitting in hybrid electric vehicles (HEVs) [1]. However, conventional AMGDRMs suffer from low mechanical strength due to high axial magnetic force. To enhance mechanical strength, an interior-modulating-rotor axial flux magnetic-geared double-rotor machine (IMR-AMGDRM) which can reduce axial magnetic force dramatically is proposed in this paper. Fig. 1 (a) and (b) illustrate the configuration of the proposed IMR-AMGDRM.As axial flux type machine, IMR-AMGDRMs have complex 3-D magnetic circuits. 3-D finite element analysis (FEA) can offer accurate results by taking into account the nonlinear factors such as magnetic saturation and flux leakage. But the major drawback of 3-D FEA is serious time cost. Analytical model which is much lower time-consuming provides an alternative for electromagnetic performance prediction in the initial design procedure.In this paper, an analytical model of the IMR-AMGDRM is proposed. The geometry of analytical model is derived based on PM magnetic energy equivalent principle to guarantee similar output performance to 3-D FEA. The solution to analytical model is calculated by subdomain method. To evaluate the accuracy of the proposed analytical model, the results computed by analytical model and that of 3-D FEA are compared.II. Configuration of IMR-AMGDRMIn conventional configuration, the inner and outer rotors are the permanent magnet (PM) rotor and the modulating rotor, respectively. Since the modulating rotor is closer to the PM rotor than stator, the modulating rotor suffers from high axial magnetic force. Furthermore, the modulating rotor is hollow and thus the low mechanical strength of modulating rotor becomes the major drawback of conventional configuration [1]. To solve this problem, the IMR-AMGDRM which switches positions of the PM rotor and the modulating rotor is proposed. In interior-modulating-rotor configuration, as shown in Fig. 1 (a) and (b), the PM rotor is between the modulating rotor and stator, i.e. the inner and outer rotors are the modulating rotor and the PM rotor, respectively. Owing to that the PM rotor suffers from reverse axial magnetic forces from both sides simultaneously, the total axial magnetic force is dramatically reduced. Hence, although the outer rotor is hollow in both configurations, the axial magnetic force of interior-modulating-rotor configuration is significantly decreased, leading to higher mechanical strength and reliability.III.Geometry of 2-D ApproximationGenerally, the unrolled section of axial flux machine at mean radius is used as 2-D approximation. However, few references are found to evaluate the electromagnetic performance equivalence of such approximation. To make the electromagnetic performance of 3-D model and 2-D approximation equal, the amount of magnetic energy of the PM should remain unchanged after approximation, i.e. PM magnetic energy equivalent principle [2]. A 2-D approximation of IMR-AMGDRM which has identical output performance is presented by using PM magnetic energy equivalent principle.IV. Analytical Calculation of IMR-AMGDRMThe proposed analytical model is illustrated in Fig. 1 (c). It can be seen that the model consists of four subdomains. Region i, I, II and III represent the ith slot of the modulating rotor, the inner air gap, the PM rotor and the outer air gap, respectively. Utilizing subdomain method, the magnetic field distributions in the inner and outer air gaps are obtained by the solution of Laplace’s and Poisson’s equations. Then, the electromagnetic performances such as no-load back EMF, torque and axial force can be derived from the calculated magnetic field distributions.Comparisons of computation accuracy between analytical model and 3-D FEA is shown in Fig. 2. As can be observed, the results of analytical model are well consistent with that of 3-D FEA, validating the proposed method. **

Relationships between narrow band directional energy spectra and probability densities of deep and shallow water waves

The requirement for intervention operations in long laterals continues to grow. For instance, in North America and North Sea, it is required to run 2 and 2 3/8-in coiled tubing (CT) in 12,000 and 25,000 ft laterals, respectively. One of the most critical well intervention problems nowadays is that many extended reach wells that need to be serviced are more than 30–40% unreachable and contribute to lost productivity for energy companies around the world. While increasing the CT diameter remains a theoretical option to improve reach, practically, it creates logistical challenges with onshore road transport and offshore crane lifting/deck loading limitations. Other options such as using fluid hammer and tractor tools may have reasonable operational range, but they have significant limitations by increasing circulating pressures and operational complexity.To reach the remaining 30–40% un-reachable length, lubricants are required to work in conjunction with other systems. Obviously, the use of lubricants for well interventions is not new. Typical field results of current systems show a 17–25% reduction in the coefficient of friction (CoF), from a generic 0.24 to 0.18 – 0.20. However, these results compare poorly to the industry-wide lab rotational friction tests that do not take into account any downhole parameters. CoF values between 0.03 and 0.08 are usually reported in such lab tests, but never achieved in the field.In this paper, the results of an extensive set of laboratory measurements using the first in industry linear friction apparatus are reported. This instrument was designed to take into account the downhole effects of temperature, pressure, CT sliding speed, surface roughness, and fluid composition. The lab results show that the pressure and the sliding speed have weak effects of friction, while temperature, surface roughness, and fluid type and composition have strong effects. More than 6,000 measurements were performed with many combinations of CT and casing samples and lubricants currently used in field operations. Based on these laboratory results, a new lubricant was designated that reduces the linear CoF by approximately 42–58% (from the default CoF of 0.24 to 0.10–0.14) under downhole conditions. Friction of this magnitude is expected to make it feasible to run CT in all previously un-reachable laterals and decrease the operational time when fluid hammer or tractor tools are used.Several North America field trials with the new lubricant are also reported. The field CoF values obtained are in the 0.12 to 0.14 range and validate the new laboratory methodology. Friction reduction of this magnitude is expected to double the reach in long lateral wells without lubricant. Previous field CoF calculation studies for determining predictable lateral reach are also reviewed. The laboratory and field results with the new lubricant challenge the current industry understanding of the CT friction and show great benefits for our industry in extending the reach of lateral wells.

During the drilling process, the whirling motion often occurs, which will cause the drill string to vibrate violently, accelerate the fatigue damage of the drill string, and eventually cause the bottom hole assembly to fail. But the existing research rarely focuses on the critical whirling velocity of drill string. To solve this problem, the whirl differential equation of drill string was set up based on the D’Alembert principle, and the critical whirling speed equation of drill string was deduced according to separation variable method. Reference to actual downhole conditions, the influence of drill stem wall thickness, tension, drilling depth, drilling fluid flow rate, and other factors on the critical whirling speed of drill string are considered. Research results indicate that when n ≤ 8324, drill string has a critical whirling speed, and when n > 8324, there is no critical whirling speed. And under different orders, as drill string wall thickness and drilling depth increase, the critical whirling velocity decreases. In general, the drill string rotation rate is 0–150 rad/min. When the drilling depth is 0–500 m, the critical speed is not considered. However, as drilling depth exceeds 500 m, the critical whirling velocity is within the general range of drill string speed. Therefore, drill string velocity should be chosen reasonably to avoid resonance. When the tension increases, critical whirling velocity increases. As the drilling fluid flow rate increases, the critical whirling velocity of drill string decreases. But when drilling fluid velocity is close to 120 L·s−1, increasing the drilling fluid velocity hardly affects the critical whirling velocity of drill string. In a word, research results of this paper have certain guiding significance to drilling engineering.

The vibration characteristics of drillstring with positive displacement motor in compound drilling Part1: Dynamical modelling and monitoring validation

The formalism for rate and state friction is extended to represent fault zones where temperature, porosity, effective normal traction, and strain rate are functions of position (measured across the fault zone). A traditional form for the instantaneous coefficient of friction is retained,where μ0is the steady state coefficient of friction at shear strain rate,aandbare small constants,is the shear strain rate, ψ is a state variable that represents damage, and ψ0a normalizing factor. Percolation theory of cracked solids is used to justify a relation between porosity and the state variable of ψ=exp[(ϕ0‐f)/Cϵ], wherecϵis a dimensionless constant, and ϕ0is the porosity at a reference steady state strain rate ϵ0and at a reference temperature where Δ≡0 and a reference effective normal traction ΔP0. These relationships and percolation theory imply an evolution law for porosity of the (normalized) formwheretis time, ΔPis the effective normal traction,Cηis a material property (related to compaction viscosity) that depends on the temperature difference ΔTfrom reference condition, 0 indicates reference conditions, and η is a power law rheology exponent. The first term represents creation of porosity by frictional dilatancy while the second term represents closure of porosity by compaction. The effects of transient changes of pressure and temperature on the coefficient of friction are represented when the normalizing factor ψ0is ΔPnCη(0)/ΔPn0Cη(ΔT). The theory is complete in the sense that the complete earthquake cycle is represented and that there are no unmeasurable state parameters. The theory was applied to investigate earthquake quenching by fluid pressure decreases associated with frictional dilatancy and the related topic of strain localization and delocalization within fault zones. It was found that strain localization will occur whenb>a. Such strain localization tends to destabilize sliding within drained faults by reducing the effective value of the critical displacement. Fault zones that are hydraulically sealed from the country rock but internally hydraulically connected are also destabilized because strain localization reduces the fluid pressure decrease from frictional dilatancy. Two mechanisms that delocalize strain once sliding is well underway were investigated. Strain rate strengthening at high‐strain rates leads to a high strain zone that gradually broadens throughout an earthquake. An increase in the coefficient of friction with temperature leads to a high strain rate zone that moves through the fault zone from hot regions created by frictional heating to cold regions.

The ability to predict accurately the circulating system pressure drop whilst drilling is a prerequisite of drilling optimisation. The quantification of the annular pressure drop is also necessary to calculate the equivalent circulating density of the drilling fluid. With invert emulsion drilling fluids, using ‘low toxicity’ paraffinic oils, these calculations are complicated by the viscosity changes under downhole conditions. This paper presents data from three separate hole sections where annular and drill string pressures were continuously monitored using Measurement While Drilling (MWD) instrumentation. Readings were taken between 2625 and 14764 ft (800 and 4500m) with mud densities ranging from 9.33 to 11.67 ppg (1120 to 1400 kg/m3). The data are summarised and tabulated with respect to the hole geometry, circulating rates and drilling fluid properties. The derivation of correction factors for the estimation of the drilling fluid rheology at elevated temperatures and pressures is detailed with results of laboratory studies using HP/HT viscometry. The theoretical pressure drops through the annular and drill string sections, with and without application of the rheology correction factors, are then presented. Two rheological models are employed, the power law with yield stress (Herschel-Bulkley) and the Bingham model. The theoretical pressure drops are compared with the actual values. The application of the rheology correction factors is discussed and the comparative merits of the two models reviewed. Finally the paper discusses the implications of the research to hydraulics planning and identifies critical areas of development required to enhance the predictions.

Today's oil and gas drilling operations often face significant technical challenges, especially in remote locations with increasingly difficult geological settings. Stuck pipe incidents have become a major operational challenge for the exploration and production industry, with events typically resulting in substantial amounts of lost time and associated costs. Real-time monitoring has emerged as an important tool to achieve drilling optimization in avoiding downtime, particularly stuck pipe incidents. With the addition of a predictive monitoring system, this process becomes much more effective and competent. Predictive monitoring is used for advanced real-time monitoring in Wells Real Time Center (WRTC) and operational workflows to aid in the drilling execution of complex or critical well sections. The emphasis will be on reducing the complexity of real-time data analysis by utilizing trends and deviations between modelled and actual data to monitor wellbore conditions. This monitoring system and trend-based predictive capability enable drilling teams to detect borehole changes and take preventive action up to several hours in advance. By maximizing productive time, it improves operational efficiency. Predictive monitoring can provide early warning of stuck pipe symptoms, allowing the rig and operations team to take corrective and step-by-step actions. In raw drilling data, the conditions that lead to the stuck pipe can be difficult to read and detect. Various factors may indicate potential problems, but these are frequently missed until the situation has progressed to the point where the drill string becomes stuck. This system could have provided the rig crew with advance notice of changes in downhole conditions, in this case, avoiding the stuck pipe situation. We will look into predictive monitoring adoption in Field B operation as an example. Well E is a highly deviated extended reach well (ERD), with a 12,000ft long horizontal section, exceptionally challenging in terms of geomechanics perspective as well as the well design. When original Well E was drilled, a stuck pipe was encountered which caused the wellbore to be sidetracked. Predictive monitoring was implemented to assist drilling operation for the sidetracked well, and it had been completed successfully with minor hole condition issues. The predictive monitoring system is built around a trio of tightly coupled real-time dynamic models consisting of hydraulic, mechanical, and thermodynamic that simulate the wellbore state and physical processes during drilling operations. These models work together continuously to assess drilling performance, borehole conditions, and any other associated risks. It uses dynamic modelling to accurately model key drilling parameters and variables such as hook load, surface torque, cuttings transport, tank volumes, standpipe pressure, and equivalent circulating density (ECD) in real-time.

Heave compensated response of long multi-segment drill strings

The offshore industry has presented an increasing demand over the last few decades, requiring the production in deep water fields. The end fittings (EF) are critical points within the production system. Therefore, structural and fatigue analyses are essential in the EF design, making it necessary to know the stress distribution experienced by the armor wires along the EF. Numerical and analytical models are often used in order to assess the stress state. However, characteristics like geometries, materials and interactions must be previously known in order to apply these models. The purpose of this work was to analyze the arithmetic mean surface roughness (Ra) and to determine the friction coefficient (μ) for two types of armor wires when in contact with resin used to fill the EF. The resin used in the interaction with the armor wires was an epoxy filled with metallic particles. For the experimental analysis straight carbon steel armor wires with different cross-sections, typically used in 2.5″ and 8″ flexible pipes were used. Surface profile was obtained for each wire by repeated measurements along two lines over each surface. A total of three repetitions were performed in each measure line. Longitudinal roughness was determined through these profiles. Finally, friction coefficients were obtained experimentally by means of a device that allows to simulate the wire pullout and sliding process. In this device, two epoxy pads were put in contact with the surface of the analyzed wire sample, and rigid bodies in contact with the pads were used to ensure that the normal load applied is transmitted uniformly through the contact surface. The displacement rate, contact pressure between the surface of the wire and the epoxy resin pads, and axial force were recorded. The roughness in the longitudinal direction of the wires was analyzed through descriptive statistic and compared by Student’s “t” test. The highest values were obtained on wires with larger sections. This behavior is exposed on the results obtained for the friction coefficient as a function of the contact pressure. Friction coefficient for both wires was analyzed and compared using a Mann-Whitney U test. Both friction coefficients have a positive slope, indicating a small increase as the contact pressure raise. The significance value obtained for the means comparisons was p = 0.0001 and confirms that the average friction coefficient of the two wires are really different. Because of that, we conclude that is necessary to treat the EF project for different flexible pipes differentially.