In the process of sliding drilling in highly deviated wells and horizontal wells, cuttings accumulate at the lower side of the borehole to form a cuttings bed, which is difficult to remove. To address the difficulty of removing cuttings beds during the sliding drilling process in horizontal and highly deviated well sections, this paper proposes awe propose a vortexing cuttings removal tool (VCRT). The internal flow field model of the VCRT has been established, and the computational fluid dynamics (CFD) method is used to analyze flow field variations. The results indicate that under the sliding drilling conditions of horizontal wells, when VCRT is installed near the bit, the cuttings volume fraction at the low side of the annulus is reduced by 18% compared to the conventional cuttings removal tool (CCRT). When the VCRT is installed in the section with a cuttings bed, the cuttings volume fraction at the low side of the annulus flow fluid is reduced by 36% compared to that with the CCRT. Therefore, the approximate installation location of the tool is determined based on comparative CFD analysis of two installation positions, and it is recommended to install the VCRT in the section with the cuttings bed. This tool has been applied in an oil field in Jiangsu, China, and field tests demonstrate that at a drilling fluid flow rate of 30 L/s, the rotational speed of the rotating blade can reach 400 rev/min, the pressure drop in the VCRT field is 1.6 MPa, and the friction resistance of the drill string will be reduced by 35.90%. Through CFD analysis, the working mechanism of the VCRT and its cuttings removal efficiency are revealed. The CFD results show good agreement with experimental data, and these findings provide important theoretical support for VCRT applications.

An accurate analysis of the three-dimensional(3D)deformed configuration of a bottom-hole assembly(BHA)is critical for predicting and controlling well paths in directional drilling.Among the various numerical approaches,the weighted residual method exhibits superior performance owing to its semi-analytical nature,enabling high accuracy in handling diverse boundary conditions.In previous studies,the weighted residual method has been coupled with a dual optimization process to determine the 3D deformation and tangency point of the BHA.However,its applicability is limited by the conventional treatment of contact interactions between the BHA and wellbore wall.Specifically,stabilizer-wellbore contacts are regarded as predefined boundary con-ditions,rather than solving these contact positions as unknown variables consistent with actual downhole conditions.This limitation reduces modeling fidelity in complex down-hole environments.To address this limitation,this study enhances the optimization-based weighted residual method by introducing ant colony optimization(ACO)to solve the 3D contact problem.In the proposed framework,the bending energy of the deformed BHA is conceptualized as"food",while the contact positions and orientations of stabilizers are assigned a measure of"taste".Through this metaphor,the ACO algorithm employs artificial"ants"to explore the optimal stabilizer locations and orientations that minimize the BHA bending energy,thereby refining the computed 3D deformation.The simulation results demonstrate that integrating ACO into the previously established dual optimiza-tion framework enables the effective determination of the contact configuration between the BHA and wellbore wall.As a result,the overall accuracy of the 3D BHA deformation analysis is significantly improved.In one representative case study,the bending energy of the BHA is reduced by 55.6％compared with that obtained from the original dual-optimization method.

Ultra-deep-well drilling is performed in long, narrow wellbores with restricted borehole clearance, where drill string-wellbore interactions promote nonlinear coupling among axial, lateral, and torsional vibrations and increase fatigue-related failure risk. This study presents a beam-solid coupled modeling strategy for full-scale drill string dynamics in ultra-deep wells with restricted borehole clearance. The three-dimensional wellbore trajectory is reconstructed from survey data using the curvature-radius method. Realistic downhole boundary conditions are represented by incorporating drilling-fluid loads as well as drill string-wellbore contact. To improve full-well modeling feasibility while retaining a refined representation of the near-bit region, the upper drill pipe is modeled using beam elements, whereas the BHA is modeled using solid elements. Simulations reveal pronounced high-frequency torsional vibrations in the near-bit region, with dominant spectral peaks around 118 Hz and 198 Hz, accompanied by significant lateral whirling. The peak lateral acceleration in the BHA pendulum section reaches 177.2 g, and stress fluctuation amplitudes vary markedly along depth. In certain intervals, repeated lateral excursions trigger frequent wall contact and promote vibration propagation along the drill string in the depth direction, indicating higher vibration sensitivity in these regions. Simulated dynamic characteristics are generally consistent with surface logging data from ultra-deep drilling operations and with downhole vibration observations reported in the literature, supporting the applicability of the proposed model for vibration mitigation and drilling-parameter optimization in ultra-deep wells.

The phenomenon of secondary makeup in threaded joints frequently occurs during ultra-deep well drilling, indicating the presence of downhole impact torque that exceeds the initial makeup torque. This excessive torque not only complicates the breakout process of drill tool connections but also increase their susceptibility to failure, posing significant safety risks. To investigate the generation mechanism of downhole impact torque, a finite element model was developed based on a comprehensive simulation of drill string dynamics under various operating conditions. Derived from Hamilton's principle, the model was solved using a combination of Newmark method and the Successive Over-Relaxation node iteration technique to obtain the dynamic response of the drill string. A case study, using a representative drill string configuration under specified borehole conditions, was conducted to analyze the self-rotation and whirl characteristics of the Bottom Hole Assembly during stick-slip events. The results reveal that secondary makeup is primarily caused by stick-slip vibration. While the impact torque arising from the drill string self-rotation is relatively small and insufficient to induce secondary makeup, the intensified whirl motion during the slip phase of stick-slip oscillations generates a significant impact torque-reaching up to 94.6 kN m-which far exceeds the initial makeup torque. This dynamic torque is identified as the primary factor leading to secondary makeup in threaded connections. The proposed model demonstrates high predicative accuracy, with a deviation of only 5.1 % from field measured breakout torque, confirming its reliability and practical relevance.

Abstract The sucker rod string—serving as the core component of rod-pumped oil production systems—exhibits an ultra-slender geometric configuration. Under downhole reciprocating motion, it is prone to complex three-dimensional spatial deformation and may come into contact with the tubing wall, thereby inducing eccentric wear or, in severe cases, mechanical failure such as fracture. Since the dynamic spatial configuration of sucker rod strings is essential for understanding and mitigating tubing–rod eccentric wear, this study proposes a method to construct its three-dimensional spatial configuration under reciprocating movement. The method is grounded in a three-dimensional coupled dynamic model of the sucker rod string within tubing, incorporates buckling stability theory, and introduces smooth transition conditions that ensure deformation continuity of sucker rod string across distinct buckling modes. Finally, engineering case studies are employed to analyze the evolution of the sucker rod string’s three-dimensional spatial configuration within the tubing across distinct phases of reciprocating motion; moreover, the pivotal role of dynamic bottomhole pressure in triggering buckling mode transitions is elucidated.

Drilling practices in Tarim Oilfield of China have shown that the combined use of a Positive Displacement Motor (PDM) and a Power Drive System can significantly enhance wellbore trajectory control and drilling efficiency, but it is likely to cause drill tools failure. Preliminary studies once attributed this failure to High-Frequency Torsional Oscillation (HFTO), but the actual failure morphology does not match HFTO induced failure features. This paper, based on finite element model (FEM) of drill string dynamics, investigates the mechanical mechanism behind the failure of the stabilizer’s threaded joint in a Bottom Hole Assembly (BHA) equipped with a PDM and a Power Drive System. The results show that when stick-slip vibration occurs, the drill tool at the fracture position experiences severe lateral vibration with a frequency as high as 211.4 Hz, and the maximum dynamic bending stress reaches 148.6 MPa in which the maximum additional bending stress caused by collision reaches 126.1 MPa when the closest rub-impact point is 2.49 m above the upper end of the stabilizer. This indicates that it is precisely these high-frequency lateral vibrations (HFLV) that induce high-frequency alternating stress within the threaded joint, thereby causing fatigue damage and ultimately leading to drill tool fracture.

Titanium alloy drill pipes exhibit promising potential for ultra-deep well drilling due to their high specific strength and superior corrosion resistance. However, the engagement surfaces of the pin and box joints feature distinct material stiffness and surface roughness, which influence both the load bearing characteristics and sealing performance. This study establishes a 3D elastoplastic finite element model for steel-titanium heterogeneous drill pipe joints and analyzes their stress distribution under complex loading conditions. Furthermore, a sealing performance evaluation model based on microscopic leakage mechanisms is proposed, and the sealing performance of single shoulder and double shoulder drill pipe joints is comparatively analyzed. The results indicate that, compared to the NC50 single-shoulder joint, the DS50 double-shoulder joint exhibits a 12.8% improvement in sealing performance under an axial tension of 2500 kN, and a 27.6% improvement under combined loading of 2500 kN axial tension and 8 kN·m bending moment. The synergistic action of the primary and secondary shoulders enhances the sealing stability of the drill pipe joint.

Titanium alloy has promising applications in the ultra-deep well drilling field. When using titanium alloy drill pipes in composite drill strings, using titanium-steel tool joints becomes inevitable. However, the mechanical properties of such titanium-steel tool joints are not fully understood. This paper develops a three-dimensional elastic-plastic finite element model to analyze the loading characteristics of API standard tool joints with different material combinations. The analysis shows that the torsional performance of titanium-steel tool joints is significantly reduced compared to traditional steel tool joints. Based on these findings, a titanium-steel double-shoulder tool joint was designed. Its model accuracy was verified through experimental testing, and its mechanical behavior was analyzed. Results indicate that incorporating a secondary shoulder structure and adjusting the clearance of the secondary shoulder can effectively enhance the torsional performance of the tool joint. Specifically, the ultimate working torque of the titanium-steel double-shoulder tool joint (DS50-H) is 84.6 kN·m, 39.15% higher than the 60.8 kN·m torque of the titanium-steel single-shoulder tool joint (NC50). This improvement significantly enhances the tool joint’s stability under complex geological conditions.

Stick-slip vibration is a common phenomenon in ultra-deep drilling that significantly impacts the failure of both drill bits and drill tools. The most direct and efficacious approach to alleviating the stick-slip vibration of the drill string in the downhole is to modify its external excitation. In recent years, the composite impact tools that can simultaneously offer axial and torsional excitation in the downhole have been applied, effectively reducing the stick-slip vibration of the drill string. However, the mechanical mechanism thereof remains undefined. In order to understand the nature of this phenomenon, A dynamic model of the drill string taking into account multi-directional excitations is presented. The governing nonlinear equations are obtained by using the Lagrangian approach, which take the work done by the multidirectional excitation into consider. The Hertz contact model is introduced considering the constraints of the wellbore, and the finite element node iteration method is employed to solve the dynamics equation of drill string. The axial vibration, torsion vibration and phase trajectory characteristics of the drill string under multidirectional excitation are analyzed, and the inhibitory effect of the excitations on stick-slip vibration is clarified. The results show that the vibration characteristics of the bottom hole assembly can be significantly altered through periodic axial and torsional excitations at higher frequencies, resulting in the emergence of high-frequency vibration responses. These responses exhibit a pronounced inhibitory effect on stick-slip suppressed.

In the early drilling process of Fuman oilfield， the bottom hole assembly （BHA） with Power-V and pendulum BHA were mainly used for deviation control and drilling acceleration. The former had good deviation control and drilling acceleration effects， but the use cost was high. The latter had low cost， but the deviation control and drilling acceleration effects were moderate. To accelerate the drilling rate， test and promotion of prebend dynamic deviation control and drilling acceleration technology were carried out in the oilfield， i.e.， using prebend BHA to carry out deviation control and drilling acceleration operations. In the paper， the 3D mechanical model of prebend BHA and the calculation model of BHA deviation control force in combination drilling were presented， the influence of key parameters on the deviation control force of prebend BHA was analyzed， and the structural parameters of prebend BHA were optimized combined with the actual conditions of drill site. The research results show that the outer diameter of the stabilizer， the relative position of the two stabilizers and the degree of bend have a great influence on the deviation control force of the prebend BHA， and the prebend BHA with large deviation control force can be obtained by adjusting the structural parameters. The field test results show that the ROP of prebend BHA deviation control and drilling acceleration technology is 29.8% to 49.5% higher than that of BHA with Power-V or conventional pendulum BHA used in adjacent wells， showing good application potential.

The complex vibration directly affects the dynamic safety of drill string in ultra-deep wells and extra-deep wells. It is important to understand the dynamic characteristics of drill string to ensure the safety of drill string. Due to the super slenderness ratio of drill string, strong nonlinearity implied in dynamic analysis and the complex load environment, dynamic simulation of drill string faces great challenges. At present, many simulation methods have been developed to analyze drill string dynamics, and node iteration method is one of them. The node iteration method has a unique advantage in dealing with the contact characteristics between drill string and borehole wall, but its drawback is that the calculation consumes a considerable amount of time. This paper presents a dynamic simulation method of drilling string in extra-deep well based on successive over-relaxation node iterative method (SOR node iteration method). Through theoretical analysis and numerical examples, the correctness and validity of this method were verified, and the dynamics characteristics of drill string in extra-deep wells were calculated and analyzed. The results demonstrate that, in contrast to the conventional node iteration method, the SOR node iteration method can increase the computational efficiency by 48.2% while achieving comparable results. And the whirl trajectory of the extra-deep well drill string is extremely complicated, the maximum rotational speed downhole is approximately twice the rotational speed on the ground. The dynamic torque increases rapidly at the position of the bottom stabilizer, and the lateral vibration in the middle and lower parts of drill string is relatively intense.

Recent advancements in drilling technology have driven substantial progress in cuttings removal tool development, particularly for addressing borehole cleaning challenges in highly deviated directional critical factors in operational safety and efficiency improvement. Despite these innovations, two fundamental challenges persist: an incomplete understanding of mechanistic cuttings removal processes and an insufficient methodological framework for optimal tool installation. Studying the installation positions and assessing the effects of two cuttings removal are essential steps to advance the application of such tools. This investigation was initiated with a comprehensive analysis of particle settling dynamics and migration behaviors in annular wellbore spaces. Building upon Moore's terminal settling velocity equation, a modified model was developed to characterize the transport patterns of cuttings. Through model integration, the precise positioning of the efficient Vortex Cuttings Removal Tool (VCRT) was determined at 188 m from the bit. Subsequently, Computational Fluid Dynamics (CFD) numerical simulation was employed to reveal distinct annular flow field characteristics between VCRT and conventional drilling tools. Field validation in Well Z401X demonstrated a strong correlation between empirical measurements and simulated predictions, with pressure drop deviations of 6.25% and rotational speed variances limited to 7.50%. Analytical results confirmed VCRT's superior performance, exhibited 36.43% reductions in cuttings accumulation at the wellbore's lower quadrant compared to conventional drilling tools. The application of VCRT accelerated cuttings migration velocity in the annular space, significantly increasing the volume of returned onsite cuttings. Friction resistance decreased by approximately 35.90%, indicating higher cuttings removal efficiency than conventional drilling tools.

Bolted joints are widely used in various industries. However, in challenging conditions such as shock, vibration, and temperature fluctuations, threads can loosen, leading to equipment damage and accidents. Scholars have introduced self-locking thread designs like wedge-shaped selflocking threads and stepped threads to improve anti-loosening performances. While experiments support their effectiveness, previous research primarily focused on optimizing thread structure parameters, and the studies of loosening mechanism are not in-depth enough, which restricts the development of anti-loosening bolted joints. This paper proposes a parametric modeling approach to create 3D elastic-plastic finite element models of bolted joints with different thread profiles. This approach allows for a comprehensive analysis of structural behavior, stress distribution, and load conditions, enabling the in-depth examination of the mechanical properties for thread loosening. A novel arc-lock anti-loosening threads design is proposed. Arc-lock threads are found to provide superior load distribution uniformity, increased normal force, and enhanced frictional resistance. Furthermore, the correctness of the finite element results is validated through photoelastic experiments and transverse vibration experiments. Results show that under a preload force of 225.5kN, the assembly of M24 Grade 10.9 bolts with Grade 10 nuts exhibit RMSE (Root Mean Square Error) values of 11.25, 9.02, and 8.76 for regular threads, wedge-shaped threads and arc-lock threads, respectively. Arc-lock threads demonstrate a more uniform stress distribution. In transverse vibration experiments under fully tightened conditions, regular threads loosened at the 2326th vibration cycle, while wedge-shaped self-locking threads and arc-lock threads maintained the preload percentages of 91.24% and 93.51%, respectively. These findings offer a scientific basis for understanding anti-loosening mechanisms in bolted joints and inform anti-loosening thread design.

Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Research on the Speed-Up Method of Drill String Dynamics Simulation in Ultra-Deep Wells 13 Pages Posted: 22 Feb 2024 See all articles by Mingming YOUMingming YOUShanghai UniversityQinfeng DIShanghai UniversityTianxin LIShanghai UniversityXing ZHOUShanghai UniversityHeyuan YANGShanghai UniversityWenChang WangShanghai University Abstract The complex vibration of drill string directly affects the dynamic safety of drill string in ultra-deep wells, typically ranging between depths of 6000 m and 9000 m. Numerical simulation and downhole testing are commonly used to understand and monitor downhole drill string vibration. However, the dynamic simulation of the drill string faces substantial challenges due to its ultra-length-slenderness ratio and the complex load environment. The node iteration method is an effective method to calculate the dynamic characteristics of drill string, especially in determining the contact features between drill string and borehole wall. Nevertheless, the extended calculation time poses a significant limitation. In order to improve the efficiency of this method and enable a rapid analysis of the dynamic characteristics of drill string in ultra-deep wells, this paper introduced successive over relaxation (SOR) iteration method on the basis of node iteration method. The proposed SOR node iteration method aims to expedite the dynamic calculation of the drill string in ultra-deep wells. Theoretical analysis and numerical examples are employed to validate the acceleration of the model solution. In comparison with the conventional node iteration method, the SOR node iteration method demonstrates a notable improvement in computational efficiency, achieving a 38.5% acceleration while yielding comparable results. It should be pointed out that the choice of the relaxation factor significantly influences the simulation efficiency of the drill string dynamic characteristics. Notably, a relaxation factor below 1.8 results in a substantial increase in acceleration effects, reaching stability beyond 1.8. A relaxation factor closes to 2, however, leads to a diminished acceleration effect. The findings emphasize that a relaxation factor of 1.9 provides the optimal acceleration effect for drill string dynamics simulation. Keywords: Drill string dynamics, Calculation Speed-up method, Node iteration method, SOR, Ultra-deep well Suggested Citation: Suggested Citation YOU, Mingming and DI, Qinfeng and LI, Tianxin and ZHOU, Xing and YANG, Heyuan and Wang, WenChang, Research on the Speed-Up Method of Drill String Dynamics Simulation in Ultra-Deep Wells. Available at SSRN: https://ssrn.com/abstract=4735692 Mingming YOU Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China Qinfeng DI Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China Tianxin LI Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China Xing ZHOU Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China Heyuan YANG Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China WenChang Wang (Contact Author) Shanghai University ( email ) 149 Yanchang RoadSHANGDA ROAD 99Shanghai 200072, 200444China Download This Paper Open PDF in Browser Do you have negative results from your research you’d like to share? Submit Negative Results Paper statistics Downloads 0 Abstract Views 6 30 References PlumX Metrics Feedback Feedback to SSRN Feedback (required) Email (required) Submit If you need immediate assistance, call 877-SSRNHelp (877 777 6435) in the United States, or +1 212 448 2500 outside of the United States, 8:30AM to 6:00PM U.S. Eastern, Monday - Friday.

Based on the three-dimensional elastic-plastic finite element analysis of the 8"(203.2 mm)drill collar joint,this paper studies the mechanical characteristics of the pin and box of NC56 drill collar joints under complex load conditions,as well as the downhole secondary makeup features,and calculates the downhole equivalent impact torque with the relative offset at the shoulder of internal and external threads.On the basis of verifying the correctness of the calculation results by using measured results in Well GT1,the prediction model of the downhole equivalent impact torque is formed and applied in the first extra-deep well with a depth over 10 000 m in China(Well SDTK1).The results indicate that under complex loads,the stress distribution in drill collar joints is uneven,with relatively higher von Mises stress at the shoulder and the threads close to the shoulder.For 203.2 mm drill collar joints pre-tightened according to the make-up torque recommended by American Petroleum Institute standards,when the downhole equivalent impact torque exceeds 65 kN·m,the preload balance of the joint is disrupted,leading to secondary make-up of the joint.As the downhole equivalent impact torque increases,the relative offset at the shoulder of internal and external threads increases.The calculation results reveal that there exists significant downhole impact torque in Well SDTK1 with complex loading environment.It is necessary to use double shoulder collar joints to improve the impact torque resistance of the joint or optimize the operating parameters to reduce the downhole impact torque,and effectively prevent drilling tool failure.

Nanoparticle-stabilized foams can overcome the problem that conventional foams are easy to defoam in complex reservoirs, thereby losing foam function and seriously affecting foam profile control and flooding effect. However, the oil displacement characteristics and effects of the nanoparticle-stabilized foam in cores with different permeabilities directly determine its application prospects. The nuclear magnetic resonance (NMR) visualization technology was combined with the traditional foam displacement method in this paper, with the nanoparticle-stabilized foam system and oil as the displacement medium and the displaced medium, respectively, and the core as the carrier to physically simulate the process of the nanoparticle-stabilized foam flooding oil. The oil displacement characteristics of the foam are visually observed by the NMR images, and the average size change of the pores where the fluid is located and the quality change of the fluid in the core are reflected by the T 2 spectrum to further study the visual profile control and displacement characteristics of the nanoparticle-stabilized foam in the core with different permeabilities.

The deepwater drilling string system consists of riser and drill string, forming a "pipe in pipe" structure with the riser as the outer pipe and the drill string as the inner pipe, thereby increasing the complexity of simulation and analyzing the dynamic characteristics of the string system. In this paper, a coupling model of the riser string and drill string is established by using Euler-Bernoulli beam model. Based on obtaining the dynamics of drill string, considering the influence of riser vibration, the dynamic characteristics of drill string are compared with those under the condition of fixed riser string. The kinematic characteristics of drill string in the "pipe in pipe" structure are analyzed as well. The distribution of contact forces between the drill string and the inner wall of riser is also studied. The results indicate that the vibration of the riser string has a significant influence on the dynamic characteristics of the inner drill string, and there is a high risk of failure due to serious contact wear between the riser and the drill string near the underwater wellhead. This observation is consistent with practical observations.