Rotary Steerable Drilling System Research Articles

Self-Stabilizing Control Strategy of Stabilized Platform for Rotary Steerable Drilling System Based on Adaptive Backstepping Control

To enhance the robustness of the toolface angle control in a fully rotary steerable drilling tool, a backstepping control law and a drilling fluid flow adaptive law are devised based on the dynamic model of the stable platform. The Lyapunov function is constructed, and it is proven that the adaptive backstepping control system of the stabilized platform is stable. Furthermore, in order to address problems such as the friction dead zone and excessive rotational kinetic energy in the stabilized platform system, which could cause toolface angle oscillations and the rapid rotation of the stabilized platform, we additionally propose an online estimation method for the balancing torque and velocity-angle control switching strategy. By combining the backstepping control law, drilling fluid flow adaptive law, and velocity-angle control switching strategy, a self-stabilizing control strategy for the stabilized platform is established. In comparison with the PID control method, the simulation results show the superiority of the proposed scheme under complex disturbances from a downhole environment. And the drilling simulation experiment results indicate that the proposed control method has a good anti-interference capability under various conditions, including drilling fluid flow rate, inclination angle, and drill collar rotational speed. Therefore, the proposed control method can improve the robustness of the stabilized platform control system.

Backstepping sliding mode control of stabilized platform for fully rotary steerable drilling system based on nonlinear disturbance observer

AbstractTo handle the disturbances and uncertainties issue in the control of the stabilized platform toolface angle, a composite control approach based on a backstepping sliding mode control (BSMC) method with a nonlinear disturbance observer (NDO) is proposed. First, a nonlinear mathematical model of the stabilized platform is established, and the NDO is employed to observe and compensate for the external disturbance. Then, the BSMC control approach based on the nonlinear mathematical model is designed to improve the robustness of the stabilized platform control system. The asymptotic stability of the designed controller and NDO convergence are mathematically verified using the Lyapunov theory. Furthermore, to address the dead zone torque caused by mechanical friction on the stabilized platform, which could lead to instability in the toolface angle, a novel dead zone torque estimation algorithm is presented. Finally, in comparison with other advanced control methods, simulation results show the superiority and robustness of the proposed scheme under complex disturbances from the downhole environment. And drilling simulation experiment results are provided to validate the robustness and adaptivity of the proposed method.

Attitude Control of Stabilized Platform Based on Deep Deterministic Policy Gradient with Disturbance Observer

A rotary steerable drilling system is an advanced drilling technology, with stabilized platform tool face attitude control being a critical component. Due to a multitude of downhole interference factors, coupled with nonlinearities and uncertainties, challenges arise in model establishment and attitude control. Furthermore, considering that stabilized platform tool face attitude determines the drilling direction of the entire drill bit, the effectiveness of tool face attitude control and nonlinear disturbances, such as friction interference, will directly impact the precision and success of drilling tool guidance. In this study, a mathematical model and a friction model of the stabilized platform are established, and a Disturbance-Observer-Based Deep Deterministic Policy Gradient (DDPG_DOB) control algorithm is proposed to address the friction nonlinearity problem existing in the rotary steering drilling stabilized platform. The numerical simulation results illustrate that the stabilized platform attitude control system based on DDPG_DOB can effectively suppress friction interference, improve non-linear hysteresis, and demonstrate strong anti-interference capability and good robustness.

Attitude Control of Rotary Steering Drilling Stabilized Platform Based on Improved Deep Deterministic Policy Gradient

Summary The rotary steerable drilling system is an advanced drilling technology, with stabilized platform toolface attitude control being a critical component. Due to a multitude of downhole interference factors, coupled with nonlinearities and uncertainties, challenges arise in model establishment and attitude control. Furthermore, considering that stabilized platform toolface attitude determines the drilling direction of the entire drill bit, the effectiveness of toolface attitude control will directly impact the precision and success of drilling tool guidance. In this paper, a mathematical model and a friction model of the stabilized platform are established, and an improved deep deterministic policy gradient (I_DDPG) attitude control method is proposed to address the friction nonlinearity problem existing in the rotary steering drilling stabilized platform. A prioritized experience replay based on temporal difference (TD) error and policy gradient is introduced to improve sample usage, and high similarity samples are pruned to prevent overfitting. Furthermore, SumTree structure is adopted to sort samples for reducing computational effort, and a double critic network is used to alleviate the overestimated value. Numerical simulation results illustrate that the stabilized platform attitude control system based on I_DDPG can achieve high control accuracy with both strong anti-interference capability and good robustness.

Motion Simulation Analysis and Experimental Verification of Drill String Rotation Controller

Abstract Conventional directional drilling mainly relies on the sliding of screw motor and drill string to realize the change of wellbore trajectory, so the friction force is large. The use of friction reduction tools that generate axial force to change the friction state can only achieve partial friction reduction, and drill string is still in a sliding state during directional drilling. These problems are solved by using rotary steerable drilling system, which can achieve directional drilling when drill string rotates. But its use cost is high. Considering the principle of high efficiency and economy, a new friction reduction tool called drill string rotation controller is proposed, which is also used to reduce friction during directional drilling through drill string rotation. By adjusting the pump pressure, the meshing state of spline module of drill string rotation controller is changed to realize the conversion of drilling mode. In rotary drilling mode, upper drill string, drill string rotation controller, and bottom hole assembly rotate together. In directional drilling mode, upper drill string rotates and drill string rotation controller slides with bottom hole assembly. The function of the tool is verified by field experiment, and motion simulation of the tool is carried out. The results show that when the driving torque is set to 25,000 N · m, more reverse torque can be overcome in the directional drilling mode, and the drilling fluid pressure is set to 25 MPa, which can be converted to the rotary drilling mode faster.

Incipient fault detection of rotary steerable drilling tool equipment

Rotary steering drilling system is a high-end piece of equipment in oil and gas development. The reliable operation of its core equipment, the dynamic point-the-bit rotary steerable drilling tool (DPRSDT), is an important prerequisite for the normal operation of the drilling system. In this paper, the problem of incipient fault detection is investigated for the DPRSDT equipment based on the model method, which is expected to provide an important guarantee for the operation, maintenance, and health management of the system. First, the mathematical model of the DPRSDT is derived using the mechanism modeling method. Then, the moving weighted average approach is employed to improve the sensitivity of residuals to incipient faults. Based on the characteristics of the noncentral $\chi^2$ distribution, the detectability of incipient faults is analyzed in a statistical sense, and the window length and weight are derived, which ensures that the false alarm rate and missed detection rate can be reduced below the tolerance level. Finally, an experiment is performed in the rotary steerable drilling tool prototype to verify the effectiveness of the proposed method.

Factors to Influence the Trajectory Control Ability of a Reverse Push-the-Bit Rotary Steerable System

The reverse push-the-bit rotary steerable method based on the principle of a “labor-saving lever” provides a feasible technical solution for further improving trajectory control ability of the rotary steerable drilling system, further prolonging the system’s service life and further increasing the system’s drilling speed. In order to reveal the working characteristics of such a method deeply, the influence of the key structural parameters of the rotary steerable drilling system on its trajectory control ability is studied based on the finite element method. The results show that, with the certain distance from the bit to the centralizer, the structural parameters of the flexible joint, the distance from the flexible joint to the paranoid mechanism, and the distance from the paranoid mechanism to the centralizer are the main factors to affect trajectory control ability. Reducing the stiffness of the flexible joint, shortening the distance from the flexible joint to the paranoid mechanism, and optimizing the distance from the paranoid mechanism to the centralizer are the keys to improve trajectory control ability to the utmost. The performance of the reverse push-the-bit rotary steerable method with optimized parameters is obviously better than the existing method, but its actual drilling effect needs to rely on on-site verification and further optimization.

Progress and prospect of CNOOC's oil and gas well drilling and completion technologies

Offshore oil and gas production has become an important growth pole to ensure national energy security. However, China's offshore oil and gas production is lack of key core technologies and weak in tool and equipment foundation and can hardly support the optimized fast development of important fields. To solve these technological difficulties, China National Offshore Oil Corporation (CNOOC) insisted on independent technological innovation and overcame a series of key core technologies through theoretical research and key technology research and test during the 13th Five-Year Plan. And the following research results are obtained. First, several key technologies are broken through, including efficient drilling and completion in the middle and deep layers of the Bohai Sea, offshore large-scale heavy oil thermal recovery, deep-water oil and gas field development, and high temperature and high pressure well drilling and completion in the South China Sea, unconventional oil and gas stimulation, and offshore emergency rescue. Domestic first independently operated ultra deep water giant gas field, namely “Deepsea 1” is successfully put into production, so that the leap from 300 m to 1500 m of water depth and from exploration to development is realized. Second, key tools and equipment are developed, such as logging while drilling and rotary steering drilling system, deep-water drilling surface conductor, underwater emergency killing device, and underwater wellhead Christmas tree, which promote the high-quality development of China's offshore oil industry. Finally, some suggestions are proposed as follows. In the future, CNOOC shall strengthen independent technological innovation, quicken the pace to deepsea oil and gas, and continue to research key core technologies for oil and gas reserves and production increase (e.g. continuous localization of drilling and completion technologies, equipment and materials in complex fields), commingled gas production and test and green energy transformation (e.g. geothermal energy), so as to make greater contributions to ensure national energy security and build a maritime power.

Influence of flex-sub on mechanical properties of rotary steerable drilling system

Abstract. In this paper we analysis of the dynamic model of the Rotary Steerable System (RSS) with a single stabilizer and flex-sub. The drill collar and joint are simplified to obtain suitable bottom-hole assembly (BHA) model of mechanical analysis and finite element analysis. Using the BHA uniform stiffness assumption (ignoring the influence of variable section and variable stiffness of drill collar in BHA), the paper takes a method of the longitudinal and transverse bending continuous beam method to analyse the stress of BHA with RSS with the flex-sub under different inclination angles and curvature conditions. In addition, a dynamic analysis model is proposed, and the dynamic stress of drilling tools with RSS is analysed. Through the software of ANSYS, the finite element analysis of the RSS with the flex-sub is carried out to verify the theoretical results. The influence of flex-sub on the steering drilling performance of RSS is studied, and the optimized parameters of flex-sub design are obtained, which provides useful suggestions for the design of RSS.

Design and Experimental Study of Non-contact Power Transmission Device in Static Push-type Rotary Steering Drilling System

For improvement of contactless power transformer which is used in rotary steering system, this paper uses simulation method to study on the influence of the shape of the ferrite, the number os turns and installation position on the efficiency and power of the contactless power transformer. As well as, the author take several test to study the influence of environment, fixed position, etc. on this equipment and the regularity of power and efficiency. The research shows that the contactless power transformer is competent for rotary steering system, and the axial installation error impact the transmission efficiency and power which has the most power and efficiency at -3mm axial fixed position and ±3mm fixed position error can meet the rotary steering system requirements.

Structural Parameters Optimization of Elastic Cell in a Near-Bit Drilling Engineering Parameters Measurement Sub.

The downhole engineering parameters measurement sub is a key component of the rotary steerable drilling system. To enable a measurement sub to serve reliably under downhole complex conditions, the structural parameters optimization of its key but weak elastic cell is systematically studied. First, the multiple relations among measurement sensitivities, structural stiffnesses, and strength during structural parameters design are summarized. Second, the selection of the structural parameters of the elastic cell is characterized as a multi-objective optimization model, which is solved using the non-dominated sorting genetic algorithm II (NSGA-II). Furthermore, the finite element method (FEM) is used to verify the measurement performance and static strength of the proposed structure. Finally, transient dynamics analysis is applied to investigate the dynamic strength of the designed structure. The results show that the proposed parameters optimization strategy can quickly obtain the database for the structural parameters design of an elastic cell. The static analysis results based on the FEM further verify the effectiveness of the proposed method. Transient dynamic analysis also reveals the relative rigor of the proposed methodology framework to some extent. This work has practical significance for improving the drilling efficiency and reducing drilling risks. In addition, this proposed methodology has good extensibility.

Analysis of motion characteristics of fully rotating internal steering drilling tools

The fully rotary internal steering drilling tool is a key execution component of the rotary steering drilling system, which is a new type of dynamic directional downhole closed loop rotary steering drilling tool. The study was aimed to investigate the motion of fully rotary steering drilling tool. According to the corresponding spatial mechanism, the kinematics model of the fully rotary built-in steering drilling tool was established, and the kinematics analysis of the system was carried out. The validity of the model was verified by comparing with the simulation results of SolidWorks. The basic kinematic parameters of the key components, such as inner and outer eccentric annulus, angular velocity and displacement of drill are obtained theoretically, and the kinematic characteristics of the guiding mechanism are revealed. In this paper, the relationship between rotational speed, eccentricity and trajectory of drill was studied, and the variation of various parameters in the system with time is obtained, which provides a theoretical basis for well trajectory control of fully rotary built-in steel drilling tools.

Dynamic Reliability Analysis of Rotary Steering Drilling System

Abstract. Vibration and high shock are major factors in the failure of downhole tools. It is important to study the causes of vibration and shock formation to prevent failure of the drillstring and bottom hole assembly (BHA). At present, it is generally recognized that the vibration of drillstring is the main reason for the failure, especially the lateral vibration. In this paper, the bottom tool of Rotary Steering Drilling System (RSS) calculation model was established based on the secondary development of ABAQUS software. Starting from the initial configuration of drilling tool, considering the contact impact of drilling tool and borehole wall, the dynamic excitation of guide mechanism and the drilling pressure, torque, rotational speed, gravity, buoyancy, drilling fluid damping. The dynamic characteristics of the inherent frequency and dynamic stress of the bottom hole assembly (BHA) were calculated and analyzed, and risk assessment method based on the quantitative vibration intensity was established. The reliability of typical drilling tool is evaluated, which provides a reference for the optimization design of BHA of Rotary Steering Drilling System.

The Effect of the Rotary Steerable Spindle Structure Parameters on the Characteristics of Cantilever Bearing

In point-the-bit rotary steerable drilling system, the internal and outer diameter of the spindles and the fillet radius of the shaft shoulder have a great influence on the life of the cantilever bearing. According to the stress bias condition of the spindle, the 3D model of the cantilever bearing was established. Simulation analysis was conducted by loading boundary condition of the spindle under bias force. Therefore, the relationship between the internal and outer diameter of the spindle, the fillet radius of the shaft shoulder and the mechanical properties of the cantilever bearing were obtained. The results show that when the outer diameter of the spindle is constant, the deformation, the equivalent stress and the contact stress of the cantilever bearing reduce gradually with the increasing of the internal diameter of the spindle. When the internal diameter of the spindle is greater than 72 mm, the deformation of the roller shows a great fluctuation with the increasing of the fillet radius of the shaft shoulder. The life of the cantilever bearing first increases and then decreases with the increasing of the internal diameter of the spindle under the different fillet radius of the shaft shoulder. When the internal diameter of the spindle is constant, the life of the cantilever bearing first increases and then decreases with the increasing of the fillet radius of the shaft shoulder. The life of the cantilever bearing decreases gradually with the increasing of the outer diameter of the spindle. According to the research results, the optimal combination of internal diameter of the spindle and fillet radius of the shaft shoulder, outer diameter of the spindle and fillet radius of the shaft shoulder was offered, which can provide basis for the design of the spindle system.

New Rotary-Steerable System Delivers High Dogleg Severity, Improves Penetration Rate

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 177836, “New Rotary-Steerable Drilling System Introduction in the UAE for ADCO Delivers High DLS Capabilities While Improving ROP and Providing Extensive Formation-Evaluation Data,” by Imran Tipu, Shurooq Abdulla Mohamed Al Jasmi, Juma Sulaiman Al Shamsi, Ali M. Danche, and Muhammad Javid, Abu Dhabi Company for Onshore Petroleum Operations, and Jehanzeb Nurzai, SPE, Enrico Biscaro, SPE, and Nour Shat, Baker Hughes, prepared for the 2015 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 9–12 November. The paper has not been peer reviewed. A new rotary-steerable system (RSS) was designed to give geometrically greater dogleg-severity (DLS) capability while still being able to withstand the increased bending stresses. This high-build-rate RSS was able to eliminate controlled rate of penetration (ROP) as a limiter, which resulted in 39% ROP improvement. In addition, the development of a high-build-rate RSS provided multiple benefits, including elimination of ROP and logging-while-drilling limitations, increased curvature capabilities, and higher reliability of the system with respect to high-bending-related issues. Introduction Directional-Drilling Methods. In the early days of directional drilling, the process involved jetting and the use of bent subs as the main methods for deviating a wellbore. These methods largely have been superseded by the use of engineered bottomhole assemblies (BHAs) for inclination-only control and motor or rotary-steerable BHAs for complete 3D control. Simple BHAs (Inclination Control). In simple BHAs, placement of stabilizer elements determines the net force on the bit and results in either a building or a dropping tendency of the BHA. A stabilizer placed close to the bit acts as a fulcrum, with one side being forced down by the weight of drill collars. Because of this, the bit will drill along a path of increasing inclination and the BHA will have a tendency to build angle. On the other hand, a stabilizer placed significantly away from the bit will cause the collars below to sink to the low side of the borehole, pushing the bit to drill a path of decreasing inclination. This BHA will have a tendency to drop angle. A BHA designed to maintain direction will have stabilizers placed so as to create a rigid BHA, which will not bend in any direction with the force of gravity, causing the bit to drill along a straight path.

Overview on vertical and directional drilling technologies for the exploration and exploitation of deep petroleum resources

The vertical and directional drilling are the key technologies for the exploration and exploitation of oil and gas resources in deep formations. Meanwhile, they are also the very important ways to exploit deep geothermal energy and geo-resources, conduct international continental scientific drilling program. The aim of the present overview is to review and discuss the vertical and directional drilling technologies and their recent developments since the pioneering work in 1890s. It starts with the historical development and classification of main drilling methods for petroleum extraction, such as the vertical drilling, directional drilling and horizontal drilling, and the main application scopes of these methods are also discussed. Then, the developments of the directional techniques, the main directional tools (deflection tools, down-hole motor, rotary steerable drilling system and vertical drilling system), the directional survey techniques (measuring and transmission techniques), the main drill bits (roller cone bits, fixed cutter bits and hybrid bits), and the main drilling fluids (gas-base drilling fluid, water-based drilling fluid and oil-based drilling fluid) are summarized and analyzed. The top 15+ deepest and top 20+ longest wells all over the world are collected from related literatures to analyze the achievements of vertical and directional drilling in petroleum industry, the challenges of vertical and directional drilling are also discussed. Finally, a brief summary and prospect of vertical and directional drilling are presented.

The chaotic dynamics of drilling

In the study of drilling dynamics, many investigations are limited to laboratory systems and simple mathematical models. Using field measurement data and a new dynamical model in a rotary steerable drilling system, we demonstrate the existence of low-dimensional chaos in drilling. The behaviors of the mathematical model and actual measurement are shown to be consistent. The revealing of chaos provides a new way to detect early fatigue cracks as weak signals in a noisy environment to reduce engineering cost and the possibility of disaster.

Torsional vibration analysis of push-the-bit rotary steerable drilling system

Ordinary drillstring torsional vibration is a very common phenomenon that has been attracted great interesting. Through Measurement data, a series of studies and analysis of torsional vibration characteristics of the bottom hole assembly (BHA) have been developed. However, for rotary steerable system (RSS), especially push-the-bit mode, its drill torsional vibration phenomenon will demonstrate the new properties, because that the underground implementing agencies will generate cycle torque and drag to the BHA in the orientation process. This process is completely different to the previous. A set of “strap-down” measurement system was developed in this paper, and the triaxial accelerometer and triaxial fluxgate were installed near the bit. Proposed a method of solver drill bit rotation speed using real-time downhole measurement data (sampling frequency 100 Hz), and the torsional vibration mathematical model of push-the-bit RSS was established. We found that the torsional vibration phenomenon of push-the-bit RSS is more serious than the ordinary drilling system by downhole measurement data analysis, even in most cases manifested as stick-slip. The torsional vibration was divided into five different modes, which showing different statistical regularities. Corresponding analysis of the angular displacement and speed, we found that the drill bit always appears low-speed in the position of oriented. This is a strong proof of that the RSS implementing agencies pushing the BHA caused the drill bit torsional vibration more serious. This work is supplemented and development of the drill string torsional vibration studies. Contribute to the better understanding of the dynamics of the push-the-bit RSS. Put forward a new way of analysis the rotary steerable drillstring fatigue damage predicted, steering ability and the torsional vibration control.

Downhole Drilling Mechanics Analysis Based on Closed-Loop Rotary Steerable Drilling System

Design of closed loop drilling tool in the rotary steering drilling system is a bit in recent installation guide controlled stabilizer, and placed on the upper drill collar two downhole assembly form of stabilizer. The set of parameters for the MATLAB software programming is used to solve the three moment equation and the downhole assembly mechanical properties. With continuous beam column theory, the mechanics features of the BHA are analyzed. It is analyzed focused on the relationship between the guiding force and the bit deflecting force, the relationship between the hole deviation angle and bit deflecting force, the relationship between the drill press and bit deflecting force, the relationship between the guiding force position on the well inclined plane and bit deflecting force through the tables and figures based on closed-loop rotary steerable drilling system.

Research on Application of Steering Drilling Technologies in Shale Gas Development

HF-1 well of Pengye is a sidetracking horizontal well for shale gas development, the directional segment of the well is long, high requirements for well trajectory control of the directional segment in construction process. In allusion to the features and challenges of this well drilling, this paper introduces the application of slide steering drilling system and rotary steerable drilling system in this well, including analyzing all these tool basic principle, the characteristics and field application. The analysis shows that using different angel screw drill tool can meet the needs of increasing hole angle, steadying hole angle and adjusting the orientation; Adoption of EZ-Pilot steerable rotary system solves the problem of remarkable resistance and low degree of hole cleanness in long horizontal section, and satisfies the requirement of drilling and completion of the well. The system also shows the desirable performance in improving ROP and hole quality.