Tool Face Angle 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.

An FSCEEMD method for downhole weak SNR signal extraction of near-bit attitude parameters

In practice, the near-bit drilling tool confronts with strong vibrations and high-speed rotation. Therein the original signal amplitude of the tool attitude measurements is relatively feeble, and the signal-to-noise ratio (SNR) is exceptionally low. To handle this issue, this paper proposes a weak SNR signal extraction method, frequency selecting complementary ensemble empirical mode decomposition, which is based on ensemble empirical mode decomposition combining with complementary noise and frequency selecting. This method firstly adds different positive and negative pairs of auxiliary white noise to the original near-bit weak SNR signal, secondly adopts empirical mode decomposition on each pair of noise-added signals, then performs ensemble averaging on the obtained multiple sets of intrinsic mode function (IMF) to output more stable IMF of each order and set suitable weights according to designed frequency threshold, and finally reconstructs the original useful signal through weighted summing IMFs. Simulation results show that the extraction accuracy of well inclination angle ranges about ± 0.51°, and the extraction accuracy of tool face angle ranges about ± 1.35°, and meanwhile experimental results are provided compared with other advanced methods, which verifies the effectiveness of our method.

Uncertainty analysis method for the output force vector control on the rib of the orienter in coiled tubing drilling

This work addresses the uncertainty associated with downhole parameters in coiled tubing drilling and proposes a new method for controlling the output force vector on the ribs of the orienter, enabling more precise control of the actual wellbore trajectory. Based on the principles of longitudinal and transverse bending beams, we construct a 3D mechanical model of the Bottom Hole Assembly (BHA) used in coiled tubing drilling. We then analyze the spatial geometry relating the force direction on the orienter's rib and the tool face angle, establishing a comprehensive steering resultant force vector model. Applying the principle of minimum energy, we explore traditional control schemes for the output force on each rib and reveal its intricate variation patterns. We conduct a statistical analysis to investigate the randomness distribution state and sensitivity of the experimental parameters, allowing us to derive the probability density and cumulative probability functions for the two-dimensional random variables linked to the output force on the ribs. Confidence interval models are constructed to predict the output forces with a predetermined level of certainty. Finally, we experimentally verify the proposed uncertainty control method in real-world coiled tubing drilling. Our results show that the randomness of weight on bit (WOB) and the tool face angle of rib 1# are the main factors influencing the uncertainty of the output force control. When the output forces vector on the ribs exceeds the uncertainty confidence interval, the actual wellbore trajectory significantly deviates from the designed one. Conversely, when the output forces vector falls within the confidence interval, the error between the actual and designed wellbore trajectories is significantly smaller. This validates the rationality and effectiveness of the proposed uncertainty analysis method, providing valuable guidance for implementing wellbore trajectory control in coiled tubing drilling.

Helical buckling of coiled tubing with initial bending curvature in three-dimensional curved wellbores

In this paper, a new buckling model of coiled tubing (CT) in a three-dimensional curved wellbore is established, considering the influence of the curvature and toolface angle of the wellbore and the initial CT bending curvature. First, with the wellbore curvature and toolface angle, the CT buckling configuration is based on the lower or outer curved side of the wellbore. When the initial CT bending curvature is less than the critical bending curvature, the initial CT configuration in the wellbore undergoes sinusoidal buckling; otherwise, the CT undergoes helical buckling. Second, the buckling model is solved by the energy method. After solving this buckling model, the critical CT helical buckling load, the critical bending curvature, and the quantitative relationship between the axial load and pitch can be obtained. Third, the CT contact force calculation method under a helical buckling configuration in a three-dimensional curved wellbore is given by combining the buckling model and the beam-column model. The influence of the initial bending curvature is also considered. Finally, the calculated values of the buckling model and contact force calculation method were compared with existing experimental data and published models to validate the proposed model. Therefore, the methods presented in this paper can be used to not only predict helical CT buckling but also optimize downhole engineering design parameters considering the influence of the initial bending curvature in more realistic drilling wellbore conditions.

Versatile Gyroinclinometer Based on a Single Axis Angular Rate Sensor

Introduction. Currently, the versatility and reliability of gyroscopic inclinometers (GI), more than accuracy, determine their configuration and design. Imperative conditions for versatility include a diameter of 42…44.5 mm and a combination of point and continuous survey modes. Reliability is primarily determined by the robustness of the main elements. The fundamental parameter is adaptability to the trajectory, in other words, equal accuracy in the operating range of zenith angles, which determines the choice of orientation of the angular velocity sensors (ARS) with incomplete (< 3) number of their axis. Presently, biaxial dynamically tuned gyroscopes (DNG) are widely used due to their dimension and accuracy criteria; however, their elastic suspension gradually degrades as a result of frequent sidetracking operations (from previously drilled ones) accompanied by high-intensity impacts.Aim. To develop an inexpensive versatile GI that maintains a balance between shock resistance and accuracy (com[1]parable to fiber-optic ARS) based on a single-axis vibrating ring gyroscope (VRG) with an induction-type resonator made using MEMS technology.Materials and methods. The method of multi-position compassing with a single uniaxial ARS was implemented by transition from simultaneous biaxial measurements to uniaxial measurements in five successive positions of the frame (through 90°) along the toolface angle. Experimental data on the drifts of the selected VRG allow statistical methods to be used to construct an Allan-variance plot to confirm that the proposed method does not increase the total compassing time compared to the basic one. The continuous mode of such a GI, studied by solving differential equations, requires holding the input axis of the ARS near the apsidal plane using the same rotating frame.Results. The obtained ratios confirm that the performance characteristics of a GI with a uniaxial ARS approximately correspond to the conventional biaxial scheme. These conclusions were also confirmed by the mathematical modeling of a survey of a typical oil and gas well.Conclusion. The described GI containing a single ARS with indirect stabilization of the input axis is the result of a consistent development of the approach to the use of incomplete information

Constrained optimization assists deviated wellbore trajectory selection from families of quadratic and cubic Bezier curves

The ease of calculation of families of cubic and quadratic Bezier curves using just one or two control variables makes them well-suited for identifying smooth, deviated wellbore trajectories using easy-to-implement, constrained optimization techniques. Most wellbore trajectory optimization methods currently applied during the wellbore planning stages aim to minimize measured depth (MD) while constraining dog-leg severity (DLS) and/or torque and drag to select drillable, smooth wellbores. This study identifies the benefits of conducting MD optimization of Bezier curves using multiple constraints related to different characteristics of DLS and absolute changes in tool-face angle (ΔTFA). Whereas DLS is a major influence on wellbore tortuosity on the multi-meter scale, ΔTFA influences wellbore roughness on a finer scale and in a different way than DLS. As rotary-steerable bottom-hole assemblages are now the standard for drilling the multiple horizontal wells required for tight gas and oil reservoirs, minimizing the magnitude of TFA changes can speed up drilling and reduce borehole roughness. This study identifies the benefits of applying a sequence of up to four constraints (maximum DLS combined with average DLS and/or average or maximum ΔTFA) to minimize MD while achieving the smoothest possible wellbore trajectory from a family of cubic Bezier curves, configured to drill from a vertical starting location to a horizontal finishing location offset in 3D space. On the other hand, families of quadratic Bezier curves drilling some relatively simple trajectories between two points located on a two-dimensional plane can be effectively optimized for MD and smoothness using solely a maximum DLS constraint.

Observer-based adaptive neural network control for stabilized platform in rotary steerable system with unknown input dead-zone

The core task of the stabilized platform in the rotary steerable system is to control the toolface angle, so that the trajectory of the whole bit can move forward to the set direction. Due to many downhole interference factors, the uncertainties of parameters related to internal friction and interference torque of stabilized platform always exist, which poses great challenges to model establishment and controller design. Moreover, the actuator dead-zone nonlinearity makes the control more complicated. Hence, a dynamic model of stabilized platform considering a variety of nonlinear factors is established, and an observer-based adaptive neural network (NN)-control law is proposed. An NN state observer is developed to cope with the uncertain states composed of unknown friction parametric uncertainties and unmodeled disturbances, the dead-zone inverse is constructed to compensate for a dead-zone, and the dynamic surface control (DSC) strategy is used to solve the “differential explosion,” all signals in the system are proved to be semi-global uniformly ultimately bounded (SGUUB) by the Lyapunov function. Finally, the MATLAB simulation is set up, and the accurate tracking effect of the system is proved by the simulation in the presence of friction, modeling error, and dead-zone nonlinearity. The validity and the superior performance of the proposed control method under the downhole harsh environment and parameter perturbation is verified by the comparison simulation experiments.

Foundation of Ultradeep Boundary Detection Based on the Electric Field Characteristics

An ultradeep boundary detection method based on the characteristics of the electric field in a single well is proposed. Unlike any conventional azimuthal electromagnetic (EM) wave logging approach, the new design employs an open-loop half-circle antenna other than the tilted or transverse closed-loop coil antenna as the receiver. The voltage on the half-circle antenna varies periodically with the tool-face angle, which provides the azimuthal information of the boundary. To explore how this new measuring method works, we investigate the electric field characteristics around the receiving antenna. The voltage is calculated by the integral of the electric field. By analyzing the voltages on each segment and their serial connection, the reason is revealed for the significantly enhanced voltage on the half-circle antenna compared to the tilted/transverse closed-loop coil. It lays a new foundation of ultradeep boundary detection based on the electric field characteristic. The voltage response behaviors are further investigated with respect to the tool offset, frequency, distance to the boundary (DTB), and conductivity anomaly. The monotonous changing of the voltage is observed within a wide range of those parameters. The results show that the half-circle antenna has great potential in realizing ultradeep boundary detection with a small offset.

Random Weighting Adaptive Estimation of Model Errors on Attitude Measurement for Rotary Steerable System

During drilling, a rotary steerable system (RSS) is affected by vibration, rotation, and other random noises. This paper presents a random weighting adaptive estimation of model errors on attitude measurement for RSS drilling tools. The algorithm is used to estimate the covariance matrix of the dynamic model errors and the state prediction vectors for RSS tools, to reduce the effect of abnormal noises of the dynamic model on the estimation of state parameters. The random weighting estimations of observation’s systematic error and covariance matrices of observation error vectors to control the effect of observation model noises anomaly on state parameter estimation, enhance the use efficiency of the latest observation information, indirectly weaken the impact of model error on state parameter vector, and improve the accuracy of attitude calculation of RSS. Experimental results and comparison analysis demonstrate that the proposed algorithm achieves better outcomes than the Kalman filtering and Extended Kalman filtering. The maximum solution error is controlled at 0.15°, and the tool face angle error is less than 3°. It cannot only control the covariance matrix of the observation error vector and predicted residual vector, but it can also effectively resist the disturbances of kinematic model error. It also can improve the dynamic measurement accuracy of attitude parameters, and solves the problem of uncertainty in dynamic attitude measurement of rotary steerable drilling tools.

Integral Modeling for Deviation Correction Trajectory of the Mechanical Vertical Drilling System

The deviation correction trajectory of the mechanical vertical drilling system (MVDS) is very important because it is the final embodiment of performance. However, it is impossible to obtain it at the design stage, except when using simulation methods. In this paper, tool face angle model and other theoretical models were established, respectively, and the trajectory simulation method was created through model coupling. Next, the method was used to simulate the trajectory of MVDS under two typical working conditions. The results indicate that the critical deviation angle is the deviation control accuracy of the MVDS. The existence of critical deflection angle makes MVDS correct deviation and change azimuth at the same time, resulting in the trajectory being a three-dimensional curve, which has the tendency of drifting to the left. Furthermore, the deviation and azimuth change rate are constantly changing in the process of drilling. The results also show that the MVDS is unable to correct the horizontal displacement of the downhole. The proposed method and analysis results are helpful to find out and solve the problem of the current design as soon as possible, and to provide guidance for the subsequent structure optimization.

Sliding Mode Variable Structure Control of the Steerable Drilling Stabilized Platform Based on Disturbance Observer

A sliding mode variable structure control based on disturbance observer (SMVSCDOB) has proposed to tackle the uncertainty caused by friction in the stabilized platform on the rotary steerable drilling. Disturbance observer (DOB) is used to estimate the uncertainty in stabilized platform, and the estimated value is compensated by sliding mode variable structure control (SMVSC) to improve the control accuracy. The simulation experiment of control system is carried out with MATLAB, comparing the SMVSCDOB control method with proportional integral derivative (PID), PID+DOB, SMVSC. The simulation results show that the proposed method SMVSCDOB can better track the tool face angle, reduce the system error, suppress the friction interference, and enhance robustness of the system.

Research on Improving Accuracy of MWD Based on Support Vector Classifier and K-Proximity Method

With the development of horizontal Wells and extended reach Wells in the field of oil and gas exploitation, it is of great significance to the development of MWD which can measure the drilling trajectory in real time. Therefore, in recent years, Measurement while drilling (MWD) has been widely recognized and rapidly developed in the field of precise target drilling. Accelerometers and fluxgates are related to well trajectory measurement in the MWD. The external environment and the processing and installation error of the sensor lead to some errors in the measured value. Deviation caused by environmental interference and installation error leads to the low control precision of drilling tool attitude. In view of the shortcomings of the current calibration methods and the time-consuming and complicated operation of the traditional tri-axis orthogonal inclinometer calibration, this paper proposes the attitude error calibration method of the MWD based on the support vector classifier and the K-proximity method. First, a neural network model is established based on the measured calibration results and the measurements errors. Then, the K-proximity method is used to further classify the drill tool attitude data, and a neural network model combining the K-proximity method is constructed. Secondly, the software and hardware experimental platform for on-line calibration of the slant meter while drilling is built by using the calibration frame and the geomagnetic sensor. Finally, the experimental results showed that the mean deviation of well inclination angle and tool face angle is controlled within ±0.2°, and the mean deviation of azimuth is controlled within ±0.5°, which verified that the algorithm can increase accurate of drilling tool attitude.

Buckling configurations of tubular strings constrained in three-dimensional curved wellbores

A new model depicting the buckling configuration of a tubular string in a three-dimensional curved wellbore is proposed. During modeling, the toolface angle is considered, and the sinusoidal buckling and helical buckling of the tubular string are considered on the basis of alignment with either the lower curved side or the outer curved side of the wellbore. After modeling, the energy method is used to solve the model, and the critical buckling load, which is related to the relationship between the buckling configuration and the axial load, can be obtained. The critical buckling loads calculated using the model presented in this paper are consistent with the measured data from published experiments and the trends of the He and Kyllingstad model. The results of the new model also show that with an increasing wellbore curvature, the influence of the toolface angle on the critical buckling load and the characteristic parameters of the buckling configuration (wavelength, amplitude, and pitch) decreases. Based on the expressions for the quantitative relationships between these characteristic parameters and the axial load, procedures for calculating the contact force and the bending moment are given. The results for the contact force show that the calculated values from the Johancsik et al. model and the Mitchell model are the average values calculated using the procedures presented in this paper for tubular strings under sinusoidal buckling and helical buckling, respectively. The calculation results show that the influence of the toolface angle on the bending moment of a tubular string under helical buckling is less than that under sinusoidal buckling. By using this model, not only can the critical buckling loads, contact forces and bending moments of tubular strings in three-dimensional curved wellbores be calculated, but the trends of these calculated values with the buckling configuration can also be identified to guide the selection of the control parameters for tubular strings in the field.

Research of Downhole Instructions Decoding with Variable Drilling Fluid Displacement

This paper studied a downlink communication mode in which the effective downhole control instruction was generated by the use of drilling fluid pump displacement to format three descending and three ascending pulse instruction encoding. The principle of the downlink communication was introduced. The encoding idea of the downlink instruction code with 5-bit pulse was described. This downlink code was used to compose the corresponding control instruction which includes the information of the tool face angle and the guide force percentage. The downhole pulse widths were recognized by using STM32 as a micro control chip. The corresponding control commands were identified through the development of the software in the downhole drilling tool. Laboratory ground experiments demonstrated the feasibility of this downlink transmission mode by using variable drilling fluid displacement and the achievability of instruction decoding software.

Analysis of the main factors affecting bottom hole assembly Re-entry into main hole in forward drilling of fishbone wells

Wellbore re-entry is one of the critical technologies in fishbone well drilling. In the sequence of forward drilling, the main hole is designed as a low wellbore and the branched hole is designed as a high wellbore to ensure that the bottom hole assembly (BHA) can re-enter the main wellbore. However, there is no quantitative theoretical analysis regarding the reliability of wellbore re-entry at present. In order to analyze the reliability of the main hole re-entry, an analysis method was provided in this paper. Firstly, a detailed description of the wellbore model around the sidetracking point was built, which can consider the different build-up rate and bending direction of the main and branched hole. Secondly, a mechanical model based on the elastic rod theory was established to calculate the force and deformation of drill strings in the wellbore and a re-entry coefficient was introduced to evaluate the reliability of the main hole re-entry. Moreover, the effects of tool face angle, build-up rate of wellbore, junction wall geometry, and motor structure on the re-entry coefficient are analyzed. Finally, the main controlling factors were analyzed to distinguish the influence degree of different parameters on the re-entry coefficient. From the results, the angle between the bending direction of the branched hole and the tool face of the BHA is the decisive factor in the process of the main hole re-entry. The BHA should be controlled so that the angle is greater than 90° as much as possible. If such angle is less than 90°, the change of wellbore build-up rate, junction wall geometry, and motor structure can be used to increase the re-entry coefficient, such as increasing the build-up rate of the branched hole, wellbore enlargement rate, depth of the slot in the junction wall, and ridge width of the junction wall. Meanwhile, decrease the angle of bent housing, distance between the bending point and the top of bit, and outer diameter of the body stabilizer of the motor can also increase the re-entry coefficient. Among the effects of re-entry coefficient, the main controlling factors are the bend point position and the angle of bent housing.

Orientation load prediction method based on randomness/stochasticity of multi-source parameters in coiled tubing drilling

Well trajectory control is always the key point of directional drilling. Downhole parameters measurements and BHA (bottom hole assembly) configuration and adjustment have the vital and coupling effect on realizing effective and efficient trajectory control. However, error exists universally in both of these phases. Compared with previous fixed value prediction models on controlling parameters prediction, uncertainty analysis based method will make the prediction results more reasonable and meaningful to control the BHA performance. With the consideration of the randomness of downhole multi-source parameters in coiled tubing drilling, an uncertainty prediction method for orientation load at a certain confidence level is proposed. Based on the beam-column theory, the probability and statistics theory is introduced and the distribution forms of main parameters are counted statistically. The probability density function and cumulative probability function of the orientation load prediction model when pump off and pump on in coiled tubing drilling are derived. The lognormal distribution has better correlation with the probability function of the orientation load, and the analysis on the confidence interval of the orientation load is described. Then, several relevant validation experiments are carried out, and the prediction of uncertain orientation load in coiled tubing drilling is also made. Several conclusions are made regarding to the field trial results. The randomness of weight on bit, friction coefficient of the interfacial between drill string and borehole wall or drill string and casing and tool face angle are the principal factors affecting the uncertainty of orientation load in coiled tubing drilling. The orientation load predicted with the uncertainty method is not a single curve or a single value, but an interval with a certain confidence level. The width of interval window is determined by the accuracy and precision of parameters information. The higher the confidence level is, the wider the predicted interval of orientation load and the larger the uncertainty range become. Compared with the predicted results of the uncertainty method, an error exists in the result of traditional single-value calculation method. The error varies with the change of weight on bit and formations and can be positive or negative. Meanwhile, retrieving more accurate principal original dada, e.g. WOB, formation properties, will make the uncertainty of the prediction lower. This orientation load prediction method is helpful to improve the efficiency of directional drilling in coiled tubing drilling.

Research on Application of BJZM-MWD1 Measurement While Drilling System

Measurement While Drilling system has been more and more widely used in directional drilling construction on the surface of mines. The system provides guidance for drilling construction, because it can transmit drilling parameter signals such as the deviation angle, azimuth and tool face angle collected by downhole tools to the ground through the mud, and then the signals are analyzed and decoded by computer software to restore the actual parameter data. In drilling construction, the self-developed BJZM-MWD1 Measurement While Drilling system encountered problems such as great variation in the amplitude and width of mud pulse signals and the interference of pulse signals. By filtering and amplifying the mud pressure generated by the pulse signal, and improving software decoding algorithm, the stability and reliability of the system have been greatly improved, meeting the requirements in site construction.

The Development of a New Sensor for Tool Face Angle Based on Electrical Resistance

Trenchless technology is a type of construction that requires pipelines to be laid in a subsurface horizontal hole drilled by a trenchless drilling rig. To prevent drilling accidents during construction, the drilling trajectory needs to be controlled in real time according to the value of the tool face angle. However, existing tool face angle sensors cannot precisely control a trenchless drilling course due to a number of limitations such as low resolution, large temperature drift, and high requirements for accurate installation. In this regard, this paper presented a new tool face angle sensor based on the change in electrical resistance value. The tests mainly include four aspects, namely, accuracy, repeatability, resolution, and temperature drift. Numbers of tests showed that the measurement error was ±6 degrees, the repeatability was 2.54%, the minimum resolution was 6 degrees, and the temperature drift had no effect during the temperature changes from 0 to 80 degrees, which proved that the sensor is applicable for practical trenchless working conditions.

LMS Adaptive Filtering of Drilling Tool Vibration Signal

As the dynamic measurement of attitude parameter of the steerable drilling tool under vibration may be not accurate, the Least Mean Square (LMS) adaptive filtering algorithm is adopted to filter the influence of drilling tool vibration on the attitude measurement in this paper. The simulation results show that the measurement error of inclination angle after LMS adaptive filtering can be less than 0.1°, and the measurement error of tool face angle is less than 6°, which could effectively improve the attitude measurement accuracy of vertical steerable drilling tools; the results of inverse analysis on actual drilling data show that the actual measurement error of inclination angle after LMS adaptive filtering is about 3°, which is much smaller than that before filtering. It shows that LMS adaptive filtering can effectively filter the vibration signal of drilling tools and greatly improve the dynamic measurement accuracy of the tool attitude.