Measurement of Mud Motor Back-Drive Dynamics, Associated Risks and Benefits of Real-Time Detection and Mitigation Measures

2021 ◽  
Author(s):  
Junichi Sugiura ◽  
Steve Jones
Keyword(s):  
Pressure Sensors ◽  
Drill String ◽  
Sensor Data ◽  
Depth Interval ◽  
Drill Bit ◽  
Motor Power ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
The Past ◽  
Drive Dynamics

Abstract North America shale drilling is a fast-paced environment where downhole drilling equipment is pushed to the limits for maximum rate of penetration (ROP). Downhole mud motor power sections have rapidly advanced to deliver more horsepower and torque, resulting in different downhole dynamics that have not been identified in the past. High-frequency (HF) compact drilling dynamics recorders embedded in the drill bit, mud-motor bit box, and motor top sub (sub-assembly) provide unique measurements to fully understand the reaction of the steerable-motor power section under load relative to the type of rock being drilled. 3-axis shock, gyro and temperature sensors placed above and below the power section measure the dynamic response of power transfer to the bit and associated losses caused by back-drive dynamics. Detection of back-drive from surface measurements is not possible, and many measurement-while-drilling (MWD) systems do not have the measurement capability to identify the problem. Motor back-drive dynamics severity is dependent on many factors, including formation type, bit type, power section, WOB (weight on bit) and drill pipe size. The torsional energy stored and released in the drill string can be high due to the interaction between surface RPM (revolutions per minute)/torque output and mud-motor downhole RPM/torque. Torsional drill string energy wind-up and release results in variable power output at the bit, inconsistent rate of penetration (ROP), rapid fatigue on downhole equipment, and motor or drillstring back-offs and twist-offs. A new mechanism of motor back-drive dynamics due to the use of an MWD pulser above a steerable motor is discovered. HF continuous gyro sensors and pressure sensors were deployed to capture the mechanism in which a positive mud pulser reduces as much as one third of the mud flow in the motor and bit rotation speed, creating a propensity for a bit to come to a complete stop in certain conditions and for the motor to rotate the drillstring backward. We have observed the backward rotation of a PDC drill bit during severe stick-slip and back-drive events (-50 RPM above the motor), confirming that the bit rotated backward for 9 mS every 133.3 mS (at 7.5Hz), using a 1000-Hz continuous sampling/recording in-bit gyro. In one field test, multiple drillstring dynamics recorders were used to measure the motor back-drive severity along the drillstring. It is discovered that the back-drive dynamics are worse at the drillstring, approximately 1110 ft behind the bit, than these measured at the motor top-sub position. These dynamics caused drillstring back-offs and twist-offs in a particular field. A motor back-drive mitigation tool was used in the field to compare the runs with and without the mitigation tool, while keeping the surface drilling parameters nearly the same. The downhole drilling dynamics sensors were used to confirm that the mitigation tool significantly reduced stick-slip and eliminated the motor back-drive dynamics in the same depth interval. Detailed analysis of the HF embedded downhole sensor data provides an in-depth understanding of mud-motor back-drive dynamics. The cause, severity, reduction in drilling performance and risk of incident can be identified, allowing performance and cost gains to be realized. This paper will detail the advantages to understanding and reducing motor back-drive dynamics, a topic that has not commonly been discussed in the past.

Measurement of Mud Motor Back-Drive Dynamics, Associated Risks, and Benefits of Real-Time Detection and Mitigation Measures

2021 ◽  
pp. 1-19
Author(s):  
Junichi Sugiura ◽  
Steve Jones
Keyword(s):  
Rotation Speed ◽  
Pressure Sensors ◽  
Sensor Data ◽  
Depth Interval ◽  
Drill Bit ◽  
Motor Power ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
The Past ◽  
Drive Dynamics

Summary North American shale drilling is a fast-paced environment where downhole drilling equipment is pushed to the limits for the maximum rate of penetration (ROP). Downhole mud motor power sections have rapidly advanced to deliver more horsepower and torque, resulting in different downhole dynamics that have not been identified in the past. High-frequency (HF) compact drilling dynamics recorders embedded in the drill bit, mud motor bit box, and motor top subassembly (top-sub) provide unique measurements to fully understand the reaction of the steerable-motor power section under load relative to the type of rock being drilled. Three-axis shock, gyro, and temperature sensors placed above and below the power section measure the dynamic response of power transfer to the bit and associated losses caused by back-drive dynamics. Detection of back-drive from surface measurements is not possible, and many measurement-while-drilling (MWD) systems do not have the measurement capability to identify the problem. Motor back-drive dynamics severity is dependent on many factors, including formation type, bit type, power section, weight on bit, and drillpipe size. The torsional energy stored and released in the drillstring can be high because of the interaction between surface rotation speed/torque output and mud motor downhole rotation speed/torque. Torsional drillstring energy wind-up and release results in variable power output at the bit, inconsistent rate of penetration, rapid fatigue on downhole equipment, and motor or drillstring backoffs and twistoffs. A new mechanism of motor back-drive dynamics caused by the use of an MWD pulser above a steerable motor has been discovered. HF continuous gyro sensors and pressure sensors were deployed to capture the mechanism in which a positive mud pulser reduces as much as one-third of the mud flow in the motor and bit rotation speed, creating a propensity for a bit to come to a complete stop in certain conditions and for the motor to rotate the drillstring backward. We have observed the backward rotation of a polycrystalline diamond compact (PDC) drill bit during severe stick-slip and back-drive events (−50 rev/min above the motor), confirming that the bit rotated backward for 9 milliseconds (ms) every 133.3 ms (at 7.5 Hz), using a 1,000-Hz continuous sampling/recording in-bit gyro. In one field test, multiple drillstring dynamics recorders were used to measure the motor back-drive severity along the drillstring. It was discovered that the back-drive dynamics are worse at the drillstring, approximately 1,110 ft behind the bit, than these measured at the motor top-sub position. These dynamics caused drillstring backoffs and twistoffs in a particular field. A motor back-drive mitigation tool was used in the field to compare the runs with and without the mitigation tool while keeping the surface drilling parameters nearly the same. The downhole drilling dynamics sensors were used to confirm that the mitigation tool significantly reduced stick-slip and eliminated the motor back-drive dynamics in the same depth interval. Detailed analysis of the HF embedded downhole sensor data provides an in-depth understanding of mud motor back-drive dynamics. The cause, severity, reduction in drilling performance and risk of incident can be identified, allowing performance and cost gains to be realized. This paper will detail the advantages to understanding and reducing motor back-drive dynamics, a topic that has not commonly been discussed in the past.

scholarly journals Kinematics and dynamics analysis of new rotary-percussive PDM drilling tool

2021 ◽  
pp. 146134842198915
Author(s):  
Jialin Tian ◽  
Xuehua Hu ◽  
Liming Dai ◽  
Lin Yang ◽  
Yi Yang ◽  
...  
Keyword(s):  
Drill String ◽  
Structure Design ◽  
Drilling Process ◽  
Analysis Model ◽  
Drilling Tool ◽  
Stick Slip ◽  
Rate Of Penetration ◽  
Bottom Hole ◽  
Bottom Hole Assembly ◽  
The Impact

This paper presents a new drilling tool with multidirectional and controllable vibrations for enhancing the drilling rate of penetration and reducing the wellbore friction in complex well structure. Based on the structure design, the working mechanism is analyzed in downhole conditions. Then, combined with the impact theory and the drilling process, the theoretical models including the various impact forces are established. Also, to study the downhole performance, the bottom hole assembly dynamics characteristics in new condition are discussed. Moreover, to study the influence of key parameters on the impact force, the parabolic effect of the tool and the rebound of the drill string were considered, and the kinematics and mechanical properties of the new tool under working conditions were calculated. For the importance of the roller as a vibration generator, the displacement trajectory of the roller under different rotating speed and weight on bit was compared and analyzed. The reliable and accuracy of the theoretical model were verified by comparing the calculation results and experimental test results. The results show that the new design can produce a continuous and stable periodic impact. By adjusting the design parameter matching to the working condition, the bottom hole assembly with the new tool can improve the rate of penetration and reduce the wellbore friction or drilling stick-slip with benign vibration. The analysis model can also be used for a similar method or design just by changing the relative parameters. The research and results can provide references for enhancing drilling efficiency and safe production.

Study of stick–slip suppression and robustness to parametric uncertainty in drill strings containing torsional vibration tool using sliding-mode control

2021 ◽  
pp. 146441932110452
Author(s):  
Jialin Tian ◽  
Jie Wang ◽  
Siqi Zhou ◽  
Yinglin Yang ◽  
Liming Dai
Keyword(s):  
Torsional Vibration ◽  
Complex Dynamics ◽  
Sliding Mode ◽  
Parametric Uncertainty ◽  
Drill String ◽  
Lumped Parameter Model ◽  
Drilling Process ◽  
Drill Bit ◽  
Stick Slip ◽  
Drilling Operations

Excessive stick–slip vibration of drill strings can cause inefficiency and unsafety of drilling operations. To suppress the stick–slip vibration that occurred during the downhole drilling process, a drill string torsional vibration system considering the torsional vibration tool has been proposed on the basis of the 4-degree of freedom lumped-parameter model. In the design of the model, the tool is approximated by a simple torsional pendulum that brings impact torque to the drill bit. Furthermore, two sliding mode controllers, U1 and U2, are used to suppress stick–slip vibrations while enabling the drill bit to track the desired angular velocity. Aiming at parameter uncertainty and system instability in the drilling operations, a parameter adaptation law is added to the sliding mode controller U2. Finally, the suppression effects of stick–slip and robustness of parametric uncertainty about the two proposed controllers are demonstrated and compared by simulation and field test results. This paper provides a reference for the suppression of stick–slip vibration and the further study of the complex dynamics of the drill string.

Torsional Vibrations and Nonlinear Dynamic Characteristics of Drill Strings and Stick-Slip Reduction Mechanism

2019 ◽  
Vol 14 (8) ◽  
Author(s):  
Jialin Tian ◽  
Genyin Li ◽  
Liming Dai ◽  
Lin Yang ◽  
Hongzhi He ◽  
...  
Keyword(s):  
Torsional Vibration ◽  
Nonlinear Dynamic ◽  
Drill String ◽  
Drilling Process ◽  
Drill Bit ◽  
Torsional Vibrations ◽  
Reduction Mechanism ◽  
Nonlinear Dynamic Model ◽  
Stick Slip ◽  
Research Results

Torsional stick–slip vibrations easily occur when the drill bit encounters a hard or a hard-soft staggered formation during drilling process. Moreover, serious stick–slip vibrations of the drill string is the main factor leading to low drilling efficiency or even causing the downhole tools failure. Therefore, establishing the stick–slip theoretical model, which is more consistent with the actual field conditions, is the key point for new drilling technology. Based on this, a new torsional vibration tool is proposed in this paper, then the multidegree-of-freedom torsional vibrations model and nonlinear dynamic model of the drill string are established. Combined with the actual working conditions in the drilling process, the stick–slip reduction mechanism of the drill string is studied. The research results show that the higher rotational speed of the top drive, smaller viscous damping of the drill bit, and smaller WOB (weight on bit) will prevent the stick–slip vibration to happen. Moreover, the new torsional vibration tool has excellent stick–slip reduction effect. The research results and the model established in this paper can provide important references for reducing the stick–slip vibrations of the drill string and improving the rock-breaking efficiency.

scholarly journals Complex dynamics of drill-strings: Theory and experiments

2018 ◽  
Vol 211 ◽  
pp. 01002
Author(s):  
Marian Wiercigroch ◽  
Marcin Kapitaniak ◽  
Vahid Vaziri ◽  
Krishnan Nandakumar
Keyword(s):  
Mechanical Characteristics ◽  
Complex Dynamics ◽  
Drill String ◽  
Drill Bit ◽  
Stick Slip ◽  
Drill Bits ◽  
Low Dimensional ◽  
The University ◽  
Experimental Rig ◽  
Theory And Experiments

We investigate complex drill-string dynamics in a downhole drilling where strong nonlinear interactions between various types of vibration take place. First, we present a low dimensional model of the downhole drilling where a drill-bit cutting a rock formation has a strong coupling between torsional and axial oscillations. The model can be used to study drilling stability as an example results are given. Then we introduce a new experimental rig developed by the Centre for Applied Dynamics Research at the University of Aberdeen, capable of reproducing all major types of drill-string vibration. One of the most important features of this versatile experimental rig is the fact that commercial drill-bits, employed in the drilling industry, and real rock-samples are used. The rig operate in different configurations, which enables the experimental study of various phenomena, such as stick-slip oscillations, whirling and drill-bit bounce. It also allows to determine mechanical characteristics of the drill-bits, which are used to calibrate mathematical models.

scholarly journals The effect of high-frequency torsional impacts on the dynamic response of a drill string in a stick state

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401982857
Author(s):  
Liping Tang ◽  
Wei He ◽  
Xiaohua Zhu
Keyword(s):  
Dynamic Response ◽  
High Frequency ◽  
Impact Load ◽  
Drill String ◽  
Superposition Method ◽  
Drill Bit ◽  
Stick Slip ◽  
Mode Superposition Method ◽  
Study Results ◽  
The Impact

Stick–slip vibration is common in the oil well drilling process and is detrimental to down-hole equipment and drilling efficiency. In recent years, a new type of drilling technology, torsional impact drilling, has been developed to mitigate the stick–slip phenomena, particularly in the drilling of deep or abrasive formations. With this drilling technique, high-frequency torsional impacts are generated and applied to the drill bit, providing the drill bit with auxiliary energy. By mitigating or suppressing the stick–slip vibration, part of the energy wasted as a result of vibration can be regained. However, the effect of these impact loads on the dynamic response of a drill string in a stick state is unknown. In order to address this issue, a continuous system model of a drill string that includes torsional impact load was constructed. In the model, a Fourier series approach was used for the impact load, and the mechanical model was resolved with the mode superposition method. Case studies were done to understand the drill string dynamics, with and without the impact. The case study results demonstrate that high-frequency torsional impacts have little influence on the dynamic response of a drill string in a stick state.

Minimising Torsional Vibration Due to Stick Slip Using Z Technology for Drilling Energy Efficiency in Multiple Hard Stringers Field in Offshore Malaysia

2021 ◽  
Author(s):  
Mohamad Haikal Nordin ◽  
Lai Keng Looi ◽  
Pete Slagel ◽  
Mohamad Hafiz Othman ◽  
Abdul Razak Affandi ◽  
...  
Keyword(s):  
Torsional Vibration ◽  
Drill Pipe ◽  
Cost Savings ◽  
Wide Band ◽  
Static Friction ◽  
Drill String ◽  
Drill Bit ◽  
Stick Slip ◽  
Pull Out ◽  
Phase 1B

Abstract Field T is well known with its multiple layers of hard stringers that can go up to 25 ksi UCS at certain intervals, predominantly in 12-1/4" and 8-1/2" hole section. This can lead to stick-slip problem whereby the drill bit momentarily stalls due to high static friction, while the drill string keeps rotating. As a result, torque will buildup in pipe until it overcomes the friction at the bit, resulting in the drill pipe unwinding itself. Over time, this issue results in reduced drilling efficiency (i.e. lower ROP), eventually causing damage to the bit or worse, twisting off the BHA, which translates into high cost exposure to the Operator. During the exploration phase, the Operator required on average, 4 to 7 bit trips to drill 12-1/4" hole section and 2 to 4 trips were required to drill 8-1/2" hole section. The most reported reason to pull out of the hole were, BHA change out, downhole tool failure (DTF) and low rate of penetration (ROP). The bits’ inner & outer cutters were also reported to be damaged with dull grading as high as wear value of 7 or 8. Z technology is a torsional vibration mitigation system that uses wide band impedance (Z) matching concept that aims to absorb all torque waves arriving at top drive by overcoming inertia of motor & gearbox. The Z Technology changes the conventional hard boundary condition of a standard top drive (TD) RPM controller that is "stiff" (constant RPM) which results in full reflection of all torsional waves. A "stiff" TD control system leads to growth of standing waves (A combination of TD constant RPM & stick-slip "unwind" RPM) in the string which eventually may lead to torsional vibrations to the drill bit and/or motor housing/BHA. While drilling Development Phase 1B, Z Technology was seen to be effective in mitigating stick-slip. As a result, more mechanical specific energy (MSE) was available to be transmitted to the bit for formation rock removal. All three wells in the Phase 1B campaign managed to achieve the highest ROP in T field. This translated into cost savings in rig time and cost avoidance to Operator due to BHA damage. The paper will discuss the details of the Z Technology mechanism, its implementation and evaluating its effectiveness in minimizing torsional vibration due to the stick-slip issue.

Preliminary Study on Stick-Slip in Drillstring With Analytical Model Expressed With Neutral Delay Differential Equation

2014 ◽  
Author(s):  
Tomoya Inoue ◽  
Tokihiro Katsui ◽  
Chang-Kyu Rheem ◽  
Zengo Yoshida ◽  
Miki Y. Matsuo
Keyword(s):  
Differential Equation ◽  
Analytical Model ◽  
Delay Differential Equation ◽  
Drill Bit ◽  
Neutral Delay ◽  
Stick Slip ◽  
Scientific Drilling ◽  
Neutral Delay Differential Equation ◽  
Delay Differential ◽  
Slip Phenomenon

Stick-slip is a major problem in offshore drilling because it may cause damage to the drill bit as well as crushing or grinding the sediment layer, which is crucial problem in scientific drilling because the purpose of the scientific drilling is to recover core samples from the layers. To mitigate stick-slip, first of all it is necessary to establish a model of the torsional motion of the drill bit and express the stick-slip phenomenon. Toward this end, the present study proposes a model of torsional waves propagating in a drillstring. An analytical model is developed and used to derive a neutral delay differential equation (NDDE), a special type of equation that requires time history, and an analytical model of stick-slip is derived for friction models between the drill bit and the layer as well as the rotation speed applied to the uppermost part of the drill string. In this study, the stick-slip model is numerically analyzed for several conditions and a time series of the bit motions is obtained. Based on the analytical results, the appearance of stick-slip and its severity are discussed. A small-scale model experiment was conducted in a water tank to observe the stick-slip phenomenon, and the result is discussed with numerical analysis. In addition, utilizing surface drilling data acquired from the actual drilling operations of the scientific drillship Chikyu, occurrence of stick-slip phenomenon is discussed.

A Semi-Analytical Study of Stick-Slip Oscillations in Drilling Systems

2010 ◽  
Vol 6 (2) ◽  
Author(s):  
B. Besselink ◽  
N. van de Wouw ◽  
H. Nijmeijer
Keyword(s):  
Dynamic Analysis ◽  
Limit Cycle ◽  
Analytical Approach ◽  
String Model ◽  
Drill String ◽  
Axial Stiffness ◽  
Torsional Vibrations ◽  
Stick Slip ◽  
Rock Interaction ◽  
Stiffness And Damping

Rotary drilling systems are known to exhibit torsional stick-slip vibrations, which decrease drilling efficiency and accelerate the wear of drag bits. The mechanisms leading to these torsional vibrations are analyzed using a model that includes both axial and torsional drill string dynamics, which are coupled via a rate-independent bit-rock interaction law. Earlier work following this approach featured a model that lacked two essential aspects, namely, the axial flexibility of the drill string and dissipation due to friction along the bottom hole assembly. In the current paper, axial stiffness and damping are included, and a more realistic model is obtained. In the dynamic analysis of the drill string model, the separation in time scales between the fast axial dynamics and slow torsional dynamics is exploited. Therefore, the fast axial dynamics, which exhibits a stick-slip limit cycle, is analyzed individually. In the dynamic analysis of a drill string model without axial stiffness and damping, an analytical approach can be taken to obtain an approximation of this limit cycle. Due to the additional complexity of the model caused by the inclusion of axial stiffness and damping, this approach cannot be pursued in this work. Therefore, a semi-analytical approach is developed to calculate the exact axial limit cycle. In this approach, parametrized parts of the axial limit cycle are computed analytically. In order to connect these parts, numerical optimization is used to find the unknown parameters. This semi-analytical approach allows for a fast and accurate computation of the axial limit cycles, leading to insight in the phenomena leading to torsional vibrations. The effect of the (fast) axial limit cycle on the (relatively slow) torsional dynamics is driven by the bit-rock interaction and can thus be obtained by averaging the cutting and wearflat forces acting on the drill bit over one axial limit cycle. Using these results, it is shown that the cutting forces generate an apparent velocity-weakening effect in the torsional dynamics, whereas the wearflat forces yield a velocity-strengthening effect. For a realistic bit geometry, the velocity-weakening effect is dominant, leading to the onset of torsional vibrations.

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