Eliminating Stick-Slip by Managing Bit Depth of Cut and Minimizing Variable Torque in the Drillstring

Davis, Joshua E.; Smyth, Gregory F.; Bolivar, Neil; Pastusek, Paul

doi:10.2118/151133-ms

Cited by 31 publications

(5 citation statements)

References 5 publications

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“…20, results in reduced torque oscillations (Ertas et al 2013)). DOCC features have often been used to improve directional control and mitigate stickslip due to the reduction in torque oscillations (Ertas et al 2013;Denney 2011;Davis et al 2012;Barton et al 2007). However, the proper design of a DOCC system has the potential to improve motor life due to the reduction in overall vibrations at the bit.…”

Section: Depth Of Cut Controlmentioning

confidence: 99%

Theoretical Vs. Actual Mud Motor Performance in Unconventional Formations and Strategies to Extend Motor Life

Elsayed

Hopkins

Dupriest

et al. 2020

IADC/SPE International Drilling Conference and Exhibition

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The continued growth in unconventional drilling has resulted in downhole motors being pushed to drill more complex geometries faster, often higher downhole temperatures. This has resulted in increased rates of failure for downhole motors. The most common method to postpone motor failure has been to select a larger motor. This option ignores the root causes of motor failure and is shown to actually not improve failure rates. Impetus for this work centered on an operator who was experiencing high rates of motor failure, however in the process of investigating the failures, important findings were made that apply to any BHA with a motor. Damage occurs in all motors in the data set, regardless of whether or not they are considered "failed." This points to a potential, unrecognized industry-wide issue wherein motor performance may be degrading over a run and is not recognized by operations teams. The result is a version of "hidden NPT" which is limiting drilling performance in wells drilled with downhole motors. Calculating the RPM factors on the operator's wells using actual motor speeds measured by downhole sensors show that motor degradation is a significant problem, resulting in a reduction of up to 40% in bit RPM. In order to measure performance, motor properties are used to convert the traditional surface MSE measurement into a more representative downhole MSE. Further refinement of this metric was tested as downhole MSE is calculated using a simple factor and a more exact but complicated multi-dimensional correlation. Drilling data is used to show that the simplicity of the simple factor more than offsets minor loses in MSE accuracy. As noted, the real time RPM factors are also computed using downhole data showing the stark differences between the actual factors and the originally reported factors. The difference is used to determine the degree of motor damage while drilling. A suite of downhole sensors was placed above and below the motor to monitor the rate of motor damage. Differential pressure was also analyzed in the frequency domain spectrum to demonstrate the damaging effect of bottom hole assembly (BHA) whirl during rotating. The use of depth of cut control (DOCC) is analyzed as a method to improve motor efficiency and decrease damage. Two identical wells and BHA's are compared, one with and one without DOCC. The uses of the first derivative of differential pressure is suggested as a method to better quantify and visualize the effects of DOCC. Ultimately, the research presented provides quantitative insights into the operation of a motor, and shows that motor performance is not as expected based specification sheet values.

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Section: Depth Of Cut Controlmentioning

confidence: 99%

Theoretical Vs. Actual Mud Motor Performance in Unconventional Formations and Strategies to Extend Motor Life

Elsayed

Hopkins

Dupriest

et al. 2020

IADC/SPE International Drilling Conference and Exhibition

View full text Add to dashboard Cite

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“…Key elements of this drilling efficiency program included vibration modeling and optimization of the bottom hole assembly (BHA) configuration [25][26][27][28] , bit redesign and depth of cut control elements [29][30][31][32] , use of larger diameter drill pipe 33 , and field trials of an active damping top-drive torque control system 34 . In addition, a real-time drilling parameter optimization system was developed to continuously monitor the Mechanical Specific Energy (MSE) while drilling 35,36 .…”

Section: Fast Drill Process Extensionsmentioning

confidence: 99%

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

Valenta

Walker

Pastusek

et al. 2014

SPE Annual Technical Conference and Exhibition

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The operator's drilling efficiency program has been expanded to a Limiter Redesign Process that seeks to optimize all rig time, including flat time. As drilling efficiency gains have been achieved, flat time now accounts for roughly 80% of the total rig time and approximately 70% of the total cost of drilling and completions operations; leaving 20% of rig time for drilling. This fact led to the generation of a comprehensive Flat Time Reduction (FTR) program.The Fast Drill Process has become a well-known workflow to identify hole-making limiters and mitigate them through "relentless redesign to the economic limit of performance". Efforts to increase drilling efficiency continue, and this process has yielded a continuous increase in the overall footage per day and a reduction in flat time within individual hole sections.To address operations that do not include drilling of rock, the operator has launched a similar effort and workflow process which focuses on "flat time" portions of the well construction process. This has become a key focal point in the organizations approach to maximize capital efficiency. The Flat Time Reduction process provides an environment in which operations are optimized while further enhancing a workplace where "Nobody Gets Hurt."This process is yielding significant savings globally and has been accomplished through planning, "real-time" recognition and response, collaboration with service providers, and a focus on Non-Productive Time (NPT) reduction while continuously improving safety performance. Field applications of limiter redesign are discussed in this paper. The purpose of this paper is to present the current status and specific approaches being used to reduce flat time and share the workflow process.In 2004, the operator started a pilot program to determine if drilling performance could be improved by analyzing and reacting to trends in Mechanical Specific Energy (MSE) 1, 2, 3 by rig site personnel on a real time basis. MSE is a performance measurement parameter that approximates the bit's drilling efficiency and is a function of the weight-on-bit (WOB), surface torque, bit rotation per revolution (RPM) and the rate of penetration (ROP) for a given hole size. When the bit is drilling efficiently, MSE will be steady and will approximate the rock's confined compressive strength. When dysfunction occurs, MSE increases

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“…These are all mitigation measures that have been used and proven by the operator. For example, Davis et al (2012) describe the successful application of increasing drillpipe size and the addition of depth of cut control elements to reduce bit aggressiveness to mitigate stick/slip and dramatically improve drilling footage per day. The particular results in Fig.…”

Section: Mitigation Via Redesignmentioning

confidence: 99%

Drillstring Mechanics Model for Surveillance, Root Cause Analysis, and Mitigation of Torsional and Axial Vibrations

Ertaş

Bailey

Wang

et al. 2013

SPE/IADC Drilling Conference

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Vibrations have been identified as one of the most frequent and persistent performance limiters by limiting weight-on-bit, rate of penetration, or borehole quality even when they may be low enough not to cause damage to downhole tools and equipment.A general purpose drillstring mechanics model has been developed to analyze axial and torsional vibrations in the frequency domain and provide vibration indices indicative of dysfunction in these modes. The model utilizes transfer matrices to solve for harmonic perturbations around a baseline solution obtained from a torque-and-drag type analysis, and accounts for effects of well path, tool joints, viscous damping due to the drilling fluid, surface boundary conditions, bit characteristics, and special vibration mitigation tools. The model supports workflows for real-time vibration surveillance as well as post-drill root cause analysis and well redesign. For example, real-time stick/slip severity monitoring is enabled using 1-second surface measurements. As a well redesign tool, a large number of design alternatives can be quickly evaluated to mitigate vibrations.Case studies utilizing high-frequency surface/downhole drilling mechanics data validated the model and identified three types of torsional dysfunctions with distinct signatures and mitigators: Unstable Stick/Slip, an instability associated mostly with the lowest-frequency torsional resonance of the drillstring; Bit/Bottomhole Assembly (BHA) Stall, intermittent, sudden mechanical jamming at the bottom of the drillstring; and Synchronous Torsional Oscillation, the amplification of periodic excitations at torsional resonances of the drillstring. In one case study, the stick/slip surveillance tool was superior to realtime downhole measurements in lag time, bandwidth, and accuracy. In another case, the root cause of prevalent Unstable Stick/Slip was identified as velocity-weakening aggressiveness of the bit. Among redesign options using a topdrive controller tuned to damp out the lowest-frequency torsional resonance was deemed most effective. One such controller was evaluated in the field and was very effective at mitigating stick/slip in subsequent wells. IntroductionThe operator's drilling performance-management process (Dupriest et al. 2005a;Dupriest et al. 2005b;Remmert et al. 2007) has identified vibrations as one of the most frequent and persistent performance limiters. The issue is not restricted to potential damage to downhole tools and equipment or non-productive time caused by severe vibrations. Even low levels of vibration may impact performance by limiting weight-on-bit, rate of penetration, or borehole quality. A recently deployed lateral vibration modeling tool, which was developed to enable drilling engineers to design vibration resistant BHAs, has been providing substantial performance gains in worldwide drilling operations (Bailey et al. 2008;Bailey et al. 2010a;Bailey et al. 2010b). In order to complement this capability for other vibrational modes, a general purpose model has been developed to ana...

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Eliminating Stick-Slip by Managing Bit Depth of Cut and Minimizing Variable Torque in the Drillstring

Cited by 31 publications

References 5 publications

Theoretical Vs. Actual Mud Motor Performance in Unconventional Formations and Strategies to Extend Motor Life

Theoretical Vs. Actual Mud Motor Performance in Unconventional Formations and Strategies to Extend Motor Life

Maximizing Capital Efficiency by Expanding the Limiter Redesign Process to Flat Time Operations

Drillstring Mechanics Model for Surveillance, Root Cause Analysis, and Mitigation of Torsional and Axial Vibrations

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