A Combined Analytical and Numerical Approach to Analyze Mud Motor Excited Vibrations in Drilling Systems

Hohl, Andreas; Hohl, Carsten; Herbig, Christian

doi:10.1115/gt2015-42144

Cited by 7 publications

(1 citation statement)

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“…Fatigue is brought on due to a combination of cyclical loading and temperature weakening (Ba et al 2016). Delpassand (1999), Gamboa et al (2003), Hohl et al (2015), and Ba et al 2016 At 100% efficiency, such as that found in lab-scale drilling, it was found that the MSE would equal the rock compressive strength (Teale 1965). In the special case of ductile rather than brittle material failure, MSE will be roughly three times rock strength (Rafatian et al 2009).…”

Section: Fig 3: Illustration Of Stator and Rotor Configuration (Dyckmentioning

confidence: 99%

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

Elsayed

Hopkins

Dupriest

et al. 2020

Day 2 Wed, March 04, 2020

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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: Fig 3: Illustration Of Stator and Rotor Configuration (Dyckmentioning

confidence: 99%

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

Elsayed

Hopkins

Dupriest

et al. 2020

Day 2 Wed, March 04, 2020

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Reaming and Drilling Practice Optimization using Modeling and Simulation Techniques

Herbig

Linke

Reckmann

et al. 2016

Day 1 Wed, September 14, 2016

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Longer wells and increasing complexity of the bottom-hole assembly (BHA) are causing drilling operations to become harder to achieve. Combined with strict timelines and the demand for higher rates of penetration (ROP), the entire drilling system operates at its physical (loads, bending moment, etc.) and operational (drilled formation, drilling parameters, well path, etc…) limits. Exceeding these limits can induce excessive drilling vibrations and dysfunctions like whirl that can be harmful for bit, bottomhole assembly, reaming device or drillpipe. Neglecting operational limits can therefore lead to damage, wear and tool failures that ultimately result in nonproductive time (NPT) and higher cost. Additionally, the number of reaming operations increases. The added challenge of complex reaming operations demands supplementary planning effort. In this paper, the authors focus on prejob and post-well analysis using simulation and modeling techniques. The result of the analysis leads to optimized reaming and drilling practices that are further elaborated following close interaction with field personnel. Applying the improved drilling practices result in best-in-class performance and lower nonproductive time. In-house dynamics simulation software is used to calculate the natural frequencies and corresponding mode shapes of the BHA. Differences in BHA setup are associated, critical excitation sources identified and forced response analysis results compared. Data from various deployments of a high-end rotary steerable system (RSS) BHA with a reaming device are analyzed and used to validate the simulation results. The data is derived exclusively from a massive salt section (similar formation being drilled) to lessen the formation’s influence on drillstring dynamics. Incorporation of sophisticated simulation tools plus the close cooperation of field personnel resulted in excellent operational and drilling performance. In today’s challenging drilling applications, the insights gained have highlighted further opportunities for delivering optimal performance, and further assuring bit, BHA, reaming device and drillstring integrity.

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Development of an efficient Vibration Modeling Technique for Design-Related Optimization of Tools in the Global Drilling Environment

Hohl¹,

Heinisch²,

Oueslati³

et al. 2017

Day 4 Thu, March 09, 2017

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Severe vibrations in drilling systems and bottom-hole assemblies can be caused by cutting forces at the bit or mass imbalances in downhole tools such as mud motors. Vibrations can lead to reduced drilling performance, poor measurement quality and reduced reliability. Models are important to understand the phenomena and predict loads. So far models are established that calculate the dynamic behavior of the drilling system from a global point of view: The drilling system is modeled with simplified geometry and placed in the drilling environment under consideration of the wall contacts with the borehole and the fluid properties. Global models are typically used for optimization of drilling parameters such as the rotary speed or the flow rate with respect to estimated dynamic loads. Global models are not suitable for detailed modeling and analysis for optimization on a tool component level. A system-approach is established to overcome the limitations. A method is developed to connect a detailed 3D-model of a downhole tool with the model of the drilling system and the bit that is placed in the global drilling environment. The method enables new insights into the behavior of downhole tools that can be used to optimize downhole tools with respect to their reliability and their performance: Dynamic loads on tool components such as probes and pockets can be calculated to optimize the tool design and increase reliability. The probe design can be optimized to reduce the dynamic loads on sensor components and significantly increase the measurement quality. In a case study the method is validated with measurements. Herein, torsional eigenfrequencies and corresponding mode shapes which are localized to the bottom-hole assembly as well as the resulting tool stresses and loads are considered. The impact of a dampening tool to mitigate torsional vibrations is discussed. In a second example the capability of the method to capture lateral vibrations under consideration of wall contacts and mass imbalances is shown. The method is used to optimize the design of a downhole tool to decrease the dynamic loads at sensor components that are placed in a probe. The system-approach of the method allows to efficiently simulating the vibrational behavior of tool parts in an arbitrary detail and in a global drilling environment. The new method enables improved tool design for performance and reliability and increased measurement quality.

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A Combined Analytical and Numerical Approach to Analyze Mud Motor Excited Vibrations in Drilling Systems

Cited by 7 publications

References 0 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

Reaming and Drilling Practice Optimization using Modeling and Simulation Techniques

Development of an efficient Vibration Modeling Technique for Design-Related Optimization of Tools in the Global Drilling Environment

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