A Physical and Experimental Investigation into the Effects of Drilling Vibrations on Drilling Efficiency Estimates: Pathway to Vibration Assisted Drilling
Date
2021-08-26
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Abstract
Mechanical Specific Energy (MSE), the amount of work done to drill a unit volume of rock, has been evolving as an important parameter to indicate drill-bit efficiency by quantifying bit-rock interactions. Until now, the industry application has been on drilling efficiency, however, the study extends this application by utilizing MSE for estimating subsurface rock properties such as rock strength. Once known, rock strength may be used for improved geosteering – since measurement of MSE is at the bit – or for completion designs. This study is divided into two parts: developing a physical model from real-time drilling data and experimental study, paving the pathway for vibration assisted drilling. For physical model, high resolution (10-second) drilling data is used for the analysis. An updated MSE calculation is proposed which incorporates mud motor dynamics, frictional losses along the drill-string, and drillstring dysfunctions (i.e., vibration). Two new parameters in the form of Hydraulic Specific Energy (HSE), that estimates role of hydraulic impact force at the formation, and Vibration Specific Energy (VSE), that estimates the energy associated with vibrations and its impact on the translational (weight on bit) and rotational energy (Torque) supplied from the top-drive, have been introduced. For experimental work, the study investigates the impact of induced low frequency axial excitations on drilling actions of Polycrystalline Diamond Compact (PDC) bits. Variations in drilling efficiency have been quantified through a series of experiments at different intensities (frequency and amplitude) of axial excitations. Prior work has identified the challenges of bit wear due to high frequency oscillations. Axial vibrations were induced using a controlled linear actuator at the cutter-rock interface, in low frequency regime (up to 5 Hz) using a rotary experimental setup.
The outcome of this study provides a physical evidence for quantifiable use of MSE as a tool to predict downhole geomechanical properties such as rock strength directly from drilling data. Experimental outcomes can also be adopted as real-time drilling practice to improve the peak drilling performance and provide evidence for the need to incorporate vibration induced force losses into the equation of drilling efficiency for correct estimations of rock strength downhole.
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Trivedi, A. S. (2021). A Physical and Experimental Investigation into the Effects of Drilling Vibrations on Drilling Efficiency Estimates: Pathway to Vibration Assisted Drilling (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.