Investigation of Bit-Rock Interaction for Rotary Drilling and Influence on Penetration Rate

Zhong, Jinghan (2016) Investigation of Bit-Rock Interaction for Rotary Drilling and Influence on Penetration Rate. Masters thesis, Memorial University of Newfoundland.

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Abstract

In this thesis a comprehensive investigation of non-natural vibration on enhanced drilling performance is studied. The Drilling Technology Laboratory (DTL) at Memorial University of Newfoundland has been working on a passive Vibration Assisted Rotational Drilling (p-VARD) tool which helps to increase the drilling rate of penetration (ROP) during laboratory testing and filed work for this couple of years. It has been proven by laboratory experiments and filed work that axial vibration can play a dramatically positive role in improving drilling ROP. Meanwhile, the laboratory measurement and field trial results show that the new passive vibration tool with sensor-sub can provide compatible and accurate data to identify drill string motions including rotatory speed, bit orientation, and bit vibrations including axial, lateral, torsional vibrations and bit whirl. These raw data from each drilling experiment can supply a sufficient research basis for numerical simulation. This thesis focuses on the effect of axial vibration on polycrystalline diamond compact (PDC) bit drilling performance using Discrete Element Method (DEM) simulation and experiments with the new vibration tool. Drill-off tests were conducted in the laboratory with axial vibration on the drill string. Vibration properties were adjusted by different settings of spring compliance and dampening layers. In order to study the cutting performance of the new tool, a PFC2D (Particle Flow Code in 2 Dimensions) numerical model was developed to simulate the micro-crack generation and propagation during the drilling process in synthetic rock samples. This experimental data was used to calibrate this numerical model to real drilling situations. The analyses of the Mechanic Specific Energy (MSE), the Material Removal Rate (MRR) and the Depth of Cut (DOC) are compared with a non-vibration case to evaluate ROP and drilling efficiency. The simulations result demonstrated significant increase in drilling performance when the p-VARD tool was used in the process. Simulation results of the two types of conditions of tools were analyzed and compared in lab and field work experiment respectively. The experimental data agrees with numerical simulation results which indicate it as a promising method to simulate PDC cutter-rock interaction with DEM modelling using the new pVARD tool.

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