Drilling Performance Research Articles

Determination of Suitable KCl Polymer Mud Properties for POK Field

Most oil and gas wellbores are drilled using water based mud (WBM), but this is the case when drilling through non-reactive formations that does not contain swelling shale. In reactive shale formation, KCl Polymer additive should be added to the mud. It will provide a source of potassium ions which will help stabilizing the reactive shale. So that the swelling process is minimized. The basis of the KCL polymer mud system is the polymer used as a wrapper for rock pieces during borehole cleaning process. In the wells in the POK Field, the use of polymer KCL mud is evaluated on trajectories of 17½", 12¼", and 8½ ". The evaluation process uses parameters that aim to find the suitable mud properties that result in the best drilling performance in each trajectory in the POK Field well. The determination of the best drilling performance is based on drilling time. The parameters used in this research are: rate of penetration, trip time, yield point (YP), K+ content, mud weight (MW), viscosity (m), plastic viscosity (PV), and gel strength (GS), mud cake, pH, and additional parameter (excess cement). Based on analysis and investigation, the best drilling performance for trajectory of 17½" occured in POK 1075 well, while the best performance for the trajectories 12¼” and 8½” occured in POK 1058 well. Therefore the KCl polymer mud properties used in these wells can be used as a reference and basis for planning mud systems for the next wells.

Rock-breaking performances of innovative triangular-shaped polycrystalline diamond compact cutter

Due to high hardness and high abrasion, conventional planar polycrystalline diamond compact (PDC) cutters can easily get broken and dull when drilling in (ultra-)deep formations. To enhance the drilling performance, an innovative kind of non-planar PDC cutter, namely, a triangular-shaped PDC cutter, has been developed by altering the 2D planar cutting face into a 3D cutting structure of a triangular trustum of a pyramid. According to the numerical simulation results, the triangular-shaped PDC cutter can easily break hard rocks by a smaller cutting force than the conventional planar PDC cutter. Furthermore, it requires less mechanical specific energy for breaking the same volume of rock than the planar PDC cutter. The triangular-shaped PDC cutter shows great potential in improving the drilling performances of the PDC bit in hard and abrasive formations.

Implementation of a novel eccentric dog leg reamer in oil well drilling

A high-quality wellbore is generally considered to have a gauge hole, a smooth wellbore and a wellbore with minimum tortuosity. Therefore, dog leg reamers (DLRs) have been recently proposed and implemented to specifically provide a high-quality wellbore which in turn improves the overall drilling performance. These improvements include smoothening the wellbore from high in place dogleg, lowering drag values, improving the tripping performance, increasing the success ratio of wireline logging tools to reach total depths and enhancing the casing and cement jobs. DLRs are an eccentric string reamers which have been recently designed and optimized using modelling software, and a mathematical model has been deduced to specify the weight and torque distribution between the bit and DLR based on mechanical specific energies at bit and DLR with a model accuracy closely matches the field data. A total of twenty five runs all over the world have been performed to date in hole sizes ranging from 12¼″ to 6″. Directional work has also been performed showing good directional control with this system, and no vibration issues have been reported. The development of this down hole tool has added new capability to the industry in the optimization of hole enlargement applications. The benefit is realized in a reduced number of days required to drill the well and in reduced total well cost. In addition, getting casing into the hole sooner reduces the accompanying risks and can contribute to reducing operational nonproductive time. Several case studies from three fields X, Y and Z from Egypt, Oman and Saudi Arabia, respectively, will be discussed to demonstrate the positive economic impact of deploying DLR in not only the deviated holes but also in vertical wells.

Effect of hyperthermal cryogenic environments on the performance of piezoelectric transducer

Abstract China’s asteroid exploration mission plans to use multiple ultrasonic drill cross-drilling to anchor the spacecraft on the asteroid surface. To solve the problem of the environmental temperature adaptability of the ultrasonic drill on the surface of asteroids, we propose an ultrasonic drill driven by the Single crystal piezoelectric rings piezoelectric transducer and studied the resonant characteristics of the piezoelectric transducer at hyperthermal and cryogenic environments. First, the ultrasonic drill’s structure and working principle are proposed along with the detailed design of the transducer. Then, the theoretical analysis and finite element method were used to establish the frequency-temperature model of the transducer, respectively. It can be simulated the effect of temperature on the resonant frequency and the nodal plane offset of the transducer. Finally, experiments were conducted to verify the change law of the resonant frequency of the transducer, and tested the drilling performance of the ultrasonic drill in hyperthermal and cryogenic. Our results showed that the transducer’s resonant frequency decreases with the increase of temperature, which is approximately linear; the ultrasonic drill can maintain good drilling performance in the temperature range of −175 to 100 °C. Meanwhile, the drilling pressure is only 5 N, and the drilling power is less than 40 W. This article fills the research gap in the resonant performance of ultrasonic drill in hyperthermal and cryogenic environments, and provides a technical reference for the application of ultrasonic drill in extraterrestrial environments.

Improving drilling performance through optimizing controllable drilling parameters

The prediction of the drilling rate of penetration (ROP) is one of the key aspects of drilling optimization due to its significant role in reducing expensive drilling costs. Many variables could affect ROP, which can be classified into two general categories; controllable operational variables and uncontrollable or environmental variables. Minimizing the drilling cost can be achieved through optimizing the controllable drilling parameters. As a direct result, the drilling speed will be increased while maintaining safe practices. The primary purpose of this study is to address the simultaneous impact of controllable parameters such as weight on bit (WOB), revolutions per minute, and flow rate (FR) on the rate of penetration (ROP). Response surface methodology was applied to develop a mathematical relation between operational controllable drilling parameters and ROP. To accomplish this, actual field datasets from several wells drilled in Southern Iraq in different fields were used. The second purpose of this study was to identify all prospective optimal ranges of these controllable parameters to obtain superior drilling performance with an optimum ROP. The obtained results showed that the developed model offers a cost-effective tool for determining the maximum ROP as a function of controllable parameters with reasonable accuracy. In addition, the proposed model was used to estimate optimal combinations of controllable drilling parameters for various depths. The results have shown that FR has the most significant effect on ROP variation with a sum of squares values of 23.47. Applying high WOB does not permanently improve ROP but could result in reducing ROP for some cases. The developed mechanical specific energy model for polycrystalline diamond compact (PDC) bit with vertical and deviated wells can estimate combinations of controllable drilling parameters. The developed model can be successfully applied to predict and optimize the drilling rate when using PDC bits, hence reducing the drilling time and the associated drilling cost for future wells.

Effect of micro double helical grooved tools on performance of electric discharge drilling of Ti-6Al-4V

Machining of complex features and holes on superalloys is a topic of both industrial and academic interest. Though the demand for high aspect ratio holes on Ti-6Al-4V is high in aerospace, biomedical and chemical industries, machining the same is very challenging due to the low thermal conductivity and debris accumulation in the machining zone. The present-day methods of hole drilling by unconventional methods like Electric Discharge Machining (EDM) make use of electrodes with poor flushing capabilities. Hence the motivation of the present work is to develop a method to modify the geometry of Electric Discharge Drilling (EDD) tools in order to enhance debris removal. For the first time an attempt has been made to machine micro double-helical grooves on EDD tools in a single pass. Solid, single-helical and double-helical electrodes are developed and through-holes are drilled on a Ti-6Al-4V workpiece. A comparative analysis of the performance of these three types of tools with respect to the machining time, electrode wear rate and hole quality is carried out. From Computational Fluid Dynamics (CFD) simulations it is seen that the double-helical grooved tool is superior in debris removal. The best values of the machining time of 183.33 s, overcut of 2.19 mm, hole taper angle of 7.93° and area of recast layer of 6.66 mm2 are obtained on the holes machined using double-helical electrodes. The mentioned tool has the potential to overcome the problem of debris removal in high aspect ratio hole drilling and surpass the present-day electric discharge drilling tools.

Analysis and optimization of laser drilling process during machining of AISI 303 material using grey relational analysis approach

Surface roughness and heat-affected zone (HAZ) are the important features which influence the performance of the laser-drilled products. Understanding the influence of laser process parameters on these responses and identifying the cutting conditions for simultaneous optimization of these responses are a primary requirement in order to improve the laser drilling performance. Nevertheless, no such contribution has been made in the literature during laser drilling of AISI 303 material. The aim of the present work is to optimize the surface roughness (Ra) and HAZ in fibre laser drilling of AISI 303 material using Taguchi-based grey relational analysis (GRA). From the GRA methodology, the recommended optimum combination of process parameters is flushing pressure at 30 Pa, laser power at 2000 W and pulse frequency at 1500 Hz for simultaneous optimization of Ra and HAZ, respectively. From analysis of variance, the pulse frequency is identified as the most influenced process parameters on laser drilling process performance.

Achieving and Maintaining Safety in Healthcare Requires Unwavering Institutional and Individual Commitments.

In 2000, “To Err Is Human” brought to light the fact that the estimated number of people dying from medical errors occurring in hospitals exceeded those that die from motor vehicle accidents (MVAs), breast cancer, or acquired immunodeficiency syndrome (AIDS) - three causes receiving far more public attention. The report prompted the gradual adoption of safety processes developed in the nuclear and aviation industries.However, sophisticated engineering solutions to operations are not enough. High and low mortality hospitals have similar processes and procedures, but low-mortality hospitals are more proficient at recognizing and managing serious complications as they unfold. This ability to rescue a deteriorating situation (resilience) reflects a healthier safety culture. Organizations move within the safety space in the direction of either more or less resilience depending on the fluctuation of their safety culture.Improving resilience requires transforming learned safety practices into a “habit” in conjunction with accepting accountability. Personal accountability means commitment to safe practices along with effective and transparent reporting of near misses/close calls and adverse events (AEs). Institutional accountability means putting safety first by ensuring the availability of appropriate resources, role leadership modeling, and effective management of sentinel events (SEs) to reduce harm occurrence and re-occurrence. This requires a more robust root cause analysis (RCA) process to guarantee that action plans produce strong and effective corrective measures.Synergistic coaching interventions include instilling the awareness that failure can and will happen, mapping team talents, and assessing gaps. These interventions will optimize group expertise, reaffirming the concept of institutional and personal accountability. The unending performance of drills will sustain the group resilience under both expected and unexpected conditions.Given the strong correlation between practice environment and outcomes, sustained improvement of the safety climate will produce more robust safety behaviors and ultimately better outcomes.

Effects of mono/hybrid nanofluid strategies and surfactants on machining performance in the drilling of Hastelloy X

This study examined the effects of dry, base fluid, mono and hybrid nanofluid cooling/lubrication conditions on machining performance in drilling of nickel based Hastelloy X superalloys. Nanofluids were prepared by adding 0.6 vol% graphene nanoplatelets (GNP) and/or hexagonal boron nitride (hBN) with or without addition of 0.25 wt% sodium dodecyl sulfate (SDS) and/or gum arabic (GA) as surfactants into the cutting lubricant. Drilling experiment were performed at two different cutting speeds (20 and 30 m/min), two different feed rates (0.04 and 0.06 mm/rev) and a constant drilling depth (13.5 mm). Cutting force, hole quality (surface roughness and deviations in diameter, circularity and cylindricity), cutting temperature, burr height, tool wear and tool life were selected as the performance criteria. The best results with regard to cutting force, hole quality, burr height, and tool wear were obtained under SDS added hBN/GNP hybrid cutting, whereas the best results for cutting temperature were achieved under hBN/GNP hybrid cutting condition without surfactants. In terms of tool wear, after 10 holes under dry cutting, flank wear on the drill was measured as 0.281 mm, whereas after 60 holes under hBN/GNP-SDS cutting condition, it was measured as 0.135 mm. This indicated a 51.96% improvement in tool wear compared to dry cutting. Among the mono nanofluids, the hBN-SDS cutting condition delivered the best performance, whereas among the hybrid nanofluids, the hBN/GNP-SDS cutting performed the best. Finally, evaluation of the surfactants added to the nanofluids revealed that SDS surpassed GA in terms of machining performance.

Physics-Based Rate of the Penetration Prediction Model for Fixed Cutter Drill Bits

Abstract The drilling process is one of the most important and expensive aspects of the oil and gas industry. Its economic feasibility is a direct relation to good planning that has high dependence on an accurate prediction of the rate of penetration (ROP). Knowledge of drilling performance through ROP prediction models is a vital tool in the development of a consistent drilling plan and allows industry players to anticipate issues that may occur during a drilling operation. Additionally, as some drilling parameters (such as rotary speed, weight on bit (WOB), and drilling fluid flowrate), an accurate prediction of the ROP is crucial to the optimization of drilling performance and contributes to reducing drilling costs. Several approaches to predict the drilling performance have been tried with varying degrees of success, complexity, and accuracy. In this paper, a review of the history of drilling performance prediction is conducted with emphasis on rotary drilling with fixed cutter drill bits. The approaches are grouped into two categories: physics-based and data-driven models. The paper’s main objective is to present an accurate model to predict the drilling performance of fixed cutter drill bits including the founder point location. This model was based on a physics-based approach due to its low complexity and good accuracy. This development is based on a quantitative analysis of drilling performance data produced by laboratory experiments. Additionally, the validation and applicability tests for the proposed model are discussed based on drill-off tests (DOTs) and field trials in several different drilling scenarios. The proposed model presented high accuracy to predict the fixed cutter drill bit drilling performance in the 27 different drilling scenarios which were analyzed in this paper.

Fractional-order controllers for stick-slip vibration mitigation in oil well drill-strings

Drillstring–borehole interaction can produce severely damaging vibrations. An example is stick–slip vibration, which negatively affects drilling performance, tool integrity and completion time, and costs. Attempts to mitigate stick–slip vibration typically use passive means and/or change the operation parameters, such as weight on bit and rotational speed. Automating the latter approach, by means of feedback control, holds the promise of quicker and more effective mitigation. The present work presents three separate fractional-order controllers for mitigating drillstring slip–stick vibrations. For the sake of illustration, the drillstring is represented by a torsional vibration lumped parameter model with four degrees of freedom, including parameter uncertainty. The robustness of these fractional-order controllers is compared with traditional proportional-integral-derivative controllers under variation of the weight on bit and the drill bit’s desired rotary speed. The results confirm the proposed controllers effectiveness and feasibility, with rapid time response and less overshoot than conventional proportional-integral-derivative controllers.

Integrating risk management concepts into the drilling non-productive time

Introducing the non-productive time (NPT) concepts in the 1960s was a necessity dictated by the ever-increasing cost and complexity of the oil and gas well drilling. The NPT definition stayed unsettled until two decades later, the definition converged toward its accepted current definition of “the time when planned or out-of-plans drilling-related activities do not add value to the operation objectives.” NPT as it is defined in drilling nowadays is a form of time waste or loss which adversely impacts the overall efficiency of the drilling operation. Since the 1980s, risk management (RM) has become a sound technique to evaluate operational losses or wastes of many resources, including time. This paper presents an attempt to couple RM techniques with NPT philosophy together with other concepts such as Systems Thinking, Synergy, Continuous Improvement, and Total Quality. These concepts and derived techniques suit well controlling the intolerable waste that shows up in the form of delay in operations and materializes into most of the undesirable costs of drilling. These concepts, adopted herein, were applied on data from 60 rigs which were used to drill 250 wells for a period of 1 year of operation. In all 19 types of NPT were considered. A Java software model was developed and used to express NPT as an undesired event with probability of happening, in order to follow with RM terminology. The probability levels (related to the NPT values) for each rig were then defined and further classified into the four familiar ranks and their colors as used in RM: Acceptable (green), Tolerable (yellow), Inadmissible (orange), and Unacceptable (red). A matrix was established for all NPT categories and for the 60 rigs and was then named Rig-NPT Risk Matrix. A maximum probability ceiling was established as a reference for unacceptable risks of all NPT categories and for all the 60 rigs. Finally, sets of risk control recommendations were proposed to minimize the NPT in order to improve rigs performance. The concept of NPT and the science of RM when integrated gave a new approach to minimize the drilling losses. Using NPT analysis coupled with risk management was used to indicate where to optimize exerted efforts in order to synergize improvement of overall drilling performance.

Optimization of operating parameters of seeding device in plot drill with seeding control system

Plot drill has a significant impact on field breeding by replacing manual seeding. However, the seeding performance of plot drill needs to be further improved as the mechanical transmission method cannot work under the optimal combination of operating parameters. In this study, a cone compartment tray of sowing device was evaluated under the laboratory conditions, using a self-designed seeding control system to adjust the operating parameters. Among them, a plot seeding control system was involved that could set operating parameters through an Android terminal, which effectively reduced the difficulty of parameters adjustment. The method of central composite experiment design was employed to conduct experiments and explore the effects of experiment factors such as lifting height of storage tube (LHST), rotation speed of cone compartment tray (RSCCT), and rotation speed seed distributor (RSSD) on the seeding uniformity coefficient of variation among rows (SUCVR) and the rate of damaged seeds (RDS). For SUCVR of wheat, the results showed that the importance order of main factors from high to low was RSSD, RSCCT and LHST. And for SUCVR of buckwheat, RSCCT had the largest influence, followed by RSSD, and LHST had the smallest influence. For RDS of wheat and buckwheat, only RSSD had a very significant effect among the main factors. The experiments data of wheat indicated that when operated at 27.2 mm for LHST, 4.5 r/min for RSCCT and 1169 r/min for RSSD, the sowing performance of wheat was optimal, with SUCVR and RDS values of 5.02% and 0.117%, respectively. The buckwheat seeding performance was found to be optimal when the LHST, RSCCT and RSSD were 26.5 mm, 3.9 r/min and 711 r/min, and SUCVR and RDS were 4.74% and 0.113%. The seeding control system realized the electromechanical control of the seeding equipment, was convenient for parameter setting and stepless adjustment, and could be operated under an optimized combination of operating parameters. The research results could provide a reference for the performance improvement and application of plot drill. Keywords: plot drill, seeding device, seeding control system, seeding performance, parameter optimization DOI: 10.25165/j.ijabe.20211403.6218 Citation: Cheng X P, Li H W, He J, Wang Q J, Lu C Y, Wang Y B, et al. Optimization of operating parameters of seeding device in plot drill with seeding control system. Int J Agric & Biol Eng, 2021; 14(3): 83–91.

Research on the Matching of Impact Performance and Collision Coefficient of Hydraulic Rock Drill

The stress wave produced by the piston impact, on the drill rod, is an important factor affecting impact performance. It is particularly important to control the stress waveform generated by the piston impact on the drill rod to meet the requirements of efficiency and component durability of some impact mechanical systems. Based on wave theory, the impact stress wave model of rock drilling is established, a dimensionless collision coefficient γ is put forward, and the matching relationship between different collision coefficients γ and stress waveforms is analysed. The length of the impact piston under the same material condition determines the change rule of the waveform. The stress waveform experimental verification is thus designed. The pressure chamber curves of different pistons in the rock drill were tested, the collision velocity of the piston was obtained, and the impact energy and impact power were calculated. The relationship between the impact performance and the collision coefficient γ is analysed. When γ is in the range of 9–11, the impact piston’s design of a high‐power rock drill can be satisfied. When γ is in the range of 3∼5, it is mainly designed for low‐power rock drills.

Effect of recirculation zone on debris evacuation during EDM deep hole drilling

Deep hole drilling is a technique used for producing holes in materials at high depth to diameter (L/D > 10) ratios. Applications demanding deep holes can be extensively found in aerospace, automotive, marine and oil & gas industries. Conventional drilling techniques such as twist drilling and gun drilling are commonly used for drilling deep holes in the aforementioned applications. However, these methods can cause problems of rapid tool degradation, chip clogging, premature tool failure and undesirable sub-surface alterations to the hole surface. Moreover, these problems get aggravated when the material is difficult-to-cut (Ni/Fe/Co based superalloys) in nature. Therefore, non-conventional machining process finds scope in order to overcome the problems associated with conventional drilling. Electrical discharge drilling (EDD) can be used for fabricating dimensionally accurate holes irrespective of hardness of the material. Nevertheless, the inefficiency in flushing of debris particles at higher depths and its subsequent accumulation is a critical challenge during EDM deep hole drilling. The reason behind flushing inefficiency based on fluid physics has not been completely explored by researchers yet. In this paper, the flow behaviour of micro debris particles in the flushing channel during EDD has been analysed using CFD simulation by employing discrete phase modelling (DPM). The developed model set up is also validated with a benchmark fluid mechanics problem. The steady state CFD analysis results show the formation of multiple recirculation zones in the flushing channel. This can be attributed to the adverse pressure gradient experienced when the dielectric fluid passes from the machining gap to annular gap. Moreover, the presence of recirculation zones reduces the flow momentum and thereby debris particle velocity. This leads to accumulation of micro debris particles in the recirculation zones over time. The results also show that the trajectory of the particles is dependent on the size of the particles generated during material removal. The outcomes of numerical analysis in the present paper can serve as a foundation for the future studies in improving the performance of EDM deep hole drilling.

Improving the micro-electrical-discharge drilling performance of carbon fibre-reinforced polymer: role of assisting-electrode and shaped tool

This paper presents the investigation on the fabrication of micro-holes in carbon fibre-reinforced polymer composites using micro-electrical-discharge drilling method coupled with assisting-electrode and rotary tools of copper and brass. Bisphenol-A based epoxy resin LY 556 having medium viscosity and hardener HY 951 were used for the fabrication of composites. The sizes of the fabricated micro-holes were in the range of 600 μm-830 μm. The input factors considered in this experimental endeavour were voltage (120 volts, 150 volts, and 170 volts), pulse duration (10 μs, 20 μs, and 30 μs), and tool speed (200 RPM, 300 RPM, and 400 RPM). The hole profile was studied under an optical microscope and the surface morphology of the micro-hole was analysed by field-emission scanning electron microscope. The voltage was the most significant factor during micro-electrical-discharge drilling of carbon fibre-reinforced polymer. Fibre breakage, matrix burning, matrix melting, and resolidified layer were evident from the field-emission scanning electron microscopic analysis.

Tribological and dry drilling performance of WS<sub>2</sub>/Cr-AlCrN coatings

Tribological and dry drilling performance of WS<sub>2</sub>/Cr-AlCrN coatings

Improving the micro-electrical-discharge drilling performance of carbon fibre-reinforced polymer: role of assisting-electrode and shaped tool

This paper presents the investigation on the fabrication of micro-holes in carbon fibre-reinforced polymer composites using micro-electrical-discharge drilling method coupled with assisting-electrode and rotary tools of copper and brass. Bisphenol-A based epoxy resin LY 556 having medium viscosity and hardener HY 951 were used for the fabrication of composites. The sizes of the fabricated micro-holes were in the range of 600 μm-830 μm. The input factors considered in this experimental endeavour were voltage (120 volts, 150 volts, and 170 volts), pulse duration (10 μs, 20 μs, and 30 μs), and tool speed (200 RPM, 300 RPM, and 400 RPM). The hole profile was studied under an optical microscope and the surface morphology of the micro-hole was analysed by field-emission scanning electron microscope. The voltage was the most significant factor during micro-electrical-discharge drilling of carbon fibre-reinforced polymer. Fibre breakage, matrix burning, matrix melting, and resolidified layer were evident from the field-emission scanning electron microscopic analysis.

A Review of the Research and Development of High‐Frequency Measurement Technologies Used for Nonlinear Dynamics of Drillstring

High‐frequency measurements can provide much more new insights for drillstring dynamics compared to traditional instruments, leading to a new realm of understanding of drillstring behaviors in great detail than before. In this paper, data acquisition tools with high‐frequency sample rates and the data processing are introduced. Based on high‐frequency data, progress of drilling dynamics is summarized, including new understandings of low‐frequency drillstring dynamics, high‐frequency torsional oscillations (HFTOs), and high‐frequency axial oscillations (HFAOs) and new findings for the coupling of vibrations and motions, as well as models and simulation methods to deeply comprehend high‐frequency dynamics of drillstring. High‐frequency measurements have been used for enabling drillers to improve drill performance, especially for field decision making, BHA selection, and bit design, usually through the ways of minimizing vibrations to obtain high‐efficient drilling conditions, the high‐frequency response near bit can also be used for lithology identification during drilling. Though there still exists a gap between research perspective and drilling practice, the industry of high‐frequency measurements has gotten off a good start, which has huge potential to avoid nonproductive time thereupon reducing drilling cost in the future.

Study on dedicated drill bit design for carbon fiber reinforced polymer drilling with improved cutting mechanism

Carbon fiber reinforced polymer (CFRP) has significant applications in the aerospace and automobile industries. However, the relatively high thermomechanical loads generated when drilling CFRP is considerably detrimental to the cutting tool. To address this issue, in this work, a step-change in the performance of CFRP drilling was conducted by switching the cutting model from crushing/compression fracture to the shear cutting of the composite workpiece to suppress the thermomechanical loads using a novel web thinning design. To evaluate the performance of the proposed drill bit, a comprehensive comparison was carried out between the dedicated and conventional drill bit designs from thermal, mechanical, and chip formation points of view. The results show that the dedicated drill bit outperformed the conventional drill bit in terms of thrust force, temperature elevation, burr, and exit-delamination. An in-depth observation revealed that the shear cutting became dominant in the drilling with the proposed drill bit while the crushing/compression was dominant with the conventional drill bit. The transition of the phenomena was induced by the properly designed rake angle. The mechanism of material removal in CFRP drilling using the dedicated drill bit design provides a new design direction to modifying the rake angle for improving the efficiency and quality of composite material drilling.