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![Fig. 3 Bit balling phenomenon during shale drilling using PDC bits [123]](profile/Demeng-Che/publication/255993860/figure/fig18/AS:668292905725974@1536344853826/Bit-balling-phenomenon-during-shale-drilling-using-PDC-bits-123_Q320.jpg)
In Part I of this paper, the issues related to temperature, stress and force were reviewed and parallels were drawn between both metal machining and rock cutting. Part II discusses the issues more directly related to polycrystalline diamond compact (PDC) bit performance and rock mechanics. However, relevant issues in various metal cutting processes...
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Context 1
... Bit balling is the phenomenon in which the drilled rock or cuttings accumulate (or are trapped) and attach to the drill bit during the drilling process [108] as shown in Fig. 3. Bit balling has detrimental effects since it reduces ROP and increases cutter temperatures that, in turn, harm cutting efficiency and bit life ...
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Citations
... Combined with the realistic working conditions of steering drilling, the calculation method for resultant force imposed on PDC bit was given by. 24,25 ...
The characteristics of a drill string system have an essential influence on the performance of directional drilling. The appropriate control method of a drill string is important to drilling efficiency and downhole operation safety. Therefore, based on a new mechanical rotary steerable tool (RST), this paper aims to analyze the Dynamic Characteristics of RST in Directional Drilling. First, considering the thrust force generated by the RST and bottom hole assembly (BHA), the governing vibration equations of a drill string system are established. Furthermore, connected with fields drilling parameters, including the effects of a new RST on a drill bit and wellbore, as the boundary and initial conditions, the dynamic characteristics of a drill string system are compared and studied in directional and straight drilling. The results show that the axial vibration of the drill string increases extremely in directional drilling process, while the weight on bit (WOB) and inclination force change in small range. Moreover, the torque and azimuth force tend to be stable soon, even its initial fluctuations are significantly. Also, the new RST can effectively enhance the steering capacity, increase the drilling efficiency, and improve drill bit force performance. The research results can provide reference for developing directional drilling technologies, including related tool design and optimization.
... One of the main tasks that is solved when planning work is the choice of rational (optimal) types, size of bits, and drilling modes, taking into consideration the physical and mechanical properties of drilled rocks. This, along with the optimization of drilling processes and costs, predetermines the introduction of new types and designs of drilling bits [7][8][9][10][11]. The use of PDC-type bits makes it possible to reduce accidents, increase the mechanical drilling speed, improve trajectory controllability and, as a result, reduce the time for the construction of wells in general. ...
To ensure the trouble-free operation of the rock-destroying tool, the peculiarities of its interaction with the rock at different stages of work must be additionally studied. Still unexplored in full is the relationship between the state of the equipment of the rock-destroying tool and the oscillatory processes during the operation of the drilling tool. The basic dependences for determining the wear indicators of the equipment of the rock-destroying tool have been proposed. The scheme for implementing the method of assessing the condition and predicting the wear of equipment, taking into account the peculiarities of its interaction with the rock, has been improved. Underlying its implementation is the presence of a law of change of at least one generalized coordinate of an arbitrary cross-section of a drilling tool. Bench experimental studies were carried out, according to the results of which the dependence of the depth of the face deepening on the mode parameters of drilling and the geometry of the equipment was established. It was found that the wear of the cutter by 1 mm causes a decrease in the amplitude of longitudinal oscillations by an average of 1.4 times. The obtained functions of deepening the face were used to determine the energy indicators of the process of rock destruction. Given the peculiarities of the implementation of the experiment, the work and power of the axial load for the destruction of the rocks of the pit were used for such indicators. It should also be noted that the construction of numerical models is necessary for a complete assessment and prediction of the wear of rock-destructive tools. They should reflect the mechanical system and provide the ability to obtain the values of parameters that are not determined by the results of a laboratory experiment.
... It shows erratic cracks and pits due to excessive frictional heating. Under dry turning conditions, globules were formed [124,125] in the surfaces due to abrasive shear between the tool and the workpiece. SEM image of monel K 500 workpiece turned with PPO lubrication under MQL condition is shown in figure 15(c). ...
Research investigations conducted in the past has shown that conventional petroleum based lubricants can be replaced with vegetable lubricants. Vegetable oil lubricants do not pollute the environment, as they are biodegradable. In this investigation, pongamia pinnata oil was used as lubricant, to during turning experiments. The physico chemical properties of modified pongamia pinnata oil were evaluated. Ag Nanoparticles were incorporated into the modified pongamia pinnata oil and it was subjected to tribological investigations. In this investigation, the effect of Ag nanoparticles in improving the lubricating aspects of the modified pongamia pinnata oil was studied. The aim of this investigation is to identify the effect of the nanoparticle incorporated bio- lubricant coolant on Monel K 500. In this study, using TiAlN coated triangular tungsten carbide inserts, Monel K 500 was subjected to turning under three conditions such as dry, minimum quantity lubrication and Ag nanoparticles incorporated vegetable oil lubrication. It was observed that the properties of the bio lubricant affected the turning output responses to such as cutting force, machining temperature, tool wear and surface roughness of the workpiece (Monel K 500). Machined surface was evaluated using scanning electron microscope, electron back scatter diffraction analysis and X-Ray diffraction analysis. Turning operation conducted with 2% Ag nanoparticles incorporated modified pongamia pinnata oil lubrication was better than turning conducted under dry and lubricated conditions. Industrial wastes and toxic effluents can be minimized by switching over to bio lubricants and coolants.
... The cylindrical PDC cutters are commonly chamfered at the cutting edge to avoid chipping of the diamond layer in hard formations (Gerbaud et al., 2006). The introduced chamfer has significant effects on bit ROP (rate of penetration) and the cutter aggressiveness (Che et al., 2012b). To investigate the influence of the chamfer at the single cutter scale, cutting simulations with various chamfer sizes were conducted. ...
In the drilling industry, Polycrystalline Diamond Compact (PDC) bits with multiple fixed PDC cutters are widely applied to cut rock under high bottom hole pressure and high temperature. The bit-rock interaction is the main excitation source of drill string vibrations and needs to be understood and controlled better to improve the performance of the drilling process. Rock cutting mechanisms can be examined best for a single PDC cutter: Limitations of dynamic control and available sensors in experimental setups are eliminated in numerical simulations. Using the Discrete Element Method (DEM), deformation and strength of rock can be modeled through its full degradation in the PDC cutting process under typical environmental conditions. Stresses and strains in the rock material and on the cutter faces become available for examination.
In this paper, numerical simulations of the cutting process are conducted using a modified bonded-particle model (specialized DEM), which is calibrated to a pressure series of high-strain triaxial laboratory tests. The simulation results are interpreted from the perspective of continuum mechanics providing stress and strain rate fields within the rock. These serve to identify two primary deformation modes predominant in two distinct zones moving with the PDC cutter: A crush zone below the chamfer and a shear zone ahead of the cutter face. The influences of two cutter design parameters, the back rake angle and the chamfer size, on these zones and the cutting force, are investigated. The shear angle is found to decrease with increasing back rake angle, resulting in a wider shear band. Moreover, the back rake angle has a considerable influence on the cutting forces both in the normal and tangential direction, whereas the chamfer size affects the normal cutting force predominantly. These results are in good accordance with experimental observations in the literature. Furthermore, the relationship between the cutting force and underlying rock failure mechanisms is clarified.
This study enhances the understanding of the rock cutting process and gives first indications for dynamic cutting force control through cutter design.
... Extensive research has been carried out in the field of drilling to gain insights into the rock-cutting mechanisms and to improve the overall process performance, regarding penetration and bit lifetime (Zijsling 1984;Feenstra 1988;Che et al. 2012;Wang et al. 2017). The single-cutter approach (Zijsling 1987;Glowka 1989;Detournay and Defourny 1992;Wise et al. 2002;Hareland et al. 2009;Che et al. 2016;Munoz et al. 2016) is commonly used to answer fundamental questions regarding the rock-cutting process and, at the same time, provides a framework for tool development. ...
To improve the economics and viability of accessing deep georesources, we propose a combined thermo-mechanical drilling (CTMD) method, employing a heat source to facilitate the mechanical removal of rock, with the aim of increasing drilling performance and thereby reducing the overall costs, especially for deep wells in hard rocks. In this work, we employ a novel experimental setup to investigate the main parameters of interest during the interaction of a cutter with the rock material, and we test untreated and thermally treated sandstone and granite, to understand the underlying rock removal mechanism and the resulting drilling performance improvements achievable with the new approach. We find that the rock removal process can be divided into three main regimes: first, a wear-dominated regime, followed by a compression-based progression of the tool at large penetrations, and a final tool fall-back regime for increasing scratch distances. We calculate the compressive rock strengths from our tests to validate the above regime hypothesis, and they are in good agreement with literature data, explaining the strength reduction after treatment of the material by extensive induced thermal cracking of the rock. We evaluate the new method's drilling performance and confirm that thermal cracks in the rock can considerably enhance subsequent mechanical rock removal rates and related drilling performance by one order of magnitude in granite, while mainly reducing the wear rates of the cutting tools in sandstone.
... (a) Cuttings removal to surface and (b) bit balling(Che et al. 2012). ...
Predicting rate of penetration (ROP) has gained considerable interest in the drilling industry because it is the most-effective way to improve the efficiency of drilling and reduce the operating costs. One way to enhance the drilling performance is to optimize the drilling parameters using real-time data. The optimization of the drilling parameters stands on the fact that drilling parameters are interrelated; that is, corrections in one factor affect all the others, positively or negatively.
Analysis of the available models in the literature showed that they did not take into account all factors, and therefore, they might underestimate the ROP. To improve the accuracy of predicting the bit efficiency, a new ROP model is developed to preplan and lower the drilling costs. This approach introduces three parts of the process that were developed to describe the challenge of predicting ROP: aggressiveness or drillability, hole cleaning, and cutters wear, which are interrelated to each other. The approach discusses each process individually, and then the influence of all three factors on ROP is assessed. Taking into account the drilling parameters and formation properties, ROP1 is estimated by use of a new equation. Then, lifting the produced cutting to the surface and evaluating how that affects the bit performance is proposed in the second part of the process (hole cleaning). Finally, wear index is introduced in the third part (wear condition) to predict the reduction of ROP2 caused by cutter/rock friction.
The approach serves and could be considered as a baseline to identify all factors that can affect the bit performance. The developed model equations are applied to estimate ROP in three vertical oil wells with different bit sizes and lithology descriptions in Libya. The results indicate that the driven model provides an effective tool to predict the bit performance. The results are found in good agreement with the actual ROP values and achieve an enhancement of approximately 40% as compared to the previous models.
... In order to enhance cutting performance and machine life, it is very important to reveal the fracture mechanism of rocks and estimate the cutting force in the rock cutting process. The mechanism of rock cutting with PDC cutters has been investigated in numerous pieces of scientific literature [1][2][3][4][5][6][7][8][9][10][11]. Since the cutting depth is shallow, typically less than 1 mm for a medium strength sandstone [12], and the rake angle is negative (or the back rake angle is positive), the ductile fracture regime usually happens in rock cutting with PDC cutters [12][13][14]. ...
Cutter suction dredgers are important pieces of rock excavation equipment in port and waterway construction. It is valuable but difficult to properly estimate the cutting force on the chisel pick of the cutter suction dredger. In this paper, an analytical model, called the crushed zone expansion induced tensile failure model (CEIT model), is proposed for rock cutting with a chisel pick in order to predict the peak cutting force (Fc) more accurately. First, a review of the existing models for rock cutting with a chisel pick is presented. Next, based on the tensile breakage theory, cavity expansion theory and some hypotheses, the mathematical formula of the CEIT model is obtained. Different from that in the previous models, the effect of the rock on both sides of the chisel pick on Fc, defined as the sidewall effect is considered in the CEIT model. Then, the predicted Fc by the CEIT model is compared with the predicted Fc by existing theoretical models and experimental results to check the validity of the CEIT model. The results show that the CEIT model can well capture the relationships of Fc to the cutting parameters, including cutting width, cutting depth, and rake angle, and can predict the experimental results much better than the existing models. Finally, the sidewall effect and its influence factors according to the CEIT model are discussed.
... Based on the Mohr-Coulomb plasticity criterion, this model considered the force equilibrium of the single shear plane in the orthogonal cutting action. Based on Coulomb's criterion and the shear plane assumption, Merchant's cutting force equation can be expressed by [4] [5]: ...
... Schematic diagram of Fairhurst and Lacanne's metal cutting model (reprinted with permission)[6] [5] ...
... Axial-Torsional coupled model for the down-hole drilling system (reprinted with permission)[8] [5] ...
... Extensive research has been carried out in the field of drilling to gain insights into the rock-cutting mechanisms and to improve the overall process performance, regarding penetration and bit lifetime (Zijsling 1984;Feenstra 1988;Che et al. 2012;Wang et al. 2017). The single-cutter approach (Zijsling 1987;Glowka 1989;Detournay and Defourny 1992;Wise et al. 2002;Hareland et al. 2009;Che et al. 2016;Munoz et al. 2016) is commonly used to answer fundamental questions regarding the rock-cutting process and, at the same time, provides a framework for tool development. ...
To improve the economics and viability of accessing deep georesources, we propose a combined thermo–mechanical drilling (CTMD) method, employing a heat source to facilitate the mechanical removal of rock, with the aim of increasing drilling performance and thereby reducing the overall costs, especially for deep wells in hard rocks. In this work, we employ a novel experiment setup to investigate the main parameters of interest during the interaction of a cutter with the rock material, and we test untreated and thermally treated sandstone and granite, to understand the underlying rock removal mechanism and the resulting drilling performance improvements achievable with the new approach. We find that the rock removal process can be divided into three main regimes: first, a wear-dominated regime, followed by a compression-based progression of the tool at large penetrations, and a final tool fall-back regime for increasing scratch distances. We calculate the compressive rock strengths from our tests to validate the above regime hypothesis, and they are in good agreement with literature data, explaining the strength reduction after treatment of the material by extensive induced thermal cracking of the rock. We evaluate the new method’s drilling performance and confirm that thermal cracks in the rock can considerably enhance subsequent mechanical rock removal rates and related drilling performance by one order of magnitude in granite, while mainly reducing the wear rates of the cutting tools in sandstone.
... Papers [8,9] provide a wide overview of studies on the distribution of temperature, forces, and stresses arising at cutting. Their authors also considered the effectiveness of the cutting elements, the mechanism of rock destruction, the theory of cutting, the wear and the causes of failure of rock-destroying tools. ...
At present, the most common tools for drilling operations are those rock-destroying ones that are equipped with cutting elements made from polycrystalline diamonds (PDC) and diamond carbide inserts (DCI). Given this, it is a relevant task to study the influence of the degree of wear of cutting elements on the strength and energy parameters of the process of rock destruction. In order to determine this influence, we have experimentally investigated the cutting process involving a single cutter under laboratory conditions. The mean values of the cutting force components (circular ((Рz) and normal (Рy)) have been established at the cutting depth 0.5; 1.0; 1.5; and 2.0 mm, at a varying degree of the cutting element wear (a flat of 0; 5.0; and 8.0 mm). We have determined the magnitude of cutting work and the specific energy of rock destruction. At a cutting depth of 0.5 mm, with an increase in the cutting element wear rate from 0 to 8 mm, the magnitude of work grows from 0.06376 to 0.121 N∙m. At a cutting depth of 2.0 mm, the magnitude of work increases from 0.624 to 3.603 N∙m. The energy intensity of the rock destruction process increases, with an increase in the cutting depth from 0.5 to 2.0 mm, from 3.88 kJ/m2 to 11.66 kJ/m2 for a sharp cutter. Based on the study results, we have built dependence charts of the average values of the cutting force components and its normal component (Рy) on cutting depth and the cutting element wear degree. The results obtained have shown a significant influence of the size of the wear flat on the increase in the process strength parameters, which is the basis for regulating a wear degree of cutting elements during drilling. We have established the tendency towards a growth in the resultant force and specific work of rock cutting by a cutting element with an increase in wear degree. This makes it possible to determine, based on the indicators of fluctuations in the instantaneous strength values during drilling of wells, or based on a change in power, the wear degree of the cutting elements, and to predict the probability of their destruction
