Drill Bit Research Articles

Sustainable Optimization of Drilling Parameters for AA2017/AlN Composite Materials: A Grey Relational Analysis Approach

Modern engineering materials have seen remarkable development. Because conventional materials can no longer meet the needs of modern applications, numerous composites are being employed as viable alternatives. Drilling is the most important production step for most uses, and the resulting holes are high-stress zones that must be handled carefully. Scientists and engineers have long been interested in the challenge of finding the best combination of drilling settings for cutting-edge composite materials. As part of this research, AA2017/AlN composites with matrices made of AA2017 aluminium alloy and reinforcements made of 5, 10, and 15 wt % AlN were produced using stir casting. By experimenting with different input parameters, we were able to utilise the L9 OA to determine the best machining arrangement for drilling materials. The investigation focused on critical drilling characteristics, including burr height (H), thrust force (T), and surface roughness (SR), with a keen emphasis on sustainability.By considering the burr height (H), thrust force (T) and surface roughness (SR) and this work used grey relational analysis (GRA) to establish the optimum cutting parameters for drilling holes in the cutting-edge composite AA2017/AlN. The significance of different machining settings and their effect on the typical characteristics of the drilling were analysed using GRA. However, a confirmation experiment was conducted to ensure the highest quality outcomes. Test results and GRA indicate that the best grey relational grade is achieved with the following parameters: spindle speed (S) of 3500 rpm, feed rate (F) of 60 m/s, drill material (D) of Tungsten Carbide, and reinforcement (R) of 10%.. Analysis of variance (ANOVA) revealed statistically significant impacts on GRG from the drill material (29.08%), the feed rate (24.24%), and the spindle speed (19.52%). The error term was a function of the reinforcement percent and its interactions with all other parameters; however, the influence of the interaction between feed rate and drill material on GRG was small. The GRG is 0.856, which is higher than the prediction of 0.824. The calculated and measured values agree quite well and 3.7% is a negligible margin of error. The mathematical models for all reactions depending on the drill bits employed was also constructed.

Procena karakteristika obrade i habanja alata tokom bušenja ugljenika / aluminijum-aluminijum

In the past few decades, fibre metal laminate (FML) machining has been facing critical challenges in quality control and tool wear monitoring due to the material's intrinsic heterogeneity and abrasiveness. Different drill tools have been used to investigate the effect of process parameters on machining performances. Composite holes and tool wear was studied for drilling forces and surface roughness. An emphasis was made on examining the tool morphologies and wear processes that influence the drilling of CARALL composites. The drilling responses obtained from both the drill bits were optimized using a decision-making approach viz; Combined Compromise Solution Analysis (CoCoSo). The SEM investigation of the machined samples was used to examine the hole quality and surface finish. A lower point angle drill with a longer chip flute length produced the best results for drilling CARALL composites up to a specific point with minimum flank wear and chip adhesion.

Real-time automatic identification methods for downhole whirling based on mechanical specific energy model of drill bit

In the drilling exploitation of hot dry rock for geothermal energy, whirling is one of the main low-efficiency conditions that affect the efficiency of Polycrystalline Diamond Compact (PDC) bit in horizontal well drilling. Realizing automatic and real-time identification with whirling is of great significance to save non-productive time and ensure drilling safety and benefit. In this paper, we first constructed a real-time drilling mechanical specific energy (MSE) model combined with while-drilling testing to reflect the real-time drilling conditions. The MSE model is used to normalize multi-source parameters. Secondly, we constructed a Back Propagation (BP) artificial neural network (ANN), and then the normalization effect verification, optimization of network parameters, and identification effect verification of whirling were carried out. The final results show that the established MSE model has a favourable effect on data normalization, which could also reduce the complexity of the required network model, and shorten the training time by 20–30 s/step. The optimal algorithm is Trainscg, whose optimal number of hidden layer nodes is 5, and the optimal maximum number of iteration steps is 1000. The established ANN model can accurately identify whirling based on MSE, the accuracy is about 0.94, and the average relative error is 1.3%. The method established in this paper provides a reference for the automatic identification of various low-efficiency conditions based on MSE.

A novel experimental setup for axial-torsional coupled vibration impact-assisted PDC drill bit drilling.

The geological conditions of hot dry rock (HDR) reservoirs are complex. The geothermal mining of HDR faces major challenges in the drilling and construction of wells, fracturing to create storage, and flowing to extract heat. Vibration impacts help improve the rock-breaking efficiency, where the axial-torsional coupled vibration impact technology can increase the bit penetration depth and reduce the stick-slip effect. To study the feasibility and efficiency of the axial-torsional-coupled vibration impact-assisted Polycrystalline Diamond Compact (PDC) bit to break high-temperature and high-pressure rocks, a new experimental setup was designed. The system includes a drilling fluid circulation system, an axial-torsional coupled impact drilling system, a formation simulation system, and a data acquisition and control system. This setup can produce a rock-breaking torque of 2000 N·m, a drilling speed of 200rpm, a weight on bit of 100kN, an axial vibration frequency of 100Hz, and a torsional vibration frequency of 50Hz. It can simulate the formation pressure of 70 MPa and the rock temperature of 400 °C. A series of rock-breaking drilling experiments were successfully conducted using this setup. The results show that the axial-torsional coupled vibration-impact assisted PDC bit has a good performance in breaking high-temperature and hard rocks, which can accelerate the application of this new technology in deep formation drilling.

First Report of Binucleate Rhizoctonia AG-G Causing Grapevine (Vitis Vinifera) Trunk Diseases in California Nurseries.

Grapevine Trunk Diseases (GTD) are caused by a consortium of fungal pathogens that affect the biological functions of the vascular system of mature and young grapevines (Gramaje et al. 2018). We conducted surveys to profile GTD pathogens in California grapevine nurseries and collected 784 cuttings of cvs. Cabernet Sauvignon and Chardonnay grafted on 1103P rootstock. Several vines exhibited wood necrotic lesions and cankers at the graft union and the root ball (Figure 1A). Symptomatic wood tissues were cultured on PDA medium and after two weeks of incubation at room temperature (22°C), several known GTD pathogens were recovered. We also identified Rhizoctonia from 42 of the 784 vines (5.3% incidence) based on the morphological characteristics of a brown pigmented mycelium (Figure 1B), hyphae branched at a right angle with constrictions at the branch point (Figure 1C) and absence of spores (González García et al., 2006). A subsample of four isolates (DCHG2B, DCSG22R, JCSG9B, and JCHG12B) were randomly selected for further DNA-based taxonomic identification and pathogenicity evaluation to grapevine. The ITS and beta tubulin regions were amplified using the ITS1/ITS4 and B36F/B12R primer sets, respectively (González et al. 2006), and sequences were deposited in the NCBI database (Accession numbers: OR052655, OR052656, OR052657, OR052658 and OR059207, OR059208, OR059209, OR059210). Sequences displayed >99% and >96% identity with the respective ITS and beta tubulin sequences of the binucleate Rhizoctonia AG-G specimen C-653 (González et al. 2006). A phylogenetic tree constructed using the Neighbor-Joining method indicated a 100% bootstrap support with the binucleate Rhizoctonia AG-G (Figure 2). Pathogenicity of the binucleate AG-G Rhizoctonia were confirmed on two separate technical replicates using standard methods. For each replicate, one-year-old rootstock 1103P were wounded with sterile drill bits and inoculated with a single 5 mm diameter agar plug collected from Rhizoctonia growing cultures, while control vines were inoculated with sterile agar. The first replicate lasted 28 weeks with (DCHG2B, DCSG22R) inoculated on seven vines. The second bioassay lasted 24 weeks with two additional isolates (JCSG9B, JCHG12B) inoculated on twelve vines. Rhizoctonia-inoculated vines developed wood symptoms similar to those observed on cuttings in nurseries, with necrotic lesions lengths significantly longer than the controls (First replicate: 3.5  0.4 cm vs. 1.3  0.6 cm; Second replicate: 6.8  0.8 cm vs. 1.1  0.2 cm), based on one-way ANOVA statistical test (P value < 0.05). Rhizoctonia isolates recovery from wood necrotic lesions were confirmed by ITS sequencing, thereby fulfilling Koch's postulate. Several binucleate Rhizoctonia anastomosis groups, including AG-G, have been found to cause root rot and stem necrosis in plant nurseries (Aiello et al., 2017; Rinehart et al., 2007). Rhizoctonia has also been reported to be associated with grapevine nurseries in Europe (Pintos et al., 2018), South Africa (Halleen et al., 2003) and Australia (Walker, 1992). However, the multinucleate Rhizoctonia solani was the only species confirmed to cause root rot on grapevine (Walker, 1992). Our data suggests that the binucleate Rhizoctonia from the AG-G anastomosis group also cause wood necrosis in grapevine. Those findings warrant further studies on the complexity of Rhizoctonia anastomosis groups in nursery and their aggressiveness to grapevine.

A study on the ultrasonic vibration on the cutting performance during ultrasonic-assisted drilling of CFRP with twist and dagger drill bits

During the drilling process of carbon fiber reinforced polymer (CFRP), defects such as exit delamination, tearing, and burrs are prone to occur, among which excessive axial force during drilling is the main reason for the generation of exit delamination defects. In this study, ultrasonic-assisted and conventional drilling with twist and dagger drills were investigated on 5 mm-thick multi-directional laminated fiber sheets made of T300-12k/AG80 carbon fiber composite with different orientations. The axial force evolutions in each case were monitored when drilling holes in CFRP plates, and the axial force of drilling and the appearance characteristics of hole outlet were compared. The experimental results showed that the ultrasonic assisted drilling reduced the axial drilling forces of twist and dagger drill by up to 20.6% and 30.7%, respectively, compared to conventional drills. In addition, as the feed rate increases, the axial force of drilling gradually increases, and the exit delamination factor shows an overall increasing trend. The ultrasonic vibrations reduced the exit delamination damage of both drills. A special structure of the dagger drill effectively avoided exit delamination during ultrasonic-assisted drilling, which makes the incision more neat to improve the processing quality.

Accuracy of assembly holes after drilling in Al/CFRP layered structure

Layered structures consisting of CFRP composites and aluminum alloys are most commonly used in the aerospace, marine, construction and automotive industries. One of the most important aspects associated with their use is the difficulty of machining them due to the anisotropic nature of the structures. These structures are often jointed to each other by mechanical joints that require mounting holes. The purpose of this study was to determine the effect of drill bit diameter, cutting speed and the way the specimen is clamped during machining (drilling strategy) on the quality of holes drilled in a II-layer structure consisting of CFRP composite and aluminum alloy. The quality of the holes was expressed by the hole accuracy index D. A visual evaluation of the holes after the drilling process was also carried out.

ACCURATE PREDICTION OF DRILL BIT PENETRATION RATE IN ROCK USING SUPERVISED MACHINE LEARNING TECHNIQUES BASE ON LABORATORY TEST DATA

Knowing the rate of penetration of a drill bit in rocks is among the most important parameters in their behaviour measurement. However, the direct measurement of ROP in rocks is a high-cost and time-intensive process. Therefore, obtaining the ROP parameter through a method other than direct measurement can be very useful and effective. Predictive machine learning methods are among the strong and precise techniques for the indirect measurement of ROP. To this end, 492 samples were tested under different UCS, µ, WOB, and ω conditions to obtain the corresponding ROP. To achieve an accurate model, three methods of linear regression analysis, lasso regression, and ridge regression were compared in terms of prediction accuracy. These models were compared through performance criteria of the prediction process and error-based charts. The performance criteria were measured using three measures: mean absolute percentage error, D-squared pinball score, and mean Poisson deviance error. For the MAPE index, the Lasso and Ridge models performed the best with values of 0.2557. Concerning the D2PS index, the linear regression model and Ridge performed better with values of 0.4083 and 0.4025, respectively. Finally, for the MPDE index, the Ridge model provided a more accurate performance with a value of 0.0105. For a better comparison, an objective function was created and calculated by combining these three indicators. The results showed the best rank for the Ridge model with an estimated value of 659.475. Finally, it was concluded that the Ridge model is a reliable and accurate model for predicting the ROP.

A New Bottom-Hole Assembly Design Method to Maintain Verticality and Reduce Lateral Vibration

Well deviation is a prevalent problem in deep oil and gas exploration, leading to a significant increase in drilling costs. The conventional bottom-hole assembly (BHA) anti-deviation design method does not consider the impact of the BHA structure on lateral vibration. This paper proposes an integrated BHA design method that takes into account both anti-deviation and vibration reduction. This method evaluates the BHA’s anti-deviation ability using the drilling trend angle. A negative value of the drilling trend angle indicates that the BHA can correct well deviation. A finite element linearized dynamics method is used to evaluate the lateral vibration intensity of the BHA. This method involves calculating the bending displacement caused by mass imbalance and then determining the magnitude of the bending strain energy based on this displacement. The structural factors affecting the anti-deviation ability and potential lateral vibration intensity of pendulum BHAs and bent-housing mud motor (BHMM) BHAs were studied, and field tests were conducted for verification. The research shows that for pendulum BHAs, the factor that has the greatest impact on anti-deviation ability and vibration intensity is the distance from the stabilizer to the drill bit. For BHMM BHAs, the length of the short drill collar has a significant impact on the vibration intensity. Compared with current design methods, the mechanical specific energy (MSE) of the single stabilizer pendulum BHA decreased by 12%, while the MSE of the BHMM BHA decreased by 26.4%. Both decreases indicate a reduction in vibration intensity. This study will help to further increase drilling speed while preventing well deviation.

Modeling and surface morphological study in drilling of Al 2024 alloy

With concern to profuse usability of drilling operations in various industries, almost 1/3rd of the all the machining operations, the main focus is to obtain a proper quality of hole in less time at optimum cost. Aluminium alloy 2024 (Al 2024) is largely applied in various industries specially, aircraft, automotive, marine etc. because of its outstanding union towards strength, corrosion resistance, and weldability. Cutting time, cutting temperature and surface morphological investigation during drilling is very much necessary for obtaining a quality hole that has not been substantially researched so much. Therefore, a proper and thorough study of these responses is quite important regarding the hole quality. With this view, in this work, drilling of Al 2024 alloy is performed with three process parameters (input) viz. spindle speed (v), feed rate (f) and drill bit diameter (d) and performance parameters (output) as cutting time (s), cutting temperature (°C) and surface roughness (μm). Three different drill bit diameters of high speed steel (HSS) of size viz. 6 mm, 8 mm and 10 mm are used in drilling. Each process parameter has three levels. The surface morphological study is also conducted to know the depth of hole morphology details after drilling. To make the drilling operation environment friendly, it is performed in dry atmosphere. Using full factorial design, total 27 experiments are conducted. The experimental results showed that high spindle speed along with high feed rate decreases the cutting time, whereas it increases the cutting temperature. For better surface finish medium spindle speed along with low feed rate is recommended. From analysis of variance (ANOVA), all the three models developed for cutting time, cutting temperature and surface roughness are found statistically significant. Spindle speed and feed are the influential parameters to cutting time, cutting temperature and surface roughness. A mathematical model is developed using response surface methodology (RSM) to predict the responses cutting time, cutting temperature and surface roughness with better accuracy. The coefficient of determination (R2) for cutting time, cutting temperature and surface roughness is found as 96.65%, 95.88% and 93.65% respectively, which indicated that the developed models could be used for prediction with better accuracy. The morphological study shows that scratches, trenches, abrasive wear are visible on the hole surface. At high spindle speed surface grain refinement is observed more which causes a better surface finish.

Drilling Tools in Prehistoric China from the Perspective of Experimental Archaeology

As a type of artifact commonly found in Chinese prehistoric sites, perforated shellfish materials can be classified into freshwater mussel materials and perforated seashell materials, and drilling tools can be classified into single and composite drilling tools. The experimental reconstruction of the two types of drilling tools and drilling methods explored the influence of the composition of drilling tools, drilling methods, and other factors on the drilling process. Meanwhile, the experiments were recorded and analyzed using a stereo microscope. The experimental results show that the composite drilling tools provide better drilling results and more dynamics than stone drill bits. The perforated weight stone stabilized the center of gravity and safeguarded the dynamic performance. The type of drilling tool, drilling method, and characteristics such as smoothness and hardness of perforated shellfish materials significantly impact the drilling effect.

Structure Design of Bionic PDC Cutter and the Characteristics of Rock Breaking Processes

The rational structural design of polycrystalline diamond compact (PDC) cutters effectively enhances the performance of drill bits in rock fragmentation and extends their service life. Inspired by bionics, a bionic PDC cutter was designed, taking the mole claw toe, shark tooth, and microscopic biomaterial structures as the bionic prototypes. To verify its rock-breaking effectiveness, the finite element method was employed to compare the rock-breaking processes of the bionic cutter, triangular prism cutter, and axe cutter. The study also investigated the influence of different back rake angles, cutting depths, arc radii, and hydrostatic pressures on rock breaking using the bionic cutter. Prior to this, the accuracy of the finite element model was validated through laboratory tests. Subsequently, a drill bit incorporating all three types of cutters was constructed, and simulations of rock breaking were conducted on a full-sized drill bit. The results demonstrate that the bionic cutter exhibits superior load concentration on the rock compared to the triangular prism cutter and the axe cutter. Additionally, its arc structure facilitates the “shoveling” of the rock, making it more susceptible to breakage under tensile stress. As a result, the efficiency of the bionic cutter surpasses that of the triangular prism and axe cutters. Similarly, it exhibits minimal fluctuations and values in cutting force. As the back rake angle and cutting depth increase, the MSE and cutting force of all three cutters also increase. However, the bionic cutter consistently maintains the lowest MSE and cutting force, confirming the superiority of its bionic structural design. The MSE and cutting force of the bionic cutter fluctuate with the increase of the arc radius, and the optimal arc radius falls within the simulation range, between 21 mm and 23 mm. Compared to the other two types of cutters, bionic cutters possess a unique structure that allows for better release of internal stress within the rock, thereby ensuring higher efficiency in rock-breaking, particularly in deep geological formations. The rock breaking simulation results of full-sized drill bits show that the use of a bionic cutter can improve the drill bit’s ability to penetrate the formation, reduce the possibility of drill bit bounce during the rock breaking process, prevent the occurrence of stick-slip, improve the drilling stability, effectively improve the efficiency and service life of the drill bit during the rock breaking process, and reduce the drilling cost. It is concluded that the research results of bionic PDC cutters are helpful to the development of high-performance drill bits and the reduction of drilling costs.

TRIBOLOGY OF DRILL BITS IN THE GEOTHERMAL INDUSTRY: A LITERATURE REVIEW

Energy from the earth’s heat is critical to the energy supply of countries with this resource. This literature review highlights the tribology applied to drill bits in the geothermal industry. Facing a diverse geological environment, drill bits are critical to energy efficiency, with significant friction, wear and lubrication challenges. This paper addresses the complexity of drill bit interaction with diverse geothermal formations, highlighting the importance of understanding tribological phenomena. Advances in materials and coatings, such as composites, heat-resistant alloys and ceramic coatings, are explored, along with innovative geometric design strategies. Attention on lubrication, cooling and continuous monitoring systems highlights the quest for efficiency and extended drill bit life. This review provides a comprehensive overview of advances in bit tribological research in the geothermal industry, identifying emerging trends and critical challenges for the sustainable development of this form of renewable energy.

Reducing delamination risk with response surface methodology-supported drilling analysis for Nomex® aramid fiber composites

This article presents a comprehensive experimental investigation into the drilling behavior of Nomex®, a type of aramid fiber. The study specifically examines the impact of various cutting parameters and drill bit types on drilling outcomes. While Nomex® offers many advantages, difficult chip evacuation during drilling of aramid fiber composites can lead to surface defects and delamination. The research aims to explore how drilling parameters—such as spindle speed, feed rate—and four distinct drill bit types affect drilling performance. The analysis encompasses factors such as thrust force, torque, and surface roughness, studied under different drilling conditions and with various drill bit types. Moreover, the research assesses peeling and push-out delamination factors to gain insights into drill bit and coating characteristics. An examination of burr and chipping further enhances the comprehension of drilling performance. To determine the most effective drilling conditions, the study employs multi-response optimization. The optimal drilling performance is achieved with a combination of a 0.1 mm/rev feed rate, 1402.82 r/min spindle speed, and HSS-TiN drill type. This configuration successfully integrates responses, resulting in a composite desirability value of 0.95.

Wear Prediction of Rock Drill Bits Based on Geomechanical Properties of Rocks

Wear Prediction of Rock Drill Bits Based on Geomechanical Properties of Rocks

New method prediction of rock mechanics parameters in drilling process based on machine learning

During the drilling process, rock mechanics parameters (RMP) are an important basis for optimizing drilling fluid density, drill bit selection, and wellbore stability. However, during the actual drilling, traditional methods cannot obtain the RMP of arbitrary wellbore sections. To solve the problem of RMP, a novel data-driven method for predicting RMP is proposed. Initially, the Pearson correlation coefficient method is used to analyze the correlation between the drilling data of the actual well and the label of RMP obtained by logging. And the major influence factors (e.g., drilling pressure, drilling speed) of RMP are chosen during drilling. Subsequently, three machine learning models of RBF, BP and KNN integrating the major influence factors of RMP are established. Furthermore, based on actual drilling parameters and RMP data as labels, the model is trained and verified, and hyperparameters are optimized. The results show that the RBF neural network exhibited strong generalization ability, achieving an accuracy of 87.69%. Compared to BP and KNN, the optimal model RBF neural network prediction accuracy is 4.74% and 6.13% higher. The new method of data-driven RMP prediction is of great significance in guiding drill bit selection and borehole stability during drilling.

Critical thrust force prediction in unidirectional CFRP drilling: An analytical modeling approach

In recent trends, unidirectional carbon fiber laminates have been extensively used in the aviation sector due to their remarkable material properties. Delamination is a major damage introduced during drilling in composite laminates. One of the prime contributing factors for delamination-induced damages is considered as the thrust force. A mathematical model is proposed using an analytical approach for accurate prediction of the thrust force for the last lamina, which experience the most damage. The linear elastic fracture mechanics (LEFM), the classical bending plate theory (CPT) and the theory of elastic behavior of composite lamina are taken into consideration for the proposed analytical model because numerical prediction greatly depends on material properties and the nature of force as well. In the current research, the mathematical equation is proposed based on assumption of combined loading of drill tip and chisel edges for the elliptical delaminated area. The Mode-I interlaminar fracture toughness of unidirectional CFRP (CTC1-FUD160/CT-E556) is experimented with as per ASTM D5528 for better experimental substantiation of the proposed model. When the outcomes of the proposed model are compared with the experiment results and available literature as well, a plausible relationship between the suggested analytical model and the experimental results is found. The result also reveals that the contribution of the drill tip is more profound than the chisel edges of drill bit in drilling operations.

A New SJ* Value Based on Sievers’ J-Miniature Drill Tests to Determine the Drillability of Limestones

This research presents a new drillability value (SJ*) that corrects the most-used Sievers’ J-value (SJ) by removing the accommodation effect of the drill bit in the first tenths of a millimetre to better represent the real drillability of limestones. Moreover, this research demonstrates how such an effect is more notable when porosity and micro-cracking increase, which in this study has been achieved by inducing thermal damage in the samples. To do so, limestone samples from the Prada formation were subjected to temperatures of 105, 300 and 600 °C and then cooled at fast and slow rates to induce porosity and micro-cracking. Two characteristic zones were identified in the penetration–time plots: (a) a shallow region (Zone 1) with a variable drilling rate including an initial peak and (b) a deeper region (Zone 2) where the drilling rate stabilises. These drilling rates increase with thermally induced porosity and micro-cracking, and the authors propose a new method to delimit Zones 1 and 2. Zone 1 is attributed to the time it takes for the drill bit to adjust and settle in the rock surface, while Zone 2 more realistically represents the drillability of the material. The above influences the SJ value derived from Sievers’ J-miniature drill tests, so a new drillability value SJ* is proposed that corrects SJ by excluding Zone 1 and giving more weight to Zone 2. The novel SJ* presented in this research constitutes a more accurate tool to assess and predict the drilling performance in limestones.

КОНТРОЛЬ НАПРУГИ ЗАНУРЮВАНИХ ЕЛЕКТРОДВИГУНІВ

The methods and means of voltage control on the clamps of submersible electric motors of electric drills are considered. The peculiarities of the submersible electric motor as a consumer of electrical energy when it is powered by three-phase voltage via a cable line with asymmetric electrical resistances of the phases are revealed. The main downhole factors influencing the functioning of the submersible electric motor that rotates the drill bit during drilling of deep oil and gas wells are analyzed. The impact of the temperature of the drilling fluid on the value of the active resistance of the cable cores and the drill pipe in deep drilling conditions has been updated. The results of the analysis of known technical solutions and concepts regarding the possibility of voltage control on the clamps of submersible motors, which would implement its physical measurement in industrial conditions, are presented. A method of analytically calculating the phase voltages on the clamps of the submersible electric motor of the electric drill, which is powered by an electric cable with asymmetric electric resistances of the phases, is proposed. The possibility of practical implementation of a laboratory installation based on the proposed method of calculating phase voltages on the clamps of the submersible electric motor of an electric drill is shown. For the practical implementation of the method of analytical calculation of phase voltages on the clamps of a submersible electric motor, the feasibility of using digital processing of signals from current and voltage transmitters located on the surface during oil or gas well drilling is substantiated. The advantages of the proposed method of controlling the voltage on the clamps of the submersible electric motor of the electric drill are the consideration of the electrical parameters of specific power supply cables obtained as a result of auxiliary measurements, and the possibility of technical implementation on a modern element base. The development and implementation of a device for monitoring phase voltages on the clamps of the submersible electric motor of an electric drill will increase the operational reliability and efficiency of drilling wells with an electric drill, which will reduce their cost.

Research on friction characteristics of the support mechanism of the drilling robot under axial-torsional load

Because the coiled tubing drilling robot (CTDR) needs to pull the coiled tubing (CT) and provide the weight on bit (WOB), the traction force is an essential parameter for evaluating the performance of the CTDR. The friction performance between the support mechanism of the CTDR and the borehole wall will directly affect the traction force. At present, there is not a research paper about the mechanical behavior of the interaction between the support mechanism and the borehole wall. On this basis, a model of contact mechanics of the friction block of the support mechanism and the borehole wall was established. The model of contact mechanics integrates the combined factors of the torsional forces and axial forces generated by the drill bit and the CTDR. The friction performance between the friction block of the support mechanism and the borehole wall under different parameters and conditions was investigated. It is found that the size of the rake angle of the tooth has little effect on the damage of the borehole wall only under normal force. And, the rake angle of the tooth is negatively correlated with the equivalent friction coefficient. The embedded depth is positively correlated with the equivalent friction coefficient. When the rake angle of the tooth is greater than 35°, the influence of the embedded depth on the equivalent friction coefficient is weakened. When the embedding depth of the friction block reaches 0.3 mm, the equivalent friction coefficient is greater than 1. When the bevel angle of the tooth is 20°, the friction block performs best. The optimized structural parameters of the friction block are as follows: rake angle of the tooth of 35°, back angle of 60°, spacing of 4 mm, and bevel angle of the tooth of 20°. Further contact experiments were conducted between a single tooth of the friction block and a rock sample. The differences between the experimental results and the numerical simulation results were analyzed. The correctness of the theoretical model is verified by experiments. This paper reveals the relationship between structural parameters and equivalent friction coefficient. The results can provide a theoretical basis for the structural design of the friction block for high-safety and high-traction CTDR.