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As an important connection method between drill pipes, the thread is prone to fatigue cracks and stress corrosion cracks due to long-term exposure to complex forces and corrosive environments. The thread crack detection system of drill pipe based on altering current field measurement (ACFM) is proposed. The crack detection model of the drill pipe thread using ACFM is developed by the finite element software COMSOL. The distribution of the induced magnetic field above the thread is extracted. The relationships between the characteristic signal and the depth and angle of the crack are analyzed. The drill pipe thread detection probes and the detection system are established, and different types of cracks on two different specifications of threads are detected. The experimental results show that the detection system can achieve full coverage detection of the thread crest and root, and cracks at different angle can be identified effectively on the thread.

In oilfield equipment, a significant place is occupied by clamping mechanisms used to grip pipes during tripping operations. They are mainly divided into 2 groups. The first includes mechanisms with a forced clamping of the part. The second group includes self-clamping devices with a wedge mechanism. Here, the clamping force increases in proportion to the axial shear force. In these clamping devices, clamping jaws serve as a common element. In addition to smooth jaws, there may be jaws with notches on the inner cylindrical surface. Such notches contribute to an increase in the coefficient of adhesion when clamping cylindrical parts, in particular pipes. During the operation of clamping devices with corrugated jaws, the teeth of the notch are introduced into the pipe walls under the action of the clamping force. The shearing force can then displace the pipe relative to the jaws. The adhesion coefficient µ is the ratio of the shear force P to the clamping force Q, i.e. P/Q. Exceeding the shear force P of the limit value causes the pipe to be clamped to move. The correct choice of the place of load application is also of great importance. Optimum clamping performance can be achieved by clamping workpieces without slipping from shear forces. At the same time, it is necessary to ensure reliability, efficiency, productivity. Therefore, all factors that determine the holding capacity of clamping mechanisms should be considered. These factors include the coefficient of adhesion, the design of the working surfaces of the clamping elements, the type of notch of the corrugated jaws and the place of application of the clamping force

Dual-tube directional drilling technology is an effective method to solve the problem of long directional drilling in soft coal seam. According to the requirements of double pipe directional drilling, this paper introduces the structure of the mainframe of double pipe drilling rig, and develops a kind of double pipe automatic loading and unloading device, which can load and unload of drill pipe and casing at the same time. According to the different working conditions of double pipe drilling, the process flow of double pipe automatic loading and unloading is introduced. The research of double pipe automatic loading and unloading device and its process method lays a foundation for the popularization and application of double pipe directional drilling technology in related fields of coal bed methane exploitation.

The dynamic Young’s modulus (Edyn) is an important factor for evaluating the static Young’s modulus which is an important parameter influences hydraulic fracturing design, drilling performance, in situ stresses estimation, and wellbore stability evaluation. Currently, the prediction of the Edyn requires the knowledge of the shear and compressional velocities and bulk density, which may not always be available. For the first time, an equation for evaluating Edyn in real-time from the weight on bit, the rate of penetration, torque, standpipe pressure, drill pipe rotation speed, and the drilling fluid flow rate is introduced. This new correlation was developed from the artificial neural networks (ANN) which were trained on 2054 data points from Well-A. The developed correlation was tested and validated on 871 and 2912 data points from Well-B and Well-C, respectively. The results showed that the ANN model evaluated Edyn with average absolute percentage error (AAPE) of 3.09%, for the training data. The developed equation estimated the Edyn with AAPE of only 3.38% and 3.73%, for the testing and validation data, respectively.

The measurement while drilling (MWD) system in underground coal mine currently uses wire for signal transmission. However, it has shortcomings such as strict technical requirements for cable drill pipe processing and high cost of use. Electromagnetic measurement while drilling (EM-MWD) is a new technology has a high rate of information transmission with fast measurement speed and low cost and is not affected by the drilling media. Hence, it is necessary to investigate a reliable electromagnetic transmission channel which is suitable for underground coal mine. This study selects the excitation method through comparison and conducts theoretical research on this basis. Based on the classical electromagnetic theory, the equivalent transmission line method is adopted to calculate and analyze the channel characteristics, while the electrical properties of the coal seam and the surrounding rock are considered. The results demonstrate that the formation resistivity, drill pipe resistivity, and the emission frequency are the main factors affecting signal transmission. On the basis of the uniform equivalent transmission line model, the theoretical model is established by combining the segmented uniform transmission line theory. The layered equivalent transmission line model can be better used to evaluate the regional applicability of the EM-MWD system.

Drilling operations consist of breaking the rock to deepen a wellbore for oil or gas extraction. A drilling fluid, circulating from the surface through the drill pipe and from the annulus to the surface, is used to remove rock cuttings and maintain hydrostatic pressure. Drilling fluid lost circulation incidents (LCIs) are major sources of non-productive time (NPT) in drilling operations. These incidents occur due to preexisting natural fractures (vugs, caverns, etc.) and/or drilling-induced hydraulic fractures. The initiation of an LCI could lead to other hazardous drilling phenomena, such as formation influx or kick/blowout, stuck pipe incidents, among others. LCIs are typically monitored at the rig site by observing drilling fluid levels in the fluid tanks. This manual process incurs missing the occurrence or late detection of LCIs. Machine learning (ML) and deep learning (DL) classification algorithms are powerful in processing time-series data and achieving early detection of such temporal phenomena. In this study, we performed a large-scale analysis of the surface drilling and rheology data obtained from historical wells with LCIs. This analysis includes primary and secondary preprocessing steps including, aggressive sampling, feature engineering, and window normalization to derive generalizable DL models for real-time operations. Focal loss was utilized to account for data class imbalance and train robust and generalizable models. The results obtained from different ML/DL algorithms showed that one-dimensional convolutional neural network models resulted in the best performance with state-of-the-art precision, recall, and F1 scores of 87.34%, 73.40%, and 79.77%, respectively, on unseen test drilling data.

Increasing the durability of drill pipe subs is a pressing problem, a solution to which will improve the efficiency of oil and gas companies when drilling wells. Outer diameter wear, tears on the end surfaces of couplings and the end surfaces of pins, as well as blemishes on external and internal conical rotary-shouldered connections are the most typical defects of the subs. A study and comparative bench tests of the 5135 steel subs with the Z-117 screw were conducted. Testing of the subs with hardening of the work surface by electromechanical processing was done in comparison with the base technology (hardening and high tempering) and carbonitriding. The drill pipe subs were manufactured and hardened by OOO Alexandrovsky Drilling Equipment Plant on the 1М63 machine modernized for electromechanical processing. The comparative bench tests of the drill pipe subs were conducted by OOO Kovrovsky Drilling Equipment Plant on the coupling makeup machine MC-4 by screwing on / unscrewing threaded connections, taking into account the Russian Federation standards and recommendations of the American Petroleum Institute API 7. Electromechanical processing, being one of the method of hardening by a concentrated flow of electric energy of industrial frequency, builds up a gradient layer with the hardness of 52–56 HRC on the surface of the drill pipe subs. The results of the screwing on / unscrewing tests of threaded connections with a toot-joint thread demonstrated high efficiency of carbonitriding and electromechanical processing (500 and more cycles) as a method of increasing hardness of the work surfaces and low efficiency of the current bulk heat treatment (up to 47–66 cycles).

The high efficiency of hole cleaning is essential and critical for drilling horizontal wells. In this study, the effects of four-lobed drill pipe on drill cuttings transport behaviors are examined using a coupled Computational Fluid Dynamics and Discrete Element Method approach. The drill cuttings concentration in annulus is used as the primary quantitative parameter, and the efficiency of hole cleaning is evaluated. Numerical results show that the curvature wall of four-lobed drill pipe by driving secondary motions and induces a local swirling flow, which promotes the transport of drill cuttings and significantly improves the hole cleaning performance. Compared with the conventional drill pipe, the hole cleaning efficiency of four-lobed drill pipe is improved by 89.7% on average, and the average kinetic energy of drill cuttings increases by one order of magnitude. These results are expected to provide a useful strategy for local hole cleaning when drilling horizontal wells.

Drilling is one of the costliest and risky activities in oil and gas industry due to complexity of interactions with downhole formation. Cyclic loads while drilling cause the initiation and growth of cracks in oil tubulars. This phenomenon, known as fatigue, results in permanent reduction of the failure-free service envelope of a certain tubular. Further, most of the drill string failures are triggered by fatigue, which results from repetitive cyclic bending loads and stresses in tensile or buckled drill strings. Fatigue is a cumulative and non-reversible condition induced by repetitive cyclic bending loads and tensile or buckled drill pipe stresses. Fatigue exists even though cyclic tension of the drill pipe material is much lower than static strength limit. Present work investigates fatigue capacity of the 4” WT38 drill pipe connection where cracks have been observed. In accordance with the geometry of connection, a hot spot stress from bending moment is calculated in the crack location in the first thread (upper) of the pin. The DNVGL-RP-C203 SN-curve B1 “in air” is used as relevant fatigue SN curve for the drill pipe thread location. Finite element method (FEM) is employed in modeling and analyzing of drill pipe on pin-box connections. With this method, various connections can be investigated relatively faster and cheaper compared with experimental tests. It is found that the fatigue failure may have been caused as a result of the cyclic load level and number of load cycles. A detailed discussion of the fatigue damage assessment concludes the paper.

The fatigue strength of a drill pipe is a critical factor governing the performance of drillings. Substantial research has been conducted related to fatigue evaluation and various factors that have an effect on fatigue. However, earlier studies have expressed concerns over the use of fatigue curves obtained from full scale tests and stress responses obtained via finite element analysis for evaluation: (a) fatigue curves were obtained by utilizing the stress measured at a point far away from the failure area rather than the stress exerted at the failure point, (b) the stress response is not equivalent to the stress expressing the fatigue curve. It is also important to obtain the stress-response amplitude by precisely considering the irregular wave and ship motion response. This study proposes a method to obtain stress and moment responses due to ship motion in irregular waves. Secondly, it proposes a method to obtain the fatigue curve from a full-scale fatigue test suitable for evaluating the cumulative fatigue with stress response and moment response results. Then, the cumulative fatigue is calculated by applying Miner’s rule. This paper also applies the proposed method to a scientific drilling program amid strong ocean currents and uses a special drill pipe. The results by the proposed method are compared with those obtained by previous methods.

Resumen El mundo actual y las tendencias de universalización de procesos que se dan a través de la globalización, la apertura de mercados, la internacionalización, la competencia y todas las nuevas situaciones que el desarrollo empresarial trae día a día hacen que los procesos empresariales deban ser más eficientes y eficaces, con lo cual existen riesgos asociados con las actividades que implican un sobre esfuerzo físico y por ende una posible lesión osteomuscular. Objetivo. Analizar las relaciones existentes entre las tareas de impacto negativo y las variables ergonómicas asociadas a la manipulación de cargas, a través del uso de las herramientas de evaluación REBA y RULA de manera que se identifiquen los factores de riesgo por parte de los trabajadores de Drilling & Well Services, especialmente cuñeros y encuelladores de una empresa petrolera. Materiales y métodos. La investigación es de tipo descriptivo, pues representa un análisis experimental que tiene como objetivo establecer las condiciones iniciales y determinar la manera como se manifiesta una determinada circunstancia particular identificando los rasgos característicos de la operación. Resultados. Se evidenciaron actividades como el levantar y posicionar la cuña, trasladar la tubería de perforación, soltar o ajustar las llaves de potencia y ajustar los brazos de los elevadores para cerrarlos y con ello asegurar la tubería de perforación, como las acciones de riesgo más importantes en las operaciones de los cuñeros y operadores. Abstract The current world and the tendencies of universalization of processes that occur through globalization, the opening of markets, internationalization, competition and all the new situations that business development brings every day make processes must be more efficient and risks, with which there are risks associated with activities that involve physical exertion and therefore a possible musculoskeletal injury. Objective. Analyze the relationships identified between the negative impact tasks and the ergonomic variables associated with cargo handling, by using the REBA and RULA assessment tools so that risk factors are identified by Drilling & Well workers Services, especially wedges and pollsters of an oil company. Materials and methods. The research is descriptive, since it represents an experimental analysis that aims to establish the initial conditions and determine the way in which a particular circumstance is manifested by identifying the characteristic features of the operation. Results. There were activities such as lifting and positioning the wedge, moving the drill pipe, releasing or adjusting the power keys and adjusting the arms of the elevators to close and with it controlling the drill pipe, as the most important risk actions in the operations of the wedges and operators.

Drilling is being used to access ever-deeper oil and gas reservoirs, thereby presenting various challenges to the design and operation of down-hole tools. Slip inserts are suspension devices that are used to lower the drill pipe into the borehole and lift it to the wellhead, and their performance determines the extended depth of the borehole. In this paper, based on the field and laboratory test of the slip system, parameter sensitivity analysis is applied to the performance of a slip insert to guide the design of the latter. First, a mechanical model is developed of the drill pipe with the slip insert acting on it, and the stress acting on the drill pipe is analyzed theoretically by regarding the drill pipe as a thick-walled cylinder. Next, a numerical model is established to investigate how the slip-insert structure influences the drill-pipe stress, wherein the drill-pipe diameter is 5″ and the axial load is 180 tons. Finally, the results of a series of numerical simulations are presented. For the present slip insert and drill pipe, the optimum slip-insert parameter values are a front-rake angle of 70°, a back-rake angle of 30°, a tooth height of 2 mm, and zero chamfer.

Improving wear resistance of drill pipe sub thread is a vital task, and finding effective solution for it would much assist oil and gas companies to enhance well construction process. The report presents the results of comparative wear resistance tests for P147/147 and P133/133 subs of the top drive manufactured by OOO «NIGMASH» in Bashkortostan. The tests were performed by OOO «Tatburneft» holding company, a division of PAO «TATNEFT». Both, series and test subs were made from 40X2H4A steel. This report shows the results of metallographic studies and tests for improvement of the parts wear resistance, including the method of final electromechanical hardening (EMH) of the box and pin threads as compared with the conventional method of bulk heat treatment. The researches has developed the equipment, tools and technology for hardening of tool joint thread of drill pipe subs. The performed tests and studies aimed at enhancing efficiency of oil and gas well drilling. Their results are of much interest for oilfield operators, drilling and service contractors, as well as drilling subs manufacturers and repair companies.

In case of an unexpected increase in the storm during drilling at sea or in other emergency cases, the drill or casing columns are cut off with cutters of pretensioners and sealed wells. The drill string remains in the well and it is kept by the pipe plugs of the pretensioners. Blind rams are fitted with a cutting blade, cutting pipes in the well, allowing blind rams to seal the well. The task was to improve the cross-cutting preventer rams to increase the efficiency of the drill pipe cutting. The proposed modernization of the cutter design makes it possible to cut the drill pipe completely. In her, as in the previous design, the cutting process is the same, but due to the shape of the cutting surfaces there is no pipe bending, but a complete cutting. However, the difference between these structures from foreign is that in the process of cutting the pipe first, its point deformation (puncture) occurs with a cutter. This, incontrast to other structures, reduces the load at the initial moment of the tube deformation on the hydraulic cylinders of the pre-filter, and therefore, the energy costs for this cutting process are reduced, and the load on other elements of the drive is reduced by the pre-plate layers.Key words: antiviral equipment, plate preventor, cut-off rams, pipe bending, finite-element analysis. To study the cutting process of a drill pipe, a three-dimensional model of the pipe itself and two dies were constructed. The three-dimensional model is created with simplified, since with the increase in the number of elements is complicated as the construction of a network of finite elements, and the calculation process itself continues for a very long time. The results obtained by the simulation model show the effectiveness of the cutting of the drill pipe and the possibility of complete closure of the pre-cutter with cross-sections.

Drilling and coal sampling is the necessary prerequisite to determine the parameters of prediction and prevention for coal and gas outburst in underground coal mine. The integrity of samples is very important for the prediction of parameters. Therefore, a novel sampling device has been developed based on a combination of reverse circulation drill technology and central ejector technology. It consists of a double-wall drill pipe, drill bit, air feeder, and pneumatic control valve set, and both drill bit and air feeder are embedded into by multi-nozzle ring ejectors. This device can realize active and rapid retrieving of high-quality samples at any given position within effective sampling range for soft coal seam. Some test boreholes for drilling and sampling were performed in underground coal mine, and enough samples were obtained within the acceptance time through the compressed air of 0.4~0.6 MPa, and the maximum sampling depth reached 124 m. The capability and reliability of the newly developed reverse circulation drilling and sampling device had been validated by field tests in Huainan coalfield, China.

Much attention has been recently paid to institutional measures aimed at improving quality of products related to petroleum machine building, in particular, the implementation of quality management systems based on the ISO standards of series 9000[1]. However, technological methods of quality assurance have not been less important. The paper considers the factors influencing the quality of a cylindrical thin-walled component during operation. The most significant factors are the efforts to which the component us exposed when it is captured by a clamping mechanism. We have performed experiments into the effects of loads on a clamped component. The aim of these experiments was to establish the impact of various factors on stresses and deformations of cylindrical thin-walled components. The main factors, in addition to the applied forces, are the capturing angle of the clamping element, the length of its contact with a part, load distribution over the teeth of the clamping element. Given the development of deep drilling and an increase in loads acting on the wedge clamps, the requirements to their gripping capacity become stricter. Insufficient gripping capacity of the wedge clamp could cause damage to a pipe at the place it is clamped by wedges. In this case, clamping efforts act in the same region of a pipe, forming a thinned neck at long operation. The result of such damage is a premature failure of a drill pipe’s operation and the risk of an emergency. Significant impact on the gripping capacity of a wedge clamp is exerted by the elements of its design. Of importance is also the stressed state of a drill pipe clamped by a wedge clamp. We have calculated the optimal geometrical characteristics for clamping jaws. The best indicators were demonstrated by the grooved jaws with oblique intersecting notch. We have considered the load distribution over the teeth of clamping jaws. It has been shown that the optimal load distribution over the teeth is provided by jaws with oblique intersecting notch. In this case, tooth 1 accounts for 26% of the load, tooth 2‒22%, tooth 3‒19%, tooth 4‒17%, tooth 5‒16%. The results obtained in the course of our research would make it possible to introduce such modifications to the design of clamping devices that could significantly improve their gripping capacity and reduce the risk of accidents

Improper hole cleaning or drilled-cutting transportation impacts drilling operations. To illustrate, inefficient cleaning of the wellbore can lead to many drilling problems such as low drilling rate (i.e. low ROP), early bit wear and, in the severe cases, a complete loss of the well due to stuck pipe. To understand efficiency in cutting transport in drilling and to provide solutions for the problem, many studies have been conducted. In all cases, they provide empirical models based on experimental data. In this study, different artificial intelligence (AI) techniques are employed to estimate the concentration of cuttings present in the wellbore. The purpose of this study is to indirectly measure the hole-cleaning efficiency in order to predict the cutting concentration from drilling parameters using artificial intelligence techniques. The study is based on 116 experimental data records from the studies. Two AI techniques were selected, namely artificial neural network (ANN) and support vector machine (SVM), to estimate the cutting concentration in the wellbore. The input parameters comprise mud density and mud rheological properties (yield point and plastic viscosity) in addition to drilling parameters including the hole inclination angle, pipe eccentricity (i.e. location of the drill pipe from the axis of the well), the rate of penetration (ROP), flow rate (GPM), drill pipe rotary speed (RPM) and temperature. The results obtained show the ability of the two employed techniques to accurately predict the cutting concentration in the wellbore with average absolute errors (AAE) less than 5% and correlation coefficients (R) higher than 0.9. Comparison of these results with a literature model showed that the AI techniques provide better predictions of cutting concentration and higher accuracy than that model. Applying the developed AI technique will help the drilling engineers to assess the hole cleaning in a real time.

Double shoulder drill pipe joint (DSJ) is a novel thread structure which appears in recent years. Its strength reduced efficiently while the structure design is not appropriately, for the DSJ’s mechanical behaviors weren’t well studied. In this paper a 3D whole structure finite element model of DSJ was established based on the Principle of Virtual Work, and validated the model’s computing results by experimental results. The authors analyzed the stress and strain distribution with the 3D whole structure finite element model’s computing results under torque moment, compression force, tension load, and bend moment. And then acquired the DSJ’s mechanical behaviors under each load. The research works of this paper refer accordance to recognize and design the DSJ. Key words: Double shoulder, Drill pipe joint, Thread, Mechanical behavior

Stuck piping is a common problem with tremendous impact on drilling efficiency and costs in oil industry. Prediction of stuck at the stage of designing and in the process of drilling wells, minimizes the risk of the occurrence of sticking, due to the choice of the optimal method of prevention for specific geological and technical conditions. The article is devoted to the development of an artificial neural network for prediction of sticking of drill pipe columns. The paper provides a literature review of existing methods of prediction of sticks. As input data elements are used important and generalizing factors influencing the emergence of all types of sticks, which allows predicting all types of sticks of drill pipe columns. In order to increase the susceptibility of the input data to the neural network, the data elements are transformed and normalized. The type and architecture of the network, as well as its hyperparameters, are chosen by the experimental method. Assessment of the quality of the network is made by the method of k-fold cross-validation. In order to find the optimal combination of activation function with various optimizers, experimental research is carried out with the analysis of their results. The experiments were implemented in the Python programming language with KERAS, TensorFlow and Matplotlib library packages, as well as in the cloud platform Colaboratory from Google. A distinctive feature of the proposed method is that the resulting forecasting model can be easily adapted to new data, which often occurs when drilling wells in new fields.

Coal and gas outburst accidents occurring in underground coal mines generally cause great casualties and economic losses, especially in construction areas of coal seams where the outburst risks are not accurately evaluated. Therefore, accurately identifying the outburst risks of coal seams is necessary and critical to prevent and control outbursts. In order to improve the prediction accuracy for outbursts in working faces of coal roadways, a self-designed drilling device that can simulate the in-situ outburst prediction of coal roadways was used in this study. We used the coal samples with different coal ranks to adsorb CO 2 and N 2 with different pressures in the laboratory, so as to simulate the coal seams with different outburst risks. Finally, boreholes for predicting the outburst risk were drilled in the simulated coal seams to study the correlation between common dynamic phenomena (e.g. gas and coal being ejected from the borehole (GCEB) and drill pipe being stuck by coal mass in the borehole (DPSC)) and outburst risks. The results show that the greater the outburst risks of coal seams, the more frequent the occurrence of GCEB and DPSC is. The GCEB phenomenon for outburst prediction is attributed to small-sized coal and gas outbursts in boreholes, while the occurrence of DPSC phenomenon does not affirm that there definitely are outburst risks on working faces. The DPSC phenomenon indicating outburst risks is generally accompanied with GCEB, which form a linkage system and are triggered successively.

As the core accoutrement of directional drilling construction, the measurement while drilling (MWD) device can be divided into three types due to the different data transmission methods: wired, mud pulse and electromagnetic wave. This paper used the mud pulse method to develop a mud pulse MWD device for mines, and the working principle of the mud pulse signal transmission, the signal encoding method and the structure of the device were described. Experimental research showed that the mud pulse wireless MWD device had the advantages of long transmission distance and strong working stability. At the same time, the device was not restricted by the drill pipe during operation, which could be combined with sliding orientation and rotary feed, and had great promotion and application value.

The longitudinal vibration of the drill pipe contains considerable energy which can be used to improve the rock-breaking efficiency during drilling. It is very important to the development of drilling speed-up tools to have a comprehensive understanding of the energy conversion efficiency of downhole drill string vibration. In this paper, the characteristics of downhole bit load and longitudinal vibration of drill string under different conditions were studied in the experiment, and the analysis method of energy conversion efficiency from drill string vibration to spring potential energy was proposed. The experimental analysis showed that the fluctuation of the downhole bit load was reduced by 10%–90% after the spring was installed in the bottom hole assembly. The rotation rate and the spring elastic stiffness had a significant and positive influence on the fluctuation amplitude of the downhole bit load. Meanwhile, the longitudinal vibration amplitude and acceleration of the drill string peaked at the elastic stiffness of 1 kN/mm. The closer the spring position to the drill bit was, the more severe the longitudinal vibration of the drill string above the spring component was. The bit load and the rotation rate had a positive influence on the severity of longitudinal vibration. The analysis of energy conversion efficiency showed that the available mechanical energy range of the longitudinal vibration of the drill pipe was about 200–420 kW. The work power of the drill string vibration to the spring component increased sharply and then decreased with the increasing of elastic stiffness. The energy conversion efficiency came to the optimal value when the elastic stiffness was between 1 kN/mm and 2 kN/mm. Increasing the rotation rate, keeping the bit load below 134.5 kN and installing the spring component near the drill bit are beneficial for improving the energy conversion efficiency of drill string vibration. This paper reveals the main factors affecting the energy conversion efficiency of drill string vibration and their influencing laws, and determines the range of WOB, rotation speed, spring position and stiffness to obtain the best energy conversion efficiency.

In order to improve the performance of slip and reduce the extrusion damage of the drill pipe in the drill rig, the optimization of structural parameters and teeth shape of the slip while clamping the drill pipe had been researched in this article. On the macroscale, the structural parameters of the slip had been optimized with response surface method (RSM) and Multiobjective Genetic Algorithm (MOGA). The optimized result showed that the single weight of the slip had been reduced from 3.99 kg to 2.91 kg and the maximum deformation of the drill pipe was reduced from 3.75 mm on both sides to 2.56 mm on both sides. On the microscale, a mathematical model for the single slip teeth while clamping the drill pipe had been established to give a detailed description to calculate the equivalent coefficient of friction and provide the relationship between the frictional torque with the allowable compression strength. In addition, the finite element model that had been set up by ABAQUS was used to verify the mathematical model, and the comparison of results had shown the accuracy of the mathematical model of the slip teeth while clamping the drill pipe. According to the mathematical model of the slip teeth in the drill rig, while clamping the drill pipe, the optimal shape of the slip teeth in the drill rig was achieved under the following condition: the slope of the slip teeth θ is 60°, the top width of the slip teeth w h is 1.5 mm, and the depth of the slip teeth clamping the drill pipe d is 0.5 mm. The equivalent coefficient of friction f v can be increased from 1.73 to 2.06, and the optimal result f v increases 11.3%.

Fatigue fracture is the main failure form of mining drill pipe joints, which directly leads to the occurrence of drill pipe drop accidents. Based on the principle of engineering bionics, the spine structure and kinematic behavior characteristics of cheetah were studied; the bionic design and trial production of drill pipe joints were carried out. For the bionic drill pipe joint, it separates the torsion transmission function from the connection function, and when the torsion transmission function of the joint fails, the connection function is still effective, so as to achieve the effect of “breaking the bones and connecting the ribs.” The mechanical and flow field properties of the bionic drill pipe joint were analyzed. Mechanical test results showed that, for the bionic drill pipe joint, the average tensile capacity was 555.48 kN and the average torsion capacity was 8914.13 N·m, which met the mechanical performance requirements. The flow field numerical simulation results showed that, when the drilling fluid velocity field and pressure field were stable and change evenly, there is no risk of leakage. The study results can provide a new research idea for the research and development of mine drill pipe joint with long life and antidropping function.

The gas emission rate of boreholes is one of the most important indices for coal and gas outburst prediction. In this work, instantaneous gas emission velocity and environmental effects on borehole gas emission were studied. Through theoretical analysis, the mechanism of crack propagation in the coal borehole was clarified, and the effect of soft and hard coal on gas desorption and gas emission. The results of numerical simulations also indicated that the initial gas emission has a function relationship to the drilling distance and the physical characteristics of the coal seam. A novel dynamic testing technology was proposed to obtain gas emission velocity. Laboratory experiments under adsorption and desorption of CO2 and N2 were performed using coal samples from Xuehu, Fenghui, Weishe, and Wuzhong coal mines. The data of initial gas emission under different coal samples were recorded, and the fitting curves were obtained. The results show a positive correlation between initial gas emission and drilling depth. However, abnormal would occur when the drill pipe enters the soft stratification, and the maximum value of the initial gas emission of the abnormal part is 3.8 times the normal value, which indicates a high degree of sensibility to soft stratification. The results were revealed the dynamic gas emission law of boreholes.

To solve the problem of drill pipe counting in coal mines, we propose a drill pipe counting method based on local dense optical flow (LDOF) estimation. Compared to the general tracking method, we provide a new perspective for resolving the problem of drill pipe counting. Taking into account the various working conditions of the drill pipe movement and the complex lighting environment in coal mines, we leverage the local dense optical flow to obtain the movement information of the drill pipe. The model is further established through optical flow to realize the counting of drill pipe. In order to validate the proposed approach, we collect 5 videos of drill pipe movement in coal mines, which cover strong light source and occlusion situations. The experiments demonstrate that our method can realize automatic counting of drill pipe, with an average drill pipe counting accuracy of 97.92% and an average frame per second (FPS) rate of 64.2.

Aiming at the problem that the traditional video-based drilling pipe counting method has low accuracy and is vulnerable to interference in the process of positioning and tracking targets, a drilling pipe counting method based on scale space and Siamese network was proposed: the shape features of the drilling machine video image were calculated by the improved scale space algorithm, the initial position of the drilling machine chuck was determined by feature matching, the chuck was tracked in real time according to the improved Siamese network algorithm and its movement trajectory was recorded, moreover, the number of drilling pipes was calculated after locally weighted regression and hierarchical classification of the chuck movement trajectory using counting rules. The test results showed that the improved method could stably track the target under the interference of bright light and realize the accurate counting of drilling pipe.

Most drilling rigs in the West Texas Delaware Basin (WTX) are supplied with 5" 19.50# S-135 grade drill pipe. Exposure of this pipe to hydrogen sulfide (H2S) creates potential of cracking from hydrogen stress cracking (HSC). Such cracked pipes often exhibit longitudinal cracks with crack origination at OD or ID depending on local stress concentrators. This poses a unique challenge as traditionally used drill pipe inspections specificed in API RP 7G-2 (2015) (referred to as API) and DS-1 Volume 3 (2012) (referred to as DS-1) are designed for transverse flaws like fatigue cracks and thus do not provide a cost-effective standardized inspection program specifically designed for drill pipe cracked from HSC. Infrastructure in WTX further complicates the issue as full-length ultrasonic units (FLUT) used for inspecting longitudinal flaws (typically used for landing strings for deep water operations) are not cost effective for onshore drilling operations and not readily available in WTX. This lack of coverage in used drill pipe inspections for HSC was identified as a contributing factor to drill pipe failures that were experienced after H2S exposure events. To remedy this problem, a drill pipe inspection program designed for cracks from exposure to H2S was developed. A trial program was undertaken, wherein various inspection technologies with specific coverage and procedures were executed on pipe exposed to H2S. Initially, the pipe was inspected and re-inspected using multiple technologies to document effectiveness of specific inspection methods. The crack morphology including location, orientation and size was cataloged to understand characteristics of H2S induced cracks and determine effectiveness of an inspection method in detecting specific crack types. Crack data collected across numerous inspections was analyzed to determine trends on crack occurrence and morphology. This analysis aided in development of an optimized inspection program that was effective and cost efficient. To address various exposure levels and pipe conditions, three inspection categories with increasing coverage and criticality were designed. Implementation of this optimized inspection program has aided in detecting over 100 cracked drill pipe joints and prevented twist off incidents. The cracks detected with this H2S specific inspection program would have gone undetected using traditional (DS-1 and API) used drill-pipe inspection categories. This paper details various inspection methods and the modified inspection coverage and procedures implemented. The H2S induced drill pipe crack data and analyzed trends on crack occurrence and morphology collected over the testing program are included. The paper presents the inspection program designed for detecting cracks induced in drill pipe from H2S exposure. Also included is discussion on three separate inspection categories with increasing criticality to address various exposure levels and pipe conditions.

The standard drill pipe for drilling in coal mine gallery is one of the main drilling tools in underground coal mine drilling. Its reliability directly affects the safety and efficiency of drilling construction. This paper describes the detection method of static torque of standard drill pipe for drilling in coal mine gallery, including detection principle, equipment used, detection method and process, and detection data analysis, which provides basis for the design, testing and inspection of the standard drill pipe for drilling in coal mine gallery, ensures that the standard drill pipe for drilling in coal mine gallery can be used within the torque range it can bear, and provides a safe and reliable guarantee for drilling construction.

In order to improve the work efficiency, reduce the labor intensity and achieve a safe, healthy and efficient drilling environment, a drill rod clamping manipulator for the automatic drill pipe handling system is designed. This article summarizes the development process of the drill pipe clamping manipulator, analyzes the characteristics of the existing drill pipe transporting and placing manipulators. Combining the problems exposed in the actual drilling processes, designed manipulator that can keep the center position of the drill rod unchanged when gripping different diameters of drill pipes. Performing force analysis and dynamic analysis of the manipulator to simulate the actual working conditions, and static analysis of important components. The analysis results show that the performance of each part of the manipulator meets the requirements, and the motion function of the manipulator conforms to the physical laws and meets the requirements of use.

Drilling is an important operation in the mining industry allowing the explorationnof reserves. A major component in a drilling operation is the drill string, whichnprovides the link between the surface of the well and the bottom hole assembly.nIt consists of multiple drill rods connected together by threaded joints. Drill rodsncommonly fail by fatigue in the pin of the threaded joint due to the fluctuatingnstresses they sustain.n n The major loads that contribute to the fatigue failure are static tension andnreverse bending. Reverse bending results from the drill rod rotating while passingnthrough doglegs in the well trajectory. The static tension load is caused by the drillnstring suspending from the surface of the well and results in a positive mean valuenof the fluctuating stress.n n The aim of this project was to investigate the fatigue resistance of taperednthreaded joints of NQ drill rods under service loads, which was achieved by applyingna two stage approach.n n The first stage of the project was to design, construct and commission a fatiguentesting facility for NQ drill rods. A four point bending arrangement was used tonapply the bending load. With an electric DC motor driving the drill rod at speedsnup to 1000rpm, a controlled reverse bending load results. A thrust bearing at eachnend of the drill rod allows a static tension load to be applied while rotating. Hydraulicnactuators apply the desired loads to the drill rod and the facility is capablenof applying loads significant enough to break the drill rod material, which has annultimate tensile strength of 725MPa. To calibrate the load transmission to the drill rod, strain gauges were used to measure the axial strain on the outside surface ofnthe drill rod under static loads.n n The second stage of the project involved the fatigue testing of tapered threadednjoints of NQ drill rods at different load levels. In all the tests performed, the tensionnload applied was 11.76MPa to minimise the number of test parameters. Tests werenperformed at six different bending moment loads, which determines the amplitudesnof the fluctuating stress. The stress amplitudes tested ranged from 27.3MPa ton126.37MPa on the outside surface of the drill rod. A test limit was set at 3 x 106ncycles to optimise the time allocated to the test program. To ensure repeatabilitynin the fatigue tests, the make up torque was equally and accurately applied to allnthe drill rods. A separate apparatus was used to apply the make up torque to thenthreaded joint using a dead weight suspended from a wrench.n n In all the fatigue tests performed, a single mode of failure was observed in thenfailed specimens. All the drill rods failed or sustained damage in the form of cracknpropagation in the lt engaged thread of the pin joint. This suggests that this is thenlocation of highest stress concentration for NQ drill rods with a tapered threadednjoint. The lowest stress amplitude tested where complete drill rod failure was obtainednwas 45.84MPa. The life of this test was approximately 1 x 106 cycles.n n The outcome of this project is that a unique fatigue testing facility for NQ drillnrods has been constructed which is capable of simulating service loads. From thenfatigue data obtained it is observed that the fatigue resistance of threaded joints,nwhich connect drill rods together, is extremely low. This is due to considerablenstress concentration present in the threaded joint and the pre-stress that resultsnfrom the applied make up torque. It was also observed that over the range of loadnlevels tested, a linear relationship existed between stress and life when the fatiguendata was plotted on an S-N diagram.n

In different inspection standards, corrosion pits in drill pipe tubes are treated in different ways. Sometimes they are considered a stress concentrator and subjected to relative depth limitations (like a maximum of 10% of the adjacent wall); sometimes they are only considered as a location of wall loss, so the steel thickness underneath them is the only acceptance parameter. This work clarifies the difference in severity between these two types of imperfections, and enables the definition of a reasonable inspection process. Slip cuts and corrosion pits with varying depths were modeled using Finite Element Analysis (FEA) techniques for multiple drill pipe sizes. The resulting stresses and strains under tension and bending loads were used to calculate the fatigue lives of these components. The resulting number of cycles to failure does not correspond to the real lifetime of real pipe—there are too many variables and neglected parameters—but the results can be compared within the data set to determine which options are better and worse and by how much. Significantly, this research validates the approach taken by some standards to neglect the stress concentration effects of corrosion pitting, only considering the wall thickness remaining for the purposes of inspection. The commercial benefit to this is huge: it allows the inspector to not have to reject or repair a drill string’s worth of light corrosion pitting. This research indicates this is valid and safe in many cases, but in the more-stringent inspections used for offshore drill pipe the relative depth of the pitting also needs to be considered.

At present, drilling rig is a common equipment for controlling gas outburst generated in underground coal mine, and rib drill pipe is an important component of drilling rig. Due to the insufficiency of slag discharge capacity, pipe-sticking accidents often occur during the drilling process, which greatly reduces the effect of gas control. In order to improve the capacity of slag discharge of rib drill pipe, the mechanism of slag removal was analyzed, and the process of slag discharge was simulated as a gas-solid two-phase flow coupling process. Utilizing the computational fluid dynamics method, the process of slag discharge was simulated on the Edem-Fluent cosimulation platform. The structural parameters of the drill pipe affecting the capacity of slag discharge were derived. Based on the analysis results, the structural parameters of rib drill pipe were optimized by orthogonal experiment method. The global optimal results were obtained as follows: its pitch, blade height, and blade width are 120 mm, 3 mm, and 15 mm, respectively. Therefore, the results of slag discharge experiment on the optimum structure of rig drill pipe show that the slag discharge efficiency is increased by 11.38%, which effectively resolves the pipe-sticking problem.

To study the shrinkage rule of borehole diameter and its effect on gas extraction, a visco-elastoplastic model for boreholes considering strain softening and the dilatancy characteristic was established to obtain the expressions of the coal stress, variation in diameter, and pressure relief range. The stress distribution and pressure relief effect of the boreholes in soft and hard coal seams were comparatively analyzed. The shrinkage rule of the borehole diameter was studied. The reasons for the rapid reduction in the extraction concentration of the borehole in soft coal seams were described. A technology of improving the gas extraction effect in soft coal seams was developed. The research results showed that the radius of the plastic softening zone is 0.405 m for a borehole in a soft coal seam and 0.224 m for that in a hard coal seam. This indicates that the borehole in a soft coal seam has a better pressure relief effect. The boreholes in both hard and soft coal seams will incur a shrinkage phenomenon; however, the soft coal seam has low strength and a weak ability to resist damage, and thus the surrounding coal will have a more intense creep deformation, leading to an instability failure during a short period of time and thus, a blocking of the extraction channel, thereby causing a rapid reduction in the gas extraction concentration. The borehole in a hard coal seam also shows a shrinkage phenomenon, but remains in a stable state without a blockage; thus, high-concentration gas can be extracted from this borehole for a long period of time. The geo-stress and coal strength are the two main factors controlling the amplitude of borehole shrinkage. From an increase in stress, the borehole in a hard coal seam shows a more intense creep deformation in a deep mine, which may lead to blockage. The key to improving the gas extraction effect in soft coal seams is to maintain a smooth extraction channel. The full screen pipe is installed through the drill pipe to retain an extraction channel, leading to an average gas extraction increase from 0.043 m3/min to 0.12 m3/min, an increase of 2.77 times. These research results are consistent with actual production, and can provide theoretical guidance for determining the gas extraction parameters.

The use of casing and drill pipes is essential in oil drilling operations. In the process of transportation and operation, thimble and drill pipe are easy to bump and squeeze, which makes thread deformation, damage and thread wear, resulting in loose sealing between the string, which can not meet the operational requirements. The drilling operation is carried out in the downhole, the situation is complex and changeable, the damaged wire buckle is easy to cause serious downhole accidents. In order to protect the buckle, reduce the injury of the buckle as much as possible, and reduce the occurrence of underground accidents, each pipe string is equipped with the guard wire at both ends when it leaves the factory. However, the traditional wire protector appears to be time-consuming, laborious and inefficient in the process of disassembly. If the cooperation between the personnel is not good, personal accidents will occur easily.

Drill pipe rotation is considered a relevant factor for cuttings transport and hole cleaning. However, in the term “rotation” is often used as a moniker for the combination of plain drill pipe rotation around its own axis and more complex lateral motion, as many laboratory setups feature an unconstrained drill string. Lateral motion is generally considered to benefit the transports of cuttings due to increased bed agitation. By means of Compu-tational Fluid Dynamics, we have investigated the effect of synchronous and asynchronous whirling drill string motion on the cuttings bed and cuttings transport for water and a more viscous, shear-thinning fluid using the Two Fluid Model in conjunction with the Kinetic Theory Of Granular Flows and closures from soil mechanics to rheologically describe granular matter. The dynamic mesh capability of ANSYS Fluent R17.2 is exploited to account for the orbital motion of the drill string. In addition, three base cases (negative eccentric, concentric, and positive eccentric) are investigated for comparison. Whirling motion helps tremendously to disperse the solids into the main flow region and hence improves the quality of cuttings transport and hole cleaning, with syn-chronous whirl by far outperforming asynchronous whirl due to the cumulative tangential and radial velocities. The effect is much more prominent for water than for the more viscous, shear-thinning fluid because the latter already shows a comparatively good cuttings transport performance. Moreover, in case of the more viscous, shear-thinning fluid, the positive eccentric annulus provides an even better cuttings transport capability, if comparison is made on equivalent pressure gradients. Because of the higher viscosity level, the whirling motion reduces the axial throughput, which despite the increased bed agitation results in worse performance compared to the positive eccentric case. © 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The equivalent circulation density (ECD) is a very important parameter in drilling high-pressure high-temperature and deepwater wells. ECD is a key parameter during drilling through formations where the margin between the pore pressure and the fracture pressure (FP) is narrow. In these critical formations, the ECD is used to control the formation pressure and prevent kicks. Recent approaches in oilfields to determine ECD depend mainly on using expensive downhole sensors for providing real-time values of ECD. Most of these tools have operational limitations such as high pressure and high temperature which may prevent using these tools in downhole conditions. The objective of this paper is to develop a new approach for predicting ECD using artificial intelligence (AI) techniques from surface drilling parameters [mud weight, drill pipe pressure, and rate of penetration (ROP)]. 2376 data points were used to develop the AI models. The data were collected during the drilling of an 8.5″ vertical hole section. Two AI models were used to estimate the ECD: artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). An empirical correlation for ECD was derived from the optimized ANN model by extracting the weights and biases. The developed ANN and ANFIS models were able to calculate ECD with a correlation coefficient (R) of 0.99 and average absolute percentage error of 0.22% for ANN and ANFIS models, respectively. The developed empirical correlation for the ANN model can be used during well design to choose a correct mud weight to safely drill the well based on the expected drilling parameters. It will also minimize the drilling problems related to ECD such as losses or gains especially in critical situations where the margin between the pore and fracture pressure is very narrow. In addition, using this technique will save cost and time by reducing the need for expensive, complicated downhole tools.

In this paper, finite element analysis is conducted to study dynamic responses of a defected drill pipe (DP) under impact loading encountered in working conditions. Longitudinal impact loading such as tensile, eccentric compressive and torsional impact loading and transverse collision loading are considered. A finite element model is firstly developed and validated, and then employed to evaluate the effects of various impact loading on dynamic responses of the defected DP. It is found that the inertial effect due to tensile impact is the most prominent among all the longitudinal impact loadings. In addition, the effect of the transverse collision between the DP and the borehole wall on the driving force of the crack is evaluated. It is concluded that the dynamic effects of the various impact loading frequently exerting on the DP should be taken into consideration for life prediction of DPs. DOI: http://dx.doi.org/10.5755/j01.mech.24.4.19503

In some situations while drilling through severe doglegs, drill strings are inevitably touching the inner wall of casing, which may wear casing harshly. For instance, this is a frequent problem in wells drilled in Bohai Bay basin in East China. In large dogleg sections of the well, casing is subjected to a dual-wear accumulation contributed by the tool joint and drill pipe (alternate wearing). Nonplanar geometry of the hole and complex geometry of the rotating drill pipe may add to the complexity of the wear process. Here, we propose a mathematical model to calculate the loss of wall thickness of the casing due to the dual wear. A finite element model is developed to incorporate wearing of the casing alternating between the tool joint and the drill pipe. Arbitrary Lagrange-Eulerian (ALE) adaptive meshing and remapping technique is utilized to specify the ablation velocity vectors at the inner casing surface. Our numerical results show that the dual wear contributions and ever changing contact geometry in alternate wearing intensifies the rate of the casing wear 150% faster than that of the single wear models. Additionally, the curvature at point with maximum wear depth has been found to significantly impact the maximum stress of worn casing. This paper provides an accumulative wear model for accurate prediction of the casing wear and its residual strength before running the casing through the dogleg section.

We introduced five types of information transmission method for Measurement While Drilling (MWD): cable method, drilling fluid pulse method, acoustic method and electromagnetic wave method and the latest technology of intelligent drill pipe at present. With the application of advanced drilling technologies such as rotary steering drilling and geosteering drilling, the real-time measurement and transmission of a large number of downhole parameters put forward higher requirements on the information transmission rate. Lower transmission rate has become the bottleneck of parameter expansion for measurement. Intelligent drill pipe (Intelli Pipe) is now the latest downhole signal transmission technology with the highest transmission rate. The communication rate can reach up to 2Mbps, and the stable communication rate can reach 56 kbps, which is too much higher than the current electromagnetic wave or mud pulse transmission applied in MWD, but high manufacturing costs are the main factors that constrain its development.

Hydraulic slotting in a gas drainage borehole is an effective method of enhancing gas drainage performance. However, it frequently occurs that a large amount of slotting products (mainly the coal slurry and gas) intensely spurt out of the borehole during the slotting, which adversely affects the slotting efficiency. Despite extensive previous investigations on the mechanism and prevention-device design of the spurt during ordinary borehole drilling, a very few studies has focused on the spurt in the slotting process. The slotting spurt is mainly caused by two reasons: the coal and gas outburst in the borehole and the borehole deslagging blockage. This paper focuses on the second reason, and investigates the hydraulic deslagging flow patterns in the annular space between the drill pipe and borehole wall. Results show that there are six deslagging flow patterns when the drill pipe is still: pure slurry flow, pure gas flow, bubble flow, intermittent flow, layering flow and annular flow. When the drill pipe rotates, each of those six flow patterns changes due to the Taylor vortex effect. Outcomes of this study could help to better understand the slotting-spurt mechanism and provide guidance on the anti-spurt strategies through eliminating the borehole deslagging blockage. Keywords: Coal hydraulic slotting, Cross-measure borehole, Borehole spurt, Deslagging flow pattern

In drilling industry, barite particles settling and barite sag as a major problem can potentially impose significant operational issues. Static conditions, in which well undergoes an extended shut-in period, could occur during different drilling and completion operations such fishing operation, tripping, and logging. Despite its importance, such phenomenon is not well understood yet. To avoid issues related to barite settlement and barite sag, a good understanding of the impact of different drilling parameters on barite settlement and sag phenomenon is required. Recently, the mathematical formulation and modeling of settlement and sag processes have gained more attention. In order to better design the drilling fluids and to optimize the operational conditions such as flow rate and drill pipe rotation speed, as well as drilling well trajectory design to avoid barite settlement, the mathematical formulation and modeling of such physical phenomena is required. This study is aimed at mathematically describing and analyzing the settling of barite particles in annular concentric space without axial flow by the means of computational fluid dynamic (CFD) simulation. The modeling approach consists of two main steps: a) simple vertical annular domain and b) complex three dimensional barite settlement process in a deviated well with rotational drill pipe. The current work is based on Eulerian two phase model. The settling of the single particle and the hindering effect of other particles on settling velocity have been investigated. Based on single particle model, the rate of barite settlement and fluid pressure reduction have been modeled. However, the single particle model cannot describe the particle to particle interactions and their impacts on settlement such as particle shearing viscosity, kinetic particle viscosity, and collisional effects. In this study, the accurate and comprehensive modeling of barite settlement has been done by applying the Eulerian-Eulerian approach. The models have been validated against available published experimental data in the literature. In addition, in order to further validate the model presented here, drill pipe rotation, fluid rheology, and inclination angle impacts have been experimental investigation and compared with results of the proposed model. The results indicate that the model based on using Eulerian-Eulerian approach accurately predicts the experimental data results. Afterward, the sensitivity analyses were carried out to show the impact of inclination angle, inner pipe rotation, fluid rheology, and barite content on the rate of settlement. This study showed that drag forces induced resuspension plays a vital role in barite settlement inside a deviated well. The results reveal that the settling rate is decreased with increasing the inner pipe rotation and the vortex effect created by inner pipe rotational, play a major role in the reduction of barite settlement. The results also show that the maximum settlement rate accrues at the deviation angles between of 45–60°.

Incidents such as borehole collapse, suction drill, and drill pipe drop resulting from borehole instability may occur in the process of drilling in loose coal bed sections for coal mine methane (CMM) drainage before mining. Grouting while drilling (GWD) is a technique used to reduce such incidents. Sodium Silicate used in GWD has the advantages of controllable consolidation-time, non-toxic material, non-pungent odor and relatively inexpensive. Although it will shrink after solidification, this could be used to connect gas channels. This paper presents the feasibility of using Sodium Silicate to make GWD slurry through results of laboratory experiments. The principal ingredients of the two Sodium Silicate grouting slurry formulae, namely 4% Glycerol Triacetate with 20–40% Sodium Silicate and 4% 1,4-Butyrolactone with 20–40% Sodium Silicate, were selected based on the requirements of GWD. The experimental results from a traditional test device revealed that coal cement stress is still low after 45 min thus limiting its field application. However, after 72 h, multiple cracks appear along the edge of the coal grains suggesting that the formulae can be used to connect gas channels naturally after hardening. If a PH stabilizer is not added, the optimal grouting time occurs within 20 min. In the process of GWD, the grouting slurry will not consolidate until it is injected into the borehole wall, which is enables the drill pipe to remain clean after grouting. Seepage grouting simulation experiments based on a self-developed device indicate that injecting certain slurry into pre-set positions of a drilling hole by circulation wind pressure is feasible to some extent when drilling in fractured, strongly fractured, and pulverized coal beds. In powder coal, however, it will close the gas channels, and thus cannot be applied.

Drill-pipe tool joints in extended reach wells often suffer a shear failure. In view of this, an ultra-high torque double-shoulder pipe joint was designed according to the deformation compatibility relation of the drill-pipe tool joint under torque. It is structurally characterized by long primary and secondary shoulders, small thread taper and large fillet radius of bottom tooth. First, a 3D numerical simulation model was established for this type of joint, named the XSJ joint here, based on the principle of virtual work, the Von Mises yield criterion and the nonlinear contact theory. Second, orthogonal optimization was performed on its key structural parameters by means of the orthogonal optimization method. The optimal combination of key structural parameters of the XSJ joint is taper 1:16, thread pitch 6.55 mm, guiding surface angle 29°, bearing surface angle 28°, and tooth height 3.755 mm. Finally, the bearing performance and fatigue performance of this tool joint and the API tool joint were calculated and compared using the Simulia Abaqus fe-safe software. Compared with the API tool joint, the XSJ joint is better, and its tensile strength, torsion strength, bending strength and compression strength increase by 10.65%, 62.5%, 2.75% and 52%, respectively. Its tension compression fatigue life, bending fatigue life, torsion fatigue life and composite fatigue life increase by 1.19 times, 1.74 times, 550 times and 28.79%, respectively. It is concluded that the designed XSJ joint is significantly improved in term of torsion capacity while its tension strength, bending strength and compression strength are not decreased, so it can better meet the drilling conditions of extended reach wells. Keywords: Extended reach well, Tool joint, Shear failure, Torsion capacity, Bending capacity, Orthogonal optimization, Bearing property, Fatigue life

Erosion of drill pipe caused by the rock particles in annular space is very serious in gas drilling. The aim of this paper is to study the erosion wear law of drill pipe by theoretical derivation and laboratory experiment. Based on the micro-cutting model of single rock particle, the erosion model of drill pipe is established to calculate the erosion wear loss. This model establishes the relationship between the erosion wear loss of drill pipe and drilling parameters, such as gas injection volume and rate of penetration (ROP). The laboratory experiment is carried out to verify and revise the erosion model, and the results show that when ROP is less than 20 m/h, the erosion wear loss of drill pipe is approximatively proportional to the square of gas injection volume and has positive correlation with ROP. However, it has negative correlation with ROP when ROP is faster than 20 m/h. In addition, it is also obtained that gas injection volume has more impact on drill pipe erosion compared to ROP based on the analysis of an engineering example, and high ROP will suppress the erosion wear of drill pipe. Therefore, under the premise of satisfying the drilling requirements, employing lower gas injection volume and higher ROP can reduce drill pipe erosion in gas drilling, which will save the drilling cost greatly.

In the process of air drilling, underground monitoring data can be transmitted by a microwave signal in the drill pipe. In this paper, we analyze the characteristics of the microwave transmission channel in a drill pipe, by regarding the drill pipe as an irregular lossy cylindrical waveguide. We use multipath transmission theory and an experimental statistical method to research the characteristics of the microwave channel and the attenuation law. The existing research results only focus on the dielectric loss of the drill stem; however, herein we point out that there are numerous reflective surfaces that can produce a great deal of reflected waves in the joint section of the drill pipe. Hence, the drill pipe has microwave multipath channel characteristics; consequently, multipath fading and delay are the main factors affecting the transmission quality. According to actual measurement results, the microwave channel composed of a drill pipe unit is in accordance with the ultra-wideband channel stan...

Well interventions in long lateral-reach wells, i.e., wells with laterals 10,000-ft or longer, continues to challenge the oil and gas industry around the world. Without specialized friction reduction technologies, typical-size coiled tubing (CT), such as 2- or 2 ⅜-, 2 ⅝-, or even 2 ⅞-in., has enough rigidity to transfer weights-on-bit (WOBs) to the bottom hole assembly (BHA) in only a part of the current horizontal wells. For instance, 2-in. CT could effectively intervene in about the first half of the 5 ½-in. completed laterals. Increasing the CT diameter or rotating the CT, entirely or partially, remain theoretical options to improve reach. However, larger-diameter CT creates logistical challenges with onshore road transport and offshore crane-lifting/deck-loading limitations. Also, CT rotation, similar to drill pipe rotation, is not economically practical with current CT technologies. Technologies such as lubricants, vibratory and tractor tools are traditionally used to extend the CT reach. Although fluid hammer tools and tractors have extended the CT reasonable operational range significantly, they also increase circulating pressures and operational complexity. To reach a 10,000-ft lateral, metal-on-metal lubricants are required to work with the other friction reduction technologies. However, most of the lubricants currently used for well interventions perform worse in the field than at atmospheric conditions in the laboratory. In addition, field success can depend on factors besides the lubricant's friction reduction capability, such as its synergy with the other commonly circulated brines and fluid friction reducers or its regain permeability performance. Despite a broad use of the CT lubricants and their importance for the predictability and success of the well interventions in extended-reach wells, reliable and consistent field validation studies of their friction reduction capabilities are rare. Field performance data are mostly anecdotal or proprietary. In addition, there was no available literature review of the knowledge gained to date. Thus, a critical review of studies addressing the CT lubricants and scientific demonstrations of their field performance will indicate the challenges and limitations currently encountered in the field. This will hopefully trigger further research and development and best field practices for CT lubricants and well intervention operations in extended-reach wells.

Failure of horizontal oilwell drilling equipment, in particular the bottom-hole-assembly, is very costly. Vibration causes tool joint failure, twist-off, and bit-damage, and has motivated extensive research on understanding and predicting the dynamic shock-loading response of the bottom-hole-assembly. This paper presents a model to analyze the dynamics of a horizontal oilwell bottom-hole-assembly. A nonlinear three-dimensional multibody shaft model has been verified and extended to include stick-slip whirl phenomena due to the contact between the rotating bottom-hole-assembly and wellbore. The model has been verified with a dynamic finite element analysis through comparisons of the response of an enclosed shaft under axially compressive load rotating inside the wellbore. Finally, a complete deviated drillstring has been simulated by combining the bottom-hole assembly model with a model of the drill pipe and collars. The pipe and collars are modeled using a lumped-segment approach that predicts axial and torsional motions. The model can predict how axial and torsional bit-rock reactions are propagated to the surface, and the role that lateral vibrations near the bit play in exciting those vibrations and stressing components in the bottom-hole-assembly. The proposed model includes the mutual dependence of these vibrations, which arises due to bit-rock interaction and friction dynamics between the drillstring and wellbore wall. A force excitation source, which simulates an axially-vibrating downhole tool, has been implemented in the horizontal section of the virtual drillstring. Simulations show a better weight transfer to the bit due to the tool, with a low frequency and high amplitude force excitation giving best performance but potentially increasing the severity of lateral shock. The model, implemented using the bond graph formalism, is a useful tool for design and sensitivity analysis due to its physically meaningful parameters and low simulation times on a personal computer.

Percussive-rotary drilling is an effective method for the hard rock drilling. As hydraulic and pneumatic hammers have many problems especially in the deep core drilling, a new electromagnetic hammer driven by a tube linear motor is introduced in this study. The study mainly covers the mechanical structure and electromagnetic design of the hammer, respectively. Due to the direct use of electric power, the electromagnetic hammer has the advantage of high efficiency while it must meet the minimal percussive energy requirement under the limitation of drill pipe diameter. In this study, the validity of electromagnetic design is verified through the finite-element analysis software Ansoft/Maxwell 2D and numerical calculation of electromagnetic force. The working temperature in deep down-hole is relatively high, the influence of high temperature in deep hole on the electromagnetic thrust of the linear motor is then analysed. A motion model of linear motor hammer is established to calculate and analyse the impact power and frequency under different conditions. The results show that the performance of linear motor hammer can reach or even exceed the one of same diameter hydraulic hammer, especially in the low-frequency range. The prototype test also confirms the validity of the design.