Downhole Drilling Tools Research Articles

A Monitoring System for Failure Risk of Downhole Drilling Tools in Complex Formations

A Monitoring System for Failure Risk of Downhole Drilling Tools in Complex Formations

Parameter optimization based on deepwater drilling system simulation: A pre-salt exploration well in Brazil

The vibration of downhole drilling tools is the primary factor that limits the ROP of deep-water salt drilling. Pre-drilling modeling is an essential method for analyzing the dynamic characteristics of the drilling system. Currently, there is limited research on coupling models between the single riser model and drill string model in deepwater drilling dynamics, which hampers offshore drilling dynamics development. In this study, we integrated the dynamic riser model with the flexible drillstring dynamic model, optimized the system's boundary conditions through experiments, and established an advanced full-scale deepwater drilling system. Through virtual drilling simulation analysis and energy flow calculations of the drilling process, we investigated the movement trajectory of the drillstring system at different positions and its correlation with downhole vibration in deepwater drilling. Finally, we performed parameter optimization on Brazil exploration well salt formation. The results indicate that the rotational speed significantly influences the vibration intensity and motion state of both the drill string and downhole drilling tool. Moreover, the kinetic energy and strain energy of BHA effectively reflect the motion state of the downhole drilling tool. When drilling salt and salt intercalation in the Brazil exploration well, the WOB was controlled within 200 kN and 180 kN, and the rotational speed was controlled within 180 rpm and 140 rpm, respectively. This ensured optimal stability and minimized vibrations within the drill string system. The virtual simulation work based on deepwater drilling systems can provide guidance for designing and planning actual drilling operations, as well as proposing reasonable drilling parameters to enhance stability and ROP in the drilling process.

Research on the Temperature Field Distribution Characteristics of Bottomhole PDC Bits during the Efficient Development of Unconventional Oil and Gas in Long Horizontal Wells

Unconventional tight oil and gas resources, including shale oil and gas, have become the main focus for increasing reserves and production. The safe and efficient development of unconventional oil and gas is a crucial demand for the energy development strategy. Deep tight oil and gas resource development generally adopts horizontal well drilling methods. During drilling, especially in long horizontal sections, the high temperature frequently causes failures of downhole drilling tools and rotary steering tools. The temperature rises sharply during rock breaking with the drill bit. Existing wellbore heat transfer models do not fully consider the impact of heat generated by the drill bit on the wellbore temperature field. This paper aims to experimentally study the temperature rise law of the cutting tooth of the bottom polycrystalline diamond compact (PDC) bit during rock breaking. A set of evaluation devices was developed to study the temperature field distribution characteristics at the bottom of the PDC bit during rock breaking under different experimental conditions. The results indicate that the flow rate of drilling fluid, bit rotation speed, and weight on bit (WOB) significantly affect the distribution of the temperature field at the well bottom. This experimental research on the temperature field distribution characteristics at the bottom of the PDC bit during rock breaking helps reveal the heat transfer characteristics of the long horizontal section wellbore, guide the optimization of drilling parameters, and develop temperature control methods. It is of great significance for the advancement of efficient development technologies for unconventional resources in long horizontal wells.

Research on Hybrid Vibration Sensor for Measuring Downhole Drilling Tool Vibrational Frequencies

The vibration parameters during drilling play a critical role in enhancing drilling speed and ensuring safety. However, traditional downhole vibration sensors face limitations in their power supply methods, hindering widespread adoption. To address this challenge, our research introduces a novel solution: a hybrid downhole vibration sensor (HDV-TENG) utilizing triboelectric nanogenerators. This sensor not only enables the measurement of low- to medium–high-frequency vibrations using self-power but also serves to energize other downhole devices. We utilized a self-constructed vibration simulator to replicate downhole drilling tool vibrations and conducted a comprehensive series of sensor tests. The test results indicate that the frequency measurement bandwidth of the HDV-TENG spans from 0 to 200 kHz. Especially, the measurement errors for vibrations within the low-frequency range of 0 to 10 Hz and the high-frequency range of 10 to 200 k Hz are less than 5% and 8%, respectively. Additionally, the experimental findings regarding load matching demonstrate that the HDV-TENG achieves an output power level in the milliwatt range, representing a significant improvement over the output power of traditional triboelectric nanogenerators. Unlike traditional downhole vibration measurement sensors, HDV-TENG operates without requiring any external power supply, thereby conserving downhole space and significantly enhancing drilling efficiency. Furthermore, HDV-TENG not only offers a broad measurement range but also amplifies output power through the synergy of a triboelectric nanogenerator (TENG), piezoelectric nanogenerator (PENG), and electromagnetic power generator (EMG). This capability enables its utilization as an emergency power source for other micropower equipment downhole. The introduction of HDV-TENG also holds considerable implications for the development of self-powered underground sensors with high-frequency measurement capabilities.

Experiment Study of Deformable Honeycomb Triboelectric Nanogenerator for Energy Collection and Vibration Measurement in Downhole

Downhole drilling tool vibration measurement is crucial for drilling exploration safety, so real-time monitoring of vibration data is required. In this research, a honeycomb triboelectric nanogenerator (H-TENG) capable of adapting to various downhole environments is proposed. It can measure the frequency of downhole drilling equipment’s vibrations and transfer mechanical energy to electrical energy for use in powering other low power downhole meters. In order to preliminarily verify the possibility of sensors used for vibration measurement of downhole drilling tools, we built a simulated vibration platform to test the sensing performance and vibration energy collection performance of H-TENG. According to the testing results, the measurement range of vibration frequency and amplitude are 0 to 11 Hz and 5 to 25 mm, respectively, and the corresponding measurement errors are less than 5% and 6%, respectively. For vibrational energy harvesting, when four sensors are wired in series with a 107 resistance, the maximum power is approximately 1.57 μW. Compared to typical methods for measuring downhole vibration, the honeycomb triboelectric nanogenerator does not need an external power source, it has greater reliability and output power, and it can vary its shape to adapt to the complicated downhole environment. In addition, the H-TENG can be combined freely according to the diameter of the drill string, and even if one sensor unit is damaged, the other units can still be used normally.

Estimation of geomagnetic components under unknown interferences for drilling tools

The geomagnetic components measurement directly influences the azimuth and magnetic Toolface of downhole drilling tools. Accurate estimation of the geomagnetic components is crucial for wellbore trajectory control. However, the unknown magnetic interferences caused by ferromagnetic drilling tools introduce significant errors in the estimation of the geomagnetic components. Firstly, this paper considers the constraint of a constant total magnetic field value and introduces the unknown axial interferences of the drilling tools as a new state. At the same time, parameter uncertainties and radial interferences within the drilling tools are regarded as unknown but bounded, leading to the establishment of a linear time-varying system model for the measurement system. Then, a state estimation method based on the Zonotopic Kalman filter (ZKF) is proposed for geomagnetic components and attitude measurements. The simulation results indicate that, compared to the ZKF method without considering nonlinear constraints, the method proposed in this paper effectively separates the axial interference of the geomagnetic components from the drilling tools during dynamic measurements. The root mean square errors of the estimated three-axis geomagnetic components are reduced to 0.0249 Gauss, 0.0082 Gauss, and 0.0148 Gauss, resulting in improvements in accuracy of 96.06%, 28.6%, and 14.1%, respectively. Furthermore, the root mean square errors of the gravity Toolface, magnetic Toolface, and azimuth estimation decreased to 1.8296°, 1.8294°, and 3.2898°, leading to enhancements in accuracy of 9.61%, 9.71%, and 96.37%, respectively. Finally, experimental validation confirms the effectiveness of the proposed method, providing a reference basis for dynamic measurement while drilling.

Cobalt-removed PDC as the diamond thrust bearing friction pair material: tribological behavior in water-based drilling fluids

To solve the problems of high vibration, low lifespan, and frequent replacement of diamond thrust bearings, the tribological behavior and friction mechanism of cobalt-removed and untreated PDC under different axial loads and rotational speeds were investigated in the WBDFs. The results indicated that the cobalt-removed PDC had lower friction coefficients, smoother friction status, better wettability, and better wear resistance than the untreated PDC. Cobalt-removed PDC could avoid the occurrence of thermal wear in the friction process, and the main forms of surface abrasion were dominated by mechanical wear. This study provides the experimental basis for the use of cobalt-removed PDC as a friction pair material for diamond thrust bearings, which can promote further research and development of downhole drilling tools.

Electrodeposition of Double Chromium Plating to Improve Corrosion Performance of Screw Drilling in Chloride Environment

To adapt to and satisfy rising energy demand, oil and gas exploration and production are gradually spreading to locations with poor underground conditions, and the demand for screw drilling instruments is rising as well. When underground drilling tool materials are subjected to these harsh operating circumstances, they corrode severely and may even cause drill pipe breakage and blowout incidents. Failure due to corrosion is still the most common type of failure, with drilling fluid being the leading cause of downhole drilling tool corrosion and equipment damage, particularly in high-temperature and high-pressure working conditions with higher corrosiveness, which must be avoided and controlled. Double chromium was successfully plated on the surface of the screw rotor using the electrodeposition method to extend the service life of screw drilling instruments. Electrochemical methods such as scanning electron microscopy, open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization curve were used to analyze the plating’s morphology and corrosion resistance. The research results show that at high chloride concentrations (50g/L∼100g/L), when the chloride ion concentration is 60g/L, corrosion resistance is the lowest, and that double chromium plating enhances threaded drilling tool corrosion resistance. The dual chromium plating’s polarization resistance has been enhanced by 18 times. The double chrome plated milky white chrome plating functions as a physical barrier to prevent corrosive substances from diffusing to the substrate interface, corrosive ions from reaching the substrate, and considerably improving the screw rotor’s anti pitting performance.

Rate of penetration estimation downhole with machine learning for drilling position control

The development of fully autonomous downhole directional drilling systems has been hindered by the lack of rate of penetration (ROP) information downhole. This information is critical for determining bit position and steering dynamics, which currently can only be determined at the rig. Consequently, drilling position controllers must be placed on the surface, which leads to significant performance limitations due to communication delays with the downhole drilling tool. This study investigates a new approach that enables downhole implementation of position control: real-time estimation of ROP downhole. Motivated by results from the field of drilling optimization, estimation is performed using machine learning. In contrast to prior work, we limit model features to only measurements acquired downhole, and we focus on minimizing model size given the constrained computing environment downhole. We use a continuous learning framework with incremental training data availability and derive relationships that reveal how prediction error can impact position measurement and controller dynamics. Additionally, we develop novel performance metrics and introduce a modified form of cross-validation for model evaluation. Using data acquired from three directional wells, experiments are conducted to compare the performance of several machine learning models and to assess the effect of varying retraining frequency and training data quantity. The results indicate that the proposed method achieves comparable accuracy to models implemented on the surface despite being constrained in size and model inputs. Additionally, the results show that increasing the retraining frequency almost always reduces test error, and that the training data can be downsampled substantially without a significant drop in accuracy.

Dual-mode acceleration sensor of downhole drilling tools based on triboelectric nanogenerator.

Downhole vibration is important for the judgment of the drilling tool conditions and the formulation of drilling technology. To meet the demand of downhole drilling tools acceleration measurement, this research proposes a self-powered acceleration sensor with two working modes based on the triboelectric nanogenerator, namely, mode A, which is based on the voltage response acceleration trend and mode B, which judges the acceleration based on the output pulses. Test results show that the acceleration measurement range is 0-11m/s2, the maximum output voltage amplitude can reach 15.3V, the working environment temperature is less than 250°C, the working environment humidity is less than 90%, and long-time working has almost no effect on the output voltage of the sensor. In addition, since the sensor will generate electrical energy during the vibration process, the power generation performance of the sensor has been tested. And the results show that the maximum output power of the sensor is 0.18 µW when a 1000 MΩ load is connected in series. Compared to traditional downhole sensors, the sensor is more flexible, because it can work normally at high temperatures and has the potential for being self-powered.

Analysis of Whirl Characteristics of Drill String Under Multidirectional Coupling Conditions

Summary The nonlinear contact between the bottomhole assembly (BHA) and the borehole can cause backward whirl. During an actual drilling process, the backward whirl will increase wear of the downhole drilling tool and lead to bending or even bulking failure. Therefore, analyzing the drillstring whirl characteristics considering multidirectional coupling effects, combined with field conditions, is a key issue and research hotspot. In this paper, considering the relationships between axial, torsional, and lateral vibrations of the drillstring system, the whirl model is established with finite element method. Research results indicate that with higher driving speed and larger friction coefficient between drillstring and borehole wall, the drillstring lateral vibration changes from forward to backward whirl. On the contrary, the increasing of drilling fluid density can effectively suppress the occurrence of backward whirl. As drilling fluid density increases, forward and backward whirl coexist, and only the forward whirl occurs at last. The research results can provide a basis for formulating whirl control strategy, and promoting the efficient and safe operations of drilling engineering.

Self-Powered Downhole Drilling Tools Vibration Sensor Based on Triboelectric Nanogenerator

The vibration state of the drilling tool is particularly important for its working condition monitoring. Here, a self-powered downhole drilling tools vibration sensor (hereafter referred to as V-TENG) based on triboelectric nanogenerator (TENG) is proposed. The V-TENG, which is designed as the single electrode and independent layer TENG, can synchronously realize the measurement of drilling tools vibration frequency and amplitude. Test results show that the frequency measuring range is 0 to 13 Hz, with an error of no more than 5%, and the amplitude measuring range is 0 to 130 mm, with a resolution of 10 mm and a maximum deviation of 5 mm. In addition, the possibility of the sensor converting vibration energy into electrical energy and providing power for other measuring instruments was explored, the test results show that the maximum power of the frequency measuring module is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$88.92\times 10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−8</sup> W with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{8} {\boldsymbol \Omega } $ </tex-math></inline-formula> resistance in series, while the amplitude measurement is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$28.62\times 10$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> W with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{9} {\boldsymbol \Omega }$ </tex-math></inline-formula> resistance in series. Compared with traditional downhole vibration sensors, the V-TENG can synchronously measure the drill string vibration frequency and amplitude in a self-powered model, which is more suitable for downhole conditions.

ШЛЯХИ ІНТЕНСИФІКАЦІЇ ВИБІЙНИХ ПОРОДОРУЙНІВНИХ ПРОЦЕСІВ ПРИ СПОРУДЖЕННІ СВЕРДЛОВИН

Purpose. Development of structural foundations for downhole devices (hydraulic hammers) to create dynamic loads on the drilling technological tool and study of the basic physical and chemical processes occurring in their hydraulic circuit and the bottomhole zone of the well. Methodology. The study of the patterns of constructive and technological interaction of the main parts and assemblies of the hydraulic percussion mechanism was carried out when testing its physical model included in the functional diagram of a special drilling stand equipped with appropriate power and hydraulic units, as well as a control and measuring unit. Studies of the physicochemical properties of flushing fluids and their influence on the course of rock mass destruction processes, intensified by the application of generated dynamic loads, were carried out using standardized devices for monitoring the parameters of special process fluids, as well as by bench destruction of experimental rock blocks with the appropriate complex technical measurements. Findings. A basic structural diagram of a hydraulic percussion device has been developed, with its physical embodiment, in which a significantly different execution and functioning of the interacting nodes creates the prerequisites for effective control of the machine in question. The presence of mutual consistency of the circulation processes implemented in the hydraulic hammer model allows its use in various modifications of the regime and technological support of progressive methods of wellbore formation. The proposed hydraulic hammer contains in its design a fairly large number of unified parts and is practically devoid of the presence of wear elements, which ensures its significant motor resource and high maintainability. Simultaneous combination of a hydraulic hammer with the use of activated flushing fluids in the technological scheme of bottomhole assemblies allows to obtain a significant increase in the mechanical fracture rate due to reduced surface tension and acceptable rheological characteristics of the dispersion medium for rock destruction. Originality. The use of alternately different pressure chambers in the design of the hydraulic hammer makes it possible to form a single closed circulation-technical system, with the possibility of effective regulation of its energy performance and operational transition between different drilling modes. Practical value. The proposed layout of the hydraulic percussion machine makes it possible to expand the areas of its possible application in the technical and technological schemes of downhole drilling tools, as well as the implementation of measures to eliminate downhole accidents and complications. Key words: well, hydraulic hammer, drilling, surfactant, rock destruction, flushing fluid, mechanical speed, bottom hole.

Dynamic research and experimental analysis of a longitudinal–torsional coupled impactor

The rock breaking efficiency of drill bit is deeply affected with the increase of drilling depth. The increase length of the drill string leads to torsional stiffness decrease, which may even result in the stick-slip phenomena. In order to improve the rock breaking efficiency and reduce the stick-slip, this paper proposed a longitudinal–torsional coupled impactor. The internal working mechanism was carried out by theoretical analysis and experimental test. Moreover, comparing the computation and test results, the following conclusions can be obtained and verified. This innovative design can provide appropriate longitudinal-torsional coupled impact to drill bit during drilling process, and the movement of the hammer and pendulum is periodic. With the increasing flow rate of drilling fluid, this tool can generate corresponding larger impact force, torque and higher impact frequency. The theoretical analysis results are consistent with the experimental test results, which verify the reliability of the innovative design and the accuracy of theoretical analysis. This paper can provide reference for the innovative design of downhole drilling tool, the development of drilling dynamics and the improvement of drilling efficiency especially in the conditions of complex and ultra-deep wells.

A novel temperature-sensitive expandable lost circulation material based on shape memory epoxy foams to prevent losses in geothermal drilling

Lost circulation will inevitably increase non-productive time (NPT) and well cost. The application of high-efficiency lost circulation materials (LCMs) plays an indispensable role in preventing and mitigating loss. The development of new LCMs based on stimuli-responsive materials is an important research direction and it is expected to realize the revolutionary development of LCMs. In recent years, the temperature-responsive plugging agent based on shape memory polymers has caused a lot of attention. In this paper, based on the shape memory epoxy polymer (SMEP) and hollow glass beads (HGBs), a shape memory epoxy foam (SMEF) was successfully synthesized. The results show that the shape memory temperature (51.6 °C - 97.5 °C) of the SMEPs has a good linear relationship with the content of curing agent 4, 4′-diaminodiphenyl methane (DDM) (12% - 20%), and the expansion ratio (0% - 120.2%) of the SMEFs has a good linear relationship with the content of HGBs (0% - 50%). The mechanism of the SMEFs was proposed. A novel temperature-sensitive and expandable plugging agent (SMP-LCM) has been developed. The plugging experiment shows that SMP-LCM has a good plugging effect on high permeability loss zone simulated by sand beds. Compared with conventional LCMs (e.g., nutshells or fibers), SMP-LCMs can eliminate the risk of plugging of downhole drilling tools and enhance the plugging effect.

A study on mechanical properties of equal wall thickness rubber bushing of positive displacement motor based on hydrogenated nitrile butadiene rubber aging test

Shale gas production has become the main driver of global gas production growth. Deep shale gas is difficult to extract, which puts forward higher requirements for drilling speed increase. The downhole power drilling tools are mainly screw drilling tools. Conventional screw drill tool stator bushing has poor heat dissipation, which is prone to thermal hysteresis failure, shortening drilling tool life, and is not suitable for high temperature and high pressure environment of deep shale gas wells. Equal wall thickness screw drilling tools and hydrogenated nitrile rubber have better high temperature resistance. Therefore, based on the thermal aging experiment and constitutive model of the rubber changes the displacement of the inner cavity of the stator bushing and the difference between the front and the back is up to 21.6%. The increase of the interference and eccentricity between rotor and motor leads to the increase of the maximum von Mises stress of the stator bushing and the thermal hysteresis temperature. The influence of the interference is greater than the influence of the eccentricity so that the interference should be given priority in the design. This paper provides a theoretical reference for the design and optimization of equal wall thickness bushing of positive displacement motor.

A self-powered vibration sensor for downhole drilling tools based on hybrid electromagnetic-triboelectric nanogenerator.

The vibration of downhole drilling tools is important to the drilling process, which needs to be measured in real time. Here, a self-powered vibration sensor for downhole drilling tools based on a hybrid electromagnetic-triboelectric nanogenerator is proposed in this research. The sensor has high reliability because the triboelectric nanogenerator (TENG) and the electromagnetic generator (EMG) parts of the sensor can be used as vibration sensors alone, and it may also supply power to other micro-power measurements while drilling instruments when the TENG and the EMG are used in parallel to increase the output power. Test results show that for the TENG part, the maximum output voltage, current, and power are 14V, 5.2 µA, and 3.2 µW, respectively, with a 1 MΩ resistance in series, and for the EMG part, they are 1.22V, 33 µA, and 21.8 mW, respectively, with a 10 Ω resistance in series. Further tests show that the measurement range of both the TENG and EMG is 0-11Hz, the measurement error of both is less than ±5%, and both can work normally in the temperature range of less than 250 °C. In addition, this research also builds a wireless vibration data transmission system based on the sensor, which shows the potential for use in the wireless sensing field.

Wringing effect prevention on a piston design in a downhole drilling tool

This research studied the wringing effect present on a piston with two contact surfaces in a downhole tool and investigated piston design guidance to prevent this occurrence. A piston on the downhole drilling tool is designed to be moved by hydraulic forces on-demand in downhole operation. The piston failed to move during an experiment at a depth of 8772 m in an oil drilling well located in the Gulf of Mexico. The wringing effect was suspected as the root cause of this failure, and subsequent laboratory experiments confirmed that wringing presence caused non-functional piston. Then, potential influencing factors causing wringing effects were analysed and investigated in a series of laboratory experiments aiming to eliminate the wringing adhesive force between the contact surface of the piston and its mandrel. The investigated factors included the roughness and area of the contact surfaces and pre-compression force. Based on the findings, the piston design was optimised and re-tested, and it was found that the optimised piston eliminated wringing adherence. With experimental data, semi-empirical design guidance regarding the influencing factors was summarised for critical piston design to eliminate possible wringing.

Tribological behaviour of thermal sprayed high velocity oxy-fuel coatings on tungsten carbide – A review

Thermal spray coating is a surface modification technique that improves the properties of the metal surface. The basic principle of this technique is the combination of melting and acceleration. Thermal spray coatings are also classified as plasma spray, High-Velocity Oxy-Fuel, wire arc, detonation, and so on. Among the types of thermal spraying, the high-velocity Oxy-fuel process is a widely used technique in various applications. Chromium and tungsten carbide are used in down-hole drilling tools and gas turbine engines because of high resistance to wear, erosion, cavitation, high hardness, and toughness. In this review article, wear characteristics, corrosion analysis, hardness, surface roughness, and microstructure of thermal sprayed High-Velocity Oxy-Fuel - Tungsten Carbide coatings have been addressed.

Research of Downhole Instructions Decoding with Variable Drilling Fluid Displacement

This paper studied a downlink communication mode in which the effective downhole control instruction was generated by the use of drilling fluid pump displacement to format three descending and three ascending pulse instruction encoding. The principle of the downlink communication was introduced. The encoding idea of the downlink instruction code with 5-bit pulse was described. This downlink code was used to compose the corresponding control instruction which includes the information of the tool face angle and the guide force percentage. The downhole pulse widths were recognized by using STM32 as a micro control chip. The corresponding control commands were identified through the development of the software in the downhole drilling tool. Laboratory ground experiments demonstrated the feasibility of this downlink transmission mode by using variable drilling fluid displacement and the achievability of instruction decoding software.