Drilling Parameters Research Articles

Rheological effects of air drilling fluids on cuttings transportation in underbalanced drilling

This research investigates factors influencing cuttings transport efficiency in air drilling operations, aiming to understand the underlying mechanisms, identify critical factors, and optimize drilling parameters for enhanced performance. The methodology includes a literature review, computational fluid dynamics (CFD) simulations, and sensitivity analysis of air velocity, drilling fluid properties, cuttings size, and outlet pressure. CFD simulations were employed to model the multi-phase flow in the annulus during air drilling, examining the effects of varying air velocities, cuttings sizes, and outlet pressures on cuttings transport and hole cleaning efficiency. Results show that increased air velocity improves cuttings transport and hole cleaning but may cause higher pressure drops and borehole erosion. Air drilling fluids' unique rheological properties significantly impact cuttings transportation, requiring careful consideration of factors like air velocity, aerodynamic lift, hole cleaning efficiency, annular pressure losses, and potential cuttings accumulation. The study reveals that cuttings size is crucial for transport efficiency, with larger cuttings necessitating higher air velocities for effective transport and being more prone to settling and accumulation. Moreover, the research demonstrates that increasing outlet pressure typically enhances cuttings transport efficiency in horizontal wells. In conclusion, this study offers valuable insights into factors affecting cuttings transport efficiency in air drilling operations, providing recommendations for optimizing drilling parameters to balance efficient cuttings removal, hole cleaning, and minimal pressure drop. The findings hold practical implications for air drilling operations' design and execution, with the potential to improve drilling performance and reduce operational risks.

Drilling Parameter Optimization of Shale Gas Wells Based on Saw-Tooth Genetic Algorithm to Reduce Drilling Costs

It is difficult to optimize the drilling parameters, which makes it difficult to reduce drilling costs in the process of drilling shale gas wells in the Fuling region of Chongqing, China. This paper takes the optimization combination of drilling parameters in drilling engineering as the research object and uses a saw-tooth genetic algorithm to perform the objective function. To solve the problem, the algorithm proposes a variable population size with periodic reinitialization, which follows a saw-tooth scheme with unequal amplitude and change period (saw-tooth GA), which can optimize the drilling parameters under constraints. According to the actual situation of the wells in the Fuling region, the three algorithms are compared for the vertical section’s drilling parameters. Example calculations show that the algorithm can achieve the best economic benefits at different revolutions per minute and WOB to reduce drilling costs. Compared with other methods, this algorithm has the characteristics of fast convergence, is easy to understand, and is simple to implement. The proposed algorithm is tested for the drilling parameter optimization of shale gas wells and from which it becomes evident that the saw-tooth scheme enhances the overall performance of GAs.

Estimation of geomechanical rock characteristics from specific energy data using combination of wavelet transform with ANFIS-PSO algorithm

The geomechanical characteristics of a drill formation are uncontrollable factors that are crucial to determining the optimal controllable parameters for a drilling operation. In the present study, data collected in wells drilled in the Marun oilfield of southwestern Iran were used to develop adaptive network-based fuzzy inference system (ANFIS) models of geomechanical parameters. The drilling specific energy (DSE) of the formation was calculated using drilling parameters such as weight-on-bit (WOB), rate of penetration (ROP), rotational speed of drilling string (RPM), torque, bit section area, bit hydraulic factor, and bit hydraulic power. A stationary wavelet transform was subsequently used to decompose the DSE signal to the fourth level. The approximation values and details of each level served as inputs for ANFIS models using particle swarm optimization (PSO) algorithm and genetic algorithm (GA). As model outputs, the Young’s Modulus, uniaxial compressive strength (UCS), cohesion coefficient, Poisson’s ratio, and internal friction angle were compared to the geomechanical parameters obtained from petrophysical logs using laboratory-developed empirical relationships. Both models predicted the Young’s modulus, UCS, and cohesion coefficient with high accuracy, but lacked accuracy in predicting the internal friction angle and Poisson’s ratio. The root mean square error (RMSE) and determination coefficient (R2) were lower for the ANFIS-PSO model than for the ANFIS-GA model, indicating that the ANFIS-PSO model presents higher accuracy and better generalization capability than the ANFIS-GA model. As drilling parameters are readily available, the proposed method can provide valuable information for strategizing a drilling operation in the absence of petrophysical logs.

Downhole vibration characteristics of 3D curved well under drillstring–bit–rock interaction

Understanding the characteristics of downhole vibration helps optimize the drilling parameters and improve the rate of penetration (ROP). This work establishes a nonlinear drillstring–bit–rock model to predict the downhole vibration behavior of 3D curved wells. The main novelty of this model is to consider the complex nonlinear bit–rock interaction and well trajectory. The model is solved by the Newmark method and verified by an indoor experiment and field data. The drillstring dynamics and effects of the main working parameters on the vibration characteristics are obtained and analyzed. Results show that, in the horizontal section, the drillstring motion and shape deformation are stable, and radial vibration is dominant. In the buildup section, the drillstring motion is irregular and messy, shape deformation becomes large, and radial vibration is significant but tangential vibration starts to become intense. In the vertical section, the drillstring motion is small in wellbore center, shape deformation is stable, and vibration severity reduces. The weight on bit (WOB) only affects drillstring vibration near the bit, and radial, tangential, and axial accelerations intensify as WOB increases. RPM has little effect on the drillstring vibration in 3D curved wells. In the buildup and horizontal sections, as the coefficient of friction (COF) increases, the radial and tangential accelerations rise while the axial vibration obviously weakens. When drilling in 3D curved wells, small WOB and large RPM can be adopted to reduce downhole vibration and increase ROP. The safety of drillstring and downhole tool also needs more attention when drilling in formations with large COF, such as gravel stone and sandstone. Large oil/water ratio or lubricant is recommended to improve the lubricity of drilling fluid. The research results could provide a valuable and useful guidance for drilling engineers to improve ROP and reduce downhole accidents.

Correction to: Identification of sand layers based on key drilling parameters

Correction to: Identification of sand layers based on key drilling parameters

Analysis of MRR, Thrust Force, and Torque in Drilling Al/BN/Al2O3 Composites using Hybrid Grey–Taguchi Technique

The demand for hybrid composite materials has been expanding globally in all kinds of mechanical industries. Drilling is one of the basic operations required in manufacturing of various components and choosing optimum parameters of drilling is vital for getting good quality holes. The main objective of our work is to determine the ideal parameters of drilling and tool coatings required to minimize the thrust force and torque in drilling and to maximize the material removal rate (MRR) using Grey–Taguchi technique. Hybrid composite specimen made by reinforcing Al7075 alloy with 4% of aluminum oxide and 2% of boron nitride in stir casting process and drilling was carried out in a sequence at different drilling feed rates (40, 80, and 120 mm/min) and spindle speeds (1,200, 2,400, and 3,600 rpm) in a vertical machining center attached with drill tool dynamometer, using twist drills of diameter 5 mm and point angle 118° made of uncoated carbide, diamond-like carbon (DLC)-coated carbide and high carbon (HC)-coated carbide. The recorded thrust force and torque from the dynamometer and the computed MRRs during each drilling operation are tabulated as per Taguchi’s L27 orthogonal array and the results are analyzed using hybrid Grey–Taguchi technique. In our analysis, the optimum thrust force of 62.12 N and torque of 0.766 Nm were obtained when using a DLC-coated tool at a maximum speed of 3,600 rpm and minimum feed rate of 40 mm/min. An optimum MRR of 178.79 mm3/s was obtained while using DLC coated at a maximum speed of 3,600 rpm and a maximum feed rate of 120 mm/min.

Identification of sand layers based on key drilling parameters

Identification of sand layers based on key drilling parameters

Finite element analysis of process parameters influences on deformation and von mises stress in drilling

Drilling is a very important machining process which accounts for more than 20% of the machining processes. Failure of drill bit is crucial when drilling difficult to machine materials such as composites and high temperature alloys. Selection of drill bit tool geometry, drill material and process parameters are vital for success of drilling difficult to machine materials. Finite element analysis and Taguchi Techniques are coupled to find out the optimum drilling parameters. Three process parameters such as material used for the drilling bit, cutting speed and drill point angle are used for analysis. Deformation and von mises stress are considered as response variables. The Taguchi method is employed to figure out the optimal process parameters for drilling operations. Based on SN ratio analysis and ANOVO, optimum drilling parameters for deformation were found to be CBN with 2000 rpm cutting speed and 114 as the drill point angle. From ANOVO analysis, it was found that drilling RPM is the most significant process parameter.

Investigation of force modeling in ultrasonic vibration-assisted drilling SiCf/SiC ceramic matrix composites

Due to their exceptional high-temperature and rust resilience, SiCf/SiC ceramic matrix composites have been regarded as potential high-temperature components. For application, to overcome issues resulting from the high hardness and brittleness, the ultrasonic vibration-assisted machining technique is primarily adopted in the machining of SiCf/SiC ceramic matrix composites. It is essential to develop a force model for a better understanding of the material removal and cutting processes by applying ultrasonic vibration. As a result, studies on force modeling during ultrasonic vibration-assisted drilling of SiCf/SiC ceramic matrix composites have been conducted in this study, taking into account the trajectory of the drilling tool, the tool-workpiece contact state, and the material removal mode. Based on the coefficient calibration experiment and least square method, the irregular coefficient of abrasive grains, the crack growth parameters of materials, and the mechanical parameters that are difficult to be measured were determined. After that, the drilling parameters and vibration parameters were merged to build the analytical force model, and the parameter influence rules on the force was also studied. The suggested drilling force model concurred well with tests under the highest relative error of 17.34 %, according to the findings of the confirmation experiments.

Optimization of CO2 laser drilling process parameters of GFRP/Al2O3/perlite composites

Glass Fiber Reinforced Polymer (GFRP) composites have excellent mechanical characteristics and are extensively used in aerospace and marine applications. Drilling GFRP composite through conventional methods leads to delamination and taperness, causing quality loss and imprecision. CO2 laser drilling, an unconventional method to drill GFRP composites, is adopted in this study to reduce the delamination and taperness. This work aims at optimizing the process parameters of CO2 laser drilling. Hybrid S-glass/Al2O3/Perlite powder composite is used in this study. Laser drilling parameters: laser power (P), cutting speed (N), focal length (L), and hole diameter(d) were studied to reduce the hole delamination and hole taperness. These results were achieved through mathematical modelling and optimization using Response Surface Methodology (RSM) and Multi-Objective Genetic Algorithm (MOGA). The optimum process parameters were found by minimizing the objective function upon considering the drilled holes economic features, deposition efficiency, geometric features, and hole diameter at larger and smaller sides. The most critical output factors, delamination and taper responses, had a deviation from the objective by less than 3%. The optimum process parameters laser power, cutting speed, and focal length is found to be 80.795 W, 7.9089 mm/sec, and − 1.9641 m respectively. From the experimental confirmation study, the optimum process parameters effectively reduced the hole delamination and taperness.

Estimation of mechanics parameters of rock in consideration of confining pressure using monitoring while drilling data

During the drilling process, high-strength rock can lead to various issues such as drilling suppression, bit wear, and increased operational costs. To ensure safe and efficient drilling operations, it is crucial to accurately predict the strength parameters of the rock and recommend modifications to operational procedures. This paper proposes a low-cost and fast measurement method for predicting the strength parameters of rock in the field. To evaluate the effectiveness of this method, a drilling process monitoring experiment was conducted on sandstone, limestone, and granite. The experiment studied the effect of confining pressure on the response of cutting with an impregnated diamond bit. By analyzing the relationship between the thrust force, torque force, and penetration depth under different confining pressures, the researchers developed an analytical model for drilling that considers confining pressure, compressed crushed zone, and bit geometry. The results show that the confining pressure has a significant effect on the cutting response. As the confining pressure increases, the thrust force, torque force, and penetration depth at the cutting point also increase. Furthermore, a new measurement method was proposed to determine the strength parameters, such as cohesion, internal friction angle, and unconfined compressive strength. The estimated strength parameters for the three rock types using the drilling method were in good agreement with those of the standard laboratory test, with an error range of 10%. This method of estimating rock strength parameters is a practical tool for engineers. It can continuously and quickly obtain the drilling parameters of in-situ rocks.

A new method for monitoring coal stress while drilling process: theoretical and experimental study

ABSTRACT Real-time acquisition of coal stress is the key to early warning and prevention of rock burst. In the drilling process, drilling parameters will change correspondingly with the change of coal stress. This paper, according to the bit drilling coal link, establishes a theoretical model of drilling in order to verify the reliability of the theoretical model of specific work of drilling crushing, use the self-developed drilling measurement experimental device, and develop the drilling tests on raw coal samples under different lateral stresses. Meanwhile, we study the variation law of drilling parameters with coal stress and reveal the energy conversion mechanism of drilling machine energy to drilling chip surface energy. Through parameter analysis of the theoretical model, it is found that the drilling pressure, torque, and rotation speed increase with increasing coal stress, while the drilling speed decreases with increasing coal stress. The drilling test results show that the particle size of drilling cuttings is approximately normally distributed, the surface energy of drilling cuttings, the mechanical energy of drilling rig, and the amount of drilling cuttings all increase with increasing stress. The mechanical energy of drilling rig is mainly converted into surface energy of drilling cuttings in the process of raw coal drilling. In addition, 8.56–33.12% of the mechanical energy is converted into other energy, with the maximum deviation of 21.50% between the coal stress of the drilling test and the theoretical model of fracture drilling. The research results show that most of the deviation percentages were basically around 10% except for a few deviation percentages, which shows that theoretical model can predict the coal stress through drilling parameters, coal rock properties, and bit parameters. The new method proposed in this paper is of great significance for obtaining the stress distribution state of coal in real time and detecting the stress concentration area of coal.

Hydraulic modeling and optimization of jet mill bit considering the characteristics of depressurization and cuttings cleaning

A jet mill bit (JMB) is proposed to increase the drilling efficiency and safety of horizontal wells, which has the hydraulic characteristics of depressurization and cuttings cleaning. This paper fills the gap in the hydraulic study of the JMB by focusing on the hydraulic modeling and optimization of the JMB and considering these two hydraulic characteristics. First, the hydraulic depressurization model and the hydraulic cuttings cleaning model of the JMB are developed respectively. In the models, the pressure ratio and efficiency are chosen as the evaluation parameters of the depressurization capacity of the JMB, and the jet hydraulic power and jet impact force are chosen as the evaluation parameters of cuttings cleaning capacity of the JMB. Second, based on the hydraulic models, the effects of model parameters [friction loss coefficient, target inclination angle, rate of penetration (ROP), flow ratio, and well depth] on the hydraulic performance of the JMB are investigated. The results show that an increase in the friction loss coefficient and target inclination angle cause a significant reduction in the hydraulic depressurization capacity, and the effect of ROP is negligible. The flow ratio is positively related to the hydraulic cuttings cleaning capacity, and the well depth determines the maximum hydraulic cuttings cleaning capacity. Finally, by combining the hydraulic depressurization model and hydraulic cuttings cleaning model, an optimization method of JMB hydraulics is proposed to simultaneously maximize the jet depressurization capacity and the cuttings cleaning capacity. According to the drilling parameters given, the optimal values of the drilling fluid flow rate, backward nozzle diameter, forward nozzle diameter, and throat diameter can be determined. Moreover, a case study is conducted to verify the effectiveness of the optimization method.

Analysis of the influence of surgical robot drilling parameters on the temperature of skull drilling based on Box-Behnken design.

It is easy to cause thermal damage to the bone tissue when the surgical robot performs skull drilling to remove bone flaps, due to the large diameter of the drill bit, the large heat-generating area, and the long drilling time. Therefore, in order to reduce the thermal damage during the robot-assisted skull drilling process, the relationship between the drilling parameters and the drilling temperature during the skull drilling was studied in this paper. Firstly, a dynamic numerical simulation model of the skull drilling process was established by ABAQUS, and a temperature simulation plan for skull drilling was designed based on the Box-Behnken method. Then according to the simulation results, a quadratic regression model of drill diameter, feed rate, drill speed, and drilling temperature was established by using the multiple regression method. By analyzing the regression model, the influence of drilling parameters on the drilling temperature was clarified. Finally, the bone drilling experiment was carried out, and the error percentage was lower than 10.5% through the experiment to verify the reliability of the conclusion, and a safety strategy was proposed to ensure the safety of the surgical drilling process based on this experiment.

The drillstring dynamic time domains harmonic response and acceleration characteristics of compound drilling for the high-quality slim borehole

The harmonic response and acceleration characteristic of drillstring is established to improve borehole quality for the hydrogen underground storage (HUS). The harmonic response laws of drillstring is discussed. Harmonic response analysis includes non-failure case and failure case. Absorber control measure is simulated to lower vibration amplitude of drillstring. The drill string collides violently with the wellbore reduces the wellbore quality and increases the unreliability of the HUS. Lateral harmonic response has the greatest damage to well wall. Torsional harmonic response causes less damage than lateral vibration. High WOB (weight on bit) and high RPM (rotary per minute) are not conducive to the quality of HUS. In course of designing drilling parameter, it is required to avoid or reduce drillstring resonance under low-order inherent frequency as much as possible. The research result is of much significance to improve wellbore quality of hydrogen underground storage.

Rock mass structural recognition from drill monitoring technology in underground mining using discontinuity index and machine learning techniques

A procedure to recognize individual discontinuities in rock mass from measurement while drilling (MWD) technology is developed, using the binary pattern of structural rock characteristics obtained from in-hole images for calibration. Data from two underground operations with different drilling technology and different rock mass characteristics are considered, which generalizes the application of the methodology to different sites and ensures the full operational integration of MWD data analysis. Two approaches are followed for site-specific structural model building: a discontinuity index (DI) built from variations in MWD parameters, and a machine learning (ML) classifier as function of the drilling parameters and their variability. The prediction ability of the models is quantitatively assessed as the rate of recognition of discontinuities observed in borehole logs. Differences between the parameters involved in the models for each site, and differences in their weights, highlight the site-dependence of the resulting models. The ML approach offers better performance than the classical DI, with recognition rates in the range 89% to 96%. However, the simpler DI still yields fairly accurate results, with recognition rates 70% to 90%. These results validate the adaptive MWD-based methodology as an engineering solution to predict rock structural condition in underground mining operations.

Hole Depth Prediction in a Femtosecond Laser Drilling Process Using Deep Learning.

In high-aspect ratio laser drilling, many laser and optical parameters can be controlled, including the high-laser beam fluence and number of drilling process cycles. Measurement of the drilled hole depth is occasionally difficult or time consuming, especially during machining processes. This study aimed to estimate the drilled hole depth in high-aspect ratio laser drilling by using captured two-dimensional (2D) hole images. The measuring conditions included light brightness, light exposure time, and gamma value. In this study, a method for predicting the depth of a machined hole by using a deep learning methodology was devised. Adjusting the laser power and the number of processing cycles for blind hole generation and image analysis yielded optimal conditions. Furthermore, to forecast the form of the machined hole, we identified the best circumstances based on changes in the exposure duration and gamma value of the microscope, which is a 2D image measurement instrument. After extracting the data frame by detecting the contrast data of the hole by using an interferometer, the hole depth was predicted using a deep neural network with a precision of within 5 μm for a hole within 100 μm.

Investigation of transient machining in the cortical bone drilling process by conventional and axial vibration-assisted drilling methods.

A temperature exceeding the safety threshold and excessive drilling force occurring during bone drilling may lead to irreversible damage to bone tissue and postoperative complications. Previous studies have shown that vibration-assisted drilling methods could have lower temperatures and drilling forces than those of the conventional drilling method; we hypothesized that the main reason for these reductions stems from the differences in the transient machining processes between conventional and vibration-assisted drilling methods. To investigate these differences, comparative experiments and two-dimensional finite element models were performed and developed. The differences in the transient machining processes were verified by experimentation and clearly exhibited by the finite element models. Compared with the steady cutting process that produced continuous-spiral chips in the conventional drilling method, transient machining in the low-frequency vibration-assisted drilling method was a periodically dynamic cutting-separation process that produced uniform petal chips with specific settings of drilling and vibration parameters. Moreover, the transient machining process in the ultrasonic vibration-assisted drilling method was transformed into a combined action with high-speed impact and negative rake angle cutting processes; this action produced a large proportion of powdery chips. Therefore, it could be concluded that the superposed axial vibration significantly changed the transient machining process and radically changed the mechanical state and thermal environment; these changes were the main reason for the apparent differences in the drilling performance levels.

Strategies for Prevention of Downhole Tool Failure Caused by High Bottomhole Temperature in Geothermal and High-Pressure/High-Temperature Oil and Gas Wells

Summary High bottomhole temperature can lead to decreased downhole tool life in geothermal and high-pressure/high-temperature (HPHT) oil and gas wells. The temperature increase is exacerbated when circulation stops (e.g., during connection, tripping, and well control situations). While continuous circulation technology is an appropriate solution for managing temperature, it is not yet widely adopted in HPHT and geothermal drilling practices. This work investigates factors that impact downhole temperature (DHT) and recommends strategies to better manage the temperature when continuous circulation is not available. An integrated thermo-hydraulic model was developed to capture the transient behavior of DHT and was applied here to study the transient temperature profile when there is no fluid circulation. The model was validated using the open-source FORGE field data set, with the mean absolute percentage error between 1% and 4%. In addition, hundreds of case scenarios were numerically studied to investigate the impact of several key factors on the DHT. The evaluated factors include the pumps-off time, type and physical properties of the drilling fluid, wellbore hydraulic diameter, reservoir temperature, geothermal gradient, total wellbore depth and profile, and operational parameters before stopping the circulation. The cooling effects of different drilling parameters were compared to a benchmark case of continuous circulation. A correlation map was generated to visualize the impact of those parameters on the DHT distribution when circulation stops. A logarithmic relationship between the pump stop time and the DHT was observed. For the FORGE case scenario, the DHT increases by 27°C and 48°C after the pump stops for 30 minutes and 60 minutes, respectively. It was observed that water-based mud (WBM) with a high viscosity increases fluid convection heat resistance between the formation and wellbore. Also, drilling with a higher flow rate before stopping the pump can cool the near-wellbore formation faster and reduce the DHT even after circulation ceases. Wells with high geothermal gradients, like FORGE wells, have a higher temperature buildup during circulation stoppage than wells with low geothermal gradients targeting the same reservoir (formation) in-situ temperature. This study investigates the efficacy of different cooling strategies to avoid DHT buildup when there is no circulation. It thereby facilitates the optimization of geothermal and HPHT well design and construction to prevent downhole tool failures. The developed correlation map can aid drilling engineers in understanding the impact of different drilling conditions on the DHT.

Identification of Soil Layers and Properties by Vibration Measurements during Dynamic Penetration Testing

Abstract A common geotechnical site investigation method in Sweden is soil-rock sounding. A steel rod is driven into the ground by a percussion drill and different drilling parameters are recorded. The penetration speed and pushing force are used to determine the soil layer profile, the presence of boulders, and the depth to bedrock. This article describes a novel concept where the ground vibrations generated by the drill bit are measured by a geophone at the ground surface to gain more information about the penetrated material. The results of vibration measurements are analyzed in terms of frequency spectra, spectrograms, and two new parameters called “spectral concentration” and “overtone ratio.” These results show that the method can identify the depth of the groundwater table, distinguish boulders from penetration into bedrock, and possibly identify silt, sand, and gravel layers. More data are needed in different soil types to verify the reliability of the concept.