Rotary-percussive Drilling Research Articles

Experimental study and analysis on a fluidic hammer—an innovative rotary-percussion drilling tool

Rotary-percussion drilling with mud as the energy carrier is a competitive method for the production of drill-holes. Fluidic hammer is a type of rotary-percussion drilling tool actuated by a fluidic oscillator based on the Coanda effect. By using a fluidic hammer, penetration rate can be significantly improved. With few movable or deformable parts, fluidic hammers are resistant to high temperatures, high pressure, corrosive and other extreme environments. Moreover, drilling through soft or inter-bedded formations need not stop to change bottom-hole assembly and can continue even though the fluidic hammer fail to operate. Given these advantages, fluidic hammers are convinced to be popular in the coming years and deserve being better known in the rotary-percussion drilling. In this work, a sequence of experimental investigations focused on the operability and effectiveness of a newly designed fluidic hammer under different sets of operational and physical parameters were performed. Some important impacting performance parameters in terms of impact velocity, impact frequency and impact force were obtained from the experimental results to evaluate the working performance of the fluidic hammer and the effect on bit life. An exponential function model was proposed to describe the piston motion. Comparison between the predicted values of the impact period obtained from the theoretical model and the experimental results reveals the rebound effect of the piston-hammer as it strikes the anvil or cylinder on the impact performance of the fluidic hammer. Furthermore, a field trial using a fluidic hammer was conducted in a horizontal directional well drilling to evaluate its effectiveness. An average improvement of 32.7% in penetration rate was recorded.

A longitudinal & longitudinal-torsional vibration actuator for rotary-percussive ultrasonic planetary drills

Ultrasonic drills, which can sample rocks using a lower weight on bit and lower power, are more suitable for sampling on a minor planet than conventional drills. To remove cutting chips and improve drilling efficiency, rotary-percussive ultrasonic drills (RPUD) drive drill tools for rotary-percussive motion. This paper proposes a novel longitudinal & longitudinal-torsional (L-LT) actuator, which is composed of a stepped horn, a piezoelectric stack, and a longitudinal-torsional (LT) coupler, for the RPUD. The horn magnifies the longitudinal vibration on the front surface of the piezoelectric stack, which is clamped between the horn and the LT coupler, and impacts the drill tool. The LT coupler transforms the longitudinal vibration on the back surface into longitudinal-torsional vibration, which generates elliptical movements that drive the rotor to rotate. Then, the rotor drives the drill tool to rotate. A method of adjusting the displacement amplitudes of the horn and the driving tips is discussed. The prototype achieved a maximum speed and torque of 193 r/min and 0.065 N·m, respectively. The maximum drilling speed through sandstone under a weight on bit of 5 N was 13 mm/min.

A rotary-percussive ultrasonic drill driven by single piezoelectric stack

A rotary-percussive ultrasonic drill driven by single piezoelectric stack

Optimization of penetration rate in rotary percussive drilling using two techniques: Taguchi analysis and response surface methodology (RMS)

The efficient use of drilling machines is one of the key factors that are considered in the economic evaluation of mining operations. A prediction of penetration rate is necessary to work in a cost effective way. In this work, drilling parameters such as air pressure, specific advance pressure, rotation speed, and bit diameter were taken into account to optimize the penetration rate of a rotary percussive drilling in the Hadjer Soud quarry using Taguchi and Surface Response Methodology. The experiments were carried out on the basis of a mixed experimental array Taguchi L18 and were analyzed using signal/noise ratio (S/N), variance analysis and regression analysis. From the optimization and the experimental analyses carried out, the results show that air pressure is statistically the most dominant factor in the rotary -percussive drilling in the quarry of Hadjer Soud with a contribution of 59.90%. The Taguchi method was used to determine the optimal rational operating values a drill bit diameter of 115 mm (level 1), the specific advance pressure of 50 Kgf/cm2 (level 2), at a rotation speed of 55 Rpm (level 3) and an air pressure of 17 Bars (level 3). A mathematical model was developed for the penetration rate to understand the effect of the control factors on the response. The predicted values are compared with the experimental data and are seen to be in good agreement. The optimal values obtained during the optimization of the study by the Taguchi method and the response surface model (RSM) were then validated by confirmatory experiments.

The rock breaking mechanism analysis of rotary percussive cutting by single PDC cutter

Rotary percussive drilling technology can solve the problems of low efficiency and high cost in deep hard formation drilling effectively; it can improve drilling efficiency and reduce stick-slip vibration in order to improve transmission efficiency of WOB (weight of bit). However, the rock breaking and ROP rising (rate of penetration) mechanism are not clear enough to some extent. This paper established three-dimensional finite element model of rotary percussive cutting by single PDC cutter. The crack propagation, chip formation, damage evolution, mechanical specific energy (MSE), and other problems are discussed. The results show that the hard rock is more prone to occur brittle failure under rotary percussive cutting, the rotary percussive drilling technology can improve the stress state of the PDC cutter, better to protect the cutter and improve the drilling efficiency; the magnitude of impact amplitude should not be too large when it reaches the threshold to break rock, the impact frequency has significant influence on MSE; rotary percussive drilling technology is not suitable for soft formations. The field applications show that the use of high-frequency impactor can bring obvious ROP rising in the hard formation drilling. The results obtained in this paper can enhance the understanding of rotary percussive drilling technology and provide theoretical basis for the design of impactor.

Penetration Rate and Specific Energy Prediction of Rotary–Percussive Drills Using Drill Cuttings and Engineering Properties of Selected Rock Units

This study discusses the prediction of penetration rate and specific energy of button bit equipped rotary–percussion drilling machines from drill cuttings and geo-mechanical properties of rocks. The operational parameters of drilling machines measured from selected locations were utilized for the calculation of specific energy of drilling operations. For this purpose three on-going hydropower projects and four active mining quarries of Pakistan were selected. The drill cuttings were further used to determine various descriptors of the chip size distribution including the coarseness index and Rosin–Rammler’s absolute size constant. A complete set of geo-mechanical rock tests were conducted in the laboratory and includes uniaxial compressive strength, Brazilian tensile strength, point load strength, Schmidt rebound hardness, P-wave velocity, dry density, porosity and brittleness indices. Regression analyses were performed to predict the penetration rate and specific energy of drilling from geo-mechanical properties of rocks. The models so developed were also validated by adopting the t-test and the F-test statistical techniques. Moreover, statistical models were also developed to evaluate penetration rate from various descriptors of the chip size distribution. Dependence of bit size on coarseness index and mean particle size was also discussed.

Geo-navigation system for rotary percussion drilling in rocks of high and low electrical conductivity

The currently available drill navigation systems, with their benefits and shortcomings are reviewed. A mathematical model is built to describe the inertial navigation system movement in horizontal and inclined drilling. A prototype model of the inertial navigation system for rotary percussion drills has been designed.

Importance of early adjustment of rotary-percussion drilling tool to mineral mining conditions

The authors discuss the technical and economic criteria for the evaluationof efficient application of rotary-percussion drilling tools. The determinants of efficiency of downhole pneumatic drilling hammers are identified. The authors set conditions of high-velocity hole-making and find maximum indices of long-term performance for downhole pneumatic rotary-percussion drilling tools.

Characterization of rotary-percussion drilling as a seismic-while-drilling source

This paper focuses on an evaluation of rotary-percussion drilling (RPD) as a seismic source. Two field experiments were conducted to characterize seismic sources from different rocks with different strengths, i.e. weak shale and hard arkose. Characterization of RPD sources consist of spectral analysis and mean power measurements, along with field measurements of the source radiation patterns. Spectral analysis shows that increase of rock strength increases peak frequency and widens bandwidth, which makes harder rock more viable for seismic-while-drilling purposes. Mean power analysis infers higher magnitude of body waves in RPD than in conventional drillings. Within the horizontal plane, the observed P-wave energy radiation pattern partially confirms the theoretical radiation pattern under a single vertical bit vibration. However a horizontal lobe of energy is observed close to orthogonal to the axial bit vibration. From analysis, this lobe is attributed to lateral bit vibration, which is not documented elsewhere during RPD. Within the horizontal plane, the observed radiation pattern of P-waves is generally consistent with a spherically-symmetric distribution of energy. In addition, polarization analysis is conducted on P-waves recorded at surface geophones for understanding the particle motions. P-wave particle motions are predominantly in the vertical direction showing the interference of the free-surface.

The optimization of the operational parameters of a rotary percussive drilling machine using the Taguchi method

PurposeThis paper aims to determine the rational operating regime of a rotary percussive drilling machine under optimal conditions.Design/methodology/approachAn orthogonal array of Taguchi, signal-to-noise (S/N) ratio, ANOVA Pareto analysis and regression analysis are used to investigate the effect of drilling operational factors on the penetration rate. A series of experiments based on orthogonal arrays L27 was carried out, and the results were collected and analyzed using the statistical software Minitab.FindingsThe statistical analysis (ANOVA Pareto) of the results showed that among all setting parameters, air pressure is the most essential element that affects the penetration rate. The rational operating regime of the rotary percussive drilling machine was determined with optimum air pressure values of 17 bar (Level 3), rotation speed of 60 rpm (Level 3) and a thrust of 825 kgf (Level 2), which maximize the penetration rate. A quadratic regression model was developed for the penetration rate. The predicted values are compared with the experimental data and are considered to be in good agreement.Originality/valueThe study uses the orthogonal array of Taguchi, S/N ratio, ANOVA Pareto analysis and regression analysis to investigate the effect of drilling operational factors on the penetration rate.

Rotary-Percussive Ultrasonic Drill: An Effective Subsurface Penetrating Tool for Minor Planet Exploration

Compared with conventional drill, an ultrasonic drill can break into rocks under lower weight on bit and lower power, which is more suitable to sample in low gravity environment for deep-space exploration. However, the ultrasonic drill cannot remove rock cuttings effectively when drilling into a certain depth. This paper proposed a rotary-percussive ultrasonic drill (RPUD), which depends on a single piezoelectric transducer to produce rotary-percussive moment to drill into rocks and remove cuttings. The RPUD consists of four parts: a piezo-ceramics, a percussive unit, a rotary unit, and a drill tool. Percussive unit magnifies the longitudinal vibration of one side of piezo-ceramics, and delivers percussive motion to the drill tool. Rotary unit transfers the longitudinal vibration of the other side of piezo-ceramics into longitudinal-torsional vibration to drive the drill tool to rotate. Percussive motion and rotary motion of drill tools are relatively independent, and thus their parameters can be adjusted separately. Finite element method is adopted to assist the design of the RPUD. Modal analysis is employed to tune the resonance frequencies of the percussive unit and rotary unit to be close. After the fabrication of a RPUD prototype, contrastive test of rotary percussive drilling and percussive drilling was carried out based on the RPUD prototype. Test results show that the RPUD can drill into the rocks and improve the efficiency of cutting removal.

Impact Dynamics Prediction of a Rotary-Percussive Ultrasonic Drill With a Free Mass

The rotary-percussive ultrasonic drill (RPUD) employs vibrations on two sides of a piezoelectric stack to drive a drill tool to achieve simultaneous rotary-percussive motion. It has the advantages of being small and requiring low power, low axial load, and small holding torque, making it suitable for extra-terrestrial rock sampling, especially for a minor planet with a weak gravitational field. This paper presents the impact dynamics prediction of the percussive system of RPUD, which is composed of a piezoelectric actuator, a free mass, and a drill tool. Considering the vibration of the RPUD and the weight on bit, the interactions between these three components before and during drilling are analyzed separately. The effects of various parameters (i.e., the coefficient of restitution between the actuator and the free mass, the damping ratio of the RPUD, the weight of the free mass, and the weight on bit) on the contact force between the free mass and the drill tool, a number of collisions per second, kinetic energy transferred to the drill tool per second, and reacting force are simulated. Simulation results show that the free mass converts the high-frequency harmonic vibration of the actuator into lower frequency impacts on the drill tool. Furthermore, the contact force and the kinetic energy transferred to the drill tool per second can be enhanced by increasing the coefficient of restitution, free mass, and weight on bit or decreasing the damping ratio of the RPUD.

Erratum to: Energy-Based Volumetric Rock Destruction Criterion in the Rotary–Percussion Drilling Technology Improvement

In the published version there is an error in the formula of air flow rate per second in equation (8). The present form in this erratum is the correct:

Penetration Rate and Specific Energy Prediction of Rotary-Percussive Drills Using Drill Cuttings and Engineering Properties of Selected Rock Units

Penetration Rate and Specific Energy Prediction of Rotary-Percussive Drills Using Drill Cuttings and Engineering Properties of Selected Rock Units

Energy-Based Volumetric Rock Destruction Criterion in the Rotary–Percussion Drilling Technology Improvement

Efficiency of energy-based criterion of volumetric rock destruction in estimation of drilling technology is theoretically validated and experimentally proved in in-situ rotary–percussion drilling in mines in Russia. The criterion is adapted to the performance of various drilling units by means of introduction of empirical coefficients for transformation of drilling energy intake to the relevant energy characteristics of stress rock fracture in face zone. The mathematical description of the criterion of minimum energy intake of rotary–percussion drilling depending on stress state and physical properties of rocks, and on force of rotary–feed mechanism is presented. The authors introduce a new geomechanical notion—factor of topological connection of rocks and give its analytical expression using experimental uniaxial compression and uniaxial tension strength of rocks, required in the design and improvement of rotary–percussion drilling in different geological and geotechnical conditions of mining.

Multiscale modeling of cemented tungsten carbide in hard rock drilling

Mechanical behavior of rotary-percussive drilling tools made of tungsten carbide (WC) hardmetal in impact interaction with hard rock is investigated. This study presents a three-step multiscale simulation strategy, developed for evaluation of stress and strain heterogeneity within the hardmetal microstructure when subjected to loadings representative for drilling applications. Two homogenization approaches are used: a full-field finite-element model and a Beta-model (a nonlinear extension of the Kröner’s uniform field model). Both models combine isotropic Drucker–Prager elasto-plastic behavior of WC grains and isotropic von Mises elasto-plastic behavior of the binder, and include nonlinear hardening. First, a three-dimensional finite-element model of a representative volume element is constructed, which closely resembles the hardmetal microstructure. Full-field simulation with applied proportional loadings allows to determine the hardmetal effective elastic properties for different binder content, and an initial yield surface, resembling in shape a Drucker–Prager surface with a cap. These simulations are also used to calibrate the Beta-model, which, however, cannot predict the correct plastic behavior for the loadings with high hydrostatic component. Second, macroscopic finite-element simulations of normal and oblique frictional impact of an elastic rock by a hardmetal spherical tip are performed using a macroscopic set-up. The calibrated Beta-model is used at every Gauss-point of the hardmetal impactor. Finally, the most critical for the hardmetal’s integrity points are identified on the impactor’s surface, and complex non-proportional stress paths associated with these points are extracted. These stress paths are used as boundary conditions in a full-field simulations employing representative volume elements of hardmetal microstructure. Analysis of stress and plastic-strain fields at the microstructural scale suggests that the major source of wear of drilling inserts may come from tensile failure of WC grains.

Application of the New Drilling Technology for Increasing Penetration Rate in Deep and Ultra-Deep Wells

The rotary percussion drilling technology can greatly increase the penetration rate of deep and ultra-deep wells; however, the short service life of the impactor limits its wide application. Therefore, the turbine type hydraulic impactor developed by the China University of Petroleum (Beijing) for the deep and ultra-deep wells was used to extend life of impactor. Based on the analysis of pressure field and velocity field under different flow conditions, the drilling fluid flow range of rotary percussion drilling was optimized to be 32-41 L/s. In this range, it can ensure that the wearing parts of the turbine hydraulic impactor can fully exert the impact of the impactor and high rock breaking efficiency without serious erosion. Application of deep well sections in ultra-deep wells in Tarim Oilfield achieved that the penetration rate of the rotary percussion drilling increased by more than 60% compared with the composite drilling technology. At the same time, the normal working life of the turbine hydraulic impactor was more than 140 hours, which is more than 2 times of the life of the screw drill. The results of field application show that the turbine hydraulic impactor has a wide application prospect in deep and ultra-deep wells drilling.

Modeling and Experiments of Rotary Percussive Drilling for Robotic Civil Infrastructure Rehabilitation

Rotary percussive drilling plays an important role in repairing defects and delami-nation in civil infrastructures such as bridge decks, tunnels, etc. Modeling of rotary percussive drilling is critical for optimization and control of the drilling performance. We present a modeling framework for rotary percussive drilling for robotic rehabilitation for bridge decks. The model uses an modified dry friction and other nonlinear elements to represent the pure percussive drilling characteristics. The contribution of the bit rotation to penetration is captured through the impact-induced crack-zone removals. An in-situ force measurement system is built to experimentally validate and demonstrate the model predictions. The experimental results confirm the modeling development and analyses.

Straight hole drilling machines for coal mines

The authors prove the demand for drilling machines capable of making long straight holes in rocks with the strength up to 120 MPa. The paper describes the designed, manufactured and tested down-the-hole hammers for rotary–percussion drilling of long straight directional holes. The hammers have been delivered to Berezovskaya Mine for further trial and commercial operation.

Impact Dynamics of a Percussive System Based on Rotary-Percussive Ultrasonic Drill

This paper presents an impact dynamic analysis of a percussive system based on rotary-percussive ultrasonic drill (RPUD). The RPUD employs vibrations on two sides of one single piezoelectric stack to achieve rotary-percussive motion, which improves drilling efficiency. The RPUD’s percussive system is composed of a percussive horn, a free mass, and a drill tool. The percussive horn enlarges longitudinal vibration from piezoelectric stack and delivers the vibration to the drill tool through the free mass, which forms the percussive motion. Based on the theory of conservation of momentum and Newton’s impact law, collision process of the percussive system under no-load condition is analyzed to establish the collision model between the percussive horn, the free mass, and the drill tool. The collision model shows that free mass transfers high-frequency small-amplitude vibration of percussive horn into low-frequency large-amplitude vibration of drill tool through impact. As an important parameter of free mass, the greater the weight of the free mass, the higher the kinetic energy obtained by drill tool after collision. High-speed camera system and drilling experiments are employed to validate the inference results of collision model by using a prototype of the RPUD.