Abstract
Although pneumatic down-the-hole (DTH) hammers have good performance of high penetration rate and minimal deviation tendency in the vertical section of oil and gas wells, they have not been successfully used in directional drilling due to drill tool wear and wellbore disturbance. Herein, we developed a novel type of pneumatic DTH hammer with a self-propelled round bit to overcome the technical difficulties of directional drilling. Nonlinear dynamic modeling developed by the authors was used to analyze the working principle and performance of the novel DTH hammer. The kinematics and dynamics simulation of this hammer were carried out using MATLAB language, and the motion law of the piston was revealed. The performance of the novel hammer was numerically simulated and evaluated by considering fluctuations of the front and rear chamber pressure, impact energy, acceleration, and frequency. The results show that our novel DTH hammer’s working principle is feasible and has an adequate structural design. The simulation results demonstrate reasonable design parameters. Compared to the numerical results for conventional DTH hammers, the velocity and acceleration of the piston of the novel hammer changed smoothly. The frequency was slightly higher than that of conventional hammers, while other parameters were nearly equal. The novel DTH hammer can be used in directional drilling, trenchless drilling, and seabed sampling drilling.
Highlights
Pneumatic DTH hammer drilling is a rotary percussive drilling technique widely used in many fields, such as openpit mines [1], geological core exploration [2], and petroleum exploration [3]. e existing pneumatic hammer drilling technology has many advantages: high drilling efficiency, excellent bit lift, and good hole quality [4,5,6,7]
In conventional DTH hammer drilling, the hammer is fixed at the bottom of the drill string that has the primary function of providing rotational torque and axial pressure. e hammer driven by compressed air transforms the inner energy into the kinetic energy of the piston, and the impact energy is transmitted to the bit in the form of stress wave for rock breaking
Ryu et al [8] developed a novel technique for micro-tunnel excavation using a multihammer drilling machine and identified the optimum operating conditions of the system
Summary
Pneumatic DTH hammer drilling is a rotary percussive drilling technique widely used in many fields, such as openpit mines [1], geological core exploration [2], and petroleum exploration [3]. e existing pneumatic hammer drilling technology has many advantages: high drilling efficiency, excellent bit lift, and good hole quality [4,5,6,7]. Kim et al [15, 16] developed a pneumatic dynamic model of DTH hammer to predict drilling performance and validated the model through laboratory tests. Klishin et al [18] created an elastic valve to enhance the air hammer’s energy performance and drilling durability in directional drilling. Liu and He [19, 20] designed a novel rotation air hammer and used the LS-DYNA program to analyze the impact dynamics problem of its piston and drill bit to obtain their stress change rule in the impact process. We redesigned the air distributor, a special-purpose piston, and the rotation joint. e ratchet wheel mechanism is introduced to realize the separate motions of the drill pipe and the bit
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