Abstract
Rapid horizontal directional well drilling in hard or fractured formations requires efficient drilling technology. The penetration rate of conventional hard rock drilling technology in horizontal directional well excavations is relatively low, resulting in multiple overgrinding of drill cuttings in bottom boreholes. Conventional drilling techniques with reamer or diamond drill bit face difficulties due to the long construction periods, low penetration rates, and high engineering costs in the directional well drilling of hard rock. To improve the impact energy and penetration rate of directional well drilling in hard formations, a new drilling system with a percussive and rotary drilling technology has been proposed, and a hydro-hammer with a jet actuator has also been theoretically designed on the basis of the impulse hydro-turbine pressure model. In addition, the performance parameters of the hydro-hammer with a jet actuator have been numerically and experimentally analyzed, and the influence of impact stroke and pumped flow rate on the motion velocity and impact energy of the hydro-hammer has been obtained. Moreover, the designed hydro-hammer with a jet actuator has been applied to hard rock drilling in a trenchless drilling program. The motion velocity of the hydro-hammer ranges from 1.2 m/s to 3.19 m/s with diverse flow rates and impact strokes, and the motion frequency ranges from 10 Hz to 22 Hz. Moreover, the maximum impact energy of the hydro-hammer is 407 J, and the pumped flow rate is 2.3 m3/min. Thus, the average penetration rate of the optimized hydro-hammer improves by over 30% compared to conventional directional drilling in hard rock formations.
Highlights
In recent years, construction activities in hard rocks have extensively emerged with the practical increase of horizontal directional wells drilling technologies [1]
To improve the penetration rate of directional well drilling in hard rock formations, the designed hydro-hammer with a jet actuator has been attached to a screw motor, which enables the orientation of directional drilling tools
To observe the distribution of pressure and flow field in the hydro-hammer with a jet actuator, the semi-implicit method for pressure-linked equations (SIMPLE) algorithm is applied to the computational fluid dynamics (CFD) numerical simulation of the hydro-hammer
Summary
Construction activities in hard rocks have extensively emerged with the practical increase of horizontal directional wells drilling technologies [1]. A hydraulic pulsed jet generator has been designed and field tested to reduce the abrasion of drill bit while drilling in medium to hard formations [7]. The influence of the impact energy of drilling tools on penetration rate are primarily investigated, especially in the horizontal directional well drilling in hard rock formations. Due to the small diameter of boreholes and the low hydraulic energy efficiency and impact energy of hydro-hammers, most hydro-hammers have only been successfully used in shallow boreholes percussion drilling technology is considered one of the best approaches for hard rock drilling. By combining the rotary and percussive drilling technologies, a new hydro-hammer design with a jet actuator has been proposed and applied to horizontal directional drilling in hard rock formations. Field tests using a hydro-hammer have been conducted in horizontal directional well drilling and showed the feasibility of using a hydro-hammer for drilling in hard rock formations
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