The directional drilling of rock crossing engineering mainly includes simple construction method, double wall drill pipe drilling method, pneumatic or hydraulic DTH hammer impact rotary directional drilling method, and mud motor directional drilling method.
Among them, the mud motor-driven directional drilling method is the most common rock directional drilling method at home and abroad. Suitable for all types of trenchless drilling rigs above 25t, especially large trenchless drilling rigs.
Mud motors are also called screw drills, and they are generally used in conjunction with roller guide bits or PDC bits and wired or wireless probe devices. During normal drilling, the drill rod and the motor rotate together to drill linearly; when steering is required, the motor bending point busbar is adjusted to the 12 o'clock direction of the probe, the drill rod and motor housing do not rotate, only the reaction torque and feed force are provided. The motor rotor drives the drill bit to rotate under the hydraulic drive of the mud pump, thereby realizing guided drilling. The motor bend angle for horizontal directional drilling is generally between 1.5-3 degrees, and different bend angles are selected according to the curvature of the pipeline design trajectory.
Motor-driven guided drilling connection form:
Wireless: drill pipe - instrument compartment - motor - cone bit
Wired: drill pipe - non-magnetic drill collar - instrument compartment - non-magnetic drill collar - motor - cone bit
After the pilot hole is completed, expand the hole according to the pipe diameter.
The current rock reamer hole opener is roughly divided into two types:
One is a fixed cone type reamer, which uses the cone palm of a petroleum cone bit as a cutting tool, which is connected to the center shaft of the reamer and the chassis by welding.
The second is a replaceable hob reamer, which uses a replaceable hob as a cutting tool. According to different installation methods, hobs are divided into tool holder installation and suspension installation.