Mastering Rock Crossing with Advanced TCI Tricone Bit.

1. Rock Crossing Directional Drilling

    ①Directional drilling methods for rock crossing include the following:

- Simple Construction Method

- DITCH WITCH Double-Wall Drill Pipe Method

- Pneumatic or Hydraulic Down-the-Hole Hammer Impact and Rotary Directional Drilling

- Mud Motor Directional Drilling Method

    The “mud motor directional drilling method” is currently the most commonly used method for rock directional drilling both domestically and internationally. It is suitable for trenchless drilling rigs of 25 tons and above, especially large trenchless rigs.

    The mud motor, also known as a screw drill, is typically paired with a “tricone drill bit” or a “PDC drill bits”, along with wired or wireless locating devices. During normal drilling, the drill rod and motor rotate together for straight-line drilling. For directional drilling, the bent housing of the motor aligns with the 12 o’clock position indicated by the locating device. In this mode, the drill rod and motor housing remain stationary, providing only counter-torque and feed force. The rotor of the motor, driven by the mud pump, rotates the drill bit, achieving directional drilling.

    The bent angle of mud motors for “horizontal drilling bits” typically ranges from 1.5° to 3°, and the choice depends on the curvature of the designed pipeline trajectory.

    ②Connection Configurations for Mud Motor Directional Drilling:

- Wireless: Drill rod → Instrument housing → Motor → Three Cones drill Bit

- Wired: Drill rod → Non-magnetic drill collar → Instrument housing → Non-magnetic drill collar → Motor →Three Cones drill Bit

 

2. Rock Crossing Reaming Drilling

    After completing the pilot hole, reaming is performed based on the pipeline diameter.

    2.1 Types of Rock reamers

    ①There are two main types of rock reamers:

- Fixed Tricone Rock Reamers: These use tricone cutter segments from oilfield Drill Bits as cutting tools, welded to the reamer's central shaft and base plate.

- Replaceable Roller Cutter Reamers: These reamers use replaceable roller cutters as cutting tools, which are installed either on brackets or in suspension.

    ②Advantages and Disadvantages of Tricone Rock Bits

    Advantages:

- Short manufacturing cycle.

- Suitable for various diameters (particularly small to medium), ranging from 220mm to 1600mm, and adaptable to different geological formations.

- Customizable tooth type and bearing structure based on rig and formation conditions.

- Efficient hydraulic rock breaking and debris removal.

    Disadvantages:

- Back wear on the cutter is difficult to address in sandstone formations.

- Hole opener bits can wear out after several repairs.

- Bearing seals at the cutter interface are prone to failure, though anti-drop devices mitigate risks.

    2.2 Features of Replaceable Roller Cutter Rock Reamers for Medium-Small Rigs

    ①These reamers:

- Address the back wear issues of drag bits.

- Have a comparable cost to rubber-sealed TCI tricone bits, reducing operational expenses.

- Ensure safe and reliable operation with easy roller cutter replacement.

    2.3 Features of Replaceable Roller Cutter Rock Reamers for Large Rigs

    ①Key features include:

- Suitable for heavy-duty rigs in large-diameter rock crossings.

- Equipped with reusable bodies and HDD reamer drill bits designed for extended use.

- Rollers with Ø19 carbide teeth and customizable profiles (blunt for hard rock, conical for soft rock).

 

3. Drilling Parameters

    3.1 Drilling Pressure

    Drilling pressure depends on factors like rock hardness, borehole diameter, and drill bit strength. Excessive pressure on tools like the PDC drag bit can lead to equipment damage.

    3.2 Rotational Speed

    Typically maintained at 40 RPM or below, ensuring proper performance for tools like core barrel drill bits.

    3.3 Mud Flow

    Proper mud flow is critical for cooling and debris removal, especially when using API standard tricone bits in sandstone formations.

 

4. Mud Recovery System

    Integrated mud purification systems improve drilling efficiency. They save resources and reduce environmental impact, aligning with modern drilling methods that often involve hole opener bits and trenchless techniques.

    Advantages:

- Recovers 80-90% of mud.

- Saves 40-50% of bentonite.

- Resolves mud disposal challenges and minimizes ecological impact.