In-seam Drilling for Gas Drainage — Rotary Drilling

• No directional control
• Excessive drilling metres
• Ineffective coverage
• Fatal Outburst can happen due to inaccurate borehole coverage

Gas and Outburst Prevention

• No directional control
• Excessive drilling metres
• Ineffective coverage
• Fatal Outburst can happen due to inaccurate borehole coverage

Introduction of Directional Drilling

• Oil field technology modified for underground
• Boreholes drilled with a down-hole motor
• Boreholes progressively surveyed for steering and to determine location
• Locate boreholes in desired horizon and location

Key Components for Directional Drilling

• Suitable stable environment
• Experienced project supervision
• Experienced drillers
• Proven and competent procedures and training
• Drill rig with high pressure water pump
• Downhole motor
• PCD drill bits
• Survey system
• Suitable and safe site management

Directional Drilling Environment

• Requires environment suitable to support directional drilling
  • High pressure ejects broken strata into borehole
  • Fracture strata collapses into borehole
  • Clay strata swells into hole with water contact
  • Target strata (coal or stone) has to be stable (drillable)

Electro-hydraulic Drill Rig for Longhole Directional Drilling

• High pressure water pumped down drill rods is forced through the power section and rotates the drill bit
• Various torque characteristics and rotational speeds available

Downhole Motor Deflection

• Standard 1.25 deg bend
• 96mm OD PCD bit
• 18.7mm deflection at bottom of the bit
• Provides the ability to be steered

DHM Steering Control — Vertical Response

• Change in vertical angle over 6m – limited curve rate

Drill Site

• Drill site provided to include all equipment
• Avoid interaction with mine transport movements
• High safety standards and operational procedures
• Ventilation requirements to manage gas, electrical requirements, water supply and pumping

Gas/Water Management — Standpiping

• Fully grouted standpipe
• Pressure rated fittings
• Fittings seal borehole and control returns
• Pressure tested for known high pressure intersections