Slickline Junk Mill

Description

Slickline Junk Mill Star Bit

Technical Description and Specifications

The Slickline Junk Mill is a heavy-duty mechanical tool used in fishing operations for milling, grinding, and breaking up soft or brittle downhole debris (e.g., solidified cement, hardened scale, shale bridges, or friable junk) that cannot be retrieved intact. It also functions as a highly aggressive drift tool to confirm passage.

Key Technical Specifications and Operation

• Function: To reduce the size and consistency of downhole obstructions via percussion (jarring) and rotational grinding, converting the solid material into manageable cuttings that can be circulated or collected by a bailer.

• Design: A solid cylindrical sub featuring a distinctive star-shaped bottom profile created by multiple radially extending wings or blades. The leading edges of these wings are often faced with wear-resistant materials (e.g., Tungsten Carbide inserts) to enhance milling efficacy and prolong tool life.

• Milling Mechanism: The tool is run above the stem and jar. The operator applies repeated heavy downward jarring (percussion) to impact the obstruction, fracturing the material. Slow rotation (imparted by surface torque or line twisting) allows the wings to mill the circumference of the debris.

• Drift Function: The maximum Outer Diameter (OD) of the Star Bit serves as a drift gauge, confirming that the internal diameter of the tubing or restriction is clear for the passage of subsequent flow control tools.

• Connection (Customizable):

  • Standard interfaces include high-strength proprietary slickline pin threads.

  • Custom order connections are available to ensure seamless integration with non-standard threads and heavy-duty jarring systems.

• Material (Customizable):

  • Base Tool: High-strength alloy steel (e.g., AISI 4140/4340) for high impact resistance.

  • Cutting Inserts: While standard inserts are hardened steel or carbide, custom Tungsten Carbide or specialized polycrystalline diamond (PDC) inserts are available for milling extremely hard materials. NACE MR0175 compliance is available for the tool body.

• Critical Parameters (Customizable Size & Wing Count):

  • Bit OD: The crucial specification, defined by the maximum tip-to-tip diameter of the wings. It must be accurately sized to the internal drift requirement. Standard ODs range from $1.00″$ up to $5.5″$.

  • Wing Profile/Count: Custom wing counts (e.g., 4-wing, 6-wing) and specific profiles can be fabricated to optimize the cutting action for different material consistencies. Clients must specify the target tubing ID and the required maximum milling diameter when placing a custom order.