Whipstock for Sidetrack Drilling

I. Working principle

1. Running and positioning: The slant tool is delivered to the predetermined depth inside the casing through the drill string or coiled tubing, and the slant is adjusted to the designed orientation.

2. Anchoring and anti-rotation: The slips expand outward under hydraulic or mechanical force to grip the inner wall of the casing, preventing upward or downward movement or rotation during operations.

3. Hand-off separation: After anchoring is completed, the delivery tool is detached from the slanting tool via hydraulic or mechanical means and then retrieved.

4. Window milling sidetracking: The milling cone is run to mill the casing along the inclined surface of the window opener, creating an inverted pear-shaped window. Subsequent drilling tools then sidetrack a new borehole from the window.

II. Key technical parameters and performance requirements

1. Slope parameters: Inclination 3° - 4°, hardness RC260-300, ensure window forming regularity and milling stability.

2. Anchoring force: Axial load capacity ≥500kN, circumferential anti-rotation torque ≥30kN・m, compatible with various casing grades and dimensions.

3. Release reliability: Hydraulic release pressure of 15-20 MPa, with shear pin specifications matching the downhole pressure and load.

III. Typical applications and advantages

1. Old well potential development: Open a window in the casing of an old well and sidetrack to the remaining oil-rich zone to enhance recovery.

2. Casing damage well remediation: Avoid the damaged casing section and sidetrack a new wellbore to resume production.

3. Branch well drilling: Create multiple branch wells by sidetracking drilling within the main wellbore to expand the oil drainage area.

4. Advantages: Compared to drilling new wells, it can save over 70% in costs, shorten the construction period, and reduce geological risks.

IV. Common issues and optimization directions

Common issues: Anchor failure leading to lateral shaker displacement, uneven wear of the inclined surface causing irregular windows, and stuck pipe due to fishing failure.

Optimization direction: Implement a dual-stage slip ring and floating ring for anti-rotation and anti-axial movement, apply wear-resistant alloy surfacing on inclined surfaces, and refine the hydraulic release mechanism design.