What are the preventive measures for stuck pipe caused by diameter reduction in external drill pipes?
07 Jul,2020
When drilling with the outer-flat drill pipe through formations that are free of spalling but exhibit shrinkage, use clear water mixed with 0.2% polyacrylamide. Drill down to 10 meters before reaching the shrinkage zone, then add either 2.5% potassium chloride, 1.5% potassium silicate, or 1% of Broad-Spectrum Wall-Stabilizing Agent Type I all at once into the overall drilling fluid. This treatment will prevent further shrinkage in the affected layer.
(1) Preventing Shrinkage from Drilling Fluid
1. In formations that are free of spalling but show shrinkage, drill using clear water mixed with 0.2% polyacrylamide. Before reaching the shrinkage layer by 10 meters, add either 2.5% potassium chloride, 1.5% potassium silicate, or 1% of a broad-spectrum shale-stabilizing agent Type I—all at once—to the overall drilling fluid. This treatment will help prevent further shrinkage in the affected layer. In formations that are free of spalling but exhibit shrinkage, drill using清水 (clear water) mixed with 0.2% polyacrylamide. Before reaching the shrinkage layer by 10 meters, add either 2.5% potassium chloride, 1.5% potassium silicate, or 1% of a broad-spectrum shale-stabilizing agent Type I all at once into the overall drilling fluid. This treatment will prevent further shrinkage in the affected layer.
2. In collapsing and borehole-shrinking formations, it’s crucial to quickly optimize the drilling fluid properties: adjust the mud weight to 1.06–1.08 specific gravity, increase the funnel viscosity to 35–40 seconds, reduce fluid loss to 5–4 ml/min, and set the salinity at 2–3%. This approach will help stabilize the wellbore walls.
3. In soft mudstone formations, the primary approach is to increase the drilling fluid density, with the minimum density requirement set at ≥1.2.
(II) Preventing Diameter Reduction in Engineering
1. Before lowering the drill bit into the well, measure its outer diameter—any drill bit larger than the normal wellbore size must not be used.
2. The maximum outer diameter of the salvage milling pipe must be 15 mm smaller than the wellbore diameter.
3. It was discovered that the outer diameter of the removed old drill bit had worn down. Therefore, when lowering the new drill bit, you should start reaming 100 meters above the wellbore bottom.
4. If there's 20-ton resistance during the drill-down, you'll need to adjust the drilling direction accordingly.
5. Drilling proceeded smoothly, and the final single joint will also be drilled below the bit.
6. In well sections drilled using tricone bits, switch to PDC or core barrels, and if you encounter slight resistance while running the drill string, be sure to ream the hole immediately.
7. The core-taking interval must be reamed.
8. When encountering resistance while pulling out of the hole, never force the drill string upward—instead, gently move it up and down. The maximum lifting force should not exceed In formations that are free of spalling but show shrinkage, drill using clear water mixed with 0.2% polyacrylamide. Before reaching the shrinkage layer by 10 meters, add either 2.5% potassium chloride, 1.5% potassium silicate, or 1% of a broad-spectrum shale-stabilizing agent Type I—all at once—to the overall drilling fluid. This treatment will help prevent further shrinkage in the affected layer. 50% of the column's self-weight—definitely too challenging, so go ahead and drill down, then advance another 20 meters.
9. Well teams equipped with the necessary tools can use the drill-through shock tool—whether encountering resistance while pulling out of the hole or running in—to help free stuck pipe.
10. In severely constricted sections, lift the drill string 4 meters and ream every 2 meters of penetration. After completing one stand of drill pipe, ream the hole repeatedly three times. Additionally, after drilling every 50 meters, make a short trip of 100 meters.
(III) Methods for Handling Diameter-Reduced Stuck Drill Bits
1. Once a stuck drill string occurs, vigorously move the drill tools to try and free the bit:
① If stuck while running in the hole, apply maximum upward force or twist forcefully;
② If encountering resistance during tripping out with a straight-shank drill pipe, push the entire drill string downward and use a hammer to strike it sharply from above;
③ If the drill string gets stuck while drilling, only strong upward pulling or twisting motions are permitted.
2. Use a vibrator to free the stuck pipe by applying shock vibrations.
3. Soak with a freeing agent.
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