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During drilling operations, a pipe is considered stuck if it cannot be freed from the hole without damaging the pipe, and without exceeding the drilling rig’s maximum allowed hook load. Pipe sticking can be classified under two categories: differential pressure pipe sticking and mechanical pipe sticking.
Causes and prevention of stuck pipe
Complications related to stuck pipe can account for nearly half of total well cost, making stuck pipe one of the most expensive problems that can occur during a drilling operation. Stuck pipe often is associated with well-control and lost-circulation events—the two other costly disruptions to drilling operations—and is a significant risk in high-angle and horizontal wells.
Drilling through depleted zones, where the pressure in the annulus exceeds that in the formation, might cause the drillstring to be pulled against the wall and embedded in the filter cake deposited there (Fig. 1). The internal cake pressure decreases at the point where the drillpipe contacts the filter cake, causing the pipe to be held against the wall by differential pressure. In high-angle and horizontal wells, gravitational force contributes to extended contact between the drillstring and the formation. Properly managing the lubricity of the drilling fluid and the quality of the filter cake across the permeable formation can help reduce occurrences of stuck pipe.
Fig. 1—Principle of differential sticking (modified from Ref. 2.).
Mechanical causes for stuck pipe include:
- Packoff from poor hole-cleaning
- Shale swelling
- Wellbore collapse
- Plastic-flowing formation (i.e., salt)
Preventing stuck pipe can require close monitoring of early warning signs, such as:
- Increases in torque and drag
- Excessive cuttings loading
- Tight spots while tripping
- Loss of circulation while drilling .
Depending on what the suspected cause of sticking is, it might be necessary to increase the drilling-fluid density (to stabilize a swelling shale) or to decrease it (to protect the depleted zone and avoid differential sticking). A drilling fluid’s friction coefficient is an important factor in its effectiveness in preventing stuck pipe and/or enabling stuck pipe to be worked free. Oil-based fluids (OBFs) and synthetic-based fluids (SBFs) offer the maximum lubricity. Inhibitive water-based fluids (WBFs) can be treated with a lubricant (typically 1 to 5% by volume) and formulated to produce a thin, impermeable filter cake that offers increased protection against sticking. High-performance-polymer WBFs that are designed specifically to serve as alternates to OBFs and SBFs exhibit a high degree of natural lubricity and might not require the addition of a lubricant.
- Isambourg, P., Ottesen, S., Benaissa, S. et al. 1999. Down-Hole Simulation Cell for Measurement of Lubricity and Differential Pressure Sticking. Presented at the SPE/IADC Drilling Conference, Amsterdam, 9–11 March. SPE-52816-MS. http://dx.doi.org/10.2118/52816-MS.
- Santos, H. 2000. Differentially Stuck Pipe: Early Diagnostic and Solution. Presented at the IADC/SPE Drilling Conference, New Orleans, 23-25 February. SPE-59127-MS. http://dx.doi.org/10.2118/59127-MS.
Noteworthy papers in OnePetro
Muhammad A. Muqeem, SPE, Alexander E. Weekse, SPE, Ali A. Al-Hajji, SPE, Saudi Aramco: Stuck Pipe Best Practices - A Challenging Approach to Reducing Stuck Pipe Costs, 160845-MS, http://dx.doi.org/10.2118/160845-MS
G. Yarim, SPE, R. Uchytil, SPE, R. May, SPE, A. Trejo, SPE, and P. Church, SPE, Schlumberger: Stuck Pipe Prevention--A Proactive Solution to an Old Problem, 109914-MS, http://dx.doi.org/10.2118/109914-MS