21 - Stuck Pipe...Prevention Is Better Than Cure
Updated: Apr 12, 2019
Stuck pipe incidents cost the Oil & Gas industry millions of dollars each year in rig time, fishing services, equipment rental, and more severely lost-in-hole and sidetracks. The irony is that most incidents are avoidable, yet they keep occurring, and in many occasions efforts fail to free stuck pipe.
A stuck pipe incident in land operation can roughly cost between $0.7M - $1.5M
What Is Stuck Pipe?
Stuck pipe is an undesired situation where drill string movement is restricted due to a downhole problem, thus preventing drilling from advancing.
What Are The Types Of Stuck Pipe?
Stuck pipe incidents are categorized according to their cause, which is known as stuck pipe mechanism. There are three mechanisms for stuck pipe:
Differential Pressure, It occurs when the hydrostatic pressure is significantly higher than the formation pressure, thus pushing the drill string towards the wellbore. Usually, three factors gather at the same time for differential sticking to occur:
static drill pipe (e.g. making connection, well control situation, performing a flow check)
permeable formation
high over balance
Wellbore Geometry, It occurs when the drill string becomes stuck in a wellbore irregularity, such as:
Keyseating, which is a groove in the wellbore made by the drill string as side forces act against the wellbore.
Ledges, which develop when sequential hard and soft formations are drilled with a high Rate Of Penetration (ROP). Also, high dogleg can result in developing ledges.
Shale swelling occurs when highly reactive shale gets exposed to water (or un-inhibited WBM) causing it to hydrate and swell
Plastic/Mobile formation occurs when the overburden pressure forces a formation to squeeze against the wellbore (e.g. mobile salt and plastic shale)
Under-gauged hole occurs when an under-gauged bit is used in drilling
Collapsed Casing occurs when the casing can't withstand the external forces acting against its wall
Packing-off, It occurs when cuttings, cavings, or other foreign material obstruct drill string movement, sush as:
Annulus overloading as cuttings accumulate due to poor hole cleaning
Wellbore collapse as unconsolidated, fractured or faulted formation fall into the wellbore due to poor mud properties or insufficient mud weight
Geopressured formation such as pressurized shale
Junk in hole caused by a tool or piece of equipment falling in the well
Any Other Types Of Stuck Pipe?
Yes, Green Cement stuck pipe might be considered the worst type. It occurs when drilling a cement plug or shoe-track while cement is not yet set. Chances of freeing Green Cement Stuck Pipe are very narrow, if not non-existent.
How To Identify The Stuck Pipe Mechanism?
Identifying stuck pipe mechanism is imperative to freeing the stuck, as it determines what first course of action which proved to be crucial. The Stuck-Pipe Calculator identifies the stuck pipe mechanism by diagnosing the following:
Pipe Motion at the moment of stuck pipe - Up/Down/Static
Pipe Motion after stuck pipe - free/restricted/impossible
Pipe Rotation after stuck pipe - free/restricted/impossible
Circulation after stuck pipe - free/restricted/impossible
Final Words
Stuck pipe incidents can be avoided by taking very simple measures such as:
Identifying problematic formations from offset wells analysis
Control Drilling Parameter to ensure proper hole cleaning and avoid creating wellbore irregularities
Designing a smooth well trajectory by minimizing doglegs
Training personnel on stuck pipe prevention and identification
Monitoring of drilling parameters on real time
Also, it is extremely important to select a drilling rig with enough overpull capacity. This is essential for enhancing the chances of freeing a stuck pipe.
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