Stuck Pipe (Determination of Mechanisms and required Jar and free point depth Calculations )

 Stuck pipe is a term used for describing a situation in which the drill string cannot be moved up or down or rotated. Stuck pipe is an expensive drilling problem because it usually halts all operations until the pipe is released.

    Industry statistics gathered since 1989 show the relative cost of non-productive time. Stuck pipe is still the drilling industry's most costly unscheduled event as:

• Lost drilling time when freeing the pipe.
• Time and cost of fishing: trying to pull out of the hole the broken part of the BHA.

There are Three Stuck pipe mechanisms :

• Hole pack off/Bridge
• Differential
• Well bore geometry

1-   Hole pack off/Bridge :

 

Pack off: Small pieces of       

formation, cement or junk

settle around the drillstring

preventing circulation with

no string movement likely.

Bridge: Medium to large

pieces of formation, cement

or junk settle around the

drillstring allowing restricted

circulation with little to no

string movement

2-  Differential Sticking :

Differential sticking is due to  Hydrostatic overbalance drives the static drillstring into the thick filter cake of a permeable zone.            

3-    Well bore geometry mechanism 

Sharp changes in hole angle/direction; an
undergauge hole diameter or increase in assembly stiffness will not allow passage  of the string.

determination of Stuck pipe mechanisms 

 while dealing with stuck pipe problem,  It is very important to determine which type of the three Mechanisms to be able to solve this problem. This Excel Sheet will help you determine which Mechanism you are dealing with depending on theses criteria . 

Download the Sheet from this link : Estimation of Stuck pipe Mechanism Excel sheet  

            Jars are very important for solving Stuck pipe problems 

types of Jars 

 -Mechanical   |   Hydraulic   |    Hydro-Mechanical   

All types of jars operate on the principle that energy can be build up by stretching the stucked string with the yield limits of the steel and suddenly releasing the energy through a tripping mechanism in the tool.

- Mechanical jar

Jarring up is achieved by applying sufficient over pull (preselected tensile force) to overcome the latch setting. At this point, the MJ release and jar upward. The position of mechanical jar in drilling string either cocked (neutral) or tripped up and never drilling with jar tripped down

- Hydraulic jar

Hydraulic jars use a hydraulic fluid to delay the firing of the jar until the driller can apply the appropriate load to the string to give a high impact. The time delay is provided by hydraulic fluid being forced through a small port or series of jets. Hydraulic jar firing delay is dependent upon the combination of load and time

Jar Calculations are very important before firing the jar .

feel free to download this sheet that contains jar Calculations :

Download from this link  Jar Calculation Excel Sheet  

Free point Estimation 

     one of the first steps is to perform a calculation to determine at what depth or point the pipe stuck has occurred. This process is called stuck pipe free point calculation.  the required  calculations are concluded in this sheet .

download from this link  Free point Estimation Excel Sheet  

for downloading complete courses of stuck pipe :

click here Stuck pipe Course 

click here Complete Stuck Pipe Course 

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ALI SOBHY