Differential pipe sticking

Pipe sticking is the hole problem often encountered during the drilling phase. Pipe sticking means their will no pipe movement and no rotation.

There are three types of pipe sticking:-

  1. Differential pipe sticking
  2. Mechanical pipe sticking
  3. Keyseats
Differential pipe sticking occurs when the pressure differential(difference between borehole pressure and formation pressure) is very high across a porous and permeable zone.
Pipe stuck up
This large overbalance may be due to:-
  • Sudden increase in mud density
  • Across abnormally low pressured zone

Conditions for Differential pipe sticking

  • Thick filter cake
  • No string movement for some time in the open hole
  • High Dog leg also tends to push the pipe to the lower side of the hole
During the Differential sticking as the pipe is stuck on only one side of borehole and rest of the hole is open, there will be free circulation.

Preventing Differential pipe Sticking

  1. By maintaining Lowest possible overbalance necessary to allow for swab and surge. Also drilling with limited ROP as high ROP causes more cuttings which results in high mud density
  2. Reducing the contact area between drill string and borehole wall by :-
    • By using stabilizers and Spiral drill collar(they have less area then normal drill collars)
    • Reducing the thickness of filter cake by maintain low solid content in mud
  3. Reducing the time during which the drill string is motionless in the open hole

Releasing Differential Stuck pipe

  1. Reducing the differential pressure by reducing the borehole pressure, by pumping low density mud and also applying extra over pull on the string
  2. Organic fluid can be pumped across the stuck zone which can reduce the filter cake thickness
  3. Back off operation is used as last resort. Its involves removal of the free portion the drill string. Stuck portion of the sting will be left in the hole and can removed after.

4 comments:

  1. Replies
    1. dog leg is the hole inclination and its unit is degree/100ft.High inclination is high dogleg

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  2. Something about Blow Out...... :D

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