Private Forums
Jars and accelerators
09 January 2009
I am interested to know peoples feelings and preferences on
accelerator placement.
My feelings are they are good in top hole to act as a kind of shock
absorber to protect the contractors equipment, but wonder about the
effectiveness of these tools in deeper environments, and would like
to poll different views on placement strategies.
3 answer(s)
Consultant [retired Shell staff]
Total Posts: 240
Join Date: 02/09/05

You may like to read the conclusions/recommendations of publication:

IADC/SPE 14746 Computerised Drilling Jar placement, Anadrill. (1994)

Dansk Geotermi
Total Posts: 9
Join Date: 20/04/11
Chris, this is late, but I just saw your posting,

Accelerators or Energizers are useful in all holesections, regardless of pipe stretch for the simple reason of friction.  When you are pulling on stuck pipe, the overpull is translated into pipe stretch.  When the jar fires, it is the contraction of the drillpipe that determines the acceleration and terminal velocity of the hammer hitting the anvil inside the jar.  The contraction of the drillpipe is dependent of the friction factor for the entire string from the jar to the surface.   If you have an energizer/accelerator in the string above the jar, it is only the pipe/DC´s from the jar to the energizer that is subjected to friction.  The energizer has mechanically de-coupled the rest of the string.  So, apart from storing energy in the Belleville springs, is if also foremost a ”œfriction remover” that provides a higher terminal velocity.

Best regards
Total Posts: 5
Join Date: 28/05/08
I recommend to position the jar above the DC if your going to use
accelerators (to be under tension)to avoid putting the jar or the
accelerator in neutral. On the other hand if the jar will be used
without accelerator i recommend to be positioned near the expected
the stuck point (to be under compression). using jars placement
software also helps when drilling a deviated and horizontal wells.

Borai ElSamari
bp, Egypt
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