Accelerator (intensifier) A down-hole tool used in conjunction with a jar to store energy that is released suddenly when the jar operates.
Annular velocity The linear velocity of a fluid passing through an annular space. The term critical annular velocity is often used to describe the flow rate or velocity at which entrained solids will be efficiently transported by the annular fluid. If the fluid velocity falls below the critical rate, there will be a risk of particles settling, forming beds or bridges that may obstruct the wellbore.
Back off To unscrew one threaded piece (as a section of pipe) from another.
Back pressure The pressure within a system caused by fluid friction or an induced resistance to flow through the system. Hydraulic ...