Industry standard definition of NPT and ILT

Dear members,

Over the past few years, we have been involved in some healthy debates about NPT (Non Productive Time). Now we are endeavouring to come up with standard definitions.

As most of you know, before the term NPT was used we had Lost Time ("our fault" e.g. stuck-pipe, Downhole Tool Failure) and Down Time ("not our fault" e.g. waiting on weather, waiting on others). And we use to spend a lot of time debating about which category to assign it to, when the key was to address the root cause and eliminate it for the future.

So far, so good.  But then NPT became such a metric ("stick") that teams would sometimes prefer not to assign an activity to NPT code. This could be because it was tied into bonus/penalty schemes or, in some countries, because operators would not get Cost Recovery for certain levels of NPT.

There is also an excellent article by Peter Rushmore on the pit-falls of using NPT %-age as a yard-stick.

Does your company have a rigorous definition of NPT and, if so, please may you share it with us all.

And the same for ILT (Invisible Lost time)- the term that grew out of Technical Limit (TL) methodology. 

The equation Total Time = Technical Limit time + NPT + Invisible Lost Time .. allows it to be calculated. And the term KILT (Known Invisible Lost Time) crept in for us to assign to activities that were not necessarily NPT (in the strictest sense) but were sub-optimal e.g.increasing mudweight due to hole condition, back-reaming due to poor hole condition.

Thanks in advance

Dave

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