You must log in to edit PetroWiki. Help with editing

Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. More information

Invisible lost time

Jump to navigation Jump to search

Invisible Lost Time (ILT) related to routine rig drilling operations is the difference between actual operational duration and a best practice target. It is invisible as it does not appear on any conventional morning reports. 
The measurement of Invisible Lost Time starts by analyzing each individual key performance indicator (KPI) that can be produced by a particular crew (drilling crew, casing crew, etc.) or by a machine automated operation or a combination of both. 
The measurement of Invisible Lost Time was first developed and used by Statoil and TDE. 

  • BOBT the time needed when drilling and producing the hole.
  • FLAT time The necessary time needed for constructing a well besides the BOBT (BHA handling, tripping, running casing, BOP work, drilling connections, etc.) 
  • LT – The deviation from plan (problem time) due to unexpected/unplanned events like hole problems, tool failures, rig repair etc. 


Source: Case History: Automated Drilling Performance Measurement of Crews and Drilling EquipmentKetil, M., Per Arild, S., StatoilHydro, Maidla, E.E., King, B., Nexen Data Solutions Inc., Thonhauser, G., Zoellner, P., TDE GmbH, SPE/IADC 119746, 2009