One Step Towards True Along Hole Logging Depths: Proper WLL corrections

Why work on depth QC??

• Depth one of the top uncertainty factors FDP’s
• Sensitivity analysis Net Present Value typical FDP
• Direct impact fluid contacts on HC vol.
  • Extreme case: >>> 1 million bbl per 1 ft change in GOC

Accuracy & precision needed

• Fluid contacts
  • A few feet difference has major impact 3
  • Not many examples about lateral error mishaps. (…yet … )

AH-depth and 3D position

• Limit to AH depth
• Surveying needed for 3D position
  • AH depth (often) important input
    • Plenty of problems challenges already

Current practice

• Wireline – loggers depth
  • Normally (some) stretch corrections applied
• LWD logs – drillers depth
  • Surface measured lengths
  • No stretch corrections applies
    • Hence grossly in error; errors not consistent
• WLL depths (used to be) believed as being better than drillers depth
  • But LWD/drillers depth taken for lack of WL in horizontals

Drillpipe and logging cable

• The WLL challenge: get a really good (accurate) measurement even with such flimsy cable..!!)

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One Step Towards True Along Hole Logging Depths: Proper WLL corrections

Harald Bolt 

Ton Loermans

 

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