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Introduction

Terms
Specifications

Cable
Construction

Portable Marking
Unit

Stationary Drum
1 Capstan

Stationary Drum
2 Capstan

Steps to Good
Cable Care

Calculating
Pull-Out Point

Rehead Strenght
Calculations

Specific Gravity
Weight and Pressure
Table

Calculating
Stuck Point

When Tool or
Cable is Stuck

Steps to Find
Stuck Point

Eliminating Errors

Things to check

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CABLE CARE

Calculating Stuck Point

There are numerous ways a cable or tool may get stuck in a well.  In an open hole well it is possible for the logging cable to be stuck many feet above the tool.  This usually is referred to as being "Differentially stuck".  It is possible for the logging tool to become differentially stuck also.  For a tool or the cable to get differentially stuck certain well bore conditions must exist.

1. The borehole hydrostatic pressure must be greater than the formation pressure.

2. The formation must have high permeability.

3. The formation must high porosity

When these conditions are present the higher pressure in the well bore can force the logging cable and/or logging tool into the thick mud cake that has built up on the bore hole wall.  Continued attempts to withdraw cable from the well will result in frictional forces so great that cable tension exceeds allowable limits.

There is extreme danger of becoming stuck if the logging tool is stopped in the well.  It is possible that the logging tool or the cable may become "Key Seated" in a well.

As the transparency shows, the well was not drilled perfectly straight. The resulting deformity or deviation is called a "dog leg".  As the cable is drawn out of the well during logging operations it wears a slot into the formation.  When the logging tool reaches the slot it stops because the diameter of the slot is much too small for the logging tool to pass through.  In many instances the logging tool will be free to go down the hole, but it cannot be pulled up past the dog leg in the well.

It must be recognized that if the logging cable is stuck above the logging tool, it will be impossible to part the weak link in the cable head.

When a tool or logging  cable is stuck and the three conditions pointed out are present in the well bore, it should be presumed possible that the cable may be stuck above the logging tool.