Method for releasing cables from an attached well tool and apparatus for exercising the method

1. Method for releasing cables ( 2 ) from an attached well tool, wherein a cable cutter ( 6 ) is arranged between the main part of a cable and a well tool, said cable cutter being controlled by an electronic timer, the method comprising:

using at least three parameters for controlling the cutter: a pulling force exerted by the cable on the well tool, the pressure in the well location, and time; and

resetting the timer from currents in the cable ( 2 ) through the use of an interface pick-up ( 3 ).

2. Method according to claim 1 , the method further comprising:

using temperature as a controlling parameter.

3. Method according to claim 1 , wherein the timer ( 1 ) is also responsive to pulses of currents, the method further comprising:

making it possible for an operative crew to remotely control preset parameter values of force, pressure, temperature, or timer delay and thus a triggering of the cutter ( 6 ).

4. Method according to claim 3 , the method further comprising:

controlling the timer by pulses smaller than reset pulses, wherein the pulses are given by the operative crew from the surface to remotely control the preset parameter value of timer delay and the triggering of the cutter.

5. Method according to claim 4 , characterised in that the preset values for the pressure tensile stress or temperature can be changed from the operative crew.

6. Method according to claim 4 , characterised in that a capacitor is arranged between the cable and ground.

7. Apparatus for releasing cables ( 2 ) from an attached well tool, wherein a cable cutter ( 6 ) is arranged between a main part of a cable and a well tool, the apparatus comprising:

an electronic timer that controls the cable cutter, the electronic timer comprising a receiver ( 1 ) for receiving reset signals generated by currents in the cable ( 2 ), auxiliary inlets for signals from sensors for physical parameters, an outlet for control of a cutter control ( 4 ), and a pick-up ( 3 ), the electronic timer in connection with the cable through the pick-up,

wherein the pick-up generates reset signals by a steady detection of the currents in the cable, to which the tool is attached.

8. Apparatus according to claim 7 , characterised in that the receiver ( 1 ) further has at least one circuit controlled by small pulses from the cable ( 2 ), which is connected to ground through a capacitor ( 5 ).

9. Apparatus according to claim 8 , characterised in that a pulse generator on the surface is connected to the cable ( 2 ).

10. Apparatus according to claim 7 , characterised in that the cutter control ( 4 ) is connected to the cable cutter ( 6 ).

11. Apparatus for releasing cables ( 2 ) from an attached well tool, wherein a cable cutter ( 6 ) is arranged between a main part of a cable and a well tool, the apparatus comprising:

an electronic timer that controls the cable cutter, the electronic timer comprising a receiver ( 1 ) for receiving reset signals generated by currents in the cable ( 2 ), auxiliary inlets for signals from sensors for physical parameters, an outlet for control of a cutter control ( 4 ), and a pick-up ( 3 ) which generates reset signals; and

the receiver having at least one circuit controlled by small pulses from the cable ( 2 ), which is connected to ground through a capacitor ( 5 ).

12. Apparatus according to claim 11 , characterised in that a pulse generator on the surface is connected to the cable ( 2 ).

13. Apparatus according to claim 11 , characterised in that the cutter control ( 4 ) is connected to the cable cutter ( 6 ).