Method of determination of a stuck point in drill pipes by measuring the magnetic permeability of pipes
AssigneeSchlumberger Technology Corporation
InventorsJacques Orban, Mikhail Iakimov
Life of this patent
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Abstract
The invention is a method of determining a free point in stuck drill pipes, comprising the steps of: a. measuring a first magnetic permeability (μ1) based on a time-induced decay of the electromagnetic field generated by application of an electric current pulse to the unextended pipe (l0); b. applying a force to the pipe to extend the pipe (l1); c. measuring a second magnetic permeability (μ2) of the extended pipe (l1); and d. comparing the first and second magnetic permeabilities (μ1 and μ2) along the drill string to determine the free point based on the change of magnetic permeability.
Claims13
A method of determining a free point in a stuck drill pipe, comprising the steps of:
- a. measuring a first magnetic permeability (μ1) based on a time-induced decay of the electromagnetic field generated by application of an electric current pulse to the pipe in a first tension state (l0);
- b. applying a force to the pipe to change the tension state of the pipe (l1);
- c. measuring a second magnetic permeability (μ2) of the extended pipe in a second tension state (l1);
- and
- d. comparing the first and second magnetic permeabilities (μ1 and μ2) along the pipe to determine the free point based on the change of magnetic permeability.
A method of using an apparatus comprising a diamagnetic shell containing a coaxially located exciting coil and two electromagnetic field measuring devices, wherein two coaxial coils are located on either side of the exciting coil to determine a free point in stuck drill pipes, the method comprising the steps of:
- moving the apparatus through the drill pipes and measuring a first time-induced electromagnetic field decay along the length of the drill pipes;
- applying a force to the drill pipes;
- moving the apparatus through the drill pipes and measuring a second time-induced electromagnetic field decay along the length of the drill pipes;
- and
- determining the free point by comparing the first and second respective time-induced electromagnetic field decays to obtain a relative variation of magnetic permeability along the drill pipes.
Dependencies are inferred from the claim text.