Detecting electrical current in a magnetic structure
AssigneeSchlumberger Technology Corporation
InventorsHong Zhang, Richard A. Rosthal
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Abstract
A current sensor measures an electrical current flowing in well casing or other magnetic structure. The current sensor can be installed in a tool for performing electromagnetic (EM) induction surveying in a wellbore lined with an electrically conductive casing. The tool includes an EM element to transmit or receive a magnetic field through the casing. The measured current using the current sensor can be used to relate the change of casing effect on the EM element (e.g., an induction receiver) placed inside the well casing for performing the EM induction survey.
Claims23
A tool for measuring current flowing in a magnetic structure, comprising:
- a magnetically permeable core;
- a winding around the magnetically permeable core;
- an expandable structure to engage the magnetically permeable core against the magnetic structure in which the current to be measured is flowing;
- and
- a detector to measure a voltage induced in the winding due to the current flowing in the magnetic structure.
A tool for performing electromagnetic (EM) induction surveying in a wellbore lined with an electrically conductive casing, comprising:
- an EM element to transmit or receive a magnetic field through the casing;
- and
- a current sensor to measure induced electrical current flowing in the casing during the EM induction surveying.
A method for use with a cased wellbore lined with a casing, comprising:
- lowering a tool into the cased wellbore, wherein the tool has at least one current sensor;
- and
- measuring electrical current flowing in the casing using the at least one current sensor.
A system comprising:
- storage media to store measurement data taken by at least one current sensor provided with a tool into a wellbore lined with casing, wherein the measurement data represents electrical current in the casing;
- and
- a processor to determine a change in characteristic of the casing based on the measurement data.
Dependencies are inferred from the claim text.