Instrument structure and measuring method for cross-casing resistivity tool
OwnerShanjun Liinventor
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Abstract
The present application provides a device and method for determining formation resistivity outside casing. The device measures the electrical signal of alternating current flowing along the casing, and then calculates phase velocity, group velocity, time difference, amplitude attenuation, and phase difference of the alternating current along the casing. Using these relationships between phase velocity, group velocity, time differences, amplitude attenuation, and phase difference, the formation resistivity outside the casing is calculated.
Claims21
A device for measuring cross casing resistivity comprising:
- at least one electrode transmitter, at least one electrode monitor, at least one current measuring circuit for measuring alternating current signal flowing through the electrode monitor along the casing, a power source, and a processor configured for calculating at least one parameter for current propagation along the casing based on the alternating current signal and for calculating resistivity of formation outside the casing based on the at least one parameter for current propagation along the casing, wherein:
- the electrode monitor and/or the electrode transmitter is installed with the current measuring circuit;
- the alternating current signal is selected from the group consisting of amplitude, phase, and combinations thereof;
- alternating current emitted by the electrode transmitter partially or entirely flows through the electrode monitor back to the power source, and
- the parameter for current propagation along the casing is selected from the group consisting of:
- time difference, phase velocity, group velocity, phase difference, amplitude attenuation, and combinations thereof.
A method of measuring cross casing resistivity comprising:
- measuring alternating current signal flowing through at least one electrode monitor along the casing;
- calculating via a processor at least one parameter for current propagation along the casing based on the alternating current signal measured in the measuring step;
- and
- calculating resistivity of formation outside the casing based on the at least one parameter for current propagation along the casing,
- wherein:
- the alternating current signal is selected from the group consisting of amplitude, phase, and combination thereof;
- and the at least one parameter for current propagation along the casing is selected from the group consisting of time difference, phase velocity, group velocity, phase difference, amplitude attenuation, and combinations thereof.
Dependencies are inferred from the claim text.