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US 7,010,429 B2Granted
Induction logging system and method featuring multi-frequency skin effect correction
AssigneeHalliburton Energy Services, Inc.
InventorJiaqi Xiao
Life of this patent
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Abstract
A system and method of correcting skin effect of conductivity measurements made by electromagnetic induction well logging instruments. A limited number of measurements using different frequencies may be used. The skin effect correction system and method is capable of processing a complex signal waveform but only requires the in-phase signal measurements which are then corrected for the skin effect value and the geometric factors of the apparent conductivity measurements, thus making the corrected measurements suitable for advanced processing with modern array-type induction logging tools.
Claims50
A method for correcting skin effect in a induction logging system, said method comprising the steps of:
- measuring first, second and third apparent conductivities at first, second and third operating frequencies, respectively;
- determining first, second and third weighting coefficients;
- determining first, second and third weights;
- determining a first low-pass filtered conductivity difference between the measured first and second apparent conductivities;
- determining a second low-pass filtered conductivity difference between the measured second and third apparent conductivities;
- determining a third low-pass filtered conductivity difference between the measured first and third apparent conductivities;
- determining a first corrected conductivity from the measured first, second and third apparent conductivities, the first, second and third weighting coefficients, and the first weight;
- determining a second corrected conductivity from the first corrected conductivity, the second weight, the third low-pass filtered conductivity difference, and the first and third operating frequencies;
- determining a third corrected conductivity from the second corrected conductivity, the first low-pass filtered conductivity difference, the second low-pass filtered conductivity difference, the first, second and third operating frequencies, and the third weight;
- determining first, second and third compensated conductivities from the first, second and third corrected conductivities, respectively, and values from a look-up table;
- determining selection coefficients;
- and
- determining a formation corrected conductivity by summing the selection coefficients combined with the first, second and third compensated conductivities.
10 more elements
A method for correcting skin effect in a induction logging system, said method comprising the steps of:
- measuring first and second apparent conductivities at first and second operating frequencies, respectively;
- determining first and second weighting coefficients;
- determining first and second weights;
- determining a low-pass filtered conductivity difference between the measured first and second apparent conductivities;
- determining a first corrected conductivity from the measured first and second apparent conductivities, the first and second weighting coefficients, and the first weight;
- determining a second corrected conductivity from the first corrected conductivity, the second weight, the low-pass filtered conductivity difference, and the first and second operating frequencies;
- determining first and second compensated conductivities from the first and second corrected conductivities, respectively, and a look-up table;
- determining selection coefficients;
- and
- determining a formation corrected conductivity by summing the selection coefficients combined with the first and second compensated conductivities.
7 more elements
A method for correcting skin effect in a induction logging system, said method comprising the steps of:
- measuring two or more apparent conductivities at two or more operating frequencies;
- determining weighting coefficients;
- determining weights;
- determining a low-pass filtered conductivity difference between the two or more apparent conductivities;
- determining a first corrected conductivity from the measured two or more apparent conductivities, the weighting coefficients, and the weights;
- determining a second corrected conductivity from the first corrected conductivity, the weights, the low-pass filtered conductivity difference, and the two or more operating frequencies;
- determining first and second compensated conductivities from the first and second corrected conductivities, respectively, and a look-up table;
- determining selection coefficients;
- combining the selection coefficients with the first and second compensated conductivities;
- and
- summing the combined selection coefficients and the first and second compensated conductivities to obtain a formation corrected conductivity.
8 more elements
A method for correcting skin effect in a induction logging system, said method comprising the steps of:
- measuring at least two apparent conductivities at two or more operating frequencies;
- determining weighting coefficients;
- determining weights;
- determining a low-pass filtered conductivity difference between the at least two apparent conductivities;
- determining at least two corrected conductivities from the measured at least two apparent conductivities, the weighting coefficients, the weights, the low-pass filtered conductivity difference and the two or more operating frequencies;
- determining at least two compensated conductivities from the at least two corrected conductivities and a look-up table;
- determining selection coefficients;
- and
- determining a formation corrected conductivity from the at least two compensated conductivities and the selection coefficients.
6 more elements
An induction logging system having skin effect correction, said system comprising:
- an induction logging tool for measuring first, second and third apparent conductivities at first, second and third operating frequencies, respectively;
- a processor, wherein:
- the processor receives the measured first, second and third apparent conductivities from the induction logging tool;
- the processor determines first, second and third weighting coefficients;
- the processor determines first, second and third weights;
- the processor determines a first low-pass filtered conductivity difference between the measured first and second apparent conductivities;
- the processor determines a second low-pass filtered conductivity difference between the measured second and third apparent conductivities;
- the processor determines a third low-pass filtered conductivity difference between the measured first and third apparent conductivities;
- the processor determines a first corrected conductivity from the measured first, second and third apparent conductivities, the first, second and third weighting coefficients, and the first weight;
- the processor determines a second corrected conductivity from the first corrected conductivity, the second weight, the third low-pass filtered conductivity difference, and the first and third operating frequencies;
- the processor determines a third corrected conductivity from the second corrected conductivity, the first low-pass filtered conductivity difference, the second low-pass filtered conductivity difference, the first, second and third operating frequencies, and the third weight;
- the processor determines first, second and third compensated conductivities from the first, second and third corrected conductivities, respectively, and values from a look-up table;
- the processor determines selection coefficients;
- and
- the processor determines a formation corrected conductivity by summing the selection coefficients combined with the first, second and third compensated conductivities.
12 more elements
An induction logging system having skin effect correction, said system comprising:
- an induction logging tool for measuring at least two apparent conductivities at two or more operating frequencies;
- a processor, wherein:
- the processor receives the measured at least two apparent conductivities from the induction logging tool;
- the processor determines weighting coefficients;
- the processor determines weights;
- the processor determines a low-pass filtered conductivity difference between at least two apparent conductivities;
- the processor determines at least two corrected conductivity from the measured at least two apparent conductivities, the weighting coefficients, the weights, the low-pass filtered conductivity difference and the two or more operating frequencies;
- the processor determines at least two compensated conductivities from the at least two corrected conductivities and a look-up table;
- the processor determines selection coefficients;
- and
- the processor determines a formation corrected conductivity from the at least two compensated conductivities and the selection coefficients.
8 more elements
Dependencies are inferred from the claim text.