Extended range, pulsed induction logging tool and method of use
First Claim
1. An apparatus for systematically logging an earth formation around a borehole using a logging sonde by generating a primary magnetic field in the formation at depth and detecting an induced secondary magnetic field indicative of a formation electrical parameter, comprising(i) means for generating a series of time spaced primary magnetic field pulses at a series of stations along the borehole;
- (ii) means for detecting response data relative to a secondary magnetic field induced in said formation by each said primary magnetic field pulse, and (iii) means for processing said response data to provide an indication of at least one electrical parameter of the formation around the borehole;
wherein said processing means includes (a) means for modeling the response of the adjacent formation using a series of assumed conductivity and bed thickness values along with actual parameters of the pulsed primary field, and (b) means for cross-checking a forward solution of (a) against detected components of the secondary magnetic field.
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Accused Products
Abstract
In accordance with the present invention, a pulsed induction logging system is provided which includes a logging sonde for traversing a borehole and having downhole microprocessor/controller circuitry in operative contact with a separate host computer/controller at the earth'"'"'s surface. The host computer/controller and two downhole microprocessor/controllers constitute a network of digital computers and generate a digital pulsed logging code for periodically permitting a radiation coil to be driven by an oscillating current having high peak power. A powerful primary pulse of electromagnetic (EM) energy is periodically generated for irradiating the adjacent formation for induction logging purposes. The sonde also includes an antenna array for detecting secondary induced fields in the formation around the borehole. The array preferably includes a series of grouped, paired coils axially spaced along the borehole. Each group of paired coils independently detects the secondary field. Thereafter each detected signal per group of paired coils, is digitized, reformatted and transmitted to the host computer/controller at the earth'"'"'s surface. The serially transmitted digital data is highly accurate and capable of frequency domain transformation in situ. After additional processing in the frequency domain, final displays are accurate indications of formation conductivity and/or dielectric values irrespective of adverse formation-borehole effects.
70 Citations
25 Claims
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1. An apparatus for systematically logging an earth formation around a borehole using a logging sonde by generating a primary magnetic field in the formation at depth and detecting an induced secondary magnetic field indicative of a formation electrical parameter, comprising
(i) means for generating a series of time spaced primary magnetic field pulses at a series of stations along the borehole; - (ii) means for detecting response data relative to a secondary magnetic field induced in said formation by each said primary magnetic field pulse, and (iii) means for processing said response data to provide an indication of at least one electrical parameter of the formation around the borehole;
wherein said processing means includes (a) means for modeling the response of the adjacent formation using a series of assumed conductivity and bed thickness values along with actual parameters of the pulsed primary field, and (b) means for cross-checking a forward solution of (a) against detected components of the secondary magnetic field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- (ii) means for detecting response data relative to a secondary magnetic field induced in said formation by each said primary magnetic field pulse, and (iii) means for processing said response data to provide an indication of at least one electrical parameter of the formation around the borehole;
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10. The apparatus of claim 31 in which the frequency-depth transforms are in matrix format in which rows and columns designations are antenna depth and frequency.
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11. An apparatus for systematically logging an earth formation around a borehole using a logging sonde by generating a primary magnetic field in the formation at depth and detecting an induced secondary magnetic field indicative of a formation electrical parameter, comprising
(i) means for generating a series of time spaced primary magnetic field pulses of high peak power at a series of stations along the borehole, said generating means including a radiation coil and a power source network in selective operative contact therewith, said power source network including a magnetohydrodynamic (MHD) source and a switch network; - (ii) means for detecting response data relative to a secondary magnetic field induced in said formation by each said primary magnetic field pulse, and (iii) means for processing said response data to provide an indication of at least one electrical parameter of the formation around the borehole.
- View Dependent Claims (12, 13)
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14. A method for systematically logging an earth formation around a borehole using a logging sonde to generate a primary magnetic field in the formation at depth and detecting an induced secondary magnetic field indicative of a formation electrical parameter, comprising the steps of:
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(i) generating a series of time spaced primary magnetic field pulses at a series of stations along the borehole; (ii) detecting response date relative to the secondary magnetic field induced in said formation by each said primary magnetic field pulse; and (iii) processing said response data to provide an indication of a formation electrical parameter around the borehole by (a) modeling response of the adjacent formation using a series of assumed conductivity and bed thickness values along with actual parameters of the pulsed primary field, and (b) cross-checking a forward solution of the model of step (a) against measured detected components of the secondary magnetic field at depth. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification