Methods of processing magnetotelluric signals
First Claim
1. A method of processing magnetotelluric data to identify subterranean deposits, wherein said data comprise the amplitude of alternating magnetic or electrical fields recorded over time in at least two vector components at one or more locations in an area of interest, said method comprising:
- (a) identifying amplitude pulses in said data, said pulses being time segments comprising an amplitude peak meeting defined threshold criteria in at least one said vector component;
(b) filtering said pulses at a set of predetermined frequencies to separate amplitude data at each said frequency from the remainder of the amplitude data in said pulses, wherein said frequencies correspond to subterranean depths over a range of interest; and
(c) statistically analyzing a differential impedance Δ
Z of said pulses at each said frequency at each said location to determine a value correlated to the resistance of the earth at each said frequency, the resistance being indicative of the presence or absence of deposits at the corresponding subterranean depth at the location;
wherein differential impedances of a given pulse x, Δ
Zx(f), are defined as follows;
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Abstract
A method for processing magnetotelluric data to identify subterranean deposits is provided for. The data comprise the amplitude of alternating magnetic or electrical fields recorded over time in at least two vector components at one or more locations in an area of interest. Amplitude pulses are identified in the data, wherein the pulses are time segments comprising an amplitude peak meeting defined threshold criteria in at least one vector component. The pulses are filtered at a set of predetermined frequencies to separate amplitude data at each frequency from the remainder of the amplitude data in the pulses. The frequencies correspond to subterranean depths over a range of interest. Differential impedances ΔZ of the pulses at each frequency at each location are then statistically analyzed to determine a value correlated to the resistance of the earth at each frequency. The resistance values are indicative of the presence or absence of deposits at the corresponding subterranean depth at the location.
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Citations
30 Claims
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1. A method of processing magnetotelluric data to identify subterranean deposits, wherein said data comprise the amplitude of alternating magnetic or electrical fields recorded over time in at least two vector components at one or more locations in an area of interest, said method comprising:
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(a) identifying amplitude pulses in said data, said pulses being time segments comprising an amplitude peak meeting defined threshold criteria in at least one said vector component; (b) filtering said pulses at a set of predetermined frequencies to separate amplitude data at each said frequency from the remainder of the amplitude data in said pulses, wherein said frequencies correspond to subterranean depths over a range of interest; and (c) statistically analyzing a differential impedance Δ
Z of said pulses at each said frequency at each said location to determine a value correlated to the resistance of the earth at each said frequency, the resistance being indicative of the presence or absence of deposits at the corresponding subterranean depth at the location;
wherein differential impedances of a given pulse x, Δ
Zx(f), are defined as follows; - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of transforming data representing magnetotelluric fields above an area of interest on the earth to values representing the resistivity of the earth at various depths below said area of interest, wherein said data comprise the amplitude of alternating magnetic or electrical fields over time in at least two vector components at one or more locations in said area of interest, said method comprising:
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(a) identifying amplitude pulses in said data, said pulses being time segments comprising an amplitude peak meeting defined threshold criteria in at least one said vector component; (b) filtering said pulses at a set of predetermined frequencies to separate amplitude data at each said frequency from the remainder of the amplitude data in said pulses, wherein said frequencies correspond to subterranean depths over a range of interest; and (c) statistically analyzing differential impedance Δ
Z of said pulses at each said frequency at each said location to determine said values correlated to the resistance of the earth at said subterranean depths in said area of interest, the resistance being indicative of the presence or absence of deposits at the corresponding subterranean depth at the location;
wherein differential impedances of a given pulse x, Δ
Zz(f), are defined as follows; - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification