Method and apparatus for obtaining a composite field response _to a variable source array using weighting coefficients
First Claim
1. A multi-channeled digital seismic field stacking system for processing seismic signals to form a stack of summed together receiver array response to a preselected number of energy impulses applied to the ground at selected impact points, thereby to obtain a composite seismic response to a variable source array, said seismic system comprising:
- (A) at least one amplifier, for amplifying said seismic signals from selected points on the ground to obtain a sampled analog output signal, each seismic channel of said multi-channeled system having a multi-plexer sample time interval;
(B) an analog-to-digital converter, for converting said smapled analog output signal to a digital sample;
(C) means for applying pre-selected weighting coefficients to said digital sample in real time to obtain weighted samples;
(D) a digital stacking unit, for summing said weighted samples with the summed-together weighted samples of the seismic signals from the preceding ones of the preselected number of impulses which have occurred for a stack, said summed-together weighted samples in each of said channels obtained from seismic signals measured at the same point on the ground; and
(E) a digital storage unit, for storing said stacked seismic signals as a record when a portion of said preselected number of impulses have occurred, said records representing composite seismic responses to variable source arrays, each source array varied in accordance with said preselected weighting coefficients.
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Abstract
A multi-channeled digital seismic field stacking system is disclosed for obtaining the composite response to a variable source array. A variable source array is synthesized by applying preselected weighting coefficients to the seismic signals produced in response to a selected number of surface energy impulses. The seismic signals produced by these impulses are amplified, multiplexed and digitized to obtain digital samples to which are applied the weighting coefficients. A digital multiplier is used to multiply each digital sample by a weighting coefficient to obtain a weighted digital sample. Each digital sample is multiplied by two weighting coefficients, a partial and a final. The partial weighted samples from each of the impulses are summed together to form a partial stack, while the final weighted samples are summed together to form a final stack. The variable source array which is synthesized covers two station intervals. At each station, the partial stack represents the first half of a variable source array, while the final stack represents a complete source array covering the two previous station intervals. At each station, the final stack is recorded on magnetic tape as a seismic field record, and the partial stack is transferred to the final stack for summation with the final weighted samples for the last half of the next variable source array.
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Citations
24 Claims
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1. A multi-channeled digital seismic field stacking system for processing seismic signals to form a stack of summed together receiver array response to a preselected number of energy impulses applied to the ground at selected impact points, thereby to obtain a composite seismic response to a variable source array, said seismic system comprising:
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(A) at least one amplifier, for amplifying said seismic signals from selected points on the ground to obtain a sampled analog output signal, each seismic channel of said multi-channeled system having a multi-plexer sample time interval; (B) an analog-to-digital converter, for converting said smapled analog output signal to a digital sample; (C) means for applying pre-selected weighting coefficients to said digital sample in real time to obtain weighted samples; (D) a digital stacking unit, for summing said weighted samples with the summed-together weighted samples of the seismic signals from the preceding ones of the preselected number of impulses which have occurred for a stack, said summed-together weighted samples in each of said channels obtained from seismic signals measured at the same point on the ground; and (E) a digital storage unit, for storing said stacked seismic signals as a record when a portion of said preselected number of impulses have occurred, said records representing composite seismic responses to variable source arrays, each source array varied in accordance with said preselected weighting coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. In a multi-channeled digital seismic field stacking system for summing the seismic signals from a preselected number of energy impulses to form a composite response, said system having,
(A) means for amplifying said seismic signals to obtain a sampled analog signal, the seismic channels of said multi-channeled system each having a sample time interval, (B) an analog-to-digital converter for converting said sampled analog signal to digital samples, (C) a digital stacking unit including a mass memory storage unit, for summing and storing channel-by-channel, the digital samples for each of said impulses with the summed-together digital samples from preceding ones of said predetermined number of impulses, and (D) a digital storage unit, for storing a record of said composited seismic signals, the improvement in said system comprising: means for multiplying each said digital sample by weighting coefficients in real time prior to summation by said stacking unit thereby to obtain records in said digital storage unit representing composite seismic responses to variable source arrays, each said source array varied in accordance with said weighting coefficients, and where each record is stored in said storage unit at the completion of a portion of said preselected number of impulses. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A seismic data acquisition system comprising:
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(A) an instantaneous floating point amplifier, for amplifying multiplexed analog seismic channel signals produced in response to a surface energy impulse, each said multiplex signal amplified during a sample time interval; (B) an analog-to-digital converter, for converting said amplified analog seismic signals to digital samples; (C) a digital multiplier, for multiplying said digital sample by a final and a partial preselected weighting coefficient during said sample time interval to obtain a final and a partial weighted digital sample, respectively; (D) a digital stacking unit, including a mass memory storage unit, for summing said weighted digital samples for a number of said impulses comprising a set of impulses, on a channel-to-corresponding channel, impulse-to-impulse basis, said stacking unit, (1) summing for said set of impulses said partial weighted samples to form a partial stack, said first impulse partial weighted samples summed with zero, (2) summing for the same said set of impulses said final weighted samples to form a final stack, said final stack at the completion of said set of impulses representing the composite response to a source array including the seismic responses to two consecutive said sets of impulses, said source array varied in accordance with said weighting coefficients, (3) summing said partial stack from the last occurring said set of impulses with the final weighted samples of the first impulse in the next said set of impulses to form the first final sum, said first impulse final weighted samples coming from the same point on the ground as said partial stack samples, and (4) storing said first final sum in said mass memory seismic channel final stack locations; and (E) a digital magnetic tape recorder for recording said composite response as a digital seismic record. - View Dependent Claims (21)
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22. The method of obtaining the composite response to a preselected number of energy impulses applied to the ground at selected impact points thereby to obtain the composite response to a variable source array comprising the steps of:
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(A) amplifying the seismic signals from seismic channels at points on the ground to generate a sampled analog output signal, each said seismic channel having a sample time interval; (B) converting said sampled analog output signal to digital samples; (C) multiplying said digital samples in real time by digital weighting coefficients to obtain weighted digital samples; (D) summing said weighted digital samples for each channel with its corresponding previously summed-together and stored weighted digital samples from the seismic signals produced in response to preceding ones of the preselected number of impulses, said summed-together weighted samples in each of said channels obtained from seismic signals measured at the same point on the ground; and (E) recording the summed-together weighted digital samples at each completion of one-half of the preselected number of impulses to obtain records representing the composite responses to source arrays varied in accordance with said weighting coefficients. - View Dependent Claims (23, 24)
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Specification