CN116068613A - Controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics - Google Patents

Controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics Download PDF

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CN116068613A
CN116068613A CN202111271062.2A CN202111271062A CN116068613A CN 116068613 A CN116068613 A CN 116068613A CN 202111271062 A CN202111271062 A CN 202111271062A CN 116068613 A CN116068613 A CN 116068613A
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frequency
harmonic
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seismic
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殷厚成
肖云飞
彭代平
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China Petroleum and Chemical Corp
Sinopec Geophysical Research Institute
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Sinopec Geophysical Research Institute
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01VGEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/003Seismic data acquisition in general, e.g. survey design
    • G01V1/005Seismic data acquisition in general, e.g. survey design with exploration systems emitting special signals, e.g. frequency swept signals, pulse sequences or slip sweep arrangements
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01VGEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/24Recording seismic data
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01VGEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V2210/00Details of seismic processing or analysis
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The invention provides a controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics, and belongs to the field of controllable seismic source seismic exploration and acquisition. According to the method, the harmonic wave is converted into an effective signal through frequency multiplication scanning by utilizing the frequency multiplication characteristic of the harmonic wave, so that the effective bandwidth of a seismic source is expanded, and the resolution of seismic wavelets is improved. The invention can simultaneously meet the two requirements of improving the production efficiency and the data signal-to-noise ratio, can be applied to independent synchronous scanning, has effective harmonic wave as an effective signal, effectively widens the actual earthquake bandwidth of the earthquake focus, and improves the wavelet resolution; the invention can meet the technical requirements of the prior type of controllable seismic source and is suitable for efficient acquisition of the controllable seismic source.

Description

Controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics
Technical Field
The invention belongs to the field of seismic exploration and acquisition of controllable seismic sources, and particularly relates to a controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics.
Background
Seismic sources are a critical technique in hydrocarbon seismic exploration.
The seismic sources are divided into land seismic sources and water seismic sources according to application areas; land seismic sources can be divided into two types, namely a pulse source and a non-pulse source according to the form of the source wavelet; the pulse seismic source comprises an explosive seismic source in a seismic well, an impact type heavy hammer seismic source, a land air gun seismic source, an aerial explosion explosive charge, an explosion cable, an energy gathering bullet, a seismic gun and the like; non-pulsed sources include searchable sources, sosie sources, and the like. The most common use in land seismic exploration is also explosives and controlled sources.
Compared with explosive sources, the controllable source has four outstanding advantages:
the frequency band most suitable for the propagation of the formation can be selected as the sweep frequency band without generating a vibration frequency that is not propagated by the formation.
No damage to the rock and no energy consumption in rock breaking.
The anti-interference capability is strong, the controllable seismic source adopts the related technology, so that a plurality of interferences can be avoided, and the signal-to-noise ratio of data materials can be improved.
The ground damage is small, and the device is particularly suitable for work areas such as dense residents, hard ground surfaces, gobi and the like.
With the great use of vibroseis in seismic exploration, many new research results have been developed in recent years, mainly focusing on how to improve the construction efficiency and data quality of the vibroseis. The controllable source technology applied to seismic acquisition mainly comprises the following steps:
-Alternate Scanning (AS) method
Time Sliding Scanning (TSS) method
Independent synchronization (ISS) scanning method
-large-range synchronous scanning (D3S) method
High Fidelity Vibroseis Seismic (HFVS) method
Alternate scanning is known as vibroseis conventional acquisition, and others as vibroseis efficient acquisition.
The use of controlled sources has also its limitations, in terms of technology: firstly, the controllable earthquake focus ground is excited to generate strong surface waves; secondly, the limited scanning bandwidth reduces the resolution of the wavelet to a certain extent; thirdly, the continuous scanning time of the low-frequency end and the high-frequency end is short under the influence of the mechanical property of the seismic source; and secondly, multiple harmonics are generated, and the single shot-to-noise ratio of the earthquake is influenced in the efficient acquisition of the controllable earthquake focus.
For a specific scanning mode, the data quality and the operation efficiency thereof have the following characteristics: alternate Scanning (AS), single gun signal-to-noise ratio is high, and operation efficiency is low; time Sliding Scanning (TSS), strong harmonic interference, low Shan Bao signal-to-noise ratio and high operation effect; independent Synchronous Scanning (ISS), the interference is strong, the signal-to-noise ratio is low, and the operation efficiency is high; large-distance synchronous scanning (D3S), single shot signal-to-noise ratio is high, working efficiency is higher than AS, but equipment investment is large; high fidelity vibroseis earthquake (HFVS), high signal-to-noise ratio, high operation efficiency, more equipment (vibroseis) investment and large indoor data processing work. Because of the single shot signal to noise ratio offset of the controllable vibration source high-efficiency acquisition method, the defect of single shot data is usually overcome by adopting high-order coverage. In production practice, the number of coverage of a bin is typically ISS > TSS > D3S > HFVS > AS.
TSS, D3S and AS are the three most common scanning modes in production.
At the present stage, the aging and single-shot signal noise of the controllable vibration source high-efficiency acquisition show a negative correlation state. The data show that Independent Synchronous Scanning (ISS) is the scanning method with highest time efficiency of current vibroseis seismic acquisition, which reaches more than 1000 cannons/hour, but has lower data signal-to-noise ratio; alternate Scanning (AS), single gun signal-to-noise ratio is high, the operation efficiency is low, and 100 gun/hour;
chinese patent publication CN103777240A discloses a controllable seismic source frequency division scanning frequency band compensation method, which is used for carrying out frequency spectrum analysis on a target layer of original data by collecting seismic data of a research area, recognizing and knowing frequency bands and energy to be compensated, establishing an absorption model, carrying out viscoelastic medium numerical simulation based on each independent frequency band technology, and carrying out statistics on simulation results to determine scanning time length of each frequency band so as to compensate stratum absorption, broaden frequency band and be applied to deep high-resolution exploration. However, the patent estimates the absorption attenuation of the stratum through frequency division scanning, and designs the scanning time in a targeted manner, namely adopts different scanning time lengths for different frequency bands to compensate the attenuation of different frequency bands; moreover, the patent is applied to the related data without considering the suppression and application of the harmonics, and is not related to the source equipment, so that the patent cannot utilize the characteristic that the controllable source generates the harmonics to eliminate and apply the harmonics.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics, which simultaneously meet the requirements of improving the production efficiency and the data signal-to-noise ratio, and meet the requirements of widening the effective bandwidth and improving the wavelet resolution.
The invention is realized by the following technical scheme:
in a first aspect of the invention, a controllable seismic source efficient scanning method based on harmonic frequency multiplication features is provided, and the method utilizes the frequency multiplication features of harmonic waves to convert the harmonic waves into effective signals through frequency multiplication scanning, so that the effective bandwidth of the seismic source is expanded, and the resolution of seismic wavelets is improved.
The invention further improves that:
the method comprises the following steps:
step 1: designing the bandwidth of the synthesized scanning signal;
step 2: designing a sectional scanning time length;
step 3: performing field construction to obtain continuous relevant pre-data of sectional scanning of all shots;
step 4: and performing data clipping and single shot reconstruction on the related pre-data to obtain a related post-seismic record.
The invention further improves that:
the operation of the step 1 comprises the following steps:
the bandwidth of the synthesized scanning signal is the difference between the cut-off frequency and the initial frequency of the scanning signal;
the cut-off frequency is the power of 2 to the N of the starting frequency.
The invention further improves that:
the operation of step 1 further comprises:
dividing the frequency into N scanning segments from a starting frequency to a cut-off frequency;
the cut-off frequency of each scanning segment is the frequency multiplication of the starting frequency, and the difference value between the cut-off frequency and the starting frequency is the scanning bandwidth of the scanning segment.
The invention further improves that:
the operation of the step 2 comprises the following steps:
and (3) uniformly distributing the long linear scanning time length according to the scanning segments to obtain the scanning time length of each scanning segment.
The invention further improves that:
the operation of the step 3 comprises the following steps:
randomly scanning the designed shot point according to the scanning bandwidth and the scanning duration of each scanning section, and continuously recording related pre-data;
the number of scans per shot position is N.
The invention further improves that:
the data clipping operation in the step 4 includes:
(41) Sequencing the related pre-data according to the scanning bandwidth and the scanning duration of each scanning segment;
(42) And adding the listening time to the scanning time of each scanning segment to serve as cutting time, and cutting the related front data by utilizing the cutting time to form a related front single gun.
The operation of single gun reconstruction in the step 4 comprises the following steps: :
(43) Performing correlation calculation on the single cannon before correlation to form a record after correlation;
(44) Reconstructing the related post records according to the positions of the shot points to obtain related post seismic records corresponding to the shot points;
(45) And separating the heavy cannons to obtain the seismic records of all the shots after the correlation of the controllable seismic sources without harmonic interference.
In a second aspect of the present invention, there is provided a vibroseis efficient scanning system based on harmonic multiplication features, the system comprising:
a bandwidth design unit: the method is used for designing the frequency width of the synthesized scanning signal;
a time length design unit: for designing a segment scan duration;
the acquisition unit: the method is used for collecting continuous relevant pre-data of all shot point sectional scanning obtained in field construction;
and a processing unit: and the data acquisition unit is connected with the acquisition unit and is used for carrying out data clipping and single shot reconstruction on the related front data to obtain the related rear seismic record.
In a third aspect of the present invention, there is provided a computer-readable storage medium storing at least one program executable by a computer, the at least one program when executed by the computer causing the computer to perform the steps in the method for efficient scanning of a vibroseis based on harmonic multiplication features as described above.
Compared with the prior art, the invention has the beneficial effects that: the invention can simultaneously meet the two requirements of improving the production efficiency and the data signal-to-noise ratio, can be applied to independent synchronous scanning, has effective harmonic wave as an effective signal, effectively widens the actual earthquake bandwidth of the earthquake focus, and improves the wavelet resolution; the invention can meet the technical requirements of the prior type of controllable seismic source and is suitable for efficient acquisition of the controllable seismic source.
Drawings
FIG. 1 illustrates the theoretical basis of aliased acquisition-vibroseis seismic excitation;
FIG. 2 is a spectrum of source force signals for vibroseis excitation;
FIG. 3-1 is an unseparated pre-data-common shot gather;
data r=3 after separation of fig. 3-2;
FIG. 4 pre-correlation record;
FIG. 5-1 is a seismic record of 8-16Hz sweep signals
FIG. 5-2 is a seismic record of 16-32Hz sweep signals
FIG. 5-3 is a seismic record of 32-64Hz sweep signals
FIGS. 5-4 are seismic recordings of 64-128Hz sweep signals
FIG. 6 shows a scan signal of 5-10Hz fundamental wave signal and 1/2-8 order harmonic synthesis
FIG. 7-1 shows 1/2 order harmonics (2.5-5 Hz)
FIG. 7-2 shows 4-order harmonics (20-40 Hz)
FIG. 7-3 shows the fundamental wave (5-10 Hz)
FIG. 7-4 shows 8-order harmonics (40-80 Hz)
FIG. 7-5 shows the 2 nd order harmonic (10-20 Hz)
FIGS. 7-6 are fundamental and harmonic synthesis;
FIG. 8 is a block diagram of the steps of the method of the present invention.
Detailed Description
The invention is described in further detail below with reference to the attached drawing figures:
the improvement of the seismic resolution is one of the pursuit targets of seismic exploration, and compared with an explosive source, the limited scanning bandwidth of the controllable source limits the resolution of the seismic wavelets. The method of the invention utilizes the frequency multiplication characteristic of the harmonic wave, converts the harmonic wave into an effective signal through frequency multiplication scanning, expands the effective bandwidth of the seismic source to a certain extent, improves the resolution of the seismic wavelet, and is more beneficial to lithologic hydrocarbon reservoir exploration.
The principle of the method of the invention is as follows:
the vibroseis is continuously single-frequency aliasing acquisition, so that the vibroseis signal can be decomposed into innumerable simple harmonic signals, and the innumerable simple harmonic signals with different frequencies can be combined into a pulse signal through superposition, as shown in fig. 1. The source sweep has harmonics in addition to the effective signal. Harmonics occur simultaneously with the scan signal, and the harmonics are typically integer multiples of the scan signal, but there are also non-integer multiples of 1/2,3/2,5/2, etc., but the non-integer multiples of the harmonics are weaker than the integer multiples of the harmonics, as shown in fig. 2.
Suppose the source sweep signal is F (ω) 1 ,ω 2 ) First order harmonic is F 1 (2ω 1 ,2ω 2 ) Second order harmonic is F 2 (4ω 1 ,4ω 2 ) The third order harmonic is F 3 (8ω 1 ,8ω 2 ) The N-order harmonic wave is F N-1 (2 N ω 1 ,2 N ω 2 ) The non-integer order harmonic wave is F (2N-1)/2 (3*2 N-1 ω 1 /2,3*2 N-1 ω 2 /2)。
The controllable seismic source is continuously acquired by single-frequency aliasing, and the expression form of the linear scanning signal mode is as follows:
Figure BDA0003328001560000071
wherein: m represents the source number; a, a m (t) represents the output of each source;
f 1 ,f 2 representing a starting frequency and a cut-off frequency;
t represents the scanning length;
Figure BDA0003328001560000072
representing the scan slope.
Let the ith omega-frequency bin of a seismic source at any spatial location be w (x, y, z), then the sweep signal for the ith omega-th frequency slice of Ns sources can be expressed as:
Figure BDA0003328001560000073
/>
wherein:
Figure BDA0003328001560000074
a sweep signal for the ith omega-frequency bin of the first source.
The source code with Ns shots may be represented by a code matrix:
Figure BDA0003328001560000075
wherein: a represents amplitude coding and can be understood as the magnitude of the source output;
Figure BDA0003328001560000076
is a phase code. N (N) S Is the gun number, representing the N S Cannon, N e Is the frequency chip number, representing the firstN e Frequency slices.
The encoding process being multiplied by a matrix
Figure BDA0003328001560000081
Representing an aliased source that excites all frequencies can be represented as:
Figure BDA0003328001560000082
the uncorrelated hyper-cannon gather is obtained after the wave propagation operator L acts:
Figure BDA0003328001560000083
the signal decoding is to utilize the scanning signal of each seismic source to be related to the aliasing acquired shot gather respectively, and the conjugate multiplication is carried out in the frequency domain:
Figure BDA0003328001560000084
the recording of all frequency slices nω can be represented by a matrix of 1×nω:
Figure BDA0003328001560000085
the related result of the scanning signal of the is gun and the data acquired by aliasing is as follows:
Figure BDA0003328001560000086
the source resonates in addition to the scanning signal. The correlation of the scan signal of the is gun with the aliased data can be expressed as:
Figure BDA0003328001560000087
wherein: (1-9) the first term on the right is the autocorrelation of the is-th shot scan signal, defined as the seismic record; the second term is the cross-correlation of the is-th gun scanning signal and the vibration source resonance; the third term is the cross-correlation of the is-th shot scan signal with other source signals.
The correlation of the 1 st shot signal and the two shots of aliasing data is as follows:
Figure BDA0003328001560000088
the autocorrelation of the signal is 1, and when the signal and the harmonic wave and other scanning signals have no cross frequency band, the cross correlation of the signal and the harmonic wave of integer multiple of the signal is 0 (because the energy of the harmonic wave of non-integer multiple is weak, the influence is small and is not considered for the moment). Assuming that ISS is adopted, the cross-correlation between the nth shot signal and the N-1 th shot signal is 0, the harmonic (integer) thereof is 0 or 1, and the condition is that the nth shot scanning signal is the frequency multiplication of the N-1 th shot, the effective scanning frequency band is divided into 5 segments, and the formula (1-10) is designed as follows:
Figure BDA0003328001560000091
TABLE 1
The effective record obtained by correlating the same signals is 1, and the record obtained by correlating the different signals is 0. The first segment scan signal is omega-2 omega, and the second to sixteen harmonics are 2 omega-4 omega, 4 omega-8 omega, 8 omega-16 omega, 18 omega-32 omega, respectively, which are identical to the second to fifth segments scan signals. Assuming that the scanning signals and the harmonics of different orders are independent or separable (according with an aliasing acquisition principle), adopting signal correlation of a first section to a fifth section for the first section scanning record, wherein the scanning signals are 1 in autocorrelation, 0 in cross correlation with the second section to the fifth section scanning signals, and 1+0+0+0 in recording marks; similarly, the first section to the fifth section scanning signals are respectively cross-correlated with first-order harmonic waves in the first section record to obtain 0+1+0+0+0; cross-correlating with the second order harmonic to obtain 0+0+1+0, cross-correlating with the third order harmonic to obtain 0+0+0+1+0, cross-correlating with the fourth order harmonic to obtain 0+0+0+0+1, and recording and synthesizing to obtain 1+1+1+1. The second to fifth sections were recorded in the same manner as described in Table 2.
Figure BDA0003328001560000092
TABLE 2
Theoretically, if the aliasing records are cross-correlated by using the fifth-stage first-order harmonic, a seismic record with a wider frequency can be obtained. Similarly, the first section scanning record adopts the 1/2-order cross correlation of the first section scanning signal, and the lower-frequency seismic record can also be obtained.
The continuous scanning record can obtain single cannon of independent seismic source through clipping and synthesizing. Taking table 1 as an example, in the most complex case, five scans are randomly and synchronously excited by five vibration sources at a certain distance, the continuous scanning time is assumed to be L, the earthquake recording time is assumed to be T, the recording time is l+T, and the scanning time of the first segment of vibration sources S1, S2, S3, S4 and S5 is respectively T 1 10 -T 1 11 ,T 2 10 -T 2 11 ,T 3 10 -T 3 11 ,T 4 10 -T 4 11 ,T 5 10 -T 5 11 The second period of scanning time is T respectively 1 20 -T 1 21 ,T 2 20 -T 2 21 ,T 3 20 -T 3 21 ,T 4 20 -T 4 21 ,T 5 20 -T 5 21 … … the N-th scanning time is T 1 N0 -T 1 N1 ,T 2 N0 -T 2 N1 ,T 3 N0 -T 3 N1 ,T 4 N0 -T 4 N1 ,T 5 N0 -T 5 N1 A total of 5N scan periods.
Seismic recording S L Is a pre-correlation record. Record S L S1 is employed for each of the 5N scan periods,and S2, S3, S4 and S5 scanning signals or force signals are subjected to cross correlation to obtain 25N scanning records.
Since the harmonic and source sweeps have isochronous properties, the record is recorded as T 1 10+T ,T 2 10+T ,T 3 10+T ,T 4 10+T ,T 5 10+T ,T 1 20 +T1 ,T 2 20+T ,T 3 20+T ,T 4 20+T1 ,T 5 20+T1 ,……,T 1 N0+T ,T 2 N0+T ,T 3 N0+T ,T 4 N0+T ,T 5 N0+T Clipping is carried out, and the independent seismic sources S1, S2, S3, S4 and S5 seismic records are obtained according to seismic source classification, synthesis and reconstruction, and 5N seismic records are counted.
Synchronous scanning, when the higher harmonic wave of the low frequency band is the same as the scanning signal of the high frequency band, the phenomenon of heavy cannon similar to the excitation of an explosive source is generated, in the data processing process, the denoising and cannon set separation can be performed by adopting a multi-domain or high-dimensional denoising and separating technology, fig. 3-1 and fig. 3-2 are the comparison of the three-dimensional analog data before and after separation, and R=3 is the separation dimension.
The invention relates to frequency multiplication independent synchronous scanning (FDISS), which can be applied to independent synchronous scanning signal design, and forward simulation scanning frequencies are respectively S1:8-16Hz; s2, 16-32Hz; s3, 32-64Hz; s4, 64-132Hz, and the scanning time length is 4S; listening time 2s. FIG. 4 shows a record before correlation, in which the mutual interference is severe. Fig. 4 is a record before forward modeling correlation of theoretical models [ S1 (100, 0): 8-16Hz; s2 (200, 0) 16-32Hz; s3 (300,0) 32-64Hz; s4 (400, 0) 64-132Hz, and the scanning time length is 4S; listening time 2s ]
The record of fig. 4 is respectively processed by adopting scanning signals to perform correlation processing, so that the seismic records of different scanning signals are respectively obtained, as shown in fig. 5-1 to 5-4, the records have higher signal to noise ratio, and forward modeling shows that frequency division independent synchronous scanning is suitable for the seismic acquisition of the controllable seismic source.
The frequency multiplication independent synchronous scanning (FDISS) can convert harmonic waves into effective waves, expand scanning bandwidth and improve the resolution of seismic wavelets.
The fundamental wave signals are designed to be 5-10Hz, the low-order harmonic wave is designed to be 2.5-5Hz, the first-order harmonic wave is designed to be 10-20Hz, the second-order harmonic wave is designed to be 20-40Hz, the third-order harmonic wave is designed to be 40-80Hz, and the synthesized scanning signal is shown in figure 6.
The fundamental wave and harmonic wave correlated wavelet and synthesized wavelet pair is shown in fig. 7-1 to 7-6, and it can be seen from fig. 7-1 to 7-6 that the fundamental wave and harmonic wave signals are synthesized to become a broadband wavelet, and the harmonic wave becomes an effective signal.
Examples of the method of the invention are as follows:
[ embodiment one ]
The invention provides a basis for the transformation of the earthquake focus equipment, and aims at solving the problem that the low frequency and high frequency of the prior controllable earthquake focus cannot be scanned for a long time, and firstly, the low frequency and high frequency controllable earthquake focus is developed in a targeted manner, so that the mechanical performance of the controllable earthquake focus has stronger adaptability; and secondly, developing a harmonic controllable seismic source and expanding the scanning bandwidth by applying harmonic.
The invention relates to a controllable seismic source efficient scanning method based on harmonic frequency multiplication characteristics, which is shown in fig. 8 and comprises four steps:
step 1: designing the bandwidth of the synthesized scanning signal:
the frequency width of the synthesized scanning signal refers to the difference between the cut-off frequency and the initial frequency of the scanning signal, and the design of the frequency width has the same principle as that of the conventional controllable source signal, wherein the difference is that the cut-off frequency is equal to the power of 2 of the initial frequency, and is usually greater than or equal to 5 octaves, namely, N is greater than or equal to 5. During the sectional scanning, the frequency is divided into N scanning segments, the cut-off frequency of each scanning segment is the frequency multiplication of the starting frequency, and the difference value between the cut-off frequency and the revealing frequency of each scanning segment is the scanning bandwidth of the scanning segment, and the specific steps are as follows:
the first section is: omega-2 omega, the second segment is: 2 omega-4 omega, the third section is: 4 omega-8 omega, the fourth section is: 8 omega-16 omega, etc., and so on, if the starting frequency is 3Hz, the first segment is: 3-6Hz, the second section is: 6-12Hz, the third section is: 12-24Hz, the fourth section is: 24 omega-48 omega, the fifth section is: 48 omega-96 omega, etc., and so on.
The magnitude of the starting frequency omega is determined based on the mechanical properties of the source, for example, by up-sweep, and the low frequency source is typically 1.5-2Hz, typically 3-4Hz, and is determined with specific reference to the source properties.
The invention is applied to a controllable seismic source signal, wherein the controllable seismic source signal is shown as the following formula:
Figure BDA0003328001560000121
where S (t) is the signal in the S matrix, A (t) is the amplitude of the signal, f s For the initial frequency of the signal, f e Is the cut-off frequency of the signal, T is time, Φ is phase, and T is the sweep duration.
Determining f according to geological task requirements s And f e The frequency is determined.
In step 1, a cut-off frequency equal to 2 of the starting frequency is required n The multiple (n is an integer), the sectional scanning cutoff frequency is the frequency multiplication of the starting frequency, so that the higher-order harmonic wave and the high-frequency scanning signal are ensured to have the same frequency width, and the higher-order harmonic wave can be converted into an effective signal after correlation.
Step 2: the segment scan duration is designed.
The relatively simple method can evenly distribute the time length of long linear scanning (generally 30-48 s) according to the scanning section, has the advantages of simplicity, and the higher harmonic wave and the high-frequency band scanning signal have the same scanning length, thereby being beneficial to cutting, separating and reconstructing the record.
The method is more scientific, the original seismic records with different scanning lengths are subjected to filtering treatment according to the scanning frequency bands designed in a segmented mode, or different scanning length tests are carried out according to the designed scanning frequency bands, and the optimal scanning time length of different frequency bands is selected according to the signal to noise ratio of a target layer.
The invention adopts the same scanning time length from the practical production efficiency.
In the step 2, through frequency multiplication scanning analysis of the previous data or test data with different time lengths, based on the signal to noise ratio of a target layer, when the scanning time length is selected, the mechanical performance of the controllable vibration source is fully considered, namely the high-frequency and low-frequency scanning servo time of the controllable vibration source is limited to a certain extent, in principle, the middle-frequency scanning time length is mainly matched with the low-frequency and high-frequency scanning time length, and the limitation of the high-frequency and low-frequency scanning servo time of the controllable vibration source is assumed to be 5S, and the sectional scanning time length is preferably 3.5-4S, so that the safe production requirement of field equipment is met; secondly, medium frequency data generally has higher signal to noise ratio, and the influence of properly shortening the scanning time length on the data is smaller.
Step 3: performing field construction to obtain continuous relevant pre-data of sectional scanning of all shots;
the construction process is basically the same AS the conventional AS construction process, and the difference is that:
(31) Randomly scanning (randomly refers to scanning time, namely each seismic source can be independently scanned according to the designed scanning bandwidth and time length at any time) at the designed shot positions according to the scanning bandwidth and the scanning time length of the sectional design, and the scanning times of each shot position are N steps similar to those of HFVS scanning, and the number of the scanning sections in the step 1 is the same as that of the scanning sections N;
(32) Continuously recording the related pre-data;
conventional AS construction flows are not recording the relevant pre-data and are not continuously recorded.
Step 3 obtains continuous pre-correlation data of all seismic source point segmented scanning, and the difference between AS and other post-correlation records is that: in the seismic record, the seismic information of higher harmonic waves is reserved except the fundamental wave signals, and a data foundation is laid for separating and applying harmonic wave signals.
Step 4: and performing data clipping and single shot reconstruction on the related pre-data to obtain a related post-seismic record.
The data clipping steps are as follows:
(41) Sequencing the related pre-data (the related pre-data of all shots in the same sectional scanning frequency) according to the sectional scanning bandwidth and the scanning time;
(42) And adding the scanning time of the sectional scanning and the listening time (the listening time refers to the length of a single shot record) as cutting time, and cutting the related front data by using the cutting time (cutting by adopting the existing method, and not repeated here) to form the related front single shot. If the number of shots is designed to be Ns, each shot is scanned N times, and the number of the related single shots after cutting is N times Ns.
The single gun reconstruction method comprises the following steps:
(43) And carrying out correlation calculation on the single shot before correlation, including fundamental wave correlation and harmonic wave correlation calculation (realized by adopting the prior art and not repeated here), and forming a record after correlation. Theoretically, N post-correlation records can be obtained for each scan segment for each shot.
In step 1, the sectional scanning cut-off frequency is the frequency multiplication of the initial frequency, so that the higher harmonic of any one frequency division band always corresponds to the fundamental wave signal of another frequency division band, as shown in table 1, the theoretical result of the correlation calculation meets the requirements of table 2, and the separation and application of the harmonic are realized.
(44) And reconstructing the related post records according to the positions of the shots, namely vertically superposing the related post records after the shot is segmented and cut (realized by adopting the prior art, and not repeated herein), so as to obtain the related post seismic records corresponding to the shots.
When reconstructing the related record according to the shot position, the possible difference of the energy or the signal to noise ratio after the correlation of the fundamental wave and the harmonic wave should be studied, and the frequency division record is firstly subjected to weighted compensation or consistency treatment according to the requirement, and then is vertically overlapped. The weighted compensation or consistency process is similar to the consistency amplitude compensation process in conventional seismic data processing.
(45) And separating heavy cannons (which are acquired simultaneously and have heavy cannon records at the same moment, for example, a first scanning frequency omega-2 omega, second order harmonic thereof is 2 omega-4 omega, and a second synchronous scanning frequency is 2 omega-4 omega to generate heavy cannons) through multi-domain denoising according to a conventional seismic data processing flow, so as to obtain the controlled seismic source related post-seismic records without harmonic interference of all shot points. This step is implemented by using the prior art, and will not be described here again.
The invention provides a method for designing a high-efficiency seismic acquisition scanning signal applied to a controllable seismic source, which has the following advantages:
through the bandwidth design of the synthesized scanning signals in the step 1 and the data clipping and single-shot reconstruction in the step 3, firstly, the separated harmonic wave is converted into an effective signal, the harmonic interference is reduced to a certain extent, secondly, the bandwidth of the higher-order harmonic wave is usually larger than that of the fundamental wave scanning signal, and when the harmonic wave is converted into the effective signal, the scanning bandwidth is relatively expanded; in step 3, the invention adopts an independent synchronous scanning mode, thereby realizing high-efficiency acquisition, shortening the operation time and improving the operation efficiency compared with the traditional AS method.
The invention also provides a controllable source efficient scanning system based on harmonic frequency multiplication characteristics, and the embodiment of the system is as follows:
[ example two ]
The system comprises:
a bandwidth design unit: the method is used for designing the frequency width of the synthesized scanning signal;
a time length design unit: for designing a segment scan duration;
the acquisition unit: the method is used for collecting continuous relevant pre-data of all seismic source points obtained in field construction in a sectional scanning mode;
and a processing unit: and the data acquisition unit is connected with the acquisition unit and is used for carrying out data clipping and single shot reconstruction on the related front data to obtain the related rear seismic record.
The present invention also provides a computer-readable storage medium, an embodiment of which is as follows:
[ example III ]
The computer readable storage medium stores at least one program executable by a computer, which when executed by the computer, causes the computer to perform the steps in the above-described vibroseis efficient scanning method based on harmonic multiplication features.
The theory basis of the invention designs a frequency multiplication independent synchronous scanning mode (FDISS) based on the cross-correlation characteristic of the scanning signals and the frequency multiplication characteristic of the harmonic signals, converts harmonic distortion into effective signals, eliminates harmonic interference, expands effective bandwidth, simultaneously meets the technical requirement of independent synchronous scanning, improves the operation efficiency, can effectively solve three problems faced by controllable seismic source acquisition in theory, and achieves better effect in numerical simulation.
The invention provides a basis for the transformation of the earthquake focus equipment, and aims at solving the problem that the low frequency and high frequency of the prior controllable earthquake focus cannot be scanned for a long time, and firstly, the low frequency and high frequency controllable earthquake focus is developed in a targeted manner, so that the mechanical performance of the controllable earthquake focus has stronger adaptability; and secondly, developing a harmonic controllable seismic source and expanding the scanning bandwidth by applying harmonic. In addition, the invention has simple field construction and is applicable to all areas where the controllable earthquake focus construction can be applied. The invention requires field collection and recording of the data before correlation, which is more beneficial to denoising.
Aiming at some defects existing in the prior vibroseis scanning mode, the invention provides a vibroseis scanning method based on harmonic frequency multiplication characteristics, and theoretical research and forward modeling data prove that the scanning mode has the following advantages:
(1) the method can be applied to independent synchronous scanning;
(2) no harmonics are generated, or the harmonics are effective signals;
(3) the excitation bandwidth can be effectively widened, and the resolution of wavelets can be improved;
(4) the method is suitable for the technical requirements of the prior type of controllable seismic source or can meet the technical requirements through limited technical transformation. The invention applies the frequency multiplication characteristic of the harmonic wave, adopts a frequency multiplication scanning mode, and uses the cutting, separating and reconstructing of a single gun to make the harmonic wave as a part of effective signals, eliminates the harmonic wave interference, expands the scanning bandwidth and improves the operation efficiency;
(5) applied to related pre-data;
(6) provides technical basis for the research and development and transformation of the seismic source equipment.
The field construction of the scanning method is the same as ISS, the production efficiency can reach ISS level theoretically, and the data signal-to-noise ratio is equivalent to that of alternate scanning.
Finally, it should be noted that the above-mentioned technical solution is only one embodiment of the present invention, and various modifications and variations can be easily made by those skilled in the art based on the application methods and principles disclosed in the present invention, and are not limited to the methods described in the above-mentioned specific embodiments of the present invention, therefore, the foregoing description is only preferred, and not meant to be limiting.

Claims (10)

1. A controllable seismic source efficient scanning method based on harmonic frequency multiplication features is characterized by comprising the following steps of: according to the method, the harmonic wave is converted into an effective signal through frequency multiplication scanning by utilizing the frequency multiplication characteristic of the harmonic wave, so that the effective bandwidth of a seismic source is expanded, and the resolution of seismic wavelets is improved.
2. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:
step 1: designing the bandwidth of the synthesized scanning signal;
step 2: designing a sectional scanning time length;
step 3: performing field construction to obtain continuous relevant pre-data of sectional scanning of all shots;
step 4: and performing data clipping and single shot reconstruction on the related pre-data to obtain a related post-seismic record.
3. The method for efficiently scanning the controllable seismic source based on harmonic multiplication features according to claim 2, wherein the method comprises the following steps of: the operation of the step 1 comprises the following steps:
the bandwidth of the synthesized scanning signal is the difference between the cut-off frequency and the initial frequency of the scanning signal;
the cut-off frequency is the power of 2 to the N of the starting frequency.
4. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 3, wherein the method comprises the following steps: the operation of step 1 further comprises:
dividing the frequency into N scanning segments from a starting frequency to a cut-off frequency;
the cut-off frequency of each scanning segment is the frequency multiplication of the starting frequency, and the difference value between the cut-off frequency and the starting frequency is the scanning bandwidth of the scanning segment.
5. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 4, wherein the method comprises the following steps: the operation of the step 2 comprises the following steps:
and (3) uniformly distributing the long linear scanning time length according to the scanning segments to obtain the scanning time length of each scanning segment.
6. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 5, wherein: the operation of the step 3 comprises the following steps:
randomly scanning the designed shot point according to the scanning bandwidth and the scanning duration of each scanning section, and continuously recording related pre-data;
the number of scans per shot position is N.
7. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 6, wherein: the data clipping operation in the step 4 includes:
(41) Sequencing the related pre-data according to the scanning bandwidth and the scanning duration of each scanning segment;
(42) And adding the listening time to the scanning time of each scanning segment to serve as cutting time, and cutting the related front data by utilizing the cutting time to form a related front single gun.
8. The method for efficiently scanning a controllable seismic source based on harmonic multiplication features according to claim 7, wherein: the operation of single gun reconstruction in the step 4 comprises the following steps: :
(43) Performing correlation calculation on the single cannon before correlation to form a record after correlation;
(44) Reconstructing the related post records according to the positions of the shot points to obtain related post seismic records corresponding to the shot points;
(45) And separating the heavy cannons to obtain the seismic records of all the shots after the correlation of the controllable seismic sources without harmonic interference.
9. A controllable source efficient scanning system based on harmonic frequency multiplication features is characterized in that: the system comprises:
a bandwidth design unit: the method is used for designing the frequency width of the synthesized scanning signal;
a time length design unit: for designing a segment scan duration;
the acquisition unit: the method is used for collecting continuous relevant pre-data of all shot point sectional scanning obtained in field construction;
and a processing unit: and the data acquisition unit is connected with the acquisition unit and is used for carrying out data clipping and single shot reconstruction on the related front data to obtain the related rear seismic record.
10. A computer-readable storage medium, characterized by: the computer readable storage medium stores at least one program executable by a computer, which when executed by the computer, causes the computer to perform the steps in the vibroseis efficient scanning method based on harmonic multiplication features as claimed in any one of claims 1 to 8.
CN202111271062.2A 2021-10-29 2021-10-29 Controllable seismic source efficient scanning method and system based on harmonic frequency multiplication characteristics Pending CN116068613A (en)

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