CN110988995B

CN110988995B - Acquisition parameter determination method and device based on long base distance

Info

Publication number: CN110988995B
Application number: CN201911284429.7A
Authority: CN
Inventors: 李艳青; 邓勇; 王子秋; 刘兴达; 唐进
Original assignee: China Oilfield Services Ltd; China National Offshore Oil Corp CNOOC
Current assignee: China Oilfield Services Ltd; China National Offshore Oil Corp CNOOC
Priority date: 2019-12-13
Filing date: 2019-12-13
Publication date: 2022-07-08
Anticipated expiration: 2039-12-13
Also published as: CN110988995A

Abstract

The invention discloses a method for determining acquisition parameters based on a long base distance, which comprises the following steps: obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed, wherein the long base distance refers to a base distance with a base distance length larger than 25 m; setting a group internal distance of the combination unit corresponding to each frequency aiming at the long base distance, wherein the combination unit is a detector/seismic source combination unit consisting of n detectors/seismic sources, and n is a positive integer greater than 1; determining the spatial distribution of the geophones/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency; according to the spatial distribution of the detectors/seismic sources, reducing the number of the combined units by adopting a preset rule to obtain the distribution of the reduced detector/seismic source combined units; seismic data acquisition is performed according to the distribution of the acquisition combining units of the reduced geophones/seismic sources. By the scheme of the invention, the workload of seismic data acquisition can be reduced when the seismic data acquisition is based on the long base distance.

Description

Acquisition parameter determination method and device based on long base distance

Technical Field

The invention relates to the field of geophysical exploration, in particular to a method and a device for determining acquisition parameters based on a long base distance.

Background

An air gun combination mode is usually adopted for an offshore air gun seismic source to enhance effective signal energy and suppress bubbles and noise. The directionality of the source combinations is also used in conventional seismic exploration to enhance the seismic wave down-transfer energy. But the method is limited by the base distance of the seismic source combined subarray, the base distance of the conventional design is about 20m, the directional enhancement of high-frequency signals is obvious, and the directional enhancement capability of low-frequency signals below 10Hz is still poor.

Seismic exploration of high velocity zone shields is a difficult point in seismic exploration. The seismic exploration of the high-speed layer shielding area is limited by the influence of the operation environment and the acquisition mode, so that the exploration of the high-speed layer shielding area is harder. However, through continuous exploration and research, effective means for solving the problems existing in the exploration of the high-speed layer shielding region are high coverage, low-frequency seismic sources and wide azimuth. In conventional exploration, the low-frequency source energy is enhanced by increasing the total capacity of the source and increasing the large gun proportion in the gun array combination, the expected effect cannot be achieved in practical application, and the effect is very little in a high-speed shielding area. The low-speed and high-speed shielding exploration area of the land is influenced by complicated geology of the earth surface and environmental background noise, so that the directional design of a seismic source is not facilitated; the sea area exploration area provides a relatively simple surface structure due to the existence of a sea water layer, the time and space change of the sea water speed is relatively small, and the directional design of a seismic source is facilitated, so that the energy enhancement seismic data acquisition method aiming at low-frequency-band seismic data is implemented, but the workload of long-base-distance seismic data acquisition based on a low frequency band is particularly large, the implementation difficulty is increased for seismic exploration, and therefore how to provide the acquisition parameter determination method for reducing the workload of seismic data acquisition when the long-base-distance seismic data acquisition is based on the long-base-distance seismic data acquisition is an urgent problem to be solved.

Disclosure of Invention

In order to solve the technical problem, the invention provides a method for determining acquisition parameters based on a long base distance, which can reduce the workload of seismic data acquisition when seismic data acquisition based on the long base distance is carried out.

In order to achieve the purpose of the invention, the invention provides a method for determining acquisition parameters based on a long base distance, which comprises the following steps:

obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed, wherein the long base distance is a base distance with a length larger than 25 m;

setting a group internal distance of the combination unit corresponding to each frequency aiming at the long base distance, wherein the combination unit is a detector/seismic source combination unit consisting of n detectors/seismic sources, and n is a positive integer greater than 1;

determining the spatial distribution of the detectors/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency;

and reducing the number of the combined units by adopting a preset rule according to the spatial distribution of the detectors/the seismic sources to obtain the distribution of the reduced detector/seismic source combined units.

In an exemplary embodiment, the obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed includes:

determining the incidence angle range of a detector of the work area to be processed according to the relevant geological information of the work area to be processed;

and obtaining the base distance corresponding to each frequency in the preset frequencies by adopting a preset phased array combination model according to the incidence angle range of the detector.

In an exemplary embodiment, the phased array combination model comprises:

wherein the content of the first and second substances,

combining the responses of the elements for the phased array; n is the number of the combined units of the detector/the seismic source; m is the sequence number of the detector/seismic source in the combined unit; the combined unit is a detector/seismic source combined unit consisting of n detectors/seismic sources; d_mThe energy intensity of the detector combination unit; r is_mThe distance from each detector/seismic source combination unit to the center of the combination unit; theta₀Azimuth angle of incoming/outgoing signal for the detector; psi₀Defined for the angle of incidence/angle of emergence of the detector; theta_mAzimuth of the detector/source; psi_mIs the incident/exit angle; v_waterIs the speed of the water, and is,

to combine responses

Phi/2 is less than or equal to psi₀Sum of absolute values in the range of ≤ pi/2, A_ηIs that-eta is less than or equal to psi₀Energy response of reception/excitation in the range of angles of incidence ≦ η, A_ηAnd

is taken as the combined response energy AP, η is the detector's angle of incidence range.

In an exemplary embodiment, the obtaining, by using a preset phased array combination model, a base distance corresponding to each of preset frequencies includes:

obtaining an energy curve corresponding to each frequency in preset frequencies according to the phased array combination model of the work area to be processed, wherein the preset frequencies are low-frequency-band frequencies set according to the frequency range of the seismic data of the work area to be processed;

and determining the long base distance corresponding to each frequency according to the energy curve of each frequency.

In an exemplary embodiment, the setting, for the long base distance, the group inner distance of the combination unit corresponding to each frequency includes:

aiming at the long base distance corresponding to each frequency, respectively designing the group inner distance of the detector/seismic source combined unit corresponding to each frequency by adopting the preset number of the detector/seismic source combined units;

and combining the group internal distances of the detector/seismic source combination units corresponding to each frequency to obtain the spatial distribution of the detectors/seismic sources of the preset frequency of the work area to be processed.

In an exemplary embodiment, the reducing the number of the combined units according to the spatial distribution of the detectors/sources by using a predetermined rule to obtain a reduced distribution of the combined units of the detectors/sources includes:

after the spatial distribution of the detectors/seismic sources with preset frequencies in the work area to be processed is obtained, the group internal distances of the detector/seismic source combination units corresponding to all the frequencies are sequenced;

and selecting the group internal distances corresponding to the minimum value and the maximum value in the group internal distances of the detector/seismic source combined units, and calculating the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula.

In an exemplary embodiment, wherein the reduction formula comprises:

wherein r is_jiThe original group inner distance of the detector/seismic source combination unit, j is the number of the frequency, i is the number of the combination unit, and min (r)_ji) Is the minimum group inner distance, max (r) in the original group inner distances_ji) The method is characterized in that the method is a method for reducing the series number of the original detector/seismic source combined units, N is the maximum group inner distance in the original group inner distances, 1/M is the ratio of reducing workload, M is an integral multiple of 2, M is 2, 4, 8, 16.

In an exemplary embodiment, the reducing the number of the combined units according to the spatial distribution of the detectors/sources by using a predetermined rule to obtain a reduced distribution of the combined units of the detectors/sources further includes:

rearranging the detector/seismic source combination units of each frequency respectively, and calculating the distribution of the corresponding reduced detector/seismic source combination units of the frequency according to the proportion of the reduced workload and a reduction formula;

after the distribution of all the reduced-frequency detector/seismic source combination units is obtained, rearranging the reduced-frequency detector/seismic source combination units of all the frequencies;

the distribution of reduced detector/source combining units is derived from the rearranged reduced detector/source combining units.

In order to solve the above problem, the present invention further provides a device for determining a long-base-distance acquisition parameter, including: a memory and a processor;

the memory is used for storing a program for determining the acquisition parameters of the long base distance;

the processor is used for reading and executing the program for determining the acquisition parameters of the long base distance, and executing the following operations:

setting a group internal distance of a combination unit corresponding to each frequency aiming at the long base distance, wherein the combination unit is a detector/seismic source combination unit consisting of n detectors/seismic sources, and n is a positive integer greater than 1;

determining the spatial distribution of the geophones/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency;

determining the incidence angle range of a detector in the work area to be processed according to the relevant geological information of the work area to be processed;

In an exemplary embodiment, the phased array combination model includes:

wherein, the first and the second end of the pipe are connected with each other,

a response for the phased array combining unit; n is the number of detector/seismic source combination units; m is the sequence number of the detector/seismic source in the combined unit; the combined unit is a detector/seismic source combined unit consisting of n detectors/seismic sources; d_mThe energy intensity of the detector combination unit; r is_mThe distance from each detector/seismic source combination unit to the center of the combination unit; theta₀Azimuth angle of incoming/outgoing signal for the detector; psi₀Defined for the angle of incidence/angle of emergence of the detector; theta.theta._mAzimuth of the detector/source; psi_mIs the incident/exit angle; v_waterWhich is the velocity of the water, is,

to combine responses

and selecting the group inner distances corresponding to the minimum value and the maximum value in the group inner distances of the detector/seismic source combined units, and calculating to obtain the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula.

In an exemplary embodiment, wherein the reduction formula comprises:

wherein r is_jiThe original group inner distance of the detector/seismic source combination unit, j is the number of the frequency, i is the number of the combination unit, and min (r)_ji) Is the minimum group inner distance, max (r) in the original group inner distances_ji) The method is characterized in that the method is a maximum group inner distance in an original group inner distance, N is the number of original detector/seismic source combination units, 1/M is the ratio of reduction workload, M is an integral multiple of 2, M is 2, 4, 8, 16.

Compared with the prior art, the invention discloses a method for determining acquisition parameters based on a long base distance, which comprises the following steps: obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed, wherein the long base distance refers to a base distance with a base distance length larger than 25 m; setting a group internal distance of the combination unit corresponding to each frequency aiming at the long base distance, wherein the combination unit is a detector/seismic source combination unit consisting of n detectors/seismic sources, and n is a positive integer greater than 1; determining the spatial distribution of the geophones/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency; and reducing the number of the combined units by adopting a preset rule according to the spatial distribution of the detectors/the seismic sources to obtain the distribution of the reduced detector/seismic source combined units. By the scheme of the invention, the workload of seismic data acquisition can be reduced when the seismic data acquisition is based on the long base distance.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a flowchart of a method for determining acquisition parameters based on a long base distance according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a device for determining acquisition parameters based on a long base distance according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of high speed shielding layer top and bottom reflection/transmission according to an exemplary embodiment of the invention;

FIG. 4 is a high-speed shield geological model representation according to an example of an embodiment of the invention;

FIG. 5 is a schematic diagram of an exemplary source and detector combination pitch design in accordance with an embodiment of the invention;

FIG. 6 is a model of the relationship between sources of multiple overburden strata in a high-speed shielded area and incident angles according to an exemplary embodiment of the invention;

FIG. 7 is a schematic representation of a down-going energy focus of an exemplary source and detector combination in accordance with an embodiment of the invention;

FIG. 8 is a schematic diagram of an exemplary energy focusing broadband according to an embodiment of the present invention;

FIG. 9 is a high dimensional diagram of an exemplary energy focusing system according to an embodiment of the present invention;

FIG. 10 is an exemplary energy focus curve for a base distance for different frequencies;

FIG. 11 is a schematic diagram of an exemplary combination unit for different frequencies in accordance with an embodiment of the present invention;

FIG. 12 is a schematic diagram of an exemplary long baseline phased array combined unit acquisition scheme in accordance with an embodiment of the present invention;

fig. 13 is a schematic diagram of a combination unit after reducing workload according to an example embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.

Fig. 1 is a flowchart of a method for determining acquisition parameters based on a long base distance according to an embodiment of the present invention.

And 101, obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed.

In the present embodiment, the preset frequency is a low-band frequency set according to the frequency range of the seismic data of the work area to be processed. The frequency of the low frequency band is analyzed according to seismic data of a work area to be processed, and in the prior art, the frequency of the low frequency band generally refers to the frequency below 10 HZ. According to the requirements of the work area to be processed, the frequency below 10HZ can be selected as the preset frequency, for example: 2HZ, 4HZ, 6HZ, 8HZ, etc. The frequency above 10Hz can be selected as the preset frequency according to requirements. The selection of the preset frequency is set according to the requirement, and is not particularly limited.

In the present embodiment, the long base pitch means a base pitch having a base pitch length of more than 25 m. In conventional seismic acquisition, the base distance is typically around 18m for source combinations and around 12.5m for detector combinations. In the embodiment, according to the base distance corresponding to the low frequency band, for example: 748m, 372m, 187m, 93m, etc., the base distance having a length greater than that used for conventional acquisition, and therefore the base distance determined based on the low frequency signal can be defined as a long base distance, i.e., a base distance having a base distance length greater than 25 m.

In an exemplary embodiment, the obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed includes: determining the incidence angle range of a detector of the work area to be processed according to the relevant geological information of the work area to be processed; and obtaining the base distance corresponding to each frequency in the preset frequencies by adopting a preset phased array combination model according to the incidence angle range of the detector. Establishing a geological model of a work area to be processed; and determining the incidence angle range of the detector in the work area to be processed according to the geological model. In this embodiment, the geological model is created based on Snell's law and the Zoeppritz equation as theoretical bases. Snell's law and the Zoeppritz equation are two important tools commonly used in seismic exploration. According to Snell's law, on the interface with impedance difference, the incident angle and the transmission angle are in a direct proportion relation with the medium speed on the upper and lower sides of the interface, when seismic waves are transmitted from a low-speed medium to a high-speed medium, reflection and transmission are generated on the interface with impedance difference, when the incident angle is larger than a critical angle, total reflection is generated, and no seismic waves are transmitted into the high-speed medium. The size of the critical angle has a strict proportional relation with the speed ratio of the upper stratum to the lower stratum of the impedance interface, the change range of the critical angle is 0-90 degrees, and the critical angle becomes smaller along with the increase of the speed difference. Taking high-speed shielded area exploration as an example, two interfaces with large speed difference exist on two sides of a high-speed layer. In the high velocity layer, the upper interface blocks downward propagation of seismic wave energy and the lower interface blocks upward propagation of seismic wave energy. The signals transmitted by the upper and lower interfaces are limited to respective critical angle ranges. As shown in fig. 3, the interface on the high-speed layer has the following relationship according to the Snell relationship,

assuming a high layer velocity V₁5000m/s, density ρ₁＝2.5g/cm³Velocity V of overburden₀2000m/s, density ρ₀＝1.8g/cm³. When theta is greater than theta₀At 21.80 deg., theta₁When the seismic wave is 90.00, the seismic wave is totally reflected, so that the incident angle of the seismic wave transmitted by the upper interface of the high-speed layer, namely the top interface of the high-speed layer, needs to be limited to theta₀Within 21.80 °.

As shown in fig. 3, there is a relationship at the bottom interface of the high-speed layer according to the Snell relationship,

high layer velocity V₁5000m/s, density ρ₁＝2.5g/cm³Lower formation velocity V ₂3000m/s, density ρ₂＝2.1g/cm³. When the seismic wave reflected from the lower strata below the lower boundary of the high-speed layer propagates upward, theta is measured₂At 30.96 deg., theta₁At 90.00 deg., the seismic wave is totally reflected, so that the upward transmission of the seismic wave at the bottom interface, which is the lower interface of the high-speed layer, is limited to θ₂Within 30.96 deg..

Through the analysis, the effective incidence angle range theta of the descending seismic wave of the high-speed layer top interface₀Within 21.80 deg., the effective incident angle range of seismic wave on the bottom interface is theta₂Within 30.96 deg.. That is, in the high-speed shielded area of this example, the effective range of the incoming firing angle below the seismic crest interface of the source excitation is θ₀Within 21.80 deg., the seismic wave propagated by the bottom interface of the corresponding high-speed layer is controlled at theta₂When the inclination angle of the high-speed layer underburden is within 0-30.96 degrees, the seismic waves of the underburden can be reflected back, when the inclination angle of the underburden is greater than 30.96 degrees, the seismic waves are totally reflected, the reflection information returns to the underground, and at the moment, the underburden cannot be imaged through the reflection waves. The high velocity layer top interfacial resistance difference defines an effective range of incident angles and the bottom interfacial resistance difference causes the formation dip of the underlying formation to be defined within the critical angle of the lower interface.

Establishing a high-speed shielding geological model according to the determined propagation rule of the top-bottom interface of the high-speed layer for designing a seismic source and an acquisition scheme, wherein the established high-speed shielding geological model is shown as a graph 4, a point A is the position of the seismic source, a point B is the position of a detection point, and an X is the offset distance between the detection point and the seismic source; h is₀Is the depth of the top boundary of the high-speed layer, h₁Is the thickness of the high-speed layer, h₂The thickness of the target layer below the high-speed layer; v₀Is the velocity of the overlying strata of the high-velocity zone, V₁Is the velocity of the high-velocity layer, V₂The velocity of the high velocity underburden; ρ is a unit of a gradient₀Is the velocity, rho, of the overburden on the high-velocity zone₁Is the velocity of the high-velocity layer, p₂The velocity of the high velocity underburden; x is a radical of a fluorine atom₀Is the projection distance, x, of the ray on the earth surface when the ray propagates in the overlying strata of the high-speed layer₁Is the projection distance, x, of the ray on the earth's surface as it travels through the high-speed horizon₂For rays lying belowThe projection distance on the earth surface during propagation in the stratum; theta.theta.₀Is the angle of incidence, θ, of the top boundary of the high-speed layer₁Angle of incidence, θ, at the bottom boundary of the high-speed layer₂Is the angle of incidence of the high-velocity layer underburden.

According to the established high-speed shielding geological model, the following relation exists on the interface of the high-speed layer according to the Snell relation,

if the velocity V of the high-speed layer in the work area to be processed is higher than the velocity V of the high-speed layer₁5000m/s, density ρ₁＝2.5g/cm³Velocity V of overburden₀2000m/s, density ρ₀＝1.8g/cm³. When theta is greater than theta₀At 21.80 deg., theta₁The total reflection of the seismic wave occurs at 90.00 degrees, so the incident angle of the seismic wave transmitted by the top interface of the upper interface, i.e. the high-speed layer, is limited to θ₀Within 21.80 °. From this, it can be determined that the effective range of the incident angle satisfying the incidence of the overburden, i.e., the upper boundary, is θ₀Less than the critical angle.

In an exemplary embodiment, the phased array combination model includes:

wherein the content of the first and second substances,

a response for the phased array combining unit; n is the number of detector/seismic source combination units; m is the sequence number of the detector/seismic source in the combined unit; the combined unit is a detector/seismic source combined unit consisting of n detectors/seismic sources; d_mThe energy intensity of the detector combination unit; r is a radical of hydrogen_mThe distance from each detector/seismic source combination unit to the center of the combination unit; theta₀Azimuth of incoming/outgoing signal for the detector; psi₀Defined for the angle of incidence/angle of emergence of the detector; theta_mAzimuth of the detector/source; psi_mIs the incident/exit angle; v_waterWhich is the velocity of the water, is,

to combine responses

Phi/2 is less than or equal to psi₀Sum of absolute values in the range of ≤ pi/2, A_ηIs that-eta is less than or equal to psi₀Energy response of reception/excitation in the range of incidence angle ≦ η, A_ηAnd

In the prior art, in a seismic source combination scheme or a detector combination scheme, the following base distance design method of phased array combination is generally adopted;

equation 3 is the existing phased array combination equation, m is the in-combination detector/seismic source sequence number, D_mV is apparent velocity, v is incident seismic wave velocity (relative to the detector) or emergent seismic wave velocity (relative to the seismic source), α is incident angle (relative to the detector) or emergent angle (relative to the seismic source), and x is the sensitivity of the detector or the energy of the seismic source_mThe distance from the detector/seismic source to the combined symmetric center is improved by combining the phased array technology to the formula (1), the combined response is expanded from two dimensions to three dimensions, and x in the formula_mIs replaced by r_m(ii) a Expanding an incident signal along an incident angle alpha to an azimuth angle theta of the incident signal/an emergent signal in a three-dimensional space₀And elevation angle psi₀(incident angle ═ pi/2-psi₀Or an angle of departure pi/2-psi₀) And azimuth theta of the detector/source_mAnd elevation angle psi_mDetermining; next, the apparent velocity V is replaced by velocity V, defined as the water velocity V_waterObtaining the effective componentThe three-dimensional combined response of sensitivity is shown in equation 4.

Combining the energy excited by the seismic source in the high-speed shielding area to be concentrated in the effective incidence angle range, and taking the effective incidence angle range and the downlink energy as limiting constraint conditions to obtain a reconstructed phased array combination model as shown in the formula 5:

in an exemplary embodiment, the obtaining, by using a preset phased array combination model, a base distance corresponding to each of preset frequencies includes: obtaining an energy curve corresponding to each frequency in preset frequencies according to the phased array combination model of the work area to be processed, wherein the preset frequencies are low-frequency-band frequencies set according to the frequency range of the seismic data of the work area to be processed; and determining the long base distance corresponding to each frequency according to the energy curve of each frequency. In the present embodiment, it is preferred that,

the first step is as follows: and obtaining a relation curve of a base distance and combined response energy according to the phased array combined model of the work area to be processed, wherein the base distance is the distance from each combined unit to a combined center. And analyzing the low-frequency range of the seismic data of the region based on the phased array combined model by combining the seismic data condition of the work area to be processed, and selecting corresponding low frequency to determine the energy curve of the frequency so as to be used for determining the base distance. For example: in a high-speed layer shielding area in igneous rock, limestone, rock salt and the like, the fact that frequency bands of seismic signals above and below the high-speed layer are suddenly changed, especially the frequency band of an underlying stratum is distributed at 3-24 Hz, and the fundamental reason of analysis is that the high-speed shielding layer shields high-frequency signals is found in practical data analysis. For the high-speed shielding area, the energy curve of signals in a low frequency band is determined according to a phased array combination model, and frequencies f1, f2, f3 and f4 in four low frequency bands can be selected to determine the base distance in the 3-24 Hz frequency band. For example: the low-frequency is selected from the frequency f 1-3 Hz, f 2-6 Hz, f 3-12 Hz and f 4-24 Hz; the selection of the low-frequency band frequency can select a corresponding frequency according to the quality of the seismic data of the corresponding work area to be processed and the requirement of the work area to be processed. After frequencies f1, f2, f3 and f4 in four low frequency bands are selected, a focused energy curve of four low frequency frequencies f1, f2, f3 and f4 along with change of base distance is obtained according to a phased array combined model of a work area to be processed, and is shown in fig. 10.

The second step is that: and determining the base distance corresponding to each frequency according to the energy curve of each frequency. The specific implementation process comprises the following steps: according to the energy curve corresponding to each frequency in the preset frequencies obtained through calculation, selecting base distances corresponding to the positions of a plurality of wave crests in the energy curve of each frequency as base distances to be determined; and comparing a plurality of base distances to be determined, and selecting the base distance with the optimal energy focusing property as the base distance corresponding to the frequency. FIG. 7 is a schematic diagram showing energy focusing of a seismic signal with a frequency of 24Hz corresponding to different base distances, as shown in FIG. 7, and FIG. 7 is a schematic diagram showing energy focusing varying with base distance, according to equation 5, in the first equation, r_mAs variable (r)_mThe distance from the center of the combined unit for each detector/source combined unit); and taking the other parameters as constants to obtain K, and then obtaining AP according to a formula 5 to obtain a curve graph 7-a of the combined response changing along with the base distance. Fig. 7-a shows that the energy focusing varies with the base distance, the limited incident angle range η is 21.10 °, the base distance increases from 0, the energy ratio reaches 54% at the maximum when the base distance reaches 93m, the energy focusing performance becomes weak as a whole with the increase of the base distance, the local oscillation occurs, and a local energy focusing high-value point exists. Selecting a combination scheme of the base distances of the first high-value point and the second high-value point for comparison to obtain a combination response

As a function of the incident angle, as shown in FIG. 7-b, the solid line shows the combined response of the first high point as a function of the incident angle, and the dotted line shows the combined response of the second high point as a function of the incident angle, and it can be seen from FIG. 7-b that the first high point is paired with the second high pointThe solution should be best energy focused. Therefore, the base distance corresponding to the first high-value point is selected as the base distance of the frequency.

As shown in fig. 10, the energy curve of the low-frequency signal is determined for the phased array combination model of the work area, and the base distances corresponding to the four frequencies are determined to be L respectively according to the implementation procedure of determining the base distances_f1＝748m，L_f2＝372m，L_f3＝187m，L_f493 m. In conventional seismic acquisition, the base distance is typically around 18m for source combinations and around 12.5m for detector combinations. In the embodiment, the base distance designed according to the low-frequency energy focusing is larger than that adopted in the conventional acquisition, so that the base distance determined based on the low-frequency signal can be defined as a long base distance.

And 102, setting the group inner distance of the combination unit corresponding to each frequency aiming at the long base distance.

In this embodiment, the combination unit is a detector/source combination unit composed of n detectors/sources, where n is a positive integer greater than 1.

In an exemplary embodiment, setting, for the long base distance, a group inner distance of the combination unit of the long base distance corresponding to each frequency includes: aiming at the long base distance corresponding to each frequency, respectively designing the group inner distance of the detector/seismic source combined unit corresponding to each frequency by adopting the preset number of the detector/seismic source combined units; and combining the group internal distances of the detector/seismic source combination units corresponding to each frequency to obtain the spatial distribution of the detectors/seismic sources of the preset frequency of the work area to be processed. In this embodiment, the spatial distribution of the detectors/sources for obtaining the preset frequency of the work area to be processed may be an optimized detector/source combination scheme or an equally spaced detector/source combination scheme. If the optimized detector/source combination scheme may include: acquiring the distance between shot points and the distance between wave detection points in a work area to be processed; regularizing the group internal distance of the combination unit corresponding to each acquired frequency by adopting a regularization method; and acquiring the seismic data by using the regularized group internal distances.

The regularization method is adopted to regularize the group internal distance of the combination unit corresponding to each acquired frequency, and comprises the following steps: carrying out differential calculation on the group inner distance of the combination unit corresponding to each frequency to obtain a differential result; carrying out rounding calculation on the differential result to obtain a differential rounding result; and performing integral calculation on the differential rounding result to obtain the group internal distance of the integral multiple of the distance between the shot points and the distance between the demodulator probes. Wherein, the regularized formula is as follows:

wherein r is_ijThe distance between the combination units corresponding to any preset frequency is set, SI is the distance between the shot points, and RI is the distance between the shot points.

In this embodiment, after the group internal distance of the detector/source combination unit corresponding to each frequency is determined, the spatial distribution of the detectors/sources of the preset frequency of the work area to be processed may be determined.

And 103, determining the spatial distribution of the detectors/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency.

In this embodiment, after the group internal distance of the combination unit corresponding to each preset frequency is determined, the gun line distance, the shot point distance, the demodulation line distance, and the demodulation point distance in the design of the seismic data acquisition observation system can be determined. The spatial distribution of the receivers/sources is determined from the determined line spacing, shot spacing, pickup spacing, and pickup spacing.

The spatial distribution of the detectors/seismic sources can be determined by the determined line spacing, the determined point spacing, the determined line spacing and the determined point spacing, the acquisition observation system is shown in fig. 12, and the unequal spacing combination scheme designed by the scheme is that, as shown in fig. 12a, the spatial distribution of the detectors/seismic sources determined for the frequency f3 ═ 12Hz in table 5 is adopted, 8 survey lines are arranged, the survey line spacing is unequal spacing, and similar to the observation system defined by the parameters, the scheme can be expanded to the scheme of unequal spacing adopted by other frequency enhancement, as shown in fig. 12b, the solid line in the figure is the detection line, the dotted line is the line, but is not limited thereto, and the scheme of mutually accumulating a plurality of frequency segments can also be adopted, as shown in fig. 12 c.

And 104, reducing the number of the combined units by adopting a preset rule according to the spatial distribution of the detectors/the seismic sources to obtain the distribution of the reduced detector/seismic source combined units.

In the present embodiment, considering the spatial distribution of the detectors/sources determined by using the long base distance, the workload of the acquisition is large, and the distribution of the reduced detector/source combination units needs to be obtained by reducing the number of the combination units by using a predetermined rule. After a reduced distribution of combined detector/source units is obtained, seismic data acquisition may be performed based on the distribution of the combined detector/source units. In the ideal scheme based on table 4, the number of combined elements is reduced by a predetermined rule to obtain a reduced distribution of combined detector/source elements, as shown in table 13.

TABLE 13 idealized scheme workload reduction Table based on TABLE 4

In an exemplary embodiment, reducing the number of combined elements according to the spatial distribution of the detectors/sources by a predetermined rule to obtain a reduced distribution of combined detector/source elements comprises:

after the spatial distribution of the detectors/seismic sources with preset frequencies in the work area to be processed is obtained, the group internal distances of the detector/seismic source combined units corresponding to all the frequencies are sequenced; and selecting the group inner distances corresponding to the minimum value and the maximum value in the group inner distances of the detector/seismic source combined units, and calculating to obtain the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula.

In an exemplary embodiment, wherein the reduction formula comprises:

In an exemplary embodiment, the reducing the number of the combined units according to the spatial distribution of the detectors/sources by using a predetermined rule to obtain a reduced distribution of the combined units of the detectors/sources further includes: rearranging the detector/seismic source combination units of each frequency respectively, and calculating the distribution of the corresponding reduced detector/seismic source combination units of the frequency according to the proportion of the reduced workload and a reduction formula; after the distribution of all the reduced-frequency detector/seismic source combination units is obtained, rearranging the reduced-frequency detector/seismic source combination units of all the frequencies; the distribution of reduced detector/source combining units is derived from the rearranged reduced detector/source combining units.

The workload reduction is performed for each frequency separately, and then the combination scheme is rearranged, for example, the workload reduction corresponding to the four frequencies f1, f2, f3 and f4 in table 3 is taken as an example, table 14 is the f1 frequency combination scheme reduction scheme, table 15 is the f2 frequency combination scheme reduction scheme, table 16 is the f3 frequency combination scheme reduction scheme, and table 17 is the f4 frequency combination scheme reduction scheme.

TABLE 14 f1 frequency combination scheme reduction scheme

TABLE 15 f2 frequency combination scheme reduction scheme

TABLE 16 f3 frequency combination scheme reduction scheme

TABLE 17 f4 frequency combination scheme reduction scheme

In the combination schemes in tables 14 to 17, three original schemes (original scheme + workload reduction 1/2 scheme + workload reduction 1/4 scheme) are calculated for the detector combination scheme of a certain frequency, and at this time, the enhanced combination design is performed on the multiple frequency segments, and as the f1+ f2+ f3+ f4 combination scheme is simultaneously adopted, a total of 81 low-frequency extension combination schemes can be generated according to the local permutation and combination formula. In practice, the scheme meeting the requirement can be selected from 81 schemes according to the requirement of frequency enhancement. As shown in table 18, the scheme for simultaneously reducing the combined workload 1/4 according to the four frequencies in tables 14 to 17.

TABLE 18 f4 frequency combination scheme reduction scheme

Fig. 13 shows the variation of the spatial positions and the number of combinations of the combination units before and after the reduction of the workload, in this case, the number of combination units is reduced from 32 to 8.

In order to solve the above problem, as shown in fig. 2, the present invention further provides a long-base acquisition parameter determining apparatus, including: a memory and a processor;

obtaining a long base distance corresponding to each frequency in preset frequencies of a work area to be processed, wherein the long base distance refers to a base distance with a base distance length larger than 25 m;

setting the group internal distance of the combination unit corresponding to each frequency aiming at the long base distance, wherein the combination unit is a detector/seismic source combination unit consisting of n detectors/seismic sources, and n is a positive integer greater than 1;

In an exemplary embodiment, the phased array combination model includes:

wherein the content of the first and second substances,

to combine responses

In an exemplary embodiment, the obtaining, by using a preset phased array combination model, a base distance corresponding to each of preset frequencies includes: obtaining an energy curve corresponding to each frequency in preset frequencies according to the phased array combination model of the work area to be processed, wherein the preset frequencies are low-frequency-band frequencies set according to the frequency range of the seismic data of the work area to be processed; and determining the long base distance corresponding to each frequency according to the energy curve of each frequency.

In an exemplary embodiment, the setting, for the long base distance, the group inner distance of the combination unit corresponding to each frequency includes: aiming at the long base distance corresponding to each frequency, respectively designing the group inner distance of the detector/seismic source combined unit corresponding to each frequency by adopting the preset number of the detector/seismic source combined units; and combining the group internal distances of the detector/seismic source combination units corresponding to each frequency to obtain the spatial distribution of the detectors/seismic sources of the preset frequency of the work area to be processed.

In an exemplary embodiment, the reducing the number of the combined units according to the spatial distribution of the detectors/sources by using a predetermined rule to obtain a reduced distribution of the combined units of the detectors/sources includes: after the spatial distribution of the detectors/seismic sources with preset frequencies in the work area to be processed is obtained, the group internal distances of the detector/seismic source combination units corresponding to all the frequencies are sequenced; and selecting the group inner distances corresponding to the minimum value and the maximum value in the group inner distances of the detector/seismic source combined units, and calculating to obtain the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula.

In an exemplary embodiment, wherein the reduction formula comprises:

An exemplary embodiment of a method for determining acquisition parameters based on a long base distance includes the following specific implementation processes:

step 1, establishing a geological model of a work area to be processed.

In this embodiment, a geological model is created based on Snell's law and the Zoeppritz equation as a theoretical basis. Snell's law and the Zoeppritz equation are two important tools commonly used in seismic exploration. According to Snell law, on an interface with impedance difference, an incident angle and a transmission angle are in a direct proportion relation with the medium speed on the upper side and the lower side of the interface, when seismic waves are transmitted from a low-speed medium to a high-speed medium, reflection and transmission are generated on the interface with impedance difference, when the incident angle is larger than a critical angle, total reflection is generated, and no seismic waves are transmitted into the high-speed medium. The size of the critical angle has a strict proportional relation with the speed ratio of the upper stratum to the lower stratum of the impedance interface, the change range of the critical angle is 0-90 degrees, and the critical angle becomes smaller along with the increase of the speed difference. Taking high-speed shielded area exploration as an example, two interfaces with large speed difference exist on two sides of a high-speed layer. In the high velocity layer, the upper interface blocks downward propagation of seismic wave energy and the lower interface blocks upward propagation of seismic wave energy. The signals transmitted by the upper and lower interfaces are limited to respective critical angle ranges. As shown in fig. 3, the interface on the high-speed layer has the following relationship according to the Snell relationship,

assuming a high layer velocity V₁5000m/s, density ρ₁＝2.5g/cm³Velocity V of overburden₀2000m/s, density ρ₀＝1.8g/cm³. When theta is greater than theta₀At 21.80 deg., theta₁The total reflection of the seismic wave occurs at 90.00 degrees, so the incident angle of the seismic wave transmitted through the top interface of the upper interface, i.e. the high-speed layer, is limited to theta₀Within 21.80 °.

As shown in fig. 3, the following relationship exists at the bottom interface of the high speed layer according to Snell relationship,

high layer velocity V₁5000m/s, density ρ₁＝2.5g/cm³Lower formation velocity V ₂3000m/s, density ρ₂＝2.1g/cm³. When the seismic wave reflected from the lower strata below the lower interface of the high-speed layer propagates upward, the velocity of the seismic wave is theta₂At 30.96 deg., theta₁At 90.00 deg., the seismic wave is totally reflected, so that the upward transmission of the seismic wave at the bottom interface, which is the lower interface of the high-speed layer, is limited to θ₂Within 30.96 deg..

Through the analysis, the effective incidence angle range theta of the descending seismic wave of the high-speed layer top interface₀Within 21.80 deg., the effective incident angle range of seismic wave on the bottom interface is theta₂Within 30.96 deg.. That is, in the high-speed shielded area of this example, the effective range of the incoming firing angle below the seismic crest interface of the source excitation is θ₀Within 21.80 deg., the seismic wave propagated on the bottom interface of corresponding high-speed layer is controlled at theta₂When the inclination angle of the high-speed layer underburden is within 0-30.96 degrees, the seismic waves of the underburden can be reflected back, when the inclination angle of the underburden is greater than 30.96 degrees, the seismic waves are totally reflected, the reflection information returns to the underground, and at the moment, the underburden cannot be imaged through the reflection waves. The difference in the top interfacial resistance of the high velocity layer defines the effective range of incidence angles, and the difference in the bottom interfacial resistance causes the formation dip of the underlying formation to be defined at the lower interface.

Establishing a high-speed shielding geological model according to the determined propagation rule of the top and bottom interfaces of the high-speed layer for designing a seismic source and an acquisition scheme, wherein in the figure 4, point A is the position of the seismic source, point B is the position of a detection point, and point X is the position between the detection point and the seismic sourceAn offset distance; h is₀Is the depth of the top boundary of the high-speed layer, h₁Is the thickness of the high-speed layer, h₂The thickness of the target layer below the high-speed layer; v₀Is the velocity of the overlying strata of the high-velocity zone, V₁Is the velocity of the high-velocity layer, V₂The velocity of the high velocity underburden; rho₀Is the velocity, rho, of the overburden on the high-velocity zone₁Is the velocity of the high-velocity layer, p₂The velocity of the high velocity underburden; x is the number of₀Is the projection distance, x, of the ray on the earth surface when the ray propagates in the overlying strata of the high-speed layer₁Is the projection distance, x, of the ray on the earth's surface as it travels through the high-speed horizon₂The projection distance of the rays on the earth surface when the rays propagate in the underlying stratum; theta₀Is the angle of incidence, θ, of the top boundary of the high-speed layer₁Angle of incidence, θ, at the bottom boundary of the high-speed layer₂Is the angle of incidence of the high velocity layer underburden.

And 2, determining the incidence angle range of the detector in the work area to be processed according to the geological model.

In the embodiment, according to the high-speed shielding geological model established in the step 1, the following relationship exists on the interface of the high-speed layer according to the Snell relationship,

if the velocity V of the high-speed layer in the work area to be processed₁5000m/s, density ρ₁＝2.5g/cm³Velocity V of overburden₀2000m/s, density ρ₀＝1.8g/cm³. When theta is greater than theta₀At 21.80 deg., theta₁The total reflection of the seismic wave occurs at 90.00 degrees, so the incident angle of the seismic wave transmitted through the top interface of the upper interface, i.e. the high-speed layer, is limited to theta₀Within 21.80 °. From this, it can be determined that the effective range of incidence angles determined to satisfy the incidence of the overburden, i.e., the upper boundary, is θ₀Less than the critical angle.

And 3, establishing an effective offset distance evaluation model of the high-speed shielding area according to the established high-speed shielding geological model and the geometrical relation of the seismic waves in the underground.

In the step, according to the established high-speed shielding geological model and the geometrical relationship of seismic waves propagating underground, a formula of the offset distance X between the detection point and the seismic source can be obtained,

X＝2(h₀ tanθ₀+h₁ tanθ₁+h₂ tanθ₂) (6)

and combining the trigonometric relationships to obtain equation 7, csc θ₀，cscθ₁，cscθ₂For the cosecant function corresponding to each incident angle,

in addition, there is a relationship according to Snell's law,

combining equation 6 with equation 7 for further simplification, θ in the equations₁And theta₂If the difference is eliminated, the formula 9 is obtained,

the effective range of incidence angles determined to satisfy the incidence of the overburden, i.e., the upper boundary, as described above is θ₀Less than the critical angle. Defining the critical angle of the top interface as θ_0cCritical angle of bottom interface is theta_2c. Equation 9 is further simplified to equation 10,

since the velocity increases with the depth of burial in actual exploration, the velocity of the overburden layer of the high-speed shielding layer is generally lower than that of the underburden layer, that is, a relation V exists₀<V₂<V₁Then theta is corresponding to_0c<θ_2cThen the boundary condition exists, equation 11,

minimum offset X defining the right side of equation 11 as offset X between pickup point and source_minDesign criteria, establishing an effective offset evaluation model of the high-speed shielding region as formula 12

And 4, determining the range of the source emergence angle and the detector incidence angle in the work area to be processed.

In equation 12, the first equation is the design equation of the minimum maximum offset distance of the high-speed shielding region, θ_0cThe critical angle of the top boundary of the high-speed layer defines the range of effective transmission information; critical angle of bottom boundary is theta_2cThe effective dip range of the high speed shield underburden is defined. Given the high-speed mask model in FIG. 4 as an example V₁＝5000m/s，ρ₁＝2.5g/cm³Velocity V of overburden₀＝2000m/s，ρ₀＝1.8g/cm³Underburden velocity V₂＝3000m/s，ρ₂＝2.1g/cm³。h₀＝1200m，h₁＝500m h₂200 m. Under the condition of the parameter, the offset design reference version of the corresponding high-speed mask can be manufactured according to the formula 12, and the manufacturing process includes: firstly, establishing an effective offset model of a high-speed shielding area according to a first formula in a 12 formula; in the second step, the offset range commonly used in the actual production is selected, for example: 1000m, 2000m, 3000m,4000m,5000m,6000m,7000m,800m,9000m,10000m,11000m,12000m, the range of incidence angles corresponding to each offset can be found in the metrology plate established in fig. 5, as shown in table 1.

TABLE 1 actual common offset versus incident angle for exploration

The model in the figure 5 is further expanded to a multilayer medium, a relation model of the same incident angle of a multi-layer overburden seismic source in a high-speed shielding area is established as shown in figure 6, the following relation exists according to Snell's law, and the water velocity V is assumed_{Water (W)}，

Then the formula corresponding to the overburden at the high velocity layer is extracted from formula 13 as shown in formula 14,

suppose water velocity V_{Water (I)}＝5000m/s，ρ_{Water (W)}＝1.03g/cm³Then, the corresponding range of the emitting angle of the seismic source corresponding to each offset in table 1 can be converted according to formula 12, as shown in table 2.

TABLE 2 seismic source emergence angle

And 5, establishing a phased array combination model of the work area to be processed.

In the present embodiment, in the prior art, for the seismic source combination or the detector combination scheme, the following base distance design method of phased array combination is generally adopted;

equation 3 is a commonly used combination equation, m is the combination geophone/seismic source sequence number, where D is_mV is the apparent velocity and v is the velocity of the incident seismic wave, the sensitivity of the detector or the energy of the seismic sourceDegree (relative to the detector) or emergent seismic velocity (relative to the source), α is the angle of incidence (relative to the detector) or angle of emergence (relative to the source), x_mThe distance from the detector/seismic source to the combined symmetric center is improved by combining the phased array technology to the formula (1), the combined response is expanded from two dimensions to three dimensions, and x in the formula_mIs replaced by r_m(ii) a Expanding an incident signal along an incident angle alpha to an azimuth angle theta of the incident signal/an emergent signal in a three-dimensional space₀And elevation angle psi₀(incident angle ═ pi/2-psi₀Or an angle of departure pi/2-psi₀) And azimuth theta of the detector/source_mAnd elevation angle psi_mDetermining; next, the apparent velocity V is replaced by velocity V, defined as the water velocity V_waterAnd obtaining a three-dimensional response formula 4 of the sensitivity.

In order to meet the requirement that the energy of the seismic source excitation in the high-speed shielding area is concentrated in the effective incidence angle range, the effective incidence angle range and the downlink energy are added, a reconstructed phased array combination model is obtained, and the reconstructed phased array combination model is shown as an equation 5,

defining eta as an effective incidence angle range, wherein n is the number of the combination units in the formula; d_mSensitivity or energy intensity of the combined unit; r is_mObtaining the distance from each combination unit to the combination center; theta₀Azimuth angle of incident/outgoing signal; psi₀Defined for the incident or exit angle; and azimuth theta of the detector/source_mAnd incident/exit angle psi_m；V_waterIs the speed of water, V₀Is the velocity of the overburden over the high velocity zone,

to make up of

Is in the range of-pi/2 to psi₀Total energy response of uniform half-space reception/excitation ≦ π/2, A_ηIs that-eta is less than or equal to psi₀Received/excited energy response in the range of incidence angles ≦ η, A_ηAnd

the ratio of (a) constitutes the discrimination formula for the combined response focus. FIG. 7 is a schematic diagram showing energy focusing of 24Hz signal corresponding to different base distances, and FIG. 7a is a schematic diagram showing energy focusing varying with base distance according to r in the first equation in equation 5_mAs variables, the other parameters are used as constants to calculate K, and then AP is calculated according to the following formula, so as to obtain a graph 7a of the combined response changing along with the base distance. Fig. 7a shows how the energy focusing is changed with the base distance, the limited incident angle range η is 21.10 °, the base distance is increased from 0, the energy ratio reaches 54% at the maximum when reaching 93m, the energy focusing performance is weakened as a whole with the increase of the base distance, oscillation is locally generated, and a local energy focusing high-value point exists. Selecting the combination scheme of the base distances of the first and second high-value points for comparison, and looking at the combined response

With the change of the incident angle, as shown in fig. 7b, the solid line shows the combined response of the first high-value point with the change of the incident angle, and the dashed line shows the combined response of the second high-value point with the change of the incident angle, it is obvious that the solution energy focusing property corresponding to the first high-value point is the best. The above example is for a signal of a single frequency, and in actual seismic exploration, the frequency band range commonly used is distributed in 0-200 Hz, and the design of a wide frequency band can be extended according to the formula 5. As shown in fig. 8, an energy focusing broadband design diagram can be used to design a base distance combination scheme for different actual exploration frequency requirements.

Formula 5 is a high-dimensional design formula, and there are many parameters, so that the application dimension of formula 5 can be further extended, for example: the design of the number N of detector combination units can be taken into consideration to obtain the high-dimensional design schematic of fig. 9, and assuming the variation range [4, 34] of the number N of detector combination units, it can be seen from the energy focusing high-dimensional schematic of fig. 9 that the overall performance of the detector combination scheme is optimal when the number N of detectors is 6. In addition, some parameters can be selected for joint design aiming at some parameters in the formula 5, so that a high-dimensional design scheme is obtained.

And 6, obtaining a long base distance corresponding to each frequency in the preset frequencies of the work area to be processed.

In the present embodiment, the long base distance means a base distance having a length of more than 25 m. The implementation process for obtaining the long base distance corresponding to each frequency in the preset frequencies of the work area to be processed comprises the following steps:

the first step is as follows: and calculating to obtain an energy curve of each frequency corresponding to a preset frequency according to the phased array combination model of the work area to be processed, wherein the preset frequency is a low-frequency-band frequency set according to the seismic data analysis of the work area to be processed.

In this step, based on the phased array combination model created in step 5, the low frequency range of the seismic data of the region is analyzed in combination with the seismic data condition of the work area to be processed, and the corresponding preset frequency is selected to determine the energy curve corresponding to the preset frequency, and further to determine the base distance corresponding to each selected frequency in the preset frequency. For example: in a high-speed layer shielding area where igneous rock, limestone, rock salt and the like exist, the analysis of seismic data of an actual work area to be processed discovers that frequency bands of seismic signals on and under the high-speed layer are mutated, particularly the frequency bands of an underlying stratum are distributed at 3-24 Hz, and the fundamental reason for the frequency band mutation is that the high-speed shielding layer shields high-frequency signals. In this step, the energy curve corresponding to the preset frequency is determined by using the established phased array combination model. In a frequency band of 3-24 Hz, four low-frequency frequencies f1, f2, f3 and f4 are selected for base distance design, for example: the low-frequency is selected from the frequency f 1-3 Hz, f 2-6 Hz, f 3-12 Hz and f 4-24 Hz; the selection of the low-frequency can be analyzed according to the quality of the seismic data of the corresponding work area to be processed to select the corresponding frequency. The energy variation curves of four low-frequency frequencies f1, f2, f3 and f4 along with the base distance are obtained according to the phased array combined model of the work area to be processed, and are shown in fig. 10.

The second step is that: and determining the long base distance corresponding to each frequency according to the energy curve.

In the step, according to the energy curve corresponding to each frequency in each preset frequency obtained in the first step, selecting a base distance corresponding to the positions of a plurality of wave crests in the energy curve of each frequency as a base distance to be determined; and comparing a plurality of base distances to be determined, and selecting the base distance of the energy focus as the base distance corresponding to the frequency. The specific implementation process is as follows: selecting the combination of the base distances of the first and second high-value points to be correspondingly compared according to the energy curve of each frequency obtained in the first step, and analyzing the combined response

As shown in fig. 7b, the solid line in fig. 7b represents the combined response of the first high point (the first high point corresponds to the first peak) and the dotted line represents the combined response of the second high point (the second high point corresponds to the second peak), and the combined response of the first high point has the best focusing performance from the perspective of the comparative analysis. According to the determination process, the base distances corresponding to the four frequencies are respectively determined to be L_f1＝748m，L_f2＝372m，L_f3＝187m，L_f493 m. In the conventional acquisition, the seismic source and the detector are combined by using a base distance, the base distance commonly used by the seismic source combination is about 18m, and the base distance commonly used by the detector combination is about 12.5 m. The base distance designed according to the low frequency energy focusing is larger than that adopted by the conventional acquisition, so that the base distance determined for the low frequency band is defined as a long base distance. The long base distance refers to a base distance with a base distance length of more than 25 m.

And 7, setting the group inner distance of the combination unit corresponding to each frequency aiming at the long base distance.

In an exemplary embodiment, for the long base distance corresponding to each frequency, the preset number of the combined units of the detectors/sources is adopted, and the group internal distance of the combined units of the detectors/sources corresponding to each frequency is respectively designed. In this embodiment, the spatial distribution of the detectors/seismic sources for obtaining the preset frequency of the work area to be processed may be an optimized detector/seismic source combination scheme, that is, a combination unit of detectors/seismic sources with unequal intervals, or may be an equidistant detector/seismic source combination scheme, that is, a combination unit of detectors/seismic sources with equal intervals.

In this embodiment, two schemes, an optimal combination design and an equidistant combination design, may be adopted according to the determined base distance of each frequency, and the specific implementation process is as follows:

and step 71, adopting an optimal combination scheme.

For the base distance corresponding to each frequency, respectively designing the group inner distance of the combination unit corresponding to each frequency by adopting the preset number of the combination units of the seismic sources/detectors; and combining the group internal distances of the combination units corresponding to each frequency to obtain the spatial distribution of the seismic source/detector of the preset frequency of the work area to be processed.

In this embodiment, the group internal distance of each combination unit in the combination scheme is respectively set according to each determined frequency, that is, the optimal combination scheme is selected and adopted, and the specific implementation process is as follows: for the example of the detector combination, assuming that the number of the combination units N is 8, four basic distances L are first determined_f1，L_f2，L_f3And L_f4And respectively designing the group internal distance r of each combined unit. f. of₁The center distance of each detector combined unit corresponding to the frequency is r₁₁，r₁₂，r₁₃，r₁₄，r₁₅，r₁₆，r₁₇，r₁₈；f₂The center distance of each detector combined unit corresponding to the frequency is r₂₁，r₂₂，r₂₃，r₂₄，r₂₅，r₂₆，r₂₇，r₂₈；f₃The central distance of each detector combination unit corresponding to the frequency is r₃₁，r₃₂，r₃₃，r₃₄，r₃₅，r₃₆，r₃₇，r₃₈；f₄The center distance of each unit corresponding to the frequency is r₄₁，r₄₂，r₄₃，r₄₄，r₄₅，r₄₆，r₄₇，r₄₈(ii) a And calculating the center distance of each detector combination unit corresponding to each frequency according to the determined base distance of each frequency, wherein the center distance is shown in a table 3.

TABLE 3 design chart of base distances

Because the base distances and the intra-group distances corresponding to different frequencies are randomly distributed, the intra-group distances are rearranged according to the sequence from large to small, and repeated workload is reduced by the scheme that the repeated intra-group distances are combined by the rearranged intra-group distances. Therefore, after the group internal distances of the combination units corresponding to each frequency are obtained, the base distances in table 3 are rearranged to obtain table 4.

TABLE 4 base distance rearrangement table

And 72, adopting an equal-interval design.

In this embodiment, in the actual implementation of seismic data acquisition, the scheme designed in fig. 11 is an unequal spacing scheme of each combination unit, that is, the group internal spacing of each unit in the geophone combination is changed. In actual production, an equally-spaced design is generally adopted, that is, the group internal distance of each unit in the detector combination is fixed. Therefore, after the long base distance of each low frequency is obtained, the shot point long base distance combination and the wave detection point long base distance combination are realized by combining parameters in actual production, and seismic data acquisition parameters can be optimized according to the shot point distance SI and the geophone distance RI, so that the base distance is integral multiple of SI/RI. The specific implementation process comprises the following steps:

step 720, acquiring shot point distance SI and geophone distance RI in the work area to be processed;

and 721, regularizing the group internal distances of the combination units corresponding to each acquired frequency by adopting a base distance regularization method to obtain the group internal distances of the shot distance SI and the integral multiple of the detector distance RI.

In the step, the group inner distance of the combination unit corresponding to each frequency is subjected to differential calculation to obtain a differential result; carrying out rounding calculation on the differential result to obtain a differential rounding result; and performing integral calculation on the result of the differential rounding to obtain a regularized base distance. The specific implementation process is as follows: so that the variation of the base distance is an integer multiple of the SI/RI. The specific formula is as follows:

firstly, the base distance is differentiated, then the integration calculation is carried out on the differentiation result, and the base distance r 'is reconstructed by integrating the integration calculation result of the differentiation'_ij. In this formula, the shot spacing SI and the detector spacing RI are calculated separately. When the pitch was adjusted for table 4, the design tables, table 5 and table 6, were obtained after adjusting the pitch of SI ═ RI ═ 25m and SI ═ RI ═ 12.5m, respectively.

TABLE 5 SI RI 25m base distance regularized design List

Table 6 base distance regularized design table of SI-RI-12.5 m

The parameters of tables 5 and 6 were rearranged to obtain new combination designs, as shown in tables 7 and 8.

TABLE 7 base distance regularized rearrangement TABLE SI 25m RI

TABLE 8 base distance regularized rearrangement TABLE SI ═ RI ═ 12.5m

The shot distance SI and the geophone distance RI adopt a 25m distance and a 12.5m distance, and the shot distance SI and the geophone distance RI adopt a 25m distance and a 12.5m distance which are two distances commonly used at sea at present, and the assumed distances are as follows: the long base distance combination mode of three pitches, namely, 6.25m of SI and 3.125m of RI, 1.5625m of SI and 1m of SI. The frequency employed is employed in keeping with the example in the above step: f 1-3 Hz, f 2-6 Hz, f 3-12 Hz and f 4-24 Hz. The above-mentioned 4 pattern base distance regularization rearrangement tables are obtained according to the above-mentioned regularization method, where SI ═ RI ═ 6.25m base distance regularization rearrangement table, SI ═ RI ═ 3.125m rearrangement table, SI ═ RI ═ 1.5625m rearrangement table, and SI ═ RI ═ 1m rearrangement table. The rearranged information is shown in the following table: table 9 is a rearrangement table of SI ═ RI ═ 6.25m, table 10 is a rearrangement table of SI ═ RI ═ 3.125m, table 11 is a rearrangement table of SI ═ RI ═ 1.5625m, and table 12 is a rearrangement table of SI ═ RI ═ 1 m.

TABLE 9 base rule rearrangement TABLE SI 6.25m

TABLE 10 base distance regularized rearrangement TABLE SI 3.125m

TABLE 11 SI & RI & 1.5625m base distance regularized rearrangement TABLE

TABLE 12 base distance regularized rearrangement TABLE SI 1m RI

For the combinations mentioned above, which are ideal in table 4, the combinations in the case of SI RI 25m, SI RI 12.5m, SI RI 6.25m, SI RI 3.125m, SI RI 1.5625m and SI RI 1m are also possible. The connection and the like do not only limit the parameters adopted at the same time, but also include the calculation and design of the shot point and demodulator probe combination schemes respectively, and different parameter designs can be adopted for the distance between the shot point and the demodulator probe respectively.

And 8, determining the spatial distribution of the detectors/seismic sources according to the group internal distance of the combination unit corresponding to each preset frequency.

In this step, the spatial distribution of the detectors/sources is determined according to the determined group internal distance of the combination unit corresponding to each preset frequency. For example: table 4 is an ideal combination scheme combining the four frequencies f1, f2, f3, and f4, and after the combination scheme in table 4 is obtained, the spatial distribution state of the ideal combination scheme combining the four frequencies f1, f2, f3, and f4 as shown in fig. 11 is obtained.

And 9, reducing the number of the combined units by adopting a preset rule according to the spatial distribution of the detectors/the seismic sources to obtain the distribution of the reduced detector/seismic source combined units.

The acquisition method implementation mainly comprises the acquisition method (mainly comprising the gun line spacing, the shot point spacing, the detection line spacing and the detection point spacing designed according to the proposed scheme) implemented according to the design of the proposed combination scheme in the actual acquisition and the scheme of simplifying the workload by performing spatial interpolation through the basic scheme. The limitation of the acquisition method mainly includes the unequal-spacing combination scheme designed according to the scheme, as shown in fig. 12a, the scheme for f in table 5 is adopted₃As for the 12Hz frequency enhancement scheme, 8 survey lines are laid, and the distance between the survey lines is unequal, similar to the observation system defined by the above parameters, the scheme can also be expanded to the scheme of unequal distance used for other frequency enhancement, as shown in fig. 12b, where the solid line is the detection line and the dotted line is the shot line, but not limited to this, the scheme of mutually accumulating a plurality of rearranged frequency segments can also be used, as shown in fig. 12 c. After data are collected, shot point data corresponding to 8 lines can be reconstructed by adopting shot point vertical superposition and vertical superposition after shot point static correction.

The implementation workload of the acquisition system based on the long base distance obtained by the above steps is large, and a combination scheme obtained by spatial interpolation based on the proposed acquisition system scheme of the long base distance through the simplified workload is needed.

Step 91, after the spatial distribution of the detectors/seismic sources with preset frequencies in the work area to be processed is obtained, sequencing the group internal distances of the detector/seismic source combined units corresponding to all the frequencies; and selecting the group inner distances corresponding to the minimum value and the maximum value in the group inner distances of the detector/seismic source combined units, and calculating to obtain the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula.

911, after obtaining the spatial distribution of the detectors/seismic sources with preset frequencies in the work area to be processed, sequencing the group internal distances of the detector/seismic source combination units corresponding to all the frequencies;

step 912, selecting the group internal distances corresponding to the minimum value and the maximum value in the group internal distances of the detector/seismic source combined units, and calculating the distribution of the reduced detector/seismic source combined units according to the proportion of the reduced workload and a reduction formula;

wherein the reduction formula comprises:

wherein r is_jiIs the original base distance, where j is the number of the frequency, i is the number of the combination unit, min (r)_ji) Is the smallest base distance, max (r), of the original base distances_ji) The method is characterized in that the method is a maximum basic distance in the original basic distances, N is the number of original combined units, the ratio of reduction workloads is 1/M, M is an integral multiple of 2, M is 2, 4, 8, 16. With the above reduction steps, fig. 11 illustrates a simplified workload scheme by performing spatial interpolation based on the ideal scheme of table 4, as shown in table 13:

TABLE 13 idealized scheme workload reduction Table based on TABLE 4

Reducing the number of the combined units by adopting a preset rule according to the spatial distribution of the detectors/seismic sources to obtain the distribution of the reduced detector/seismic source combined units, and further comprising the following steps of: step 92, rearranging the detector/seismic source combination units of each frequency, and calculating the distribution of the corresponding reduced detector/seismic source combination units of the frequency according to the proportion of the reduced workload and a reduction formula; after the distribution of all the reduced-frequency detector/seismic source combination units is obtained, rearranging the reduced-frequency detector/seismic source combination units of all the frequencies; the distribution of reduced detector/source combining units is derived from the rearranged reduced detector/source combining units.

Step 921, rearranging the combination units of the detectors of each frequency, and calculating the distribution of the corresponding reduction combination units of the frequency according to the proportion of the reduction workload and a reduction formula;

and 922, after the distribution of the reduced combination units of all the preset frequencies is obtained, rearranging the reduced combination units of all the preset frequencies.

The workload reduction is performed on the combination scheme in step 92, and the workload reduction is performed on each frequency, and then the combination scheme is rearranged, for example, the workload reduction corresponding to the four frequencies f1, f2, f3, and f4 in table 3 is performed, for example, the frequency combination scheme reduction scheme of f1 in table 14, the frequency combination scheme reduction scheme of f2 in table 15, the frequency combination scheme reduction scheme of f3 in table 16, and the frequency combination scheme reduction scheme of f4 in table 17.

TABLE 14 f1 frequency combination scheme reduction scheme

TABLE 15 f2 frequency combination scheme reduction scheme

TABLE 16 f3 frequency combination scheme reduction scheme

TABLE 17 f4 frequency combination scheme reduction scheme

In the combination schemes in tables 14 to 17, three combinations (original scheme + workload reduction 1/2 scheme + workload reduction 1/4 scheme) are calculated for a certain frequency enhancement combination scheme, and then the enhancement combination design is performed on multiple frequency bands, and as the f1+ f2+ f3+ f4 combination scheme is simultaneously adopted, 81 schemes of the detector combination scheme can be generated according to the permutation combination formula. In practice, the scheme in 81 can be selected to meet the requirement according to the requirement of low-band frequency enhancement. As shown in table 18, the scheme for simultaneously reducing the combined workload 1/4 according to the four frequencies in tables 14 to 17.

TABLE 18 f4 frequency combination scheme reduction scheme

Fig. 13 shows the variation of the spatial positions of the combination units and the number of combination units before and after the reduction of the workload, in this case, the number of combination units is reduced from 32 to 8. After obtaining the reduced distribution of combined detector/source units, seismic data acquisition may be performed based on the reduced distribution of combined detector/source units.

According to the method, the number of the combined units is reduced by adopting a preset rule according to the spatial distribution of the detectors/seismic sources, and the distribution of the reduced detector/seismic source combined units is obtained; seismic data acquisition is performed according to the distribution of the acquisition combining units of the reduced geophones/seismic sources. By the scheme of the invention, the workload of seismic data acquisition can be reduced when the seismic data acquisition is based on the long base distance.

It will be understood by those of ordinary skill in the art that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.

Claims

1. A method for determining acquisition parameters based on a long base distance is characterized by comprising the following steps:

according to the spatial distribution of the detectors/seismic sources, reducing the number of the combined units by adopting a preset rule to obtain the distribution of the reduced detector/seismic source combined units, wherein the distribution of the reduced detector/seismic source combined units comprises the following steps:

2. The method for determining the acquisition parameters based on the long base distance as claimed in claim 1, wherein the obtaining the long base distance corresponding to each frequency in the preset frequency of the work area to be processed comprises:

3. The method of claim 2, wherein the phased array combined model comprises:

wherein the content of the first and second substances,

a response for the phased array combining unit; n is a detectorNumber of source combining units; m is the sequence number of the detector/seismic source in the combined unit; the combined unit is a detector/seismic source combined unit consisting of n detectors/seismic sources; d_mThe energy intensity of the detector combination unit; r is a radical of hydrogen_mThe distance from each detector/seismic source combination unit to the center of the combination unit; theta₀Azimuth of incoming/outgoing signal for the detector;

defined for the angle of incidence/angle of emergence of the detector; theta_mAzimuth of the detector/source;

is the incident/exit angle; v_waterWhich is the velocity of the water, is,

to combine responses

4. The method for determining the acquisition parameters based on the long base distance according to claim 3, wherein the obtaining the base distance corresponding to each frequency in the preset frequencies by using a preset phased array combination model comprises:

5. The method according to claim 4, wherein the setting the group inner distance of the combination unit corresponding to each frequency for the long base distance comprises:

6. The method of claim 1, wherein the long base distance-based acquisition parameter is determined,

wherein the reduction formula comprises:

wherein r is_jiThe original group internal distance of the detector/seismic source combination unit, j is the number of frequency, i is the number of combination unit, min (r)_ji) Is the minimum group inner distance, max (r) in the original group inner distances_ji) The method is characterized in that the method is a maximum group inner distance in an original group inner distance, N is the number of original detector/seismic source combination units, 1/M is the ratio of reduction workload, M is an integral multiple of 2, M is 2, 4, 8, 16.

7. The method of claim 6, wherein said reducing the number of combined elements according to the spatial distribution of said detectors/sources by a predetermined rule to obtain a reduced distribution of combined detector/source elements, further comprises:

after the distribution of all the reduced frequency detector/seismic source combination units is obtained, rearranging the reduced frequency detector/seismic source combination units;

the distribution of reduced detector/source combination units is derived from the rearranged reduced detector/source combination units.

8. An apparatus for long base distance based acquisition parameter determination, the apparatus comprising: a memory and a processor; the method is characterized in that:

9. The device for determining the acquisition parameters based on the long base distance as claimed in claim 8, wherein the obtaining the long base distance corresponding to each frequency in the preset frequencies of the work area to be processed comprises:

10. The apparatus of claim 9, wherein the phased array combined model comprises:

wherein the content of the first and second substances,

a response for the phased array combining unit; n is the number of the combined units of the detector/the seismic source; m is the sequence number of the detector/seismic source in the combined unit; the combined unit is a detector/seismic source combined unit consisting of n detectors/seismic sources; d_mEnergy intensity of the combined unit of the detector; r is_mThe distance from each detector/seismic source combination unit to the center of the combination unit; theta₀Azimuth of incoming/outgoing signal for the detector;

is the incident/exit angle; v_waterWhich is the velocity of the water, is,

to combine responses

11. The apparatus for determining acquisition parameters based on long base distance according to claim 10, wherein the obtaining of the base distance corresponding to each frequency in the preset frequencies by using the preset phased array combination model comprises:

12. The apparatus according to claim 11, wherein the setting, for the long base distance, the group inner distance of the combination unit corresponding to each frequency includes:

13. The long base distance based acquisition parameter determination apparatus according to claim 8,

wherein the reduction formula comprises:

wherein r is_jiThe original group inner distance of the detector/seismic source combination unit, j is the number of the frequency, i is the number of the combination unit, and min (r)_ji) Is the minimum inter-group distance, max (r), of the original inter-group distances_ji) The method is characterized in that the method is a maximum group inner distance in an original group inner distance, N is the number of original detector/seismic source combination units, 1/M is the ratio of reduction workload, M is an integral multiple of 2, M is 2, 4, 8, 16.

14. The apparatus for determining acquisition parameters based on long base distance according to claim 13, wherein said reducing the number of combined units according to the spatial distribution of the detectors/sources by a predetermined rule to obtain a reduced distribution of the combined detectors/sources, further comprises: