阅读说明：本技术 一种地震勘探***阵列远场子波模拟方法、脸谱评价方法及装置 (Seismic exploration air gun array far-field wavelet simulation method, facial makeup evaluation method and device ) 是由 张栋 刘怀山 邢磊 尉佳 王建花 于 2019-08-26 设计创作，主要内容包括：本发明涉及一种地震勘探气枪阵列远场子波模拟方法、脸谱评价方法及装置。地震勘探气枪阵列远场子波模拟方法包括步骤S10、设置范德瓦耳斯气体方程的初始变量,计算气室内气体初始物质的量；步骤S20、获取关于气泡的数据；步骤S30、水听器记录来自气枪的远场子波信号,以获取单气枪远场子波模型；步骤S40、重复步骤S20和S30,直到t＞t<Sub>max</Sub>,最终得到时间长度t<Sub>max</Sub>的单气枪远场子波模型；步骤S50、气枪阵列激发；步骤S60、建立气枪阵列远场子波模型。它可针对不同的海洋地震勘探目的,对设计的气枪阵列进行定量分析,不断优化震源的组合模式,达到高精度地震勘探要求。(The invention relates to a seismic exploration air gun array far-field wavelet simulation method, a facial makeup evaluation method and a device. The seismic exploration air gun array far-field wavelet simulation method comprises the steps of S10, setting initial variables of van der Waals gas equations, and calculating the amount of initial substances of gas in a gas chamber; step S20, acquiring data about the bubble; step S30, recording far-field wavelet signals from the air gun by the hydrophone to obtain a single air gun far-field wavelet model; step S40, repeating steps S20 and S30 until t > t max Finally, the time length t is obtained max The single air gun far field sub-wave model; step S50, exciting an air gun array; and step S60, establishing an air gun array far-field wavelet model. The air gun array can be quantitatively analyzed aiming at different marine seismic exploration purposes, the combined mode of the seismic sources is continuously optimized, and the high-precision seismic exploration requirement is met.)

1. A seismic exploration air gun array far-field wavelet simulation method comprises the following steps:

step S10, setting the initial variable of van der Waals gas equation, and calculating the amount m of the initial gas in the gas chamber by using van der Waals gas state equation_g0；

Step S20, acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles; and obtaining variable values related to the bubbles at the next moment;

step S30, the hydrophone records far-field wavelet signals from the air gun, and the far-field wavelet signals are the superposition of direct waves and seismic source ghost reflection signals to obtain a single air gun far-field wavelet model;

step S40, repeating steps S20 and S30 until t > t_maxFinally, the time length t is obtained_maxThe single air gun far field sub-wave model;

s50, establishing an air gun array, exciting the air gun array, and recording signals by using a hydrophone;

and step S60, establishing an air gun array far-field wavelet model.

2. The method for simulating far-field wavelets of a seismic exploration air gun array according to claim 1, wherein: the initial variables in step S10 include: standard atmospheric pressure P_atmReference pressure constant P_conSea water density rho, gravity acceleration g, air gun sinking depth h and bubble hydrostatic pressure P_∞＝P_atm+ ρ gh, throttling coefficient τ, throttling power exponent ζ, release ratio η, heat transfer coefficient k, circumferential ratio π, van der Waals correction amounts a and b, and constant specific heat capacity C_V，mSpecific heat capacity at constant pressure C_P，mConstant of universal gas R_g＝C_P，m-C_V，mTemperature T of seawater_wSea water sound wave velocity V_seaSea surface reflection coefficient R_sWavelet time length t_maxSampling interval delta t, air gun air chamber volume V_gAir gun working pressure P_gInitial temperature T of air chamber of air gun_g0＝T_w*(1+P_g/P_con) Initial volume V of air gun air chamber releasing air to generate bubbles_b0，V_b0Has an initial value of V_gThe initial radius of the bubble is

3. The method for simulating far-field wavelets of a seismic exploration air gun array according to claim 2, wherein: the step S20 is

Obtaining the temperature change rate in the air bubble by using a quasi-static open thermodynamic system equation

Wherein: v_bIs the gas volume in the bubble, the initial volume V_b0，

wherein: m is_gIs the amount of gas material in the gas chamber, and its initial value is m_g0，m_bIs the amount of gas material in the bubble, and its initial value is m_b0，P_ggIs the pressure of the gas chamber, and has a value of

Acquiring acceleration of bubble wall by using fluid motion equation at bubble wall

Wherein:

Wherein

According to Taylor series expansion, acquiring the radius R of the bubble_b，newParticle velocity at bubble wallAnd the volume V of the bubbles_b，new；

Obtaining the amount m of gas substances in the next time bubble_b，newTemperature T_b，newAnd the amount m of the gaseous substance in the gas chamber_g，newThe expressions are respectively

Calculating the gas pressure P within the bubble using the van der Waals gas equation of state_bAnd the pressure P of the air chamber_ggThe expressions are respectively

Using Herring formula

4. The method for simulating far-field wavelets of a seismic exploration air gun array according to claim 3, wherein: the single airgun far-field wavelet model in the step S30 is:

D₁is the distance between the air gun and the hydrophone, D₂Is the distance between the air gun image and the hydrophone,

5. The method for simulating far-field wavelets of the seismic exploration air gun array according to claim 4, wherein the method comprises the following steps: in the step S50, the pressure wave fields of the air gun arrays from different air guns are designed to interact with each other, the pressure field at the hydrophone position is the superposition of the direct wave pressure fields generated by all the air guns and the pressure field reflected by the sea surface, and the effective hydrostatic pressure at the ith bubble is:

6. The method of claim 5, wherein the far field wavelet of the seismic exploration air gun array is simulated by the following steps: the far-field wavelet model of the air gun array in the step S60 is as follows:

7. A seismic exploration air gun array far-field wavelet simulation device is characterized by comprising:

the van der Waals gas equation initial variable setting module is used for setting the initial variable of the van der Waals gas equation;

the quantity acquisition module of the initial gas substance in the gas chamber is used for calculating the quantity m of the initial gas substance in the gas chamber by utilizing the van der Waals gas state equation_g0；

The bubble data acquisition module is used for acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles;

a hydrophone for recording far-field wavelet signals from the air gun;

the single-air-gun far-field wavelet model establishing module is used for establishing a single-air-gun far-field wavelet model according to far-field wavelet signals recorded by the hydrophone;

the single-air-gun far-field wavelet model building module is used for repeatedly building a single-air-gun far-field wavelet model within a certain time length and finally building a single-air-gun far-field wavelet model within a certain time length;

the air gun array excitation module is used for exciting the air gun array after the air gun array is established;

and the air gun array far-field wavelet model establishing module is used for establishing an air gun array far-field wavelet model.

8. A method for evaluating a far-field wavelet facial makeup of a seismic exploration air gun array, which is characterized by comprising the method for simulating the far-field wavelet of the seismic exploration air gun array according to any one of the claims 1 to 6, and further comprising the following steps:

s70, simulating a plane square matrix and a plane long matrix by using an air gun array far-field wavelet model, simultaneously exciting a vertical gun array and delaying to excite a far-field wavelet space wave field of the four arrays of the vertical gun array;

and step S80, performing time-frequency domain quantitative analysis on the far-field wavelet space wave fields of the four gun arrays obtained through simulation in the form of the air gun wavelet facebook according to the air gun array wavelet evaluation parameters.

And step S90, evaluating the air gun array and screening the optimal air gun array.

9. The method of claim 8, wherein the method comprises the following steps: in the step S90, whether the air gun array seismic source meets the exploration requirement is mainly considered whether the excitation energy, the wavelet amplitude spectrum, the initial bubble ratio, and the directivity meet the requirement, and the preferable criteria are as follows: in a specific pass-band, the larger the excitation energy is, the better the excitation energy is, and the pressure and the capacity of the air gun determine the excitation energy; the amplitude spectrum of the wavelet is smooth, the low and high frequency components are rich, the low frequency energy is strong, the effective bandwidth is achieved, and the trap effect is effectively inhibited; the initial bubble ratio is used for measuring important parameters of wavelet quality, the larger the initial bubble ratio is, the higher the signal-to-noise ratio of the air gun array is, and the low-frequency bubble pulse is strongly inhibited; the weaker the directivity of the air gun array is, the more advantageous for marine seismic exploration, an important principle of preferring far-field wavelets is that the wavelets are not affected by the array directivity to some extent.

10. A seismic exploration air gun array far-field wavelet facial makeup evaluation device is characterized in that: the seismic exploration air gun array far-field wavelet simulation device comprising the seismic exploration air gun array far-field wavelet simulation device as claimed in claim 7 or 8, further comprising:

the far field wavelet space wave field simulation module is used for simulating a plane square array and a plane long array by using an air gun array far field wavelet model, simultaneously exciting a vertical gun array and delaying to excite the far field wavelet space wave field of the vertical gun array;

the quantitative analysis module is used for carrying out time-frequency domain quantitative analysis on far-field wavelet space wave fields of the four gun arrays obtained through simulation in the form of air gun wavelet faceplates according to the air gun array wavelet evaluation parameters;

and the evaluation screening module is used for evaluating the air gun array and screening the optimal air gun array.

Technical Field

The invention relates to the field of seismic exploration, in particular to a seismic exploration air gun array far-field wavelet simulation method, a facial makeup evaluation method and a device.

Background

The existing evaluation indexes of the air gun array comprise a zero peak value, a peak value, a bubble period, a primary bubble ratio, a wavelet spectrum, a frequency bandwidth for suppressing ghost reflection, a spectrum smoothness degree, low-frequency energy, a trapped wave point spectrum energy, gun array directivity and the like, wherein the zero peak value, the peak value, the bubble period and the primary bubble ratio in the evaluation indexes are only specific to a single far-field wavelet and cannot embody the distribution characteristics of the far-field wavelet in a three-dimensional space. The waveform structure and the distribution change rule of the far-field wavelet are important parameters for evaluating an air gun seismic source, the waveform shape is the comprehensive reflection of response parameters such as amplitude, phase and frequency, the change of the waveform directly influences the change of each parameter of the wavelet, the main parameters comprise the number, height, waveform lifting, concave-convex, extreme points, inflection points and the like, the existing evaluation indexes cannot effectively identify the waveform shape of the far-field wavelet, the continuity of the wavelet with different vertical incident angles is difficult to judge, the transverse fine changes of the wavelet with different offset distances cannot be reflected, and particularly under the condition of weak energy, the frequency resolution of the far-field wavelet with different vertical incident angles cannot be distinguished.

Disclosure of Invention

The invention aims to provide a far-field wavelet simulation method, a face spectrum evaluation method and a device for a seismic exploration air gun array aiming at the problems that evaluation parameters of an air gun wavelet in the prior art, such as zero peak value, bubble period and initial bubble ratio, are only used for a single far-field wavelet and are lack of identification of effective information such as waveform continuity, weak signals, frequency resolution and the like, the designed air gun array is subjected to quantitative analysis aiming at different marine seismic exploration purposes, the combined mode of seismic sources is continuously optimized, and the high-precision seismic exploration requirement is met, and the adopted technical scheme is as follows:

a seismic exploration air gun array far-field wavelet simulation method comprises the following steps:

step S10, setting the initial variable of van der Waals gas equation, and calculating the amount m of the initial gas in the gas chamber by using van der Waals gas state equation_g0；

Step S20, acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles; and obtaining variable values related to the bubbles at the next moment;

step S30, the hydrophone records far-field wavelet signals from the air gun, and the far-field wavelet signals are the superposition of direct waves and seismic source ghost reflection signals to obtain a single air gun far-field wavelet model;

step S40, repeating steps S20 and S30 until t > t_maxFinally, the time length t is obtained_maxThe single air gun far field sub-wave model;

s50, establishing an air gun array, exciting the air gun array, and recording signals by using a hydrophone;

and step S60, establishing an air gun array far-field wavelet model.

Optionally, the initial variables in step S10 include: standard atmospheric pressure P_atmReference pressure constant P_conSea water density rho, gravity acceleration g, air gun sinking depth h and bubble hydrostatic pressure P_∞＝P_atm+ ρ gh, throttling coefficient τ, throttling power exponent ζ, release ratio η, heat transfer coefficient k, circumferential ratio π, van der Waals correction amounts a and b, and constant specific heat capacity C_V，mSpecific heat capacity at constant pressure C_P，mConstant of universal gas R_g＝C_P，m-C_V，mTemperature T of seawater_wSea water sound wave velocity V_seaSea surface reflection coefficient R_sWavelet time length t_maxSampling interval delta t, air gun air chamber volume V_gAir gun working pressure P_gInitial temperature T of air chamber of air gun_g0＝T_w*(1+P_g/P_con) Initial volume V of air gun air chamber releasing air to generate bubbles_b0，V_b0Has an initial value of V_gThe initial radius of the bubble is

Initial velocity of bubble wall

Initial temperature T of bubble_b0Initial value T_b0＝T_g0Bubble initial pressure P_b0，P_b0The initial value is hydrostatic pressure P_∞The amount m of the gaseous substance in the bubble_bInitial value of

Optionally, step S20 is

Obtaining the temperature change rate in the air bubble by using a quasi-static open thermodynamic system equation

Wherein: v_bIs the gas volume in the bubble, the initial volume V_b0，

Is the rate of change of the volume of the bubbles,

is the thermal conversion rate of the gas at the bubble wall and the surrounding water, and the expression:

R_bis the bubble radius, k is the heat transfer coefficient, T_wIs the temperature of the sea water, T_bIs the temperature within the gas bubble and is,

is the gas ejection rate in the air chamber of the air gun, and the expression is as follows:

wherein: m is_gIs the amount of gas material in the gas chamber, and its initial value is m_g0，m_bIs inside the air bubbleAmount of gaseous substance of initial value m_b0，P_ggIs the pressure of the gas chamber, and has a value of

P_bIs the pressure of the bubbles, with an initial value of P_∞；

Acquiring acceleration of bubble wall by using fluid motion equation at bubble wall

Wherein:

determining acceleration of bubble wall

When the acceleration derivative is obtained, the velocity is determined by the wall velocity of the bubble

Much less than the velocity V of sound waves in sea water_seaAnd therefore neglect

Term, then get

Wherein

According to Taylor series expansion, acquiring the radius R of the bubble_b，newParticle velocity at bubble wall

And the volume V of the bubbles_b，new；

Obtaining the amount m of gas substances in the next time bubble_b，newTemperature T_b，newAnd the amount m of the gaseous substance in the gas chamber_g，newThe expressions are respectively

Calculating the gas pressure P within the bubble using the van der Waals gas equation of state_bAnd the pressure P of the air chamber_ggThe expressions are respectively

Using Herring formula

Calculating the floating velocity v of the bubbles_zTo obtain the depth z of the next moment of the bubble_b，new＝h-v_zDt, where h is the air gun setting depth, the bubble hydrostatic pressure changes P_∞＝P_atm+ρgz_b，new。

Optionally, in step S30, the single airgun far-field wavelet model is:

D₁is the distance between the air gun and the hydrophone, D₂Is the distance between the air gun image and the hydrophone,is a time delay.

Optionally, in step S50, the pressure wavefields from different air guns interact with each other, and the pressure at the hydrophone locationThe field is the superposition of direct wave pressure fields generated by all air guns and pressure fields reflected by the sea surface, and the effective hydrostatic pressure at the ith bubble is as follows:

wherein P is_∞Is hydrostatic pressure, Sigma_k≠iΔP_ikIs the sum of the pressures generated by all other air guns in the array, Δ P_ikIs the hydrostatic pressure perturbation that the k bubble acts on the i bubble:

wherein r is_ikIs the distance between the k-th bubble and the i-th bubble when generated, R_kIs the radius of the k-th bubble,

is the velocity of the kth bubble, H_kIs the enthalpy difference of the kth bubble.

Optionally, in step S60, the far-field wavelet model of the air gun array is:

wherein n is the number of air guns, P_i(t) is the ith airgun far-field wavelet model.

A seismic exploration air gun array far-field wavelet simulation device is characterized by comprising:

the van der Waals gas equation initial variable setting module is used for setting the initial variable of the van der Waals gas equation;

the quantity acquisition module of the initial gas substance in the gas chamber is used for calculating the quantity m of the initial gas substance in the gas chamber by utilizing the van der Waals gas state equation_g0；

The bubble data acquisition module is used for acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles;

a hydrophone for recording far-field wavelet signals from the air gun;

the single-air-gun far-field wavelet model establishing module is used for establishing a single-air-gun far-field wavelet model according to far-field wavelet signals recorded by the hydrophone;

the single-air-gun far-field wavelet model building module is used for repeatedly building a single-air-gun far-field wavelet model within a certain time length and finally building a single-air-gun far-field wavelet model within a certain time length;

the air gun array excitation module is used for exciting the air gun array after the air gun array is established;

and the air gun array far-field wavelet model establishing module is used for establishing an air gun array far-field wavelet model.

A seismic exploration air gun array far-field wavelet facial makeup evaluation method is characterized by comprising the seismic exploration air gun array far-field wavelet simulation method, and further comprising the following steps:

s70, simulating a plane square matrix and a plane long matrix by using an air gun array far-field wavelet model, simultaneously exciting a vertical gun array and delaying to excite a far-field wavelet space wave field of the four arrays of the vertical gun array;

and step S80, performing time-frequency domain quantitative analysis on the far-field wavelet space wave fields of the four gun arrays obtained through simulation in the form of the air gun wavelet facebook according to the air gun array wavelet evaluation parameters.

And step S90, evaluating the air gun array and screening the optimal air gun array.

Preferably, whether the air gun array seismic source meets the exploration requirement in step S90 mainly considers whether the excitation energy, the wavelet amplitude spectrum, the initial bubble ratio, and the directivity meet the requirement, and the preferable criteria are as follows: in a specific pass-band, the larger the excitation energy is, the better the excitation energy is, and the pressure and the capacity of the air gun determine the excitation energy; the amplitude spectrum of the wavelet is smooth, the low and high frequency components are rich, the low frequency energy is strong, the effective bandwidth is achieved, and the trap effect is effectively inhibited; the initial bubble ratio is used for measuring important parameters of wavelet quality, the larger the initial bubble ratio is, the higher the signal-to-noise ratio of the air gun array is, and the low-frequency bubble pulse is strongly inhibited; the weaker the directivity of the air gun array is, the more advantageous for marine seismic exploration, an important principle of preferring far-field wavelets is that the wavelets are not affected by the array directivity to some extent.

A seismic exploration air gun array far-field wavelet facial makeup evaluation device is characterized in that: the seismic exploration air gun array far-field wavelet simulation device comprises the following components:

the far field wavelet space wave field simulation module is used for simulating a plane square array and a plane long array by using an air gun array far field wavelet model, simultaneously exciting a vertical gun array and delaying to excite the far field wavelet space wave field of the vertical gun array;

the quantitative analysis module is used for carrying out time-frequency domain quantitative analysis on far-field wavelet space wave fields of the four gun arrays obtained through simulation in the form of air gun wavelet faceplates according to the air gun array wavelet evaluation parameters;

and the evaluation screening module is used for evaluating the air gun array and screening the optimal air gun array.

The invention has the beneficial effects that: aiming at the problems that in the prior art, evaluation parameters of air gun wavelets such as zero peak value, peak-to-peak value, bubble period and initial bubble ratio are only used for a single far-field wavelet and effective information such as waveform continuity, weak signals and frequency resolution is not identified, an evaluation method for simulating an air gun wavelet space wave field based on a van der Waals gas model and establishing a wavelet facial mask is provided, a designed air gun array is subjected to quantitative analysis aiming at different ocean seismic exploration purposes, a combined mode of seismic sources is continuously optimized, and the high-precision seismic exploration requirement is met.

Drawings

FIG. 1 is a schematic flow chart of a seismic exploration air gun array far-field wavelet facial makeup evaluation method according to the present invention;

FIG. 2 is a schematic diagram of single-gun far-field wavelet formation;

FIGS. 3a and b are respectively the single-gun far-field wavelet and the frequency spectrum simulated by the Ziolkowski model;

FIGS. 4a and b are the far-field wavelet and the frequency spectrum of a single gun simulated by Van der Waals model, respectively;

FIGS. 5a and b are far-field wavelet and frequency spectrum of gun array simulated by Van der Waals model, respectively;

FIGS. 6a and b are the far-field wavelet and frequency spectrum of the actual gun array;

FIG. 7 is a schematic diagram of an airgun wavelet simulation observation system;

FIG. 8 is a diagram showing a face (a) long array (b) near-field wavelet (c) far-field wavelet (d) near-field wavelet spectrum (e) far-field wavelet spectrum (f) 0-degree azimuth far-field wavelet (g) 90-degree azimuth far-field wavelet (h) 0-degree azimuth spectrum (i) 0-degree azimuth instantaneous amplitude (j) 0-degree azimuth instantaneous phase (k) 0-degree azimuth instantaneous frequency (l) zero peak (m) peak (n) period (o) initial bubble ratio (p)30Hz energy distribution (q)60Hz energy distribution consisting of 4 single guns with a total capacity of 270cu in long array sinking 5 m;

FIG. 9 is a diagram showing a face (a) square array (b) of a near-field wavelet (c) of a far-field wavelet (d) of a near-field wavelet spectrum (e) of a far-field wavelet spectrum (f) of a 0-degree azimuth far-field wavelet (g) of a 90-degree azimuth far-field wavelet (h) of a 0-degree azimuth spectrum (i) of a 0-degree azimuth instantaneous amplitude (j) of a 0-degree azimuth instantaneous phase (k) of a 0-degree azimuth instantaneous frequency (l) of a zero peak (m) of a 0-degree azimuth instantaneous phase (k) of a period (o) of a bubble ratio (p) of 30Hz energy distribution (q) of 60Hz energy distribution consisting of 4 single guns with a total capacity of 270cu. in a square array;

FIG. 10 is a diagram of a face (a) simultaneously exciting a vertical array with a total capacity of 270cu.in consisting of 4 single guns, (b) a near-field wavelet (c) a far-field wavelet (d) a near-field wavelet spectrum (e) a far-field wavelet spectrum (f) a 0-degree azimuth far-field wavelet (g) a 90-degree azimuth far-field wavelet (h) a 0-degree azimuth spectrum (i) a 0-degree azimuth instantaneous amplitude (j) a 0-degree azimuth instantaneous phase (k) a 0-degree azimuth instantaneous frequency (l) a zero peak value (m) a peak-to-peak value (n) a period (o) a bubble ratio (p)30Hz energy distribution (q)60Hz energy distribution;

fig. 11 is a face spectrum of a delayed excitation vertical array with a total capacity of 270cu.in consisting of 4 single guns (a) a delayed excitation vertical array (b) a near-field wavelet (c) a far-field wavelet (d) a near-field wavelet spectrum (e) a far-field wavelet spectrum (f) a 0-degree azimuth far-field wavelet (g) a 90-degree azimuth far-field wavelet (h) a 0-degree azimuth spectrum (i) a 0-degree azimuth instantaneous amplitude (j) a 0-degree azimuth instantaneous phase (k) a 0-degree azimuth instantaneous frequency (l) a zero peak value (m) a peak-to-peak value (n) a period (o) a bubble ratio (p) a 30Hz energy distribution (q) a 60Hz energy distribution;

Detailed Description

The invention is further illustrated by the following examples:

as shown in FIG. 1, a method for simulating far-field wavelets of a seismic exploration air gun array comprises the following steps:

step S10, setting the initial variable of van der Waals gas equation, and calculating the amount m of the initial gas in the gas chamber by using van der Waals gas state equation_g0；

Step S20, acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles; and obtaining variable values related to the bubbles at the next moment;

step S30, the hydrophone records far-field wavelet signals from the air gun, and the far-field wavelet signals are the superposition of direct waves and seismic source ghost reflection signals to obtain a single air gun far-field wavelet model;

step S40, repeating steps S20 and S30 until t > t_maxFinally, the time length t is obtained_maxThe single air gun far field sub-wave model; as shown in fig. 3a, fig. 3b, fig. 4a and fig. 4b are Ziolkowski single-gun far-field wavelets and van der waals gas single-gun far-field wavelets and frequency spectra, respectively, the bubble oscillation attenuation of the van der waals gas model considering the actual influence factors is faster and closer to the actual situation;

s50, establishing an air gun array, exciting the air gun array, and recording signals by using a hydrophone;

and step S60, establishing an air gun array far-field wavelet model.

Preferably, the initial variables in step S10 include: standard atmospheric pressure P_atmReference pressure constant P_conSea water density rho, gravity acceleration g, air gun sinking depth h and bubble hydrostatic pressure P_∞＝P_atm+ ρ gh, throttling coefficient τ, throttling power exponent ζ, release ratio η, heat transfer coefficient k, circumferential ratio π, van der Waals correction amounts a and b, and constant specific heat capacity C_V，mSpecific heat capacity at constant pressure C_P，mConstant of universal gas R_g＝C_P，m-C_V，mTemperature T of seawater_wSea water sound wave velocity V_seaSea surface reflection coefficient R_sWavelet time length t_maxSampling interval delta t, air gun air chamber volume V_gAir gun working pressure P_gInitial temperature T of air chamber of air gun_g0＝T_w*(1+P_g/P_con) Initial volume V of air gun air chamber releasing air to generate bubbles_b0，V_b0Has an initial value of V_gThe initial radius of the bubble is

Initial velocity of bubble wall

Initial temperature T of bubble_b0Initial value T_b0＝T_g0Bubble initial pressure P_b0，P_b0The initial value is hydrostatic pressure P_∞The amount m of the gaseous substance in the bubble_bInitial value of

Preferably, the step S20 is

Obtaining the temperature change rate in the air bubble by using a quasi-static open thermodynamic system equation

Wherein: v_bIs the gas volume in the bubble, the initial volume V_b0，

Is the rate of change of the volume of the bubbles,

is the thermal conversion rate of the gas at the bubble wall and the surrounding water, and the expression:R_bis the bubble radius, k is the heat transfer coefficient, T_wIs the temperature of the sea water, T_bIs the temperature within the gas bubble and is,is the gas ejection rate in the air chamber of the air gun, and the expression is as follows:

wherein: m is_gIs the amount of gas material in the gas chamber, and its initial value is m_g0，m_bIs the amount of gas material in the bubble, and its initial value is m_b0，P_ggIs the pressure of the gas chamber, and has a value of

P_bIs the pressure of the bubbles, with an initial value of P_∞；

Acquiring acceleration of bubble wall by using fluid motion equation at bubble wall

Wherein:

determining acceleration of bubble wall

When the acceleration derivative is obtained, the velocity is determined by the wall velocity of the bubble

Much less than the velocity V of sound waves in sea water_seaAnd therefore neglect

Term, then get

Wherein

According to Taylor series expansion, acquiring the radius R of the bubble_b，newParticle velocity at bubble wallAnd the volume V of the bubbles_b，new；

Obtaining the amount m of gas substances in the next time bubble_b，newTemperature T_b，newAnd the amount m of the gaseous substance in the gas chamber_g，newThe expressions are respectively

Calculating the gas pressure P within the bubble using the van der Waals gas equation of state_bAnd the pressure P of the air chamber_ggThe expressions are respectively

Using Herring formula

Calculating to obtain the floating velocity v of the bubbles_zTo obtain the depth z of the next moment of the bubble_b，new＝h-v_zDt, where h is the air gun setting depth, the bubble hydrostatic pressure changes P_∞＝P_atm+ρgz_b，new。

Fig. 2 is a schematic diagram of the formation of a single-gun far-field wavelet recorded by a hydrophone, and preferably, the single-air-gun far-field wavelet model in step S30 is:

D₁is the distance between the air gun and the hydrophone, D₂Is the distance between the air gun image and the hydrophone,

is a time delay.

Preferably, in step S50, the pressure wavefields from different air guns interact with each other, and the pressure field at the hydrophone position is the superposition of the direct wave pressure fields generated by all the air guns and the pressure field reflected by the sea surface, and the effective hydrostatic pressure at the ith bubble:

wherein P is_∞Is hydrostatic pressure, Sigma_k≠iΔP_ikIs the sum of the pressures generated by all other air guns in the array, Δ P_ikIs the hydrostatic pressure perturbation that the k bubble acts on the i bubble:

wherein r is_ikIs the distance between the k-th bubble and the i-th bubble when generated, R_kIs the radius of the k-th bubble,

is the velocity of the kth bubble, H_kIs the enthalpy difference of the kth bubble.

Preferably, in step S60, the far-field wavelet model of the air gun array is:

wherein n is the number of air guns, P_i(t) is the ith airgun far-field wavelet model. FIGS. 5a, 5b and FIGS. 6a, 6b are respectively simulation and actual measurement of Van der Waals gas gun array modelsThe far-field wavelet and the frequency spectrum have good simulation effect, and the effectiveness of the model is proved.

A seismic exploration air gun array far-field wavelet simulation device is characterized by comprising:

the van der Waals gas equation initial variable setting module is used for setting the initial variable of the van der Waals gas equation;

the quantity acquisition module of the initial gas substance in the gas chamber is used for calculating the quantity m of the initial gas substance in the gas chamber by utilizing the van der Waals gas state equation_g0；

The bubble data acquisition module is used for acquiring the temperature change rate in the bubbles, the acceleration of the bubble walls, the bubble radius, the particle speed at the bubble walls and the bubble volume; acquiring gas pressure in the bubble and chamber pressure; acquiring the floating speed of bubbles;

a hydrophone for recording far-field wavelet signals from the air gun;

the single-air-gun far-field wavelet model establishing module is used for establishing a single-air-gun far-field wavelet model according to far-field wavelet signals recorded by the hydrophone;

the single-air-gun far-field wavelet model building module is used for repeatedly building a single-air-gun far-field wavelet model within a certain time length and finally building a single-air-gun far-field wavelet model within a certain time length;

the air gun array excitation module is used for exciting the air gun array after the air gun array is established;

and the air gun array far-field wavelet model establishing module is used for establishing an air gun array far-field wavelet model.

As shown in fig. 1, a method for evaluating a far-field wavelet facial mask of a seismic exploration air gun array is characterized by comprising the method for simulating the far-field wavelet of the seismic exploration air gun array, and further comprising the following steps:

s70, simulating a plane square matrix and a plane long matrix by using an air gun array far-field wavelet model, simultaneously exciting a vertical gun array and delaying to excite a far-field wavelet space wave field of the four arrays of the vertical gun array; as shown in the schematic diagram of the air gun wavelet simulated observation system of fig. 7, the air gun seismic source combination is shown in fig. 8a, 9a, 10a and 11a, the position is at the center of fig. 7, the arrangement range of hydrophones is 4kmx4km, and the interval is 100 m; utilizing far-field wavelet space wave fields of four arrays (a plane square array, a plane long array, a simultaneous excitation vertical gun array and a delayed excitation vertical gun array) obtained by simulation; wherein the delayed excitation vertical gun array air gun is sequentially excited from shallow to deep, and is delayed for 2 ms;

step S80, as shown in fig. 8 to 11, performs quantitative analysis of time-frequency domain on the far-field wavelet spatial wave field of the four gun arrays obtained by simulation in the form of the airgun wavelet facial mask according to the airgun array wavelet evaluation parameters.

And step S90, evaluating the air gun array and screening the optimal air gun array.

Whether the air gun array seismic source meets the exploration requirement or not is mainly considered whether the excitation energy, the wavelet amplitude spectrum, the initial bubble ratio and the directivity meet the requirement or not, and the preferred standards are as follows: in a specific pass-band, the larger the excitation energy is, the better the excitation energy is, and the pressure and the capacity of the air gun determine the excitation energy; the amplitude spectrum of the wavelet is smooth, the low and high frequency components are rich, the low frequency energy is strong, the effective bandwidth is achieved, and the trap effect is effectively inhibited; the initial bubble ratio is used for measuring important parameters of wavelet quality, the larger the initial bubble ratio is, the higher the signal-to-noise ratio of the air gun array is, and the low-frequency bubble pulse is strongly inhibited; the weaker the directivity of the air gun array is, the more advantageous for marine seismic exploration, an important principle of preferring far-field wavelets is that the wavelets are to some extent unaffected by the array directivity, which is a goal of the array design. The traditional evaluation parameters only comprise a, b, c, d, e, p and q in the facial spectrogram 8-11, wherein the energy (zero peak value, peak value), initial bubble ratio and bubble period are evaluated by an airgun wavelet recorded in one direction, but not a spatial wave field of the wavelet, and judgment on wavelet energy and frequency change of different azimuth angles is lacked.

It can be seen from fig. 8 b-8 e and 9 b-9 e that the larger the capacity of the air gun is, the larger the bubble period is under the same depth condition, the more the near-field wavelets are not affected by the reflection of the sea surface and the sea bottom, the damped oscillation of the bubble pulse can be clearly seen, the far-field pulse is recorded 500 meters below the array, the pulses generated by the air guns with different capacities interact with each other, the main pulse is enhanced, the bubble pulse is suppressed, and the far-field wavelets and the frequency spectrums of the two arrays are very similar because the recording position is not affected by the array directivity. The wavelet energy of the long array is concentrated in the 90 ° azimuth direction, while the energy of the 0 ° azimuth direction is attenuated, whereas the energy of the square array is nearly isotropic, as shown in fig. 8f-8k and fig. 9f-9 k; the amplitude spectrum of the long matrix shows a strong notching effect, as in fig. 8h, while the notching effect of the amplitude spectrum of the square matrix is effectively suppressed, as in fig. 9 h. At 0 ° azimuth, the wavelet instantaneous amplitude energy of the long array decays rapidly with increasing angle (fig. 8i), and the multi-bubble effect causes the wavelet to produce multiple peaks, resulting in poor continuity of the instantaneous phase (fig. 8j), and thus noisy instantaneous frequency (fig. 8 k). The square array can make up for the deficiency, the energy is enhanced in a large angle range (fig. 9i), the slow change of the phase period shows that the wave field has good continuity (fig. 9j), and as the angle is increased, the main pulse width is reduced, the instantaneous frequency is increased, and the resolution of the wavelet is improved (fig. 9 k); figures 8l-8o and 9l-9o compare the characteristics of zero peak, peak to peak, bubble period and initial bubble ratio for two air gun arrays, the long array having energy centered at 90 deg. azimuthal direction, and the square array having a radiation pattern very similar to an ideal point source under the free surface. Figures 8p-8q and 9p-9q show the energy distribution over a range of angles from 0 deg. to 60 deg., over a range of frequencies (frequencies 30Hz and 60Hz are selected). At 60Hz, the energy of the long array is more concentrated in the 90-degree direction, the energy distribution of the square array is uniform, and compared with the long array seismic source, the square array seismic source is weaker in directivity and more suitable for marine seismic exploration.

For a vertical array with simultaneous excitation, the designed array consists of 4 single guns vertically deployed, with depths of 5m, 8m, 11m, and 14m from top to bottom, respectively, and fig. 10a shows an array with this design, for a vertical array with delayed excitation, the air guns are sequentially excited from top to bottom, and the delay time is related to the speed of sound wave in seawater, as shown in fig. 11 a. FIGS. 10b-10e and 11b-11e show the time and frequency domain information of the near-field and far-field wavelets for these two arrays, with the depth of the airgun affecting the bubble energy, period and frequency (FIGS. 10b, 10e, 11b and 11 e).

As can be seen from fig. 10c and fig. 11c, this delay design can suppress ghost effect, increase the initial bubble ratio, and thus increase the signal-to-noise ratio. The simultaneously excited vertical array was strongly notched in the amplitude spectrum and the delayed array suppressed the notching (fig. 10e, 11 e). The vertical array directivity of simultaneous excitation is perpendicular to the array layout direction (fig. 10f and 10g), in contrast to the delayed vertical array, which can enhance the downward pressure wave within a predetermined angle and attenuate the wavelet energy in other directions (fig. 11f and 11 g). The high frequency components of the delayed vertical array wavefield have a narrower angular range, and therefore, the delayed arrays enhance the high frequency components of the vertical direction spectrum compared to the simultaneously excited vertical arrays (fig. 10h, 11 h).

The aim of the air gun array design is to ensure that the energy is incident perpendicularly and simultaneously avoid radiating energy to any direction. The simultaneous excitation vertical array does not satisfy (fig. 10i), instead the delayed vertical array satisfies this requirement (fig. 11 i). Both arrays showed good instantaneous phase continuity (fig. 10j and 11 j). By adjusting the excitation delay time, the maximum frequency component of each airgun spectrum can be increased and optimized. As can be seen from fig. 10k and 11k, the delayed excitation wavefield has a higher frequency in the vertical direction than in any other direction.

Because the azimuth angle signals emitted by the seismic source array are uniform, the arrangement of the vertical array is beneficial to three-dimensional seismic exploration. Due to the difference in emission time, in fig. 10l, 10m, 11l, 11m, the zero peak and the peak exhibit completely opposite characteristics, while the bubble period and the initial bubble ratio exhibit the same change law (fig. 10n, 10o, 11n, 11 o). At 30Hz, the energy of the delayed excitation array is more concentrated, as shown in FIGS. 10p and 11 p. At 60Hz, the energy in the vertical direction of the delayed excitation array is significantly higher than that of the simultaneous excitation vertical array, and furthermore, as described above, the delayed excitation vertical array is effective in suppressing ghost effects, as shown in fig. 10q and 11 q. Delayed excitation is therefore suitable for marine seismic exploration, compared to a simultaneously excited vertical array.

A seismic exploration air gun array far-field wavelet facial makeup evaluation device is characterized in that: the seismic exploration air gun array far-field wavelet simulation device comprises the following components:

the far field wavelet space wave field simulation module is used for simulating a plane square array and a plane long array by using an air gun array far field wavelet model, simultaneously exciting a vertical gun array and delaying to excite the far field wavelet space wave field of the vertical gun array;

and the quantitative analysis module is used for carrying out time-frequency domain quantitative analysis on the far-field wavelet space wave fields of the four gun arrays obtained by simulation in the form of the air gun wavelet facial makeup according to the air gun array wavelet evaluation parameters.

And the evaluation screening module is used for evaluating the air gun array and screening the optimal air gun array.

While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.