CN104614765A - Design method for enhancing seismic waves to stimulate illumination - Google Patents

Abstract

The invention mainly relates to a design method for enhancing seismic waves to stimulate illumination in a complex structure region. The design method comprises the following steps that (1) exploration area data are collected, a geological model of the complex structure region is established, and a geological target is determined; (2) an artificial seismic source is arranged at the target position, and illumination simulation is conducted through a wave equation forward modeling method; (3) statistics of illumination energy, upwards spread to the ground surface, of the seismic waves is conducted when illumination simulation is conducted; (4) an optimal encryption shot region on the ground surface is determined according to the statistical result of the illumination energy on the ground surface; (5) the main direction of emergence, on the ground surface, of the seismic waves stimulated by a target seismic source is calculated through a poynting vector, and the spread direction of a seismic wave beam stimulated by a phase-controlled seismic source is determined; (6) combined stimulation parameters of the phase-controlled seismic source are designed on the basis of a phase-controlled theory and the theoretical signal-to-noise ratio maximization principle of combined seismic sources; (7) a construction scheme for enhancing the illumination energy provided by the seismic waves for the target on the ground surface in the complex structure region is determined. The design method is good in application effect and can reduce the collection cost.

Description

A kind ofly strengthen the method for designing that seismic event excites illumination

Technical field

The present invention relates to a kind of seismic exploration technique in oil, gas prospecting field, be applied to complex structural area enhancing seismic event and excite the recording geometry of illumination to design.

Background technology

Along with petroleum natural gas exploration constantly extends to complex structural area, the seismic geological codition that oil-gas exploration faces also becomes increasingly complex, main manifestations is that surface relief is violent, top layer velocity variations is large, subsurface geological structure is complicated, exploration targets is buried deeply, high speed nappe growth etc., causes seismic wave field complexity, geologic objective difficult in imaging.

The conventional field earthquake-capturing recording geometry based on HORIZONTAL LAYERED MEDIUM WITH HIGH ACCURACY and horizontal earth's surface hypothesis designs, and cannot meet the requirement of complex structural area oil-gas exploration and development.In order to improve reliability and the validity of complex structural area earthquake data acquisition, Some Comments On Geophysical Work person proposes the recording geometry optimal design based on geologic model and seismic forward modeling simulation.By following the trail of or Wave Equation Numerical the seismic ray of geologic model, the illumination of field layout to subsurface reflective boundary and the position of specular dead can be determined, thus instruct field layout to design.

Seismic illumination analytical technology carrys out Forecast and evaluation collection effect by Analysis of Forward Modeling underground lighting energy distribution, and then optimizes acquisition parameter.At present, seismic illumination analytical technology is divided into two large classes: the ray illumination analysis based on ray theory and the wave equation illumination analysis based on wave theory.Due to the inherent shortcoming (high-frequency approximation and ray blind area) of ray theory, ray tracing illumination analysis is only applicable to the little naive model of lateral variation in velocity.But wave equation illumination analysis to rate pattern without any restriction, and the energy distribution of seismic wave propagation process in underground medium can be reflected more truly, for recording geometry optimal design provides favourable guarantee.Dong Liangguo etc. (2006) are according to wave equation lighting result, propose and utilize illumination statistic law and wave field to upload method, determine for the ground optimum of exploration targets shot point encryption scope, tentatively achieve from by illuminance evaluation concept examining system to the transformation carrying out recording geometry optimal design.Zhao Hu etc. (2010) are by analyzing the intensive shot point Forward modelling result towards complex structure, determine zone of interest illumination energy minimum position, and carry out local shot point encryption, automatically try to achieve the highest shot point set of zone of interest illumination energy homogeneity according to energy uniformity judgment criterion.Zhu Jinpings etc. (2011) determine based on three dimension wave equation in wavelets illumination analysis and excite scope towards the favourable of exploration targets, have developed the 3-d seismic exploration recording geometry Optimization Design towards exploration targets.

Conventional illumination analysis only considers the illumination of focus shot point to underground medium, and does not consider the inclination angle of underground structure.For this reason, people also been proposed earthquake Directional illumination analysis method, namely by Local plane wave decomposition operator (as Poynting vector, wavelet transformation, window Fourier transform etc.), simulated earthquake wave field is decomposed into the plane wave of the different direction of propagation, then calculates the earthquake directional lighting of different directions (combination).But earthquake Directional illumination analysis just by quantitatively calculating the seismic event of all directions to the lighting condition of target geological body, thus filters out and to throw light on good predominant direction, the but not substantive illumination energy improving target geological body to target geological body.

In fact, as far back as 20 century 70s, American Oil Co. has carried out seismic beam first time and has formed test in Tulsa area, confirm the relation of seismic beam direction propagation direction and snooze interval, has pulled open the prelude of source pattern directivity characteristics research.Hu Qiyu (1981) describes principle and the method for Forming The Directional Beam By Pre-set Time Sequence Shot of Equal Interval Sources Array in detail.Jiang Tao etc. (2008,2012) quantitative test has been carried out to the directed seismic signal of phased focus, respectively by numerical simulation and field test, show that phased focus excites combination focus relative to routine simultaneously, the conclusion that its reflection wave signal signal to noise ratio (S/N ratio) significantly improves, and propose the time domain seismic beam formation method based on receiving array.Preferably parameters such as () focus number, element intervals, explosive source orientation excite in quantitative test and the application in seismic exploration etc. thereof to excite quantitative test and Analysis signal-to-noise ratio (SNR), source pattern shooting parameter for the seismic combination under condition of flatly expressing one's feelings, (2011), Liu Fulie etc. (2013) such as Wang Renfu etc. (2011), Xu Feng, Cai Jiyan (2013) has carried out discussing in detail respectively in its article.Combination source wavefield orientation method is extended to arbitrary relief surface by Gong Xiangbo etc. (2014), utilizes the time delay of Coordinate Rotating Algorithm calculation combination epicenter excitation, for the combination focus guided wave field excitation in complicated relief surface situation provides theoretical foundation.Outdoors practice and theoretical research all prove, greatly can improve the irradiation energy on the signal to noise ratio (S/N ratio) of collection data and seismic beam direction propagation direction based on the source pattern of phase compress.

Integrate, the earthquake-capturing at present for complex structural area is solve from two aspects respectively, and one is determine at earth's surface regional area encryption shot point, to increase the illumination energy to zone of interest by illumination simulation; Two is excite position, by the shooting on group of multiple shot point, to increase the seismic wave energy to underground propagation in each of earth's surface.The present invention is for complex structural area, underground equally, as the stratum of steep dip, tomography, on be covered with the destination layer etc. of high-velocity anomaly body, by the illumination analog result of seismic event, both the region of earth's surface encryption shot point had been calculated, also calculate the direction that seismic event is propagated to underground zone of interest simultaneously, thus realization to complex structural area zone of interest seismic event the most favourable with the most effectively excite design.

Summary of the invention

(1) goal of the invention

The object of this invention is to provide a kind of seismic observation system method for designing exciting illumination at complex structural area enhancing seismic event.Encryption big gun thought is seen in change for it and phased source pattern technology combines with seismic illumination analysis, based on the seismic illumination analysis of wave equation, at target location earthquake-wave-exciting, upload method and earth's surface directional statistics by wave field, obtain source pattern parameter and the encryption big gun region larger to target geological body illumination contributions.Arrange encryption shot point in encryption big gun region, the advantage energy simultaneously utilizing phased source pattern to guarantee that each encrypts big gun can be concentrated and propagate to target geological body.Not only increase the launching efficiency of focus like this, and target geological body can be made to obtain better illuminating effect, improve image quality.The method is that complex structural area provides more effective, more economical recording geometry comprehensive designing method.

(2) technical scheme

A kind ofly strengthen the method for designing that seismic event excites illumination, adopt the design standards of theoretical signal to noise ratio (S/N ratio) maximization principle as source pattern parameter of phase compress and combination focus, be the design standards of element interval and focus number, other optimal design standards improved, belong to the method series together; It is not limited to flatly express one's feelings condition, goes for the region of complicated earth surface complex structure; Its concrete steps are as follows:

A. according to available data, that sets up complex structural area just drills Geological Model, and determines geologic objective; Collect the geologic information in work area, seismic data, survey the data of well logging, drilling well, comprehensively known interpretation results and geological knowledge, set up the accurate geologic model in work area by modeling software, determine geologic objective, be i.e. geologic objective position, shape and scope in a model;

B. in the man-made explosion of buried target location arrangements, Wave equation forward modeling method is adopted to carry out illumination simulation; According to the feature of target in geologic model, at target location s=(x _s, z _s) place man-made explosion, i.e. target focus, the seismic wave field propagated in underground medium by omnidistance Acoustic Wave-equation forward simulation, calculate lighting result I (x, the z at target focus (x, z) place in a model; S), it is defined as follows:

$I(x,z;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}P(x,z,t;s)P(x,z,t;s)---\left(1\right)$

Wherein, P (x, z, t; S) for (x, z) place in model by the seismic wave field of the t of target epicenter excitation, T is the T.T. that wave field is propagated;

C., while illumination simulation, on earth's surface, statistically seismic wave upwards propagates into the illumination energy on earth's surface; Throw light in stepb while simulation, statistically sheet lighting energy, throw light on statistics T _surfcan be expressed as:

$I_{\mathrm{surf}}=I(x,z_0;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}p(x,z_0,t;s)p(x,z_0,t;s)---\left(2\right)$

Wherein, I (x, z ₀; S) be the illumination energy at each point place, earth's surface, p (x, z _0,t; S) be the seismic wave field propagating into earth's surface of t target epicenter excitation, (x, z ₀) represent landscape position coordinate; The principle of reciprocity of base area seismic wave propagation, zone of interest is arranged focus carries out illumination analysis, if arrange focus in the region that earth's surface illumination energy is strong, this zone of interest just can be made to reach optimal illumination;

D. the encryption big gun region of earth's surface the best is determined according to illumination energy statistics; According to the earth's surface illumination energy statistics I obtained in step C _surf, using the mean value of earth's surface illumination energy as energy threshold I _ts, earth's surface illumination energy is defined as exciting scope for ground the best of this subsurface geology target higher than this energy threshold region, namely encrypts big gun region; If energy threshold is excessive, easily causes best encryption big gun region too small, reduce acquisition quality and imaging precision; If energy threshold is too small, the best encryption big gun region determined can be excessive, causes unnecessary cost waste; Therefore, in actual production process, the selection of energy threshold the requirement of integrated exploration cost and acquisition quality on this basis can do further adjustment;

E., while illumination simulation, utilize Poynting vector to calculate target epicenter excitation seismic event in the principal direction of earth's surface outgoing, determine the direction of propagation of phased epicenter excitation seismic beam; The computing formula of Poynting vector P in sound wave seismic wave field:

P＝-vp (3)

Wherein, v is velocity, and p is acoustic pressure, stress; In the computation process of step B, utilize the Kinematic parameters of earth's surface first arrival seismic event, speed and the components of stress, adopt formula (3) to calculate earth's surface Poynting vector; In order to calculate the direction of earth's surface Poynting vector, if unit vector n=vertically downward (0,1) is reference direction, according to the cosine law, by earth's surface Poynting vector P (x, z ₀, t ₀; S) with the angle theta of unit vector n _u(x, z ₀; S) first arrival seismic event is defined as at earth's surface each point (x, z ₀) exit direction:

${\mathrm{\θ}}_u(x,z_0;s)=\arccos \frac{P(x,z_0,t_0;s)\·n}{\left|P(x,z_0,t_0;s)\right|}---\left(4\right)$

Wherein, earth's surface Poynting vector P (x, z ₀, t ₀; S)=-v (x, z ₀, t ₀; S) p (x, z ₀, t ₀; S), t ₀for the time of arrival of earth's surface primary wave; The exit direction of the primary wave of earth's surface diverse location can be calculated by (4) formula; According to reciprocity principle, the direction of phased source pattern earthquake-wave-exciting bundle is the opposite direction of the primary wave direction of propagation, therefore phased source pattern parameter (direction of earthquake-wave-exciting bundle) θ _dcan be expressed as:

θ _d＝π-θ _u(5)

F., based on phase compress and the theoretical signal to noise ratio (S/N ratio) maximization principle combining focus, on the basis of the acquired phased focus seismic beam direction of propagation, best focus element interval and focus number is designed; According to radar array phase compress, based on horizontal earth's surface uniform dielectric, obtain the direction factor F (θ) combining epicenter excitation wave field:

$F\left(\mathrm{\θ}\right)=\frac{\sin [n(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}{n\sin [(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}---\left(6\right)$

Wherein: n is focus number, d is focus element interval, and θ is the deflection (θ=θ of seismic wave propagation _d), k is wavelet wave number, and β is the phase differential of wavelet between adjacent sources;

The seismic event that phased focus produces has directivity, its strongest direction θ _maxbe called directionally seismic wave direction or main beam direction; To make the seismic event of combination epicenter excitation at θ _maxdirection is propagated the strongest, namely makes:

kd sinθ+β＝0 (7)

The seismic wave propagation deflection obtained according to relation (β=2 π f τ) and the step e of the mistiming between phase delay and focus again obtains the delay time T between adjacent combination focus:

τ＝-kdsinθ/2πf ₀＝-dsinθ/v ₀＝-dsinθ _d/v ₀(8)

Wherein: f ₀for the dominant frequency of seismic wavelet, v ₀for surface materials speed;

The theoretical signal to noise ratio (S/N ratio) of combination focus is maximized the foundation as evaluation and composite design parameter, is finally determined element interval and the focus number of source pattern by numerical simulation;

G. determine that complex structural area strengthens the arrangement and method for construction of seismic event to the illumination energy of objective body on earth's surface, phased focus is arranged at equal intervals in the encryption big gun region that step D optimizes, the source pattern shooting parameter corresponding with encryption big gun region adopting step F to obtain, completes the recording geometry optimal design of complex structural area based on geologic objective.

Further, the exploratory area geologic model of setting up described in steps A can be that different modeling softwares realizes, and it is applicable to two dimensional model and is also applicable to three-dimensional model.

Further, the Wave equation forward modeling method described in step B can adopt one-way wave equation, omnidistance ACOUSTIC WAVE EQUATION, viscoelastic wave equation or elastic wave wave equation to carry out forward simulation.

Further, the illumination energy statistical method described in step C can be at earth's surface diverse location earthquake-wave-exciting, adds up the illumination energy of each focus in buried target position, and the method can find out the earth's surface encryption big gun region best to underground target illumination.

Further, the mean value of what the encryption big gun regional choice standard of the earth's surface the best described in step D adopted is earth's surface general ambient light energy; Threshold value also can be 10% ~ 20% of illumination energy maximal value, and this is completely desirable when illumination energy distribution in earth's surface is more smooth.

Further, the exit direction of calculating first arrival seismic event on earth's surface described in step e, can be realized by additive method, comprises Radon transform, window Fourier transform, wavelet transformation and local slowness analysis technology; For increasing antimierophonic ability, when asking for first arrival seismic event exit direction, can add up the exit direction within the scope of the timing window from primary wave due in, namely window is not more than single Wavelet Duration T _winterior average exit direction.

(3) beneficial effect

The present invention compared with prior art, it has following beneficial effect: a kind of of the present invention's proposition strengthens the method for designing that seismic event excites illumination, combine to become and see encryption big gun thought, phased source pattern technology and seismic illumination analytical technology, be a kind of comprehensive method for designing, greatly can improve quality and the imaging precision of the earthquake-capturing data of complex structural area.Present invention uses based on wave equation seismic illumination analytical technology, can be good at adapting to the violent velocity variations in complex area, obtain the energy distribution of seismic event in underground medium exactly.The principal direction that present invention employs the surface seismic ripple outgoing obtained based on Poynting vector determines to combine the direction of propagation of focus seismic beam, ensure that the energy of each encryption focus focuses on to geologic objective, improve the illumination energy of seismic event to geologic objective to greatest extent.The phased source pattern technology that the present invention adopts, while exceeding increase seismic source energy, can improve the launching efficiency of focus, the signal to noise ratio (S/N ratio) gathering data and image quality.In a word, the present invention is that the oil-gas exploration of complex structural area provides a kind of more effective, more economical recording geometry comprehensive designing method.

Accompanying drawing explanation

Fig. 1 is overall flow schematic diagram of the present invention.

Fig. 2 is earth's surface of the present invention directional statistics schematic diagram.

Embodiment

As shown in Figure 1, a kind ofly strengthen the method for designing that seismic event excites illumination, adopt the design standards of theoretical signal to noise ratio (S/N ratio) maximization principle as source pattern parameter of phase compress and combination focus, be the design standards of element interval and focus number, other optimal design standards improved, belong to the method series together; It is not limited to flatly express one's feelings condition, goes for the region of complicated earth surface complex structure; Its concrete steps are as follows:

A. according to available data, that sets up complex structural area just drills Geological Model, and determines geologic objective; Collect the geologic information in work area, seismic data, survey the data of well logging, drilling well, comprehensively known interpretation results and geological knowledge, set up the accurate geologic model in work area by modeling software, determine geologic objective, be i.e. geologic objective position, shape and scope in a model;

B. in the man-made explosion of buried target location arrangements, Wave equation forward modeling method is adopted to carry out illumination simulation; According to the feature of target in geologic model, at target location s=(x _s, z _s) place man-made explosion, and target focus, the seismic wave field propagated in underground medium by omnidistance Acoustic Wave-equation forward simulation, calculate lighting result I (x, the z at target focus (x, z) place in a model; S), it is defined as follows:

$I(x,z;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}P(x,z,t;s)P(x,z,t;s)---\left(1\right)$

Wherein, P (x, z, t; S) for (x, z) place in model by the seismic wave field of the t of target epicenter excitation, T is the T.T. that wave field is propagated;

C., while illumination simulation, on earth's surface, statistically seismic wave upwards propagates into the illumination energy on earth's surface; Throw light in stepb while simulation, statistically sheet lighting energy, throw light on statistics I _surfcan be expressed as:

$I_{\mathrm{surf}}=I(x,z_0;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}p(x,z_0,t;s)p(x,z_0,t;s)---\left(2\right)$

Wherein, I (x, z ₀; S) be the illumination energy at each point place, earth's surface, p (x, z ₀, t; S) be the seismic wave field propagating into earth's surface of t target epicenter excitation, (x, z ₀) represent landscape position coordinate; The principle of reciprocity of base area seismic wave propagation, zone of interest is arranged focus carries out illumination analysis, if arrange focus in the region that earth's surface illumination energy is strong, this zone of interest just can be made to reach optimal illumination;

D. the encryption big gun region of earth's surface the best is determined according to illumination energy statistics; According to the earth's surface illumination energy statistics I obtained in step C _surf, using the mean value of earth's surface illumination energy as energy threshold I _ts, earth's surface illumination energy is defined as exciting scope for ground the best of this subsurface geology target higher than this energy threshold region, namely encrypts big gun region; If energy threshold is excessive, easily causes best encryption big gun region too small, reduce acquisition quality and imaging precision; If energy threshold is too small, the best encryption big gun region determined can be excessive, causes unnecessary cost waste; Therefore, in actual production process, the selection of energy threshold the requirement of integrated exploration cost and acquisition quality on this basis can do further adjustment;

E., while illumination simulation, utilize Poynting vector to calculate target epicenter excitation seismic event in the principal direction of earth's surface outgoing, determine the direction of propagation of phased epicenter excitation seismic beam; The computing formula of Poynting vector P in sound wave seismic wave field:

P＝-vp (3)

Wherein, v is velocity, and p is acoustic pressure, stress; In the computation process of step B, utilize the Kinematic parameters of earth's surface first arrival seismic event, speed and the components of stress, adopt formula (3) to calculate earth's surface Poynting vector; As shown in Figure 2, in order to calculate the direction of earth's surface Poynting vector, if unit vector n=vertically downward (0,1) is reference direction, according to the cosine law, by earth's surface Poynting vector P (x, z ₀, t ₀; S) with the angle theta of unit vector n _u(x, z ₀; S) first arrival seismic event is defined as at earth's surface each point (x, z ₀) exit direction:

${\mathrm{\θ}}_u(x,z_0;s)=\arccos \frac{P(x,z_0,t_0;s)\·n}{\left|P(x,z_0,t_0;s)\right|}---\left(4\right)$

Wherein, earth's surface Poynting vector P (x, z ₀, t ₀; S)=-v (x, z ₀, t ₀; S) p (x, z ₀, t ₀; S), t ₀for the time of arrival of earth's surface primary wave; The exit direction of the primary wave of earth's surface diverse location can be calculated by (4) formula; According to reciprocity principle, the direction of phased source pattern earthquake-wave-exciting bundle is the opposite direction of the primary wave direction of propagation, therefore phased source pattern parameter (direction of earthquake-wave-exciting bundle) θ _dcan be expressed as:

θ _d＝π-θ _u(5)

F., based on phase compress and the theoretical signal to noise ratio (S/N ratio) maximization principle combining focus, on the basis of the acquired phased focus seismic beam direction of propagation, best focus element interval and focus number is designed; According to radar array phase compress, based on horizontal earth's surface uniform dielectric, obtain the direction factor F (θ) combining epicenter excitation wave field:

$F\left(\mathrm{\θ}\right)=\frac{\sin [n(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}{n\sin [(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}---\left(6\right)$

Wherein: n is focus number, d is focus element interval, and θ is the deflection (θ=θ of seismic wave propagation _d), k is wavelet wave number, and β is the phase differential of wavelet between adjacent sources;

The seismic event that phased focus produces has directivity, its strongest direction θ _maxbe called directionally seismic wave direction or main beam direction; To make the seismic event of combination epicenter excitation at θ _maxdirection is propagated the strongest, namely makes:

kd sinθ+β＝0 (7)

The seismic wave propagation deflection obtained according to relation (β=2 π f τ) and the step e of the mistiming between phase delay and focus again obtains the delay time T between adjacent combination focus:

τ＝-kd sinθ/2πf ₀＝-dsinθ/v ₀＝-dsinθ _d/v ₀(8)

Wherein: f ₀for the dominant frequency of seismic wavelet, v ₀for surface materials speed;

The theoretical signal to noise ratio (S/N ratio) of combination focus is maximized the foundation as evaluation and composite design parameter, is finally determined element interval and the focus number of source pattern by numerical simulation;

G. determine that complex structural area strengthens the arrangement and method for construction of seismic event to the illumination energy of objective body on earth's surface, phased focus is arranged at equal intervals in the encryption big gun region that step D optimizes, the source pattern shooting parameter corresponding with encryption big gun region adopting step F to obtain, completes the recording geometry optimal design of complex structural area based on geologic objective.

Wherein, the exploratory area geologic model of setting up described in steps A can be that different modeling softwares realizes, and it is applicable to two dimensional model and is also applicable to three-dimensional model.

Wherein, the Wave equation forward modeling method described in step B can adopt one-way wave equation, omnidistance ACOUSTIC WAVE EQUATION, viscoelastic wave equation or elastic wave wave equation to carry out forward simulation.

Wherein, the illumination energy statistical method described in step C can be at earth's surface diverse location earthquake-wave-exciting, adds up the illumination energy of each focus in buried target position, and the method can find out the earth's surface encryption big gun region best to underground target illumination.

Wherein, the mean value of what the encryption big gun regional choice standard of the earth's surface the best described in step D adopted is earth's surface general ambient light energy; Threshold value also can be 10% ~ 20% of illumination energy maximal value, and this is completely desirable when illumination energy distribution in earth's surface is more smooth.

Wherein, the exit direction of calculating first arrival seismic event on earth's surface described in step e, can be realized by additive method, comprises Radon transform, window Fourier transform, wavelet transformation and local slowness analysis technology; For increasing antimierophonic ability, when asking for first arrival seismic event exit direction, can add up the exit direction within the scope of the timing window from primary wave due in, namely window is not more than single Wavelet Duration T _winterior average exit direction.

Embodiment recited above is only be described the preferred embodiment of the present invention, not limits the spirit and scope of the present invention.Under the prerequisite not departing from design concept of the present invention; the various modification that this area ordinary person makes technical scheme of the present invention and improvement; all should drop into protection scope of the present invention, the technology contents of request protection of the present invention, all records in detail in the claims.

Claims (6)

1. one kind strengthens the method for designing that seismic event excites illumination, adopt the design standards of theoretical signal to noise ratio (S/N ratio) maximization principle as source pattern parameter of phase compress and combination focus, be the design standards of element interval and focus number, other optimal design standards improved, belong to the method series together; It is not limited to flatly express one's feelings condition, goes for the region of complicated earth surface complex structure; Its concrete steps are as follows:

A. according to available data, that sets up complex structural area just drills Geological Model, and determines geologic objective; Collect the geologic information in work area, seismic data, survey the data of well logging, drilling well, comprehensively known interpretation results and geological knowledge, set up the accurate geologic model in work area by modeling software, determine geologic objective, be i.e. geologic objective position, shape and scope in a model;

B. in the man-made explosion of buried target location arrangements, Wave equation forward modeling method is adopted to carry out illumination simulation; According to the feature of target in geologic model, at target location s=(x _s, z _s) place man-made explosion, i.e. target focus, the seismic wave field propagated in underground medium by omnidistance Acoustic Wave-equation forward simulation, calculate lighting result I (x, the z at target focus (x, z) place in a model; S), it is defined as follows:

$I(x,z;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}P(x,z,t;s)P(x,z,t;s)---\left(1\right)$

Wherein, P (x, z, t; S) for (x, z) place in model by the seismic wave field of the t of target epicenter excitation, T is the T.T. that wave field is propagated;

C., while illumination simulation, on earth's surface, statistically seismic wave upwards propagates into the illumination energy on earth's surface; Throw light in stepb while simulation, statistically sheet lighting energy, throw light on statistics I _surfcan be expressed as:

$I_{\mathrm{surf}}=I(x,z_0;s)=\underset{t=0}{\overset{T}{\mathrm{\Σ}}}p(x,z_0,t;s)p(x,z_0,t;s)---\left(2\right)$

Wherein, I (x, z ₀; S) be the illumination energy at each point place, earth's surface, p (x, z ₀, t; S) be the seismic wave field propagating into earth's surface of t target epicenter excitation, (x, z ₀) represent landscape position coordinate; The principle of reciprocity of base area seismic wave propagation, zone of interest is arranged focus carries out illumination analysis, if arrange focus in the region that earth's surface illumination energy is strong, this zone of interest just can be made to reach optimal illumination;

D. the encryption big gun region of earth's surface the best is determined according to illumination energy statistics; According to the earth's surface illumination energy statistics I obtained in step C _surf, using the mean value of earth's surface illumination energy as energy threshold I _ts, earth's surface illumination energy is defined as exciting scope for ground the best of this subsurface geology target higher than this energy threshold region, namely encrypts big gun region; If energy threshold is excessive, easily causes best encryption big gun region too small, reduce acquisition quality and imaging precision; If energy threshold is too small, the best encryption big gun region determined can be excessive, causes unnecessary cost waste; Therefore, in actual production process, the selection of energy threshold the requirement of integrated exploration cost and acquisition quality on this basis can do further adjustment;

E., while illumination simulation, utilize Poynting vector to calculate target epicenter excitation seismic event in the principal direction of earth's surface outgoing, determine the direction of propagation of phased epicenter excitation seismic beam; The computing formula of Poynting vector P in sound wave seismic wave field:

P＝-vp (3)

Wherein, v is velocity, and p is acoustic pressure, stress; In the computation process of step B, utilize the Kinematic parameters of earth's surface first arrival seismic event, speed and the components of stress, adopt formula (3) to calculate earth's surface Poynting vector; In order to calculate the direction of earth's surface Poynting vector, if unit vector n=vertically downward (0,1) is reference direction, according to the cosine law, by earth's surface Poynting vector P (x, z ₀, t ₀; S) with the angle theta of unit vector n _u(x, z ₀; S) first arrival seismic event is defined as at earth's surface each point (x, z ₀) exit direction:

${\mathrm{\θ}}_u(x,z_0;s)=\arccos \frac{P(x,z_0,t_0;s)\·n}{\left|P(x,z_0,t_0;s)\right|}---\left(4\right)$

Wherein, earth's surface Poynting vector P (x, z ₀, t ₀; S)=-v (x, z ₀, t ₀; S) p (x, z ₀, t ₀; S), t ₀for the time of arrival of earth's surface primary wave; The exit direction of the primary wave of earth's surface diverse location can be calculated by (4) formula; According to reciprocity principle, the direction of phased source pattern earthquake-wave-exciting bundle is the opposite direction of the primary wave direction of propagation, therefore phased source pattern parameter (direction of earthquake-wave-exciting bundle) θ _dcan be expressed as:

θ _d＝π-θ _u(5)

F., based on phase compress and the theoretical signal to noise ratio (S/N ratio) maximization principle combining focus, on the basis of the acquired phased focus seismic beam direction of propagation, best focus element interval and focus number is designed; According to radar array phase compress, based on horizontal earth's surface uniform dielectric, obtain the direction factor F (θ) combining epicenter excitation wave field:

$F\left(\mathrm{\θ}\right)=\frac{\sin [n(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}{n\sin [(\mathrm{kd}\sin \mathrm{\θ}+\mathrm{\β})/2]}---\left(6\right)$

Wherein: n is focus number, d is focus element interval, and θ is the deflection (θ=θ of seismic wave propagation _d), k is wavelet wave number, and β is the phase differential of wavelet between adjacent sources;

The seismic event that phased focus produces has directivity, its strongest direction θ _maxbe called directionally seismic wave direction or main beam direction; To make the seismic event of combination epicenter excitation at θ _maxdirection is propagated the strongest, namely makes:

kd sinθ+β＝0 (7)

The angle, the direction of propagation of the seismic beam obtained according to the relation (β=2 π f τ) of the mistiming between phase delay and focus and step e again obtains the delay time T between adjacent combination focus:

τ＝-kd sinθ/2πf ₀＝-d sinθ/v ₀＝-d sinθ _d/v ₀(8)

Wherein: f ₀for the dominant frequency of seismic wavelet, v ₀for surface materials speed;

The theoretical signal to noise ratio (S/N ratio) of combination focus is maximized the foundation as evaluation and composite design parameter, is finally determined element interval and the focus number of source pattern by numerical simulation;

G. determine that complex structural area strengthens the arrangement and method for construction of seismic event to the illumination energy of objective body on earth's surface, phased focus is arranged at equal intervals in the encryption big gun region that step D optimizes, the source pattern shooting parameter corresponding with encryption big gun region adopting step F to obtain, completes the recording geometry optimal design of complex structural area based on geologic objective.

2. according to claim 1ly a kind ofly strengthen the method for designing that seismic event excites illumination, it is characterized in that: the exploratory area geologic model of setting up described in steps A can be that different modeling softwares realizes, and it is applicable to two dimensional model and is also applicable to three-dimensional model.

3. according to claim 1ly a kind ofly strengthen the method for designing that seismic event excites illumination, it is characterized in that: the Wave equation forward modeling method described in step B can adopt one-way wave equation, omnidistance ACOUSTIC WAVE EQUATION, viscoelastic wave equation or elastic wave wave equation to carry out forward simulation.

4. according to claim 1ly a kind ofly strengthen the method for designing that seismic event excites illumination, it is characterized in that: the illumination energy statistical method described in step C can be at earth's surface diverse location earthquake-wave-exciting, add up the illumination energy of each focus in buried target position, the method can find out the earth's surface encryption big gun region best to underground target illumination.

5. according to claim 1ly a kind ofly strengthen the method for designing that seismic event excites illumination, it is characterized in that: the mean value of what the encryption big gun regional choice standard of the earth's surface the best described in step D adopted is earth's surface general ambient light energy; Threshold value also can be 10% ~ 20% of illumination energy maximal value, and this is completely desirable when illumination energy distribution in earth's surface is more smooth.

6. according to claim 1ly a kind ofly strengthen the method for designing that seismic event excites illumination, it is characterized in that: the exit direction of calculating first arrival seismic event on earth's surface described in step e, can be realized by additive method, comprise Radon transform, window Fourier transform, wavelet transformation and local slowness analysis technology; For increasing antimierophonic ability, when asking for first arrival seismic event exit direction, can add up the exit direction within the scope of the timing window from primary wave due in, namely window is not more than single Wavelet Duration T _winterior average exit direction.