CN104898162A - Crack detection method in geological exploration - Google Patents

Abstract

The invention discloses a crack detection method in geological exploration. The method comprises the following steps: obtaining converted wave signals in each acquisition orientation; based on an Alford rotation method, educing an analytical expression of two-component data of the converted wave signals in each acquisition orientation expressed by assumed orthogonally-arranged four-component data, orthogonally-arranged azimuth angles being randomly-assumed angles; based on the analytical expression, associating the two-component data in each acquisition orientation and the assumed orthogonally-arranged four-component signals, and carrying out calculating to obtain the four-component data in orthogonally-arranged orientation; and obtaining crack azimuth angle according to the four-component data in orthogonally-arranged orientation obtained through calculating, and carrying out detection to obtain orientation and time difference of the generation of a crack. The method breaks the limitation of orthogonal arrangement in a convention four-component Alford rotation shear wave splitting algorithm, and realizes a non-orthorhombic multi-component Alford rotation shear wave splitting algorithm.

Description

Crack detection method in geologic prospecting

Technical field

The present invention relates to geologic prospecting and oil-gas field development, furthermore, relate to the crack detection method in geologic prospecting.

Background technology

Mainly p-wave source excites current multicomponent seismic survey technology, three-component or four component wave detectors receive.Compressional wave is descending run into reflecting interface after can occur under certain condition wave mode conversion, compressional wave is converted to shear wave and is called transformed wave (PS).Can be there is shear wave splitting phenomenon when encountering fracture medium in the up shear wave of conversion, this phenomenon can be detected device and record, and it can play important effect when the hydrocarbon-bearing pool of fracture detection type.In the reservoir of fracture development, the speed of longitudinal wave propagation and amplitude line direction change and change.But this variable quantity is maximum less than 3%, in data process is explained, slightly this Orientation differences just may be covered by error.

And shear wave can be split into two Shear Waves Splittings in different polarization direction (usually orthogonal) after entering crack.These two shear waves have various amplitude size and speed velocity of propagation, and general strong amplitude is fireballing is referred to as fast transverse wave (S1), otherwise is slow shear-wave (S2).The principal direction in crack is exactly the direction of fast transverse wave.Gather in recording geometry at multi-component seismic data, the component obtained along the wave detector that line direction is embedding is referred to as X component, and the component obtained along the wave detector that cross line direction is embedding is referred to as Y-component.A unknown angle θ is there is between the acquisition system coordinate determined by X, Y-component and " natural coordinates " (Fracture System defined by S1 ripple and S2 ripple).

In order to the main orientation of the hydrocarbon-bearing pool of fracture detection type and crack thereof and development degree of micro cracks in oil effectively, this wave phenomenon of shear wave splitting can be utilized to estimate the angle between coordinate acquisition and natural coordinates, thus determine the main orientation of fracture development.The time difference of seeking between fast transverse wave and slow shear-wave can judge the development degree in crack.Exist at present and multiplely utilized the method for shear wave splitting phenomenon fracture detection, substantially can be divided into two components method and four components method according to the number of components related to.Wherein, more influential: the four component spinning solutions based on pure shear wave exploration of Alford proposition in 1986, it is commonly referred to Alford spinning solution; Two component spinning solutions of Thomsen proposition in 1988; And Harrison proposed the spinning solution of two components in 1992 based on waveform similarity hypothesis.Two components method are more suitable for Converted P-SV-Waves Exploration in theory, because transformed wave cannot build the data matrix of four components as Alford.But Comparatively speaking, four components method are more stable.James E.Gaiser1997 gives the Alford spinning solution based on transformed wave four componets data, and his method is extensively accepted in industry member.This method utilizes the transformed wave data of two mutually orthogonal collections in orientation to build the data matrix of four components, is used for the four componets data that approximate pure shear wave exploration obtains.

As mentioned above, four component A lford spinning solutions of transformed wave perpendicular array receive two restrictions gathering arrangement must be orthogonal.Therefore, data a large amount of in the data collection of reality are in fact non-orthogonal, they or do not have two of strict orthogonal and gather orientation, or the data meeting orthogonality condition will be lacked much relatively.And, there is not arrangement orthogonal with it yet, therefore, these data can only be avoided when Crack Detection.And the less correctness that will inevitably affect result of the data volume used when Crack Detection.Therefore, in order to utilize the multi-component data collected fully, orthogonal restriction will be broken.

For this reason, need to provide a kind of do not need gathered component data all to meet orthogonal property just can according to Alford rotary process determination fracture azimuth thus the method for position occurs fracture detection.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, propose the crack detection method in a kind of geologic prospecting, it comprises the following steps:

Obtain the transformed wave signal in each collection orientation;

Derive two the component data Analytical Expression being represented the described transformed wave signal gathering arbitrarily orientation by the four componets data of the perpendicular array supposed based on Alford rotary process, wherein the orientation angles of perpendicular array is the angle of arbitrary assumption;

Based on described Analytical Expression, four component signals on two component datas in each collection orientation and the perpendicular array orientation of hypothesis are connected, thus try to achieve the four componets data in perpendicular array orientation;

Obtain fracture azimuth based on the four componets data in the perpendicular array orientation calculated, thus detect the orientation and the time difference that obtain crack generation.

According to one embodiment of present invention, suppose that the orientation angles of two perpendicular array is 0 degree and 90 degree, then gathering arbitrarily two of the orientation analytical expression between component data and the four componets data of perpendicular array is:

${\mathrm{PS}}_{11}^i={\cos }^2{\mathrm{\θ}}_i{a}_1+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_2+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_3+{\sin }^2{\mathrm{\θ}}_i{a}_4$

${\mathrm{PS}}_{12}^i=-\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_1+{\cos }^2{\mathrm{\θ}}_i{a}_2-{\sin }^2{\mathrm{\θ}}_i{a}_3+{\sin {\mathrm{\θ}}_i\cos \mathrm{\θ}}_i{a}_4$

Wherein, represent i-th two component data gathered in orientation respectively, a1, a2, a3, a4 represent the four componets data in 0 degree, 90 degree orientation perpendicular array respectively, θ _irepresent i-th angle gathered between orientation and 0 degree of orientation.The 0 degree of angle obtained selected by this formula does not provide constraints to the present invention.

In one embodiment, the relation of the four componets data of two component datas in N number of any collection orientation and perpendicular array is tried to achieve according to following Analytical Expression:

$\left[\begin{array}{c}{\mathrm{PS}}_{11}^1\\ {\mathrm{PS}}_{12}^1\\ .\\ .\\ .\\ .\\ .\\ .\\ {\mathrm{PS}}_{11}^N\\ {\mathrm{PS}}_{12}^N\end{array}\right]\left[\begin{array}{cccc}{\cos }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\sin }^2{\mathrm{\θ}}_1\\ -\sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\cos }^2{\mathrm{\θ}}_1& -{\sin }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ {\cos }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\sin }^2{\mathrm{\θ}}_N\\ -\sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\cos }^2{\mathrm{\θ}}_N& -{\sin }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N\end{array}\right]\left[\begin{array}{c}{a}_1\\ a_2\\ a_3\\ a_4\end{array}\right]$

Wherein, a1, a2, a3, a4 represent the four componets data in perpendicular array orientation respectively, represent two component datas in N number of any collection orientation respectively, θ ₁θ _nrepresent the position angle gathering orientation respectively.

In one embodiment of the invention, the fast transverse wave component data f of the shear wave splitting caused according to four componets data a1, a2, a3, the a4 in perpendicular array orientation and crack ₁₁, f ₁₂with slow shear-wave component data f ₂₁, f ₂₂between rotation relationship, based on theoretical model shear wave splitting hypothesis calculate fracture azimuth θ:

$\mathrm{\θ}=\frac{1}{2}\arctan \frac{a_2+a_3}{a_1-a_4}.$

In shear wave splitting hypothesis, suppose the cross stream component f of fast transverse wave ₁₂with the cross stream component f of slow shear-wave ₂₁be zero, or the cross stream component sum of hypothesis fast transverse wave and slow shear-wave is zero:

f ₁₂+f ₂₁＝0。

In one embodiment of the invention, crack detection method also comprises the division time difference calculating fracture development orientation and Shear Waves Splitting further according to angle and time shift scanning.

In one embodiment of the invention, fracture azimuth is determined according to capacity volume variance is maximum, then utilize rotation matrix to be rotated in fracture azimuth by the four componets data in shear wave splitting orientation, thus determine to divide the time difference based on the relation of the cross-correlation between fast transverse wave and slow shear-wave.

In one embodiment of the invention, described transformed wave signal comprises the component data of perpendicular array and the component data of nonopiate arrangement.

Present invention offers following beneficial effect:

The present invention can realize non-orthogonal Alford and rotate, it can make full use of the data collected and determine fracture azimuth and the Concerning With Fast-slow Waves time difference more accurately, and based on reasonably supposing that the shear wave splitting theory hypothesis as theoretical model provides the analytical expression of fracture azimuth.Method of the present invention has broken the restriction that traditional four component A lford rotate the perpendicular array of shear wave splitting algorithm, achieves non-orthogonal multi-components Alford and rotates shear wave splitting algorithm.Collection array data for any angle can realize the crack angle calculation of shear wave splitting.In addition, the fracture azimuth angle computing method of angle rotation sweep are additionally provided.

Other features and advantages of the present invention will be set forth in the following description, and partly become apparent from instructions, or understand by implementing the present invention.Object of the present invention and other advantages realize by structure specifically noted in instructions, claims and accompanying drawing and obtain.

Accompanying drawing explanation

Fig. 1 shows Alford rotation of coordinate schematic diagram;

Fig. 2 is the method flow diagram of one embodiment of the present of invention;

Fig. 3 is the picture of the input component data before implementing the present invention; And

Fig. 4 implements the picture that the present invention carries out the output component data after Concerning With Fast-slow Waves TEC time error correction.

Embodiment

Describe embodiments of the present invention in detail below with reference to accompanying drawing, to the present invention, how application technology means solve technical matters whereby, and the implementation procedure reaching technique effect can fully understand and implement according to this.It should be noted that, only otherwise form conflict, each feature in various embodiments of the present invention and each embodiment can be combined with each other, and the technical scheme formed is all within protection scope of the present invention.

Classical way Alford spin theory in shear wave splitting fracture detection proposes based on pure shear wave exploration.It requires that the shear-wave generation of perpendicular array and shear wave receive.Afterwards, the people such as J.E.Gaiser were expanded in Converted P-SV-Waves Exploration, were the orthogonal arrangement of requirement two equally.

As shown in Figure 1, two dotted lines represent the converted-wave acquisition arrangement of two different azimuth respectively, their orthogonal thereto relations.Collect four components according to theoretical any two perpendicular array of Alford and meet Alford rotation formula, as formula (1) with four components collected on parallel fracture and vertically oriented fracture orientation:

$\left[\begin{array}{cc}{\mathrm{PS}}_{11}^{\′}& {\mathrm{PS}}_{12}^{\′}\\ {\mathrm{PS}}_{21}^{\′}& {\mathrm{PS}}_{22}^{\′}\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{cc}{\mathrm{PS}}_{11}& {\mathrm{PS}}_{12}\\ {\mathrm{PS}}_{21}& {\mathrm{PS}}_{22}\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]---\left(1\right)$

The wherein four componets data that collects of any perpendicular array of the matrix representative on the equation left side, the right represents the four componets data that collects in fracture azimuth, just can obtain four components in any orthogonal orientation in the left side after its rotation matrix through shot point and geophone station rotates.Therefore, suppose that parallel fracture orientation and vertically oriented fracture orientation collect four components and can be represented by a1, a2, a3, a4, as the matrix in the middle of formula (2) the right.θ _ithe representative fracture azimuth that will find and the angle gathering orientation, θ 1 as shown in Figure 1.The matrix on formula (2) left side then represents actual perpendicular array and collects four components.

$\left[\begin{array}{cc}{\mathrm{PS}}_{11}^i& {\mathrm{PS}}_{12}^i\\ {\mathrm{PS}}_{21}^i& {\mathrm{PS}}_{22}^i\end{array}\right]=\left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& \sin {\mathrm{\θ}}_i\\ -\sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]\left[\begin{array}{cc}{a}_1& a_2\\ a_3& a_4\end{array}\right]\left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& -\sin {\mathrm{\θ}}_i\\ \sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]---\left(2\right)$

Because the orientation in crack itself is unknown, although the position angle gathered is known, we also cannot know the angle gathering orientation and fracture azimuth.Therefore, rotation matrix relevant to angle in formula (2) cannot be built in the case.According to formula (2), we can obtain four components of the Concerning With Fast-slow Waves represented by four components of any perpendicular array, are first out of shape by (2) formula and obtain (3) formula:

$\left[\begin{array}{cc}{a}_1& a_2\\ a_3& a_4\end{array}\right]=\left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& -\sin {\mathrm{\θ}}_i\\ \sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]\left[\begin{array}{cc}{PS}_{11}^i& {\mathrm{PS}}_{12}^i\\ {\mathrm{PS}}_{21}^i& P{S}_{22}^i\end{array}\right]\left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& \sin {\mathrm{\θ}}_i\\ -\sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]---\left(3\right)$

Now θ _ibe i-th angle gathering orientation and fracture azimuth, suppose that the i-th+1 collection orientation and fracture azimuth angle are θ _i+ Δ θ, then can obtain following relation by four component types in four representation in components the i-th+1 orientation in i-th orientation:

$\begin{array}{c}\left[\begin{array}{cc}{\mathrm{PS}}_{11}^{i+1}& {\mathrm{PS}}_{12}^{i+1}\\ {\mathrm{PS}}_{21}^{i+1}& {\mathrm{PS}}_{22}^{i+1}\end{array}\right]=\left[\begin{array}{cc}\cos ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})& \sin ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})\\ -\sin ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})& \cos ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})\end{array}\right]\left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& -\sin {\mathrm{\θ}}_i\\ \sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]*\\ \left[\begin{array}{cc}{\mathrm{PS}}_{11}^i& {\mathrm{PS}}_{12}^i\\ {\mathrm{PS}}_{21}^i& {\mathrm{PS}}_{22}^i\end{array}\right]*\\ \left[\begin{array}{cc}\cos {\mathrm{\θ}}_i& \sin {\mathrm{\θ}}_i\\ -\sin {\mathrm{\θ}}_i& \cos {\mathrm{\θ}}_i\end{array}\right]\left[\begin{array}{cc}\cos ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})& -\sin ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})\\ \sin ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})& \cos ({\mathrm{\θ}}_i+\mathrm{\Δ\θ})\end{array}\right]\end{array}---\left(4\right)$

It is out of shape further and can obtains following relational expression;

$\left[\begin{array}{cc}{\mathrm{PS}}_{11}^{i+1}& {\mathrm{PS}}_{12}^{i+1}\\ P{S}_{21}^{i+1}& {\mathrm{PS}}_{22}^{i+1}\end{array}\right]=\left[\begin{array}{cc}\cos \left(\mathrm{\Δ\θ}\right)& \sin \left(\mathrm{\Δ\θ}\right)\\ -\sin \left(\mathrm{\Δ\θ}\right)& \cos \left(\mathrm{\Δ\θ}\right)\end{array}\right]\left[\begin{array}{cc}{\mathrm{PS}}_{11}^i& {\mathrm{PS}}_{12}^i\\ {\mathrm{PS}}_{21}^i& {\mathrm{PS}}_{22}^i\end{array}\right]\left[\begin{array}{cc}\cos \left(\mathrm{\Δ\θ}\right)& -\sin \left(\mathrm{\Δ\θ}\right)\\ \sin \left(\mathrm{\Δ\θ}\right)& \cos \left(\mathrm{\Δ\θ}\right)\end{array}\right]---\left(5\right)$

In relational expression (5), only there is the cut angle of azimuths in two known collection orientation, and eliminate the factor of unknown fracture azimuth.Therefore, when fracture azimuth the unknown, the component of any two groups of perpendicular array can represent mutually.In one embodiment, one group of perpendicular array can be specified arbitrarily.Four components of other perpendicular array are represented with four components of this group perpendicular array.Such as can specify 0 degree and 90 degree of perpendicular array formed.The present invention is not limited thereto angle.In this example embodiment, get the convenience that " 0 degree " is only used to illustrate, and expression formula also can simplify (because θ-0 just equals θ) further, thus not fuzzy principle of the present invention and purport.

After assume that 0 degree of angle, the orientation angles of any perpendicular array of angle is its angle theta.Therefore, when the data matrix on formula (2) the right is 0 degree of data with 90 degree, we get two components of the first row of left side matrix, just can obtain formula (6) and formula (7) according to formula (2).

${\mathrm{PS}}_{11}^i={\cos }^2{\mathrm{\θ}}_i{a}_1+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_2+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_3+{\sin }^2{\mathrm{\θ}}_i{a}_{4---\left(6\right)}$

${\mathrm{PS}}_{12}^i=-\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_1+{\cos }^2{\mathrm{\θ}}_i{a}_2-{\sin }^2{\mathrm{\θ}}_i{a}_3+{\sin {\mathrm{\θ}}_i\cos \mathrm{\θ}}_i{a}_4---\left(7\right)$

So far, the expression formula how being obtained two components in any one orientation by four components in 0 degree and 90 orientation is just obtained.Now, if collect again two component datas in N number of orientation, and these data might not meet the requirement of perpendicular array.According to formula (6) and formula (7), the expression formula that formula (8) is so just can be obtained:

$\left[\begin{array}{c}{\mathrm{PS}}_{11}^1\\ {\mathrm{PS}}_{12}^1\\ .\\ .\\ .\\ .\\ .\\ .\\ {\mathrm{PS}}_{11}^N\\ {\mathrm{PS}}_{12}^N\end{array}\right]\left[\begin{array}{cccc}{\cos }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\sin }^2{\mathrm{\θ}}_1\\ -\sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\cos }^2{\mathrm{\θ}}_1& -{\sin }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ {\cos }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\sin }^2{\mathrm{\θ}}_N\\ -\sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\cos }^2{\mathrm{\θ}}_N& -{\sin }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N\end{array}\right]\left[\begin{array}{c}{a}_1\\ a_2\\ a_3\\ a_4\end{array}\right]---\left(8\right)$

Wherein, 2N the amount on the equation left side represents two components in the known N number of orientation collected.The right is that the matrix representative of 2NX4 gathers the orientation compute matrix relevant to fracture azimuth angle, represents position angle and 0 degree of azimuthal angle here.

According to formula (8) just no longer can be confined to when shear wave splitting fracture detection Alford rotate required by perpendicular array, non-orthogonal arrangement can calculate shear wave splitting problem equally.

According to orientation two component data collected, build such as formula (8) such system of equations.Solving equations can obtain a1, a2, a3, a4.Two components making the fast transverse wave of the shear wave splitting caused by crack are f ₁₁and f ₁₂, two components of slow shear-wave are f ₂₁and f ₂₂, then can obtain:

$\left[\begin{array}{cc}{a}_1& a_2\\ a_3& a_4\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& -\sin \mathrm{\θ}\\ \sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{cc}{f}_{11}& f_{12}\\ f_{21}& f_{22}\end{array}\right]\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]---\left(9\right)$

Further, can derive,

a ₂+a ₃＝(f ₁₁-f ₂₂)sin2θ+(f ₁₂+f ₂₁)cos2θ （10）

a ₁-a ₄＝(f ₁₁-f ₂₂)cos2θ-(f ₁₂+f ₂₁)sin2θ （11）

Again according to wave theory, in shear wave splitting situation, wave field is divided into parallel fracture to propagate and vertically oriented fracture is propagated.Therefore, the cross stream component of fast wave and the cross stream component of slow wave should not have in theory.Often really not so in practical situations both, but also can provide following hypothesis according to theory,

f ₁₂+f ₂₁＝0 （12）

Can obtain thus,

$\mathrm{\θ}=\frac{1}{2}\arctan \frac{a_2+a_3}{a_1-a_4}---\left(13\right)$

Also fracture development orientation and the Concerning With Fast-slow Waves division time difference can be calculated according to angle and time shift scanning.Under appointment time shift weight range and angle rotating range situation, according to wave theory, postrotational main energetic concentrates on and involves on slow wave soon, namely on principal diagonal composition.Therefore, can provide criterion is that the energy of the elements in a main diagonal is maximum, or the energy of minor diagonal element is minimum, is greater than slow wave energy, is specially according to the fast wave energy of general hypothesis:

f ₁₁ ²＞f ₂₂ ²（14）

ΔE＝f ₁₁ ²+f ₂₂ ²-f ₁₂ ²-f ₂₁ ²（15）

When the time difference and angle meet inequality and energy difference is maximum, corresponding angle and time shift amount are exactly the time difference of fracture azimuth and Concerning With Fast-slow Waves.

Can not certainly suppose that fast wave energy is greater than slow wave energy.Now, first according to the maximum i.e. formula (15) of capacity volume variance, a fracture azimuth can be determined.Then, rotation matrix is utilized by data rotation in fracture azimuth.Now, diagonal entry must have one be fast wave another for slow wave.Here, determine which is the time difference involving Concerning With Fast-slow Waves soon by cross-correlation.Work as f ₂₂for the fracture azimuth angle determined before during fast wave has the correction of 90 degree, f ₁₁for fast wave does not then have fracture azimuth Correction Problems.

Above-mentioned principle can be realized by devices such as computing machines.As shown in Figure 2, be the process flow diagram of the inventive method.

First, in step s 201, the transformed wave signal in each collection orientation is obtained.

In step S202, derive the Analytical Expression of two component datas being represented the described transformed wave signal gathering arbitrarily orientation by the four componets data of the perpendicular array supposed based on Alford rotary process, wherein the orientation angles of perpendicular array is the angle of arbitrary assumption.Suppose that the orientation angles of two perpendicular array is 0 degree and 90 degree, then gathering arbitrarily two of the orientation analytical expression between component data and the four componets data of perpendicular array is above-mentioned formula (6) and formula (7).In this formula, represent i-th two component data gathered in orientation respectively, a1, a2, a3, a4 represent the four componets data in 0 degree, 90 degree orientation perpendicular array respectively, θ _irepresent i-th angle gathered between orientation and 0 degree of orientation.

In step S203, based on above-mentioned Analytical Expression, four component signals on two component datas in each collection orientation and the perpendicular array orientation of hypothesis are associated, thus try to achieve the four componets data in perpendicular array orientation.This four componets data computing formula is as formula (8).

In step S204, obtain fracture azimuth based on the four componets data in the perpendicular array orientation calculated, thus detect the orientation and the time difference that obtain crack generation.

Specifically, the fast transverse wave component data f of the shear wave splitting caused according to four componets data a1, a2, a3, the a4 in perpendicular array orientation and crack ₁₁, f ₁₂with slow shear-wave component data f ₂₁, f ₂₂between rotation relationship, the shear wave splitting hypothesis based on theoretical model is come to calculate fracture azimuth θ by above formula (13):

$\mathrm{\θ}=\frac{1}{2}\arctan \frac{a_2+a_3}{a_1-a_4}$

In shear wave splitting hypothesis, suppose the cross stream component f of fast transverse wave ₁₂with the cross stream component f of slow shear-wave ₂₁be zero, or the cross stream component sum of hypothesis fast transverse wave and slow shear-wave is zero, i.e. above-mentioned formula (12):

f ₁₂+f ₂₁＝0。

First, the present invention has broken the restriction of perpendicular array, achieves non-orthogonal Alford spinning solution.Secondly, under the constraint of all bearing datas collected, the value of four components is calculated, as shown in Equation (8).Finally, these four components calculate main orientation, crack and Concerning With Fast-slow Waves time shift amount.Now, can calculate fracture azimuth according to the method rotated, the present invention simultaneously give also the fracture azimuth computing formula of parsing.

Because Crack Detection comprises the time difference and the orientation of fracture detection, and the present invention mainly emphasizes the orthogonal precondition breaching original ALFORD method in Crack Detection, therefore achieves the crack detection method of nonopiate arrangement ALFORD.And for TEC time error correction, usually can adopt scanning and be correlated with to ask the time difference.Also really better seismic section can be obtained after TEC time error correction.Those of ordinary skill in the art can carry out various deformation on principle of the present invention, all can realize object of the present invention to some extent as adopted any one TEC time error correction disclosed in various prior art.Therefore scope of the present invention claim related content of having the right limits.

In an experiment, the theoretical model of four layers is devised.Wherein, table 1 gives the time difference of the degree of depth of model layer, fracture development orientation and Concerning With Fast-slow Waves.

Table 1

Layer position	T0 (millisecond)	Fracture azimuth (degree)	Time delay (millisecond)
				1	90	30	15
2	150	95	10
				3	250	280	12
4	310	170	8

Based on this theoretical model, adopt the present invention can calculate fracture azimuth and the Concerning With Fast-slow Waves time difference of every one deck well.The theoretical record finding out as input from accompanying drawing to result in imaging effect because Concerning With Fast-slow Waves mixes very poor, makes R component there is obvious sinusoidal wave phenomenon.Calculate the main orientation of fracture development and after the Concerning With Fast-slow Waves time difference through the present invention, correct R, T component of input, the R component image quality after correction significantly improves.In addition, lineups also no longer exist time delay, T component presents the reversal of poles phenomenon of 90 degree, indicates the growth orientation in crack exactly.

The picture of R, T component data as input is given in Fig. 3 and 4.Due to before shear wave splitting corrects, Shear Waves Splitting is present on R, T component simultaneously, and Concerning With Fast-slow Waves itself exists the time difference, has therefore just occurred the sinusoidal phenomenon in R component after superposition.

After the time difference in the orientation and Concerning With Fast-slow Waves that calculate each slabbing seam, input data are corrected.After rotating to Concerning With Fast-slow Waves, correct time difference of Concerning With Fast-slow Waves, slow wave is corrected to fast wave time consistency after again rotate on R, T component, this is R, T component exported.

Although the embodiment disclosed by the present invention is as above, the embodiment that described content just adopts for the ease of understanding the present invention, and be not used to limit the present invention.Technician in any the technical field of the invention; under the prerequisite not departing from the spirit and scope disclosed by the present invention; any amendment and change can be done what implement in form and in details; but scope of patent protection of the present invention, the scope that still must define with appending claims is as the criterion.

Claims (7)

1. the crack detection method in geologic prospecting, is characterized in that, comprises the following steps:

Obtain the transformed wave signal in each collection orientation;

Derive the Analytical Expression of two component datas being represented the described transformed wave signal gathering arbitrarily orientation by the four componets data of the perpendicular array supposed based on Alford rotary process, wherein the orientation angles of perpendicular array is the angle of arbitrary assumption;

Based on described Analytical Expression, four component signals on two component datas in each collection orientation and the perpendicular array orientation of hypothesis are associated, thus try to achieve the four componets data in perpendicular array orientation;

Obtain fracture azimuth based on the four componets data in the perpendicular array orientation calculated, thus detect the orientation and the time difference that obtain crack generation.

2. crack detection method as claimed in claim 1, is characterized in that,

Suppose that the orientation angles of two perpendicular array is 0 degree and 90 degree, then gathering arbitrarily two of the orientation analytical expression between component data and the four componets data of perpendicular array is:

${\mathrm{PS}}_{11}^i={\cos }^2{\mathrm{\θ}}_i{a}_1+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_2+\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_3+{\sin }^2{\mathrm{\θ}}_i{a}_4$

${\mathrm{PS}}_{12}^i=-\sin {\mathrm{\θ}}_i\cos {\mathrm{\θ}}_i{a}_1+{\cos }^2{\mathrm{\θ}}_i{a}_2-{\sin }^2{\mathrm{\θ}}_i{a}_3+{\sin {\mathrm{\θ}}_i\cos \mathrm{\θ}}_i{a}_4$

Wherein, represent i-th two component data gathered in orientation respectively, a1, a2, a3, a4 represent the four componets data in 0 degree, 90 degree orientation perpendicular array respectively, θ _irepresent i-th angle gathered between orientation and 0 degree of orientation.

3. crack detection method as claimed in claim 2, is characterized in that, tries to achieve the relation of the four componets data of two component datas in N number of any collection orientation and perpendicular array according to following Analytical Expression:

$\left[\begin{array}{c}{\mathrm{PS}}_{11}^1\\ {\mathrm{PS}}_{12}^1\\ .\\ .\\ .\\ .\\ .\\ .\\ {\mathrm{PS}}_{11}^N\\ {\mathrm{PS}}_{12}^N\end{array}\right]\left[\begin{array}{cccc}{\cos }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\sin }^2{\mathrm{\θ}}_1\\ -\sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1& {\cos }^2{\mathrm{\θ}}_1& -{\sin }^2{\mathrm{\θ}}_1& \sin {\mathrm{\θ}}_1\cos {\mathrm{\θ}}_1\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ {\cos }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\sin }^2{\mathrm{\θ}}_N\\ -\sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N& {\cos }^2{\mathrm{\θ}}_N& -{\sin }^2{\mathrm{\θ}}_N& \sin {\mathrm{\θ}}_N\cos {\mathrm{\θ}}_N\end{array}\right]\left[\begin{array}{c}{a}_1\\ a_2\\ a_3\\ a_4\end{array}\right]$

Wherein, a1, a2, a3, a4 represent the four componets data in perpendicular array orientation respectively, represent two component datas in N number of any collection orientation respectively, θ ₁θ _nrepresent the position angle gathering orientation respectively.

4. crack detection method as claimed in claim 3, is characterized in that, according to the fast transverse wave component data f of the shear wave splitting that four componets data a1, a2, a3, the a4 in perpendicular array orientation and crack cause ₁₁, f ₁₂with slow shear-wave component data f ₂₁, f ₂₂between rotation relationship, based on theoretical model shear wave splitting hypothesis calculate fracture azimuth θ:

$\mathrm{\θ}=\frac{1}{2}\arctan \frac{a_2+a_3}{a_1-a_4}$

In shear wave splitting hypothesis, suppose the cross stream component f of fast transverse wave ₁₂with the cross stream component f of slow shear-wave ₂₁be zero, or the cross stream component sum of hypothesis fast transverse wave and slow shear-wave is zero:

f ₁₂+f ₂₁＝0。

5. crack detection method as claimed in claim 4, is characterized in that, also comprises the division time difference calculating fracture development orientation and Shear Waves Splitting further according to angle and time shift scanning.

6. crack detection method as claimed in claim 4, it is characterized in that, fracture azimuth is determined according to capacity volume variance is maximum, then utilize rotation matrix to be rotated in fracture azimuth by the four componets data in shear wave splitting orientation, thus determine to divide the time difference based on the relation of the cross-correlation between fast transverse wave and slow shear-wave.

7. the crack detection method according to any one of claim 1-6, is characterized in that, described transformed wave signal comprises the component data of perpendicular array and the component data of nonopiate arrangement.