CN104005760A - Azimuthal anisotropic elastic impedance based crack detection method - Google Patents

Abstract

The invention relates to an azimuthal anisotropic elastic impedance based crack detection method. With a Connolly elastic impedance equation and a Ruger equation serving as the basis, anisotropic elastic impedance and crack parameters and the dominance relation formula between crack density and crack azimuth are deduced. A set of elastic impedance based crack inversion process is established, and anisotropic parameter information is added into inversion well logging constraint. Numerical model testing is performed in the method, the inversion result is roughly identical to the theoretical value, and the inversion density shows high noise immunity. The method has the advantages that anisotropic elastic impedance can be used, the crack density and the crack azimuth are calculated simultaneously, good application effects are provided in actual data, and high practicality is provided.

Description

Crack detection method based on azimuthal anisotropy elastic impedance

Technical field

The invention belongs to petroleum exploration field, relate to the method for utilizing the feature of elastic impedance azimuthal anisotropy to detect effective fracture in fracture reservoir overall merit.

Background technology

Slit formation reservoir accounts for greatly 1/3rd of world's oil and gas reserves.As hydrocarbon migration channel and reservoir space, fracture detection is significant for finding oil-bearing reservoir.The research in crack is also the important step of current era reservoir evaluation and prediction.And elastic impedance in the seismic wave reservoir in crack has the feature of azimuthal anisotropy, therefore can utilize this character fracture detection.Connolly in 1999 propose the concept of elastic impedance first, he utilizes approximate reflectance factor that Aki & Richards the proposes elastic impedance formula (Connolly under isotropic medium that derived, 1999), this formula connects log and petrophysical parameter, has improved reservoir prediction precision.Yet, extensively there is anisotropy in underground medium, Thomsen thinks that the impact of weak anisotropy factor cannot ignore, therefore, many scholars have carried out the research of the elastic impedance based in direction anisotropy medium situation on the basis of this formula, as Martins takes the lead in broad sense Thomsen type anisotropic parameters system, concept (the Martins of calculation of elastic impedance in anisotropic media has been proposed, 2002), and the impedance of anisotropic medium Elastic has been described with angle of incidence and azimuthal variation by numerical model, and the relation of the longitudinal wave reflection coefficient in Connolly formula and elastic impedance is extended in HTI medium, obtained the compressional wave elastic impedance formula relevant with orientation, emphasized the importance of azimuthal anisotropy in elastic impedance.Chen Tiansheng (2006) etc. are for again the derived compressional wave elastic impedance formula of HTI medium of the too complicated shortcoming of Martins calculation of elastic impedance in anisotropic media parameter.Yuan Shujin etc. (2006) from Shuey, propose based on P wave reflection coefficient approximate expression VTI medium, derived weak anisotropy elastic impedance equation.Longitudinal wave reflection coefficient approximate expression under the VTI medium that Li Aishan etc. (2008) propose based on Ruger, also derive the elastic impedance equation in a kind of VTI medium, equation has been carried out to standardization, eliminated the deficiency that equation dimension changes with angle, and by numerical simulation, carried out the method research of extracting petrophysical parameter from elastic impedance data volume.Introduce the universal relation formula between longitudinal wave reflection coefficient and elastic impedance under HTI medium below:

Reflectance factor approximate equation in the HTI medium that given first is proposed by Ruger (Ruger, 1998),

When angle of incidence i hour:

$R(i,\mathrm{\φ})=\frac{1}{2}\frac{\mathrm{\ΔZ}}{Z}+\frac{1}{2}\{\frac{\mathrm{\Δ\α}}{\mathrm{\α}}-{\left(\frac{2\mathrm{\β}}{\mathrm{\α}}\right)}^2\frac{\mathrm{\ΔG}}{\mathrm{\α}}+[{\mathrm{\Δ\δ}}^V+2{\left(\frac{2\mathrm{\β}}{\mathrm{\α}}\right)}^2\mathrm{\Δ\γ}\left]\cos \mathrm{\Φ}\right\}{\sin }^{2}i---\left(1\right)$

Wherein α, β are P-wave And S speed, σ ^(V), γ is Thomsen parameter, Φ=ф-ф _s, ф is azimuth, ф _sfor the fracture orientation that inverting obtains, i is angle of incidence.Wave impedance Z=ρ α during compressional wave vertical incidence; α=(α ₁+ α ₂)/2, Δ Z=Z ₂-Z ₁, tangential modulus G=ρ β ², β=(β ₂-β ₁)/2, Δ G=G ₂-G ₁.

Here, can regard the longitudinal wave reflection coefficient in HTI medium as isotropism reflection R ^iso(i) with anisotropic emission coefficients R ^ani(i, φ) sum, that is,

R(i,φ)=R ^iso(i)+R ^ani(i,φ) (2)

Under the isotropic medium that Connolly proposes, elastic wave impedance (EI) formula is:

EI(i)=α ^(1+sin2i)β ^-8K2sin2iρ ^1-4K2sin2i (3)

Wherein, ρ is density; K=beta/alpha is transverse and longitudinal wave velocity ratio, gets the average of adjacent layer.

By the relational expression between isotropism longitudinal wave reflection coefficient and elastic wave impedance, and the relational expression of longitudinal wave reflection coefficient and elastic impedance under the Martins HIT medium of deriving:

$R^{\mathrm{iso}}\left(i\right)=\frac{1}{2}\frac{\mathrm{\ΔEI}\left(i\right)}{\mathrm{EI}\left(i\right)}=\frac{1}{2}\mathrm{\Δ}1n\left(\mathrm{EI}\left(i\right)\right),R(i,\mathrm{\φ})=\frac{1}{2}\frac{\mathrm{\ΔEI}(i,\mathrm{\φ})}{\mathrm{EI}(i,\mathrm{\φ})}=\frac{1}{2}\mathrm{\Δ}1n\left(\mathrm{EI}(i,\mathrm{\φ})\right)---\left(4\right)$

Can set up following relational expression:

△lnEI(i,φ)=△lnEI(i)+2R ^ani(i,φ) (5)

Thus, can, by the data volume of isotropic elasticity impedance EI (i) and calculation of elastic impedance in anisotropic media EI (i, φ), ask for anisotropic emission coefficients R ^ani(i, φ), and then try to achieve anisotropic parameters.General algorithm can cause equation comparatively complicated with Thomsen type anisotropic parameters system for solving target like this, and parameter is more, in numerical model, can obtain certain effect, but is difficult in actual applications accurately solve.The more important thing is, in actual production, we generally utilize fracture spacing and trend etc., and anisotropic parameters is as the foundation in prediction crack intuitively, and above-mentioned algorithm is not set up this type of Explicit functions of fracture parameters and elastic impedance intuitively, so is unfavorable for actual FRACTURE PREDICTION work.

Summary of the invention

Reflectance factor approximate equation in the HTI medium that the elastic impedance that the present invention derives in conjunction with Connolly and Ruger propose, has set up the Explicit functions between elastic impedance and fracture parameters (fracture spacing and fracture orientation).Utilize prestack road, orientation collection, in conjunction with well logging, rock physics and conventional AVOZ inversion result, as constraints, carry out the inverting of azimuthal anisotropy elastic impedance.In conjunction with isotropic elasticity impedance, finally solve the density and the fracture orientation information that obtain crack again.The method has improved the actual application value of elastic impedance in fracture detection.

It is as follows that the present invention realizes the concrete scheme of above-mentioned purpose:

Crack detection method based on azimuthal anisotropy elastic impedance, it is characterized in that, comprise the steps: step 1: (comprise and protect width migration processing) processed in seismic data minute orientation, extract a minute orientation common reflection point CRP(Common Reflection Point) road collection;

Step 2: obtain fracture parameters, fracture spacing B from conventional AVOZ inversion result ^aniand fracture azimuth ф _s, in conjunction with well logging and rock physics information, the dominance relation formula with fracture parameters and calculation of elastic impedance in anisotropic media EI (i, φ), simulates the calculation of elastic impedance in anisotropic media Log-constrained curve under different azimuth road collection;

Step 3: implement the Sparse Pulse Inversion of well constraint in Jason software, try to achieve the calculation of elastic impedance in anisotropic media EI (i, φ) that road, each minute orientation set pair is answered, ф is for gathering azimuth;

Step 4: divide angle of incidence to process to seismic data, comprise and protect width migration processing, obtain angle of incidence partial stack road collection;

Step 5: utilize different incidence angles stack road collection, implement the Sparse Pulse Inversion of well constraint in Jason software, ask for isotropic elastic impedance EI (i), i is angle of incidence;

Step 6: calculate the ratio of calculation of elastic impedance in anisotropic media EI (i, φ) and isotropic elasticity impedance EI (i), ask for fracture spacing B with inversion algorithm ^aniand fracture azimuth ф _s;

Step 7: prediction fracture reservoir development belt.

The beneficial effect that the present invention compares prior art generation is:

Crack is the reservoir space of oil gas, is again the migration pathway of fluid, and fracture detection is significant to finding oil and gas reservoir.The identification in crack is current study hotspot and difficult point.

1, the present invention proposes a kind of in HTI medium the fracture parameters inversion method based on azimuthal anisotropy elastic impedance.Take the elastic impedance equation of Connolly and Ruger equation is basis, has derived the dominance relation formula of calculation of elastic impedance in anisotropic media and fracture parameters (fracture spacing and fracture orientation).

2, the present invention has set up a set of crack inverting flow process based on orientation elastic impedance, and the anisotropic parameters information being obtained by conventional AVOZ inverting is added in the Log-constrained of inverting.The method is carried out to numerical model test, and inversion result and theoretical value are roughly the same, and the fracture spacing of inverting demonstrates stronger noise immunity.In real data test, inversion result and FMI imaging logging data coincidence are higher.

3, advantage of the present invention is to utilize calculation of elastic impedance in anisotropic media to ask for fracture spacing and fracture orientation simultaneously, and in real data, has good effect, has stronger practicality.

Accompanying drawing explanation

Fig. 1 is the fracture parameters inverting flow chart based on azimuthal anisotropy elastic impedance;

Fig. 2 (a) is the comprehensive collection schematic diagram of single CRP point in numerical model data;

Fig. 2 (b) is HTI dielectric model schematic diagram in numerical model data;

Fig. 3 does not add the fracture spacing B of noise inverting in numerical model ^aniand fracture azimuth ф _swith theoretical value comparison diagram;

Fig. 4 (a-f) is that in numerical model, signal to noise ratio is respectively 10,8, the fracture spacing B of inverting in 5,3,2,1 o'clock ^aniwith theoretical value comparison diagram;

Fig. 5 is that in numerical model, signal to noise ratio is respectively 10,8, the fracture azimuth ф of inverting in 5,3,2,1 o'clock _swith theoretical value comparison diagram;

Fig. 6 is Xinjiang block different azimuth calculation of elastic impedance in anisotropic media Log-constrained curve map;

Fig. 7 is calculation of elastic impedance in anisotropic media inversion result figure under this block different azimuth of Xinjiang;

Fig. 8 is fracture spacing orientation and the well data comparison diagram that this block of Xinjiang is crossed well A inverting;

Fig. 9 is fracture spacing orientation and the well data comparison diagram that this block of Xinjiang is crossed well B inverting;

Figure 10 is the superimposed plan view of fracture spacing and orientation and the well C of a room group inverting of this block of Xinjiang, D, the partial enlarged drawing at E place.

The specific embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention will be further described.

Fig. 1 is the flow chart of the fracture parameters inversion method based on azimuthal anisotropy elastic impedance in the present invention: step 1: (comprise and protect width migration processing) processed in seismic data minute orientation, extract a minute orientation common reflection point CRP(Common Reflection Point) road collection;

Step 2: obtain fracture parameters (fracture spacing B from conventional AVOZ inversion result ^aniand fracture azimuth ф _s), in conjunction with well logging and rock physics information, the dominance relation formula of the fracture parameters of deriving with the present invention and calculation of elastic impedance in anisotropic media EI (i, φ), simulates the calculation of elastic impedance in anisotropic media Log-constrained curve under different azimuth road collection;

Step 3: implement the Sparse Pulse Inversion of well constraint in Jason software, try to achieve the calculation of elastic impedance in anisotropic media EI (i, φ) that road, each minute orientation set pair is answered, ф is for gathering azimuth;

Step 4: seismic data minute angle of incidence is processed to (comprise and protect width migration processing), obtain angle (angle of incidence) partial stack road collection;

Step 5: utilize different incidence angles stack road collection, implement the Sparse Pulse Inversion of well constraint in Jason software, ask for isotropic elastic impedance EI (i), i is angle of incidence;

Step 6: calculate the ratio of calculation of elastic impedance in anisotropic media EI (i, φ) and isotropic elasticity impedance EI (i), ask for fracture spacing B with inversion algorithm of the present invention ^aniand fracture azimuth ф _s;

Step 7: prediction fracture reservoir development belt.

Calculation of elastic impedance in anisotropic media Log-constrained curve in described step 2, is reflectance factor approximate equation in the HTI medium proposing based on Ruger and the elastic impedance equation of Connolly, the calculation of elastic impedance in anisotropic media of foundation and fracture parameters, fracture spacing B ^aniand fracture azimuth ф _sbetween Explicit functions simulate.Wherein, p-and s-wave velocity, density is obtained by log data, and fracture parameters is obtained by conventional AVOZ inversion result.

The described fracture parameters inversion method based on azimuthal anisotropy elastic impedance is to combine to utilize isotropic elasticity impedance and calculation of elastic impedance in anisotropic media to ask for fracture spacing B simultaneously ^aniand fracture azimuth ф _s.

The described fracture parameters inversion method based on azimuthal anisotropy elastic impedance, the scope of application in actual data application is as follows: the incident angle in angle-angle of incidence partial stack data is little, is generally less than 30 degree; The fracture spacing of surveying in the present invention, refers to the strength of anisotropy that effective fracture causes.So-called effective fracture referred to open and filling the crack of fluid, be effective reservoir space of oil, gas, water.Strength of anisotropy is the coefficient result in many group cracks: when within the scope of certain depth, effective fracture moves towards roughly the same, anisotropic degree is high; Otherwise if in certain depth bounds, the trend in crack presents different directions, the anisotropic character of seismic wave can be weakened, even can demonstrate isotropic feature, and this just cannot obtain by inverting the information of subterranean fracture.

The basic principle based on azimuthal anisotropy elastic impedance fracture detection method providing in the present invention is as follows: in the relational expression of isotropism, calculation of elastic impedance in anisotropic media and anisotropic emission coefficient, on the basis of formula (5), improve.

By the fracture spacing formula defining in Ruger equation:

$B^{\mathrm{ani}}=\frac{1}{2}[{\mathrm{\Δ\δ}}^V+2{\left(2K\right)}^2\mathrm{\Δ\γ}]---\left(6\right)$

Substitution anisotropic emission coefficients R ^aniin (i, φ), formula (5) can be rewritten into:

△lnEI(i,φ)=△lnEI(i)+2B ^anicos ²(φ-φ _s)sin ²i (7)

And then obtain isotropism, calculation of elastic impedance in anisotropic media and fracture spacing B ^ani, fracture azimuth ф _sdominance relation formula

EI(i,φ)/EI(i)=exp(2B ^anicos ²(φ-φ _s)sin ²i) (8)

The present invention asks for fracture spacing B ^aniand fracture azimuth ф _stime according to following equation group:

$\left\{\begin{array}{c}1n(\mathrm{EI}(i,\mathrm{\φ})/\mathrm{EI}\left(i\right))=C_1{\cos }^2\mathrm{\φ}{\sin }^{2}i+2C_2\sin \mathrm{\φ}\cos \mathrm{\φ}{\sin }^{2}i+C_3{\sin }^2\mathrm{\φ}{\sin }^{2}i\\ C_1=B^{\mathrm{ani}}{\cos }^2{\mathrm{\φ}}_s\\ C_2{B}^{\mathrm{ani}}{\sin }^2{\mathrm{\φ}}_s\\ C_3{B}^{\mathrm{ani}}{\sin }^2{\mathrm{\φ}}_s\end{array}\right.---\left(9\right)$

Solve above formula overdetermination system of linear equations, obtain C ₁, C ₂, C ₃, have:

B ^ani=C ₁+C ₃，φ _s=arctan(2C ₃/C ₂) (10)

In the present invention, the scope of application of fracture detection is as follows: the incident angle little (being generally less than 30 degree) in angle of incidence partial stack data; The fracture spacing of surveying in the present invention, refers to the strength of anisotropy that effective fracture causes.So-called effective fracture referred to open and filling the crack of fluid, be effective reservoir space of oil, gas, water.When effective fracture moves towards roughly the same, show stronger anisotropic character, use this algorithm effectively to survey; When effective fracture moves towards different, show weak anisotropic character, this algorithm can not effectively be surveyed.

Fig. 2 is numerical model design data, and wherein (a) is the comprehensive acquisition system of single CRP point, and regulation directions X is 0 degree, and clockwise direction angle increases, and is total to azimuth is divided into altogether 6 azimuth Dao Ji by one of 30 degree.(b) be double-deck single Interface Crack model, upper strata A is homogeneous isotropic medium layer, and the B of lower floor is HTI fracture medium layer.The context parameter of each layer of medium and layer thickness are as table 1.

The background velocity of table 1 medium and layer thickness

(note: speed unit: meter per second; Density unit: kilograms per cubic meter; Thickness unit: rice)

Design one and comprise the survey line that 41 CRP are ordered.The from the 1st to the 41st CRP point, characterizes anisotropic three coefficients and is given as successively: ε ^v=-0.2, γ ^v=0, n=0～0.39, δ ^v=n ².Utilize Ruger formula to can be calculated the fracture spacing on each CRP, the azimuth of designing this list group crack is 90 degree.

Fig. 3 does not add the fracture spacing B of noise inverting in numerical model ^aniand fracture azimuth ф _swith theoretical value contrast, fracture spacing changes line as shown in blue solid lines in figure with No. CRP.Can find out from CRP1～CRP41, fracture spacing is conic section to be increased.And red dispersion point is inverting value.During data noiselessness, the fracture spacing of inverting fits like a glove with CRP change curve with the fracture spacing of just drilling from CRP1～CRP41, has confirmed in noiselessness situation the accuracy of this inversion algorithm and reliability.

In Fig. 4, a-f is for having added after certain noise, and signal to noise ratio is respectively 10,8, the fracture spacing of inverting in 5,3,2,1 o'clock and theoretical value contrast.Under different state of signal-to-noise, the noise immunity of fracture spacing is stronger, and inversion result is all near theoretical curve, and along with the increase of signal to noise ratio, the inversion result degree of accuracy improves gradually, and when signal to noise ratio is 10, inverting value and theoretical value are substantially identical.

Fig. 5 is that in numerical model, signal to noise ratio is respectively 10,8, and the contrast of the fracture orientation of inverting in 5,3,2,1 o'clock and theoretical value, compares and fracture spacing, the noise immunity of fracture orientation a little less than, when signal to noise ratio is less than 5, more than 50% CRP point tolerance is all larger; Be greater than at 5 o'clock, CRP point and the theoretical value goodness of fit are higher, only have small part singular value point.Therefore,, when data signal to noise ratio is higher, just more accurately and reliably, and no matter fracture spacing is at anti-noise ability in the fracture orientation of inverting, or in the inverting degree of accuracy, is all more better than fracture orientation.

Fig. 2～Fig. 5 illustrates that, in numerical model, the fracture detection method based on azimuthal anisotropy elastic impedance can be asked for fracture spacing and fracture orientation effectively, and the fracture spacing of inverting demonstrates stronger noise immunity.

With this algorithm, in the block real data of Xinjiang, be applied as the reality that example illustrates the method below

Border effect.

Fig. 6 is calculation of elastic impedance in anisotropic media Log-constrained curve under different azimuth.4 orientation corresponding to curve that show in figure are respectively 23 degree, 53 degree, 83 degree, 113 degree.This is to be incorporated into firing angle, azimuth information, the fracture spacing and the bearing data that by conventional AVOZ inverting, are obtained, and velocity of longitudinal wave, shear wave velocity, density in well logging, the dominance relation formula of the fracture parameters of deriving according to the present invention and calculation of elastic impedance in anisotropic media, the calculation of elastic impedance in anisotropic media Log-constrained curve under the different azimuth road collection simulating.When angle of incidence or azimuth difference, elastic impedance value can produce the difference in magnitude, therefore, we introduce Whitcombe to the normalized thought (Whitcombe of Connolly elastic equation, et al., 2002), different elastic impedances are grouped under same dimension.What in figure, show is standardization result afterwards, and the approximate trend of curve is identical, but at target zone section, at the bottom of pushing up a room group from a room group, curve difference is comparatively obvious, changes more violently, and this is to cause because this section exists stronger anisotropic character.Therefore, than conventional method, this elastic impedance matching mode has better retained the feature of Reservoir anisotropy, has better followed algorithm principle, makes to calculate more accurately credible.

Fig. 7 is calculation of elastic impedance in anisotropic media inversion result under this block different azimuth of Xinjiang.Elastic impedance under different azimuth has shown obvious difference, has embodied the effect of anisotropy Log-constrained.

Fig. 8 is fracture spacing orientation and the contrast of well data that this block of Xinjiang is crossed well A inverting.Using Conventional Logs shows, locates fracture porosity higher in group layer position, a room, and imaging logging data show this position growth slit formation carbonate rock, and are single group crack.Contrasting inversion result can find out, it is abnormal that the fracture spacing of this layer of position place's inverting is high value, matches with log data; In the crack polar plot of inverting, the direction of arrow represents fracture strike, and length and bin shade represent density height, and the fracture orientation of inverting that hence one can see that is 3 degree; Meanwhile, the rose diagram of imaging logging statistics has shown the trend in target location crack, and red direction of principal axis represents fracture strike, and length represents fracture spacing height.Contrast knownly, the fracture strike that the fracture orientation of inverting and FMI show is consistent.

Fig. 9 is fracture spacing orientation and the contrast of well data that this block of Xinjiang is crossed well B inverting.B well is lower in group place, a room of target reservoir fracture porosity, and imaging logging shows free from flaw; In inversion result, fracture spacing is a little less than target location shows, and similar to background value, without abnormal show, and crack polar plot also shows that this place is without anisotropic character, all matches with log data.

Figure 10 is the superimposed plan view of fracture spacing and orientation and the well C of a room group inverting of this block of Xinjiang, D, the partial enlarged drawing at E place.Single group crack is all grown at three mouthfuls of well location places in figure, and the fracture spacing of inverting has also demonstrated relatively high value.In the fracture orientation of inverting, well H601-4, H601-14, H601-5 and actual trend are substantially identical.Known by above-mentioned analysis, based on azimuthal anisotropy elastic impedance crack inversion method, can ask for comparatively accurately fracture spacing and orientation, there is stronger practicality.

Claims (6)

1. the crack detection method based on azimuthal anisotropy elastic impedance, is characterized in that, described method comprises the steps:

Step 1: divide orientation to process to seismic data, comprise and protect width migration processing, extract a minute orientation common reflection point CRP(Common Reflection Point) road collection;

Step 2: obtain fracture parameters, fracture spacing B from conventional AVOZ inversion result ^aniand fracture azimuth ф _s, in conjunction with well logging and rock physics information, the dominance relation formula with fracture parameters and calculation of elastic impedance in anisotropic media EI (i, φ), simulates the calculation of elastic impedance in anisotropic media Log-constrained curve under different azimuth road collection;

Step 3: implement the Sparse Pulse Inversion of well constraint in Jason software, try to achieve the calculation of elastic impedance in anisotropic media EI (i, φ) that road, each minute orientation set pair is answered, ф is for gathering azimuth;

Step 4: divide angle of incidence to process to seismic data, comprise and protect width migration processing, obtain angle of incidence partial stack road collection;

Step 5: utilize different incidence angles stack road collection, implement the Sparse Pulse Inversion of well constraint in Jason software, ask for isotropic elastic impedance EI (i), i is angle of incidence;

Step 6: calculate the ratio of calculation of elastic impedance in anisotropic media EI (i, φ) and isotropic elasticity impedance EI (i), ask for fracture spacing B with inversion algorithm ^aniand fracture azimuth ф _s;

Step 7: prediction fracture reservoir development belt.

2. the crack detection method based on azimuthal anisotropy elastic impedance according to claim 1, it is characterized in that, calculation of elastic impedance in anisotropic media Log-constrained curve in described step 2, reflectance factor approximate equation in the HTI medium proposing based on Ruger and the elastic impedance equation of Connolly, calculation of elastic impedance in anisotropic media and the fracture parameters set up, fracture spacing B ^aniand fracture azimuth ф _sbetween Explicit functions simulate; Wherein, p-and s-wave velocity, density is obtained by log data, and fracture parameters is obtained by conventional AVOZ inversion result.

3. the crack detection method based on azimuthal anisotropy elastic impedance according to claim 1, is characterized in that, the dominance relation formula with fracture parameters and calculation of elastic impedance in anisotropic media EI (i, φ) described in step 2 is:

EI(i,φ)/EI(i)=exp(2B ^anicos ²(φ-φ _s)sin ²i) (8)

4. the crack detection method based on azimuthal anisotropy elastic impedance according to claim 1, is characterized in that, the inversion algorithm relational expression described in step 6 is:

EI(i,φ)/EI(i)=exp(2B ^anicos ²(φ-φ _s)sin ²i) (8)

Ask for fracture spacing B ^aniand fracture azimuth ф _stime according to following equation group:

$\left\{\begin{array}{c}1n(\mathrm{EI}(i,\mathrm{\φ})/\mathrm{EI}\left(i\right))=C_1{\cos }^2\mathrm{\φ}{\sin }^{2}i+2C_2\sin \mathrm{\φ}\cos \mathrm{\φ}{\sin }^{2}i+C_3{\sin }^2\mathrm{\φ}{\sin }^{2}i\\ C_1=B^{\mathrm{ani}}{\cos }^2{\mathrm{\φ}}_s\\ C_2{B}^{\mathrm{ani}}{\sin }^2{\mathrm{\φ}}_s\\ C_3{B}^{\mathrm{ani}}{\sin }^2{\mathrm{\φ}}_s\end{array}\right.---\left(9\right)$

5. the crack detection method based on azimuthal anisotropy elastic impedance according to claim 1, is characterized in that, described method is to combine to utilize isotropic elasticity impedance and calculation of elastic impedance in anisotropic media to ask for fracture spacing B simultaneously ^aniand fracture azimuth ф _s.

6. the crack detection method based on azimuthal anisotropy elastic impedance according to claim 1, is characterized in that, the scope of application of described method in actual data application is as follows: the incident angle in angle of incidence partial stack data is less than 30 degree; The fracture spacing of surveying, refers to the strength of anisotropy that effective fracture causes; Effective fracture referred to open and filling the crack of fluid, be effective reservoir space of oil, gas, water; Strength of anisotropy is the coefficient result in many group cracks: when within the scope of certain depth, effective fracture moves towards roughly the same, anisotropic degree is high; Otherwise if in certain depth bounds, the trend in crack presents different directions, the anisotropic character of seismic wave can be weakened, even can demonstrate isotropic feature, cannot obtain by inverting the information of subterranean fracture.