CN105891885A - Prestack amplitude preservation focusing and imaging technology for specific geologic body underground - Google Patents

Abstract

The invention belongs to a geophysical exploration technology, and relates to a prestack amplitude preservation focusing and imaging technology for a specific geologic body underground. According to the invention, seismic data is acquired, conventional processing such as prestack noise elimination, de-convolution and first arrival blanking, and a geologic body at a specific depth underground can be accurately imaged by using the prestack amplitude preservation focusing and imaging technology. A corresponding focusing parameter can be estimated according to the spatial position of the specific geologic body underground, the focusing parameter is applied to prestack amplitude preservation focusing offset for the geologic body, and an accurate imaging result can be acquired. Provided by the invention is a high-precision imaging method for the specific geologic body underground, a problem that special geologic bodies such as a salt dome, a buried hill and a fracture at the medium depth underground are difficult to be imaged is solved, geometric diffusion effects in seismic wave propagation can be eliminated, and an offset section with relatively preserved amplitude is acquired.

Description

The prestack being directed to underground specifically plastid protects width focal imaging technology

Technical field

The present invention relates to seism processing, the prestack guarantor's width being particularly directed to the specifically plastid in underground gathers Burnt migration and imaging techniques.

Background technology

In recent years, the bundle migration technology with Kirchhoff and wave equation migration associating advantage causes The extensive concern of Chinese scholars.Wherein it is typically Hill (1990), Hill (2001), the Gaussian beam offset method that Gray (2005), Gray (2009) etc. propose, the method both had The Kirchhoff skew flexibility to irregular observation system, has again and wave equation imaging essence Spend suitable accuracy.But in Gaussian beam offsets, effective half width of bundle is with the increase of ray path Form hyperbolic rule to increase so that at the complex geologic body of underground (salt dome, buried hill, volcanic crater etc.) Imaging precision lowers significantly, and the most many scholars have also been made a lot of research to this problem, as inclined in complex value bundle Shifting, Gaussian beam linear inversion etc., but these methods are all in the starting stage of research, the most very well Solve complex geologic body target imaging problem

Being directed to the problems referred to above, the present invention uses the thought of focused beam acts so that with a tight waist (the narrowest on bundle, Stable position) it is positioned specifically on plastid so that and the wave field of this position structure is more stable, more Add accurately, and then the precision of migration imaging result is greatly improved.

Summary of the invention

Present invention aim at providing a kind of guarantor's width seismic imaging technology for underground specifically plastid.

The present invention can be realized by techniques below means:

1) conventional Prestack seismic data (single big gun data before superposition) and Depth Domain velocity field are used；

2), after seismic data being carried out the conventional treatment such as the denoising of prestack, deconvolution, initial blanking, carry out speed and divide Analysis, dynamic(al) correction, horizontal overlap-add procedure obtain preliminary stacked section, on stacked section judge salt dome, The self excitation and self receiving whilst on tour of the special geobody such as buried hill, volcanic crater, then asks according to time and depth transfer relation Obtain the degree of depth of this geologic body.

3) according to 2) the middle degree of depth estimated, determine and be directed to this geologic body focusing parameter, its expression formula is:

ε=ε_r-iε_i=-S₀v₀-iω_refl_m(formula 1)

In formula: ε is complex value focusing parameter, ε_rAnd ε_iIt is respectively its real part and imaginary part, S₀For the depth of focus, v₀For Focal imaging carries out initial point speed during ray tracing, ω_refFor the reference frequency (in focal imaging As take the low side of seismic data frequency spectrum), l_mEffective half width for place with a tight waist (typically takes relative to reference The mean wavelength of frequency, it may be assumed that l_m=v_avg/ω_ref, v_avgAverage for velocity field).

4) focusing parameter tried to achieve is applied to point source reverse wave field structure in, can in the hope of with geology The focused beam acts sign Green's function that the body place degree of depth is corresponding, its expression formula is as follows:

$G(x,x^g,\mathrm{\ω})=-\frac{1}{4\mathrm{\π}}{\left(\frac{\mathrm{\ϵ}}{v^{s_0}}\right)}^{1/2}\∫\frac{{\mathrm{dp}}_x^g}{p_z^g}{u}_{\mathrm{gb}}(x,x^{s_0},p^g,\mathrm{\ω})\exp \left\{\mathrm{i\ω}\right[p_x^g(x_x^g-x_x^{s_0})+\frac{k_x\left(s_0\right){(x_x^g-x_x^{s_0})}^2}{2v^{s_0}}\left]\right\}$

(formula 2)

In formula: x is subsurface imaging point, x_gFor receiving point,WithRay tracing initial point s when being respectively imaging₀'s Position and speed, ω is circular frequency,WithIt is respectively the horizontal and vertical slowness received at point,With It is respectively geophone station and the horizontal component of initial point, k_x(s₀) it is the wave-front curvature of initial point, its expression formula is:

$k_x\left(s_0\right)=\frac{-{\left(v^{s_0}\right)}^2{s}_0}{{\left(v^{s_0}{s}_0\right)}^2+{\left({\mathrm{\ω}}_{\mathrm{ref}}{l}_m\right)}^2},$ (formula 3)

u_gb For from initial pointPropagating to the focused beam acts of x, its expression formula is:

$u_{\mathrm{gb}}(x,x^{s_0},p^g,\mathrm{\ω})=\sqrt{\frac{Q\left(s_0\right)}{Q\left(s\right)}}\exp \left[\mathrm{i\ω}(\mathrm{\τ}\left(s\right)+\frac{1}{2}\frac{P\left(s\right)}{Q\left(s\right)}{n}^2)\right],$ (formula 4)

In formula: s and n be imaging point x coordinate under ray center coordinate system, P (s) and Q (s) be that the kinetics of focused beam acts is penetrated Line parameter.

5) in point source forward wave field constructs, using the Green's function that focused beam acts characterizes, its expression formula is such as Under:

$G(x,x^s,\mathrm{\ω})=-\frac{i}{4\mathrm{\π}}{\left(\frac{\mathrm{\ϵ}}{v^s}\right)}^{1/2}\∫\frac{{\mathrm{dp}}_x^s}{p_z^s}{u}_{\mathrm{gb}}(x,x^s,p^s,\mathrm{\ω})$ (formula 5)

In formula:WithFor the horizontal slowness at shot point and vertical slowness, u_gb(x, x^s, p^s, ω) and it is from shot point x^sPropagate to underground The focused beam acts of imaging point x, its expression is such as formula 4.

6) according to deconvolution imaging principle, available guarantor's width imaging results for underground specifically plastid, Its expression formula is:

$R(x,x^s)=\frac{1}{2\mathrm{\π}}\frac{\cos {\mathrm{\θ}}_s}{v^s}\∫\mathrm{d\ωi\ω}\frac{P_U(x,x^s,\mathrm{\ω})P_D^{*}(x,x^g,\mathrm{\ω})}{P_D(x,x^s,\mathrm{\ω})P_D^{*}(x,x^g,\mathrm{\ω})}$ (formula 6)

In formula: $P_U(x,x^g,\mathrm{\ω})=-2\mathrm{i\ω}\∫d{x}^g\frac{\cos {\mathrm{\θ}}_g}{v^g}G{(x,x^g,\mathrm{\ω})}^{*}{P}_U(x^g,x^s,\mathrm{\ω}),$ (formula 7)

$P_D(x,x^s,\mathrm{\ω})=-2\mathrm{i\ω}\frac{\cos {\mathrm{\θ}}_s}{v^s}G(x,x^s,\mathrm{\ω}),$ (formula 8)

θ_sAnd θ_gIt is respectively at shot point and ray emergence angle, p at geophone station_u(x^g, x^s, ω) and it is the record wave field at ground receiver, on Mark " * " represents complex value conjugation.

The thought of focusing is incorporated in bundle skew by the present invention, it is possible to achieve in the underground arbitrary target degree of depth On focal imaging.According to the differently plastid place degree of depth, calculate corresponding focusing parameter, can obtain High-precision target imaging result.This method has widened the range of application of Gaussian beam imaging, enriches Gauss The research space of bundle skew, and have that stability is strong, efficiency is high and result of calculation is more true and reliable Advantage.

Accompanying drawing explanation

Fig. 1 is the naive model for theory test；

The sound wave of Fig. 2 naive model is just drilling big gun record；

Fig. 3 for be directed to first scattering point (250 meters of depths) carry out vertical propagation focused beam acts protect width inclined Move the imaging results obtained；

Fig. 4 for be directed to second scattering point (500 meters of depths) carry out vertical propagation focused beam acts protect width inclined Move the imaging results obtained；

Fig. 5 for be directed to the 3rd scattering point (750 meters of depths) carry out vertical propagation focused beam acts protect width inclined Move the imaging results obtained；

Fig. 6 is directed to second scattering point be focused restrainting single big gun imaging knot that Amplitude preserving process obtains Really；

Fig. 7 is that application normal Gaussian bundle offset method is to the imaging of the 120th big gun record in Marmous data set Result；

Fig. 8 be application present invention is directed at rift structure at 1000 meters of Marmous model be focused bundle protect Single big gun (the 120th big gun) imaging results that width migration processing obtains.

Detailed description of the invention

For making the method for the present invention, objects, features and advantages to become apparent, cited below particularly go out two Typical examples, and coordinate institute's accompanying drawings, it is described in detail below.

Example one:

1) choosing typical speckle spot speed model as shown in Figure 1, mesh generation is 201 × 201, and vertically and horizontally mesh spacing is 5m；

2) scatter times is carried out sound wave just to drill, obtain single shot record, as in figure 2 it is shown, record length is 1200ms, Time sampling interval is 2ms, totally 201 road；

3) it is respectively directed to three scattering points (degree of depth is respectively 250m, 500m and 750m) and carries out vertical propagation focused beam acts Amplitude preserving, obtains the imaging results as shown in Fig. 3, Fig. 4, Fig. 5；

4) it is focused restrainting Amplitude preserving to middle scattering point (at 500m), obtains as single big gun skew is tied as shown in Figure 6 Really；

Example one:

1) the 120th big gun in Marmous data set is carried out normal Gaussian bundle skew, obtain imaging knot as shown in Figure 7 Really；

2) it is directed to rift structure at 1000 meters of Marmous model, is focused restrainting Amplitude preserving and processes, obtain such as Fig. 8 Shown imaging results；

Comparison diagram 3, Fig. 4 Yu Fig. 5 understand, and the guarantor's width seismic imaging technology for underground specifically plastid can be It is focused imaging on different depth, on the premise of ensureing that view picture section imaging results is rationally, improves at the depth of focus Imaging precision, make the imaging results of scattering point become apparent from reliably, and deconvolution image-forming condition make imaging results have Certain guarantor's width.

Comparison diagram 6 understands with Fig. 7, offsets relative to normal Gaussian bundle, and focused beam acts skew makes the depth of focus Place's lineups become thinner, improve section resolution, and make to be positioned at 500m-1500m the most disconnected The profile of layer the most clearly manifests, and improves the imaging precision of single big gun.Comprehensive analysis results shows for underground Specifically guarantor's width imaging results of plastid is substantially better than normal Gaussian bundle imaging results.

Claims (1)

1. the prestack being directed to underground specifically plastid protects width focal imaging technology, it is characterised in that should Imaging technique handling process includes:

1) single big gun data and Depth Domain velocity field before using conventional stacking；

2), after seismic data being carried out the conventional treatment such as the denoising of prestack, deconvolution, initial blanking, carry out speed and divide Analysis, dynamic(al) correction, horizontal overlap-add procedure obtain preliminary stacked section, on stacked section judge salt dome, The self excitation and self receiving whilst on tour of the special geobody such as buried hill, volcanic crater, then asks according to time and depth transfer relation Obtain the degree of depth of this geologic body；

3) according to 2) the middle degree of depth estimated, determine and be directed to this geologic body focusing parameter；

4) focusing parameter is applied in point source reverse wave field structure, tries to achieve and geologic body place degree of depth phase Corresponding focused beam acts characterizes Green's function；

5) in point source forward wave field constructs, the Green's function that focused beam acts characterizes is utilized, according to deconvolution Imaging principle, obtains the guarantor's width imaging results for underground specifically plastid.