CN103576194A - Accurate depth field complex earth surface seismic structure imaging method - Google Patents

Abstract

The invention discloses an accurate depth field complex earth surface seismic structure imaging method. Rectangular meshing is carried out on a three-dimensional depth field velocity field, the floating reference surface elevations of each position in an imaging space is determined, the travel-time from the position to any underground point is calculated with the reference surface as the starting plane, floating reference surface low-frequency components corresponding to all shot point positions and floating reference surface low-frequency components corresponding to all demodulator points are determined from prestack shot gather seismic data, the vertical time difference is converted, the accurate imaging time is worked out based on the vertical time difference, the prestack depth migration process is carried out on the prestack shot gather data based on the imaging time to obtain a common imaging point set, and the structure imaging result of a depth field is obtained through stacking. The floating reference surface integration prestack depth migration is carried out on the seismic data with the large undulating surface characteristics, and a reliable basis is provided for the structure imaging.

Description

A kind of complicated earth surface of Depth Domain accurately seismic structure imaging method

Technical field

The present invention relates to the Depth Domain complicated earth surface seismic structure imaging technology in reflection wave geological data processing procedure, formation method is made in a kind of complicated earth surface of Depth Domain accurately earthquake specifically.

Background technology

Prestack depth migration is one of very important Seismic Data Processing Technique in producing present stage, it can provide the data of seismic structure imaging the most accurately that in Depth Domain, we can see, thus because of its can be directly and well data set up contact have very important effect in finding scale oil field.This technology is main target and then large-scale promotion application mainly for the oil-gas exploration of complex reservoir (hydrocarbon reservoir structure is complicated) in actual production.Under a few cases, due to earth's surface relatively mild (as marine data and exploratory area, northeast), all shot points and geophone station can be corrected on same surface level, and on this surface level, complete pre-stack depth migration and process.Earth's surface very complicated (as exploratory area, south China, Gan Ning exploratory area, Shan and exploratory area, Xinjiang etc.) yet as a rule, now in work area, the discrepancy in elevation of shot point and geophone station is very large, if cautious being corrected on same surface level of all big guns carried out to pre-stack depth migration processing, the imaging results of its shallow-layer is very poor.So, when the type data is carried out to pre-stack depth migration, must remove the image error that complicated earth surface brings as far as possible.

Integral method (Kirchhoff integral method under current complex near surface conditions, down together) Prestack depth migration has been the special technology of the external well-known softwares such as GeoDepth and CGG, and realized suitability for industrialized production, but its treatment technology for relief surface is not open.There is at present the processing thinking of some Kichhoff integral pre-stack depth migrations to relief surface district, also do not form suitability for industrialized production.

Summary of the invention

The object of the invention is to provide a kind of improved on the basis of horizontal earth's surface Kichhoff integral pre-stack depth migration, applicable suitability for industrialized production, Depth Domain complicated earth surface seismic structure imaging method accurately.

The present invention comprises by following concrete steps:

1), at exploratory area acquiring seismic data, utilize data to ask for corresponding Depth Domain velocity field;

2) according to imaging space, velocity field is divided to rectangular node, making has corresponding velocity amplitude in each bin;

3) be specified to the floating datum elevation of each bin position, image space;

Floating datum described in step 3) is the initial surface of ray tracing.

4) in each bin position, take floating datum calculates this position to the whilst on tour of underground any point as reference position;

5) determine the floating datum low frequency component that every one sp location and geophone station position are corresponding;

And utilize the following formula conversion shot point time difference vertical with geophone station;

The vertical time difference of shot point is: Δ T _s=DACT _cmp-DACT _cmps

The vertical time difference of geophone station is: Δ T _r=DACT _cmp-DACT _cmpr

Wherein, Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, DACT for geophone station _cmplow frequency component, DACT for point midway _cmpslow frequency component, DACT for sp location _cmprlow frequency component for geophone station position.

6) according to step 4) whilst on tour and rapid 5) the vertical time difference calculates imaging time accurately with following formula, utilizes imaging time to carry out pre-stack depth migration processing to prestack shot gather data, obtains common image gather;

$T\≈\sqrt{T_s^{\′2}+\mathrm{\Δ}{T}_s^2-2T_s^{\′}\mathrm{\Δ}{T}_s\cos {\mathrm{\θ}}_s}+\sqrt{T_r^{\′2}+\mathrm{\Δ}{T}_r^2-2T_r^{\′}\mathrm{\Δ}{T}_r\cos {\mathrm{\θ}}_r}$

$=T_s+T_r$

Wherein: T is total whilst on tour, T ' _sfor imaging point is to shot point whilst on tour, T ' _rfor imaging point is to geophone station whilst on tour, T _sfor the imaging whilst on tour of shot point, T _rfor the imaging whilst on tour of geophone station, Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, θ for geophone station _sfor angle, the θ of shot point to imaging point start ray direction and vertical direction _rfor the angle of geophone station to imaging point start ray direction and vertical direction;

7) common image gather data are superposeed and obtain structure imaging result and the stratigraphic section image of exploratory area Depth Domain.

Depth Domain complicated earth surface Kichhoff integral pre-stack depth migration structure imaging method of the present invention, obtains Kichhoff integral pre-stack depth migration imaging results accurately by whilst on tour table on Real-time solution floating datum seismologic record and floating datum and the corresponding time difference.Traditional horizontal earth's surface Kichhoff integral pre-stack depth migration method is because needs are done prestack seismogram when vertical and moved on on unified reference field, thereby make propagation path in seismologic record farther departed from original travel path (as shown in Figure 1), so imaging effect is undesirable, the no good cake of the imaging effect of shallow-layer (as shown in Figure 3) especially.Relief surface Kichhoff integral pre-stack depth migration algorithm based on floating datum of the present invention will carry out imaging (as shown in Figure 2) along seismic event in underground original propagation trajectories as far as possible, so imaging effect better (as shown in Figure 4).

Be the Kichhoff integral pre-stack depth migration result of somewhere real data as shown in figure 10, wherein left figure is the Kichhoff integral pre-stack depth migration result of unified reference field, and right figure is floating datum Kichhoff integral pre-stack depth migration result.From result, can see, floating datum migration result of the present invention is better than the migration result of unified reference field, the part shown in circle especially in the drawings, and the migration result of floating datum is clearer and axle is more continuous in the same way.

Accompanying drawing explanation

Fig. 1 unifies the propagation path schematic diagram of reference field;

The propagation path schematic diagram of Fig. 2 floating datum of the present invention;

Fig. 3 unifies the Kichhoff integral pre-stack depth migration imaging results of reference field;

The Kichhoff integral pre-stack depth migration imaging results of Fig. 4 floating datum of the present invention;

The velocity field of Fig. 5 floating reference surface model of the present invention;

In floating datum velocity field, certain a bit carries out ray tracing in Fig. 6 the present invention;

Fig. 7 the present invention on floating datum to often proofreading and correct together time difference schematic diagram calculation;

Common image gather after Fig. 8 floating reference surface model skew of the present invention;

Seismic imaging section after Fig. 9 floating reference surface model skew of the present invention;

The unified reference field skew (left figure) of Figure 10 real data and floating datum migration result of the present invention (right figure) contrast.

Embodiment

In conjunction with marginal data embodiment:

Depth Domain complicated earth surface Kichhoff integral pre-stack depth migration structure imaging method of the present invention, its embodiment is:

1), at exploratory area acquiring seismic data, utilize data to ask for corresponding Depth Domain velocity field;

2) according to imaging space, velocity field is divided to rectangular node, making has corresponding velocity amplitude (as shown in Figure 5) in each bin;

3) determine the floating datum elevation of each bin position of this imaging space.

4) in each bin position, take floating datum calculates this position to the whilst on tour (as shown in Figure 6) of underground any point as reference position;

5) determine floating datum low frequency component corresponding to every one sp location and geophone station position (schematic diagram as shown in Figure 7);

And utilize the following formula conversion shot point time difference vertical with geophone station:

The vertical time difference of shot point is: Δ T _s=DACT _cmp-DACT _cmps

The vertical time difference of geophone station is: Δ T _r=DACT _cmp-DACT _cmpr

Wherein, Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, DACT for geophone station _cmplow frequency component, DACT for point midway _cmpslow frequency component, DACT for sp location _cmprlow frequency component for geophone station position.

According to step 4) whilst on tour and rapid 5) the vertical time difference calculates imaging time accurately with following formula, utilizes imaging time to carry out pre-stack depth migration processing to prestack shot gather data, obtains common image gather (as shown in Figure 8);

$T\≈\sqrt{T_s^{\′2}+\mathrm{\Δ}{T}_s^2-2T_s^{\′}\mathrm{\Δ}{T}_s\cos {\mathrm{\θ}}_s}+\sqrt{T_r^{\′2}+\mathrm{\Δ}{T}_r^2-2T_r^{\′}\mathrm{\Δ}{T}_r\cos {\mathrm{\θ}}_r}$

$=T_s+T_r$

Wherein: T is total whilst on tour, T ' _sfor imaging point is to shot point whilst on tour, T ' _rfor imaging point is to geophone station whilst on tour, T _sfor the imaging whilst on tour of shot point, T _rfor the imaging whilst on tour of geophone station,

Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, θ for geophone station _sfor angle, the θ of shot point to imaging point start ray direction and vertical direction _rfor the angle of geophone station to imaging point start ray direction and vertical direction.

6) common image gather data are superposeed and obtain structure imaging result and the stratigraphic section image (as shown in Figure 9) of exploratory area Depth Domain.

The present invention can well solve the Kichhoff integral pre-stack depth migration imaging problem under relief surface condition, and has following features:

(1) ray tracing initial surface of the present invention is floating datum, it has good continuity and slickness, this floating datum is very near apart from actual rough ground surface simultaneously, so can reduce as much as possible the time error of bringing because of reference field time shift, and then be that the imaging problem solving under complicated rough ground surface has been opened up new thinking.

(2) the present invention adopts point-device imaging whilst on tour computing formula, not only considered every shot point time difference vertical with geophone station together, and calculate more accurate imaging whilst on tour in conjunction with the ray tracing whilst on tour of floating datum, thereby the imaging results that can obtain being satisfied with very much, this is core of the present invention place.

Claims (2)

1. a Depth Domain complicated earth surface seismic structure imaging method accurately, feature is to realize by following concrete steps:

1), at exploratory area acquiring seismic data, utilize data to ask for corresponding Depth Domain velocity field;

2) according to imaging space, velocity field is divided to rectangular node, making has corresponding velocity amplitude in each bin;

3) be specified to the floating datum elevation of each bin position, image space;

4) in each bin position, take floating datum calculates this position to the whilst on tour of underground any point as reference position;

5) determine the floating datum low frequency component that every one sp location and geophone station position are corresponding;

And utilize the following formula conversion shot point time difference vertical with geophone station;

The vertical time difference of shot point is: Δ T _s=DACT _cmp-DACT _cmps

The vertical time difference of geophone station is: Δ T _r=DACT _cmp-DACT _cmpr

Wherein, Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, DACT for geophone station _cmplow frequency component, DACT for point midway _cmpslow frequency component, DACT for sp location _cmprlow frequency component for geophone station position.

6) according to step 4) whilst on tour and rapid 5) the vertical time difference calculates imaging time accurately with following formula, utilizes imaging time to carry out pre-stack depth migration processing to prestack shot gather data, obtains common image gather;

$T\≈\sqrt{T_s^{\′2}+\mathrm{\Δ}{T}_s^2-2T_s^{\′}\mathrm{\Δ}{T}_s\cos {\mathrm{\θ}}_s}+\sqrt{T_r^{\′2}+\mathrm{\Δ}{T}_r^2-2T_r^{\′}\mathrm{\Δ}{T}_r\cos {\mathrm{\θ}}_r}$

$=T_s+T_r$

Wherein: T is overall travel time, T ' _sfor imaging point is to shot point whilst on tour, T ' _rfor imaging point is to geophone station whilst on tour, T _sfor the imaging whilst on tour of shot point, T _rfor the imaging whilst on tour of geophone station, Δ T _sthe vertical time difference, Δ T for shot point _rthe vertical time difference, θ for geophone station _sfor angle, the θ of shot point to imaging point start ray direction and vertical direction _rfor the angle of geophone station to imaging point start ray direction and vertical direction;

7) common image gather data are superposeed and obtain structure imaging result and the stratigraphic section image of exploratory area Depth Domain.

2. method according to claim 1, feature is the initial surface that the floating datum described in step 3) is ray tracing.

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