CN103576194B - A kind of depth field complex earth surface seismic structure imaging method - Google Patents

Abstract

The present invention is one depth field complex earth surface seismic structure imaging method accurately, three dimensional depth territory velocity field is carried out gridding, be specified to the floating datum elevation of each position, image space, with this reference field for initial surface calculates the whilst on tour of this position to underground any point, the floating datum low frequency component corresponding with geophone station position from every one sp location of prestack big gun collection geological data also converses the vertical time difference, applying the vertical time difference calculates imaging time accurately, this imaging time is utilized to carry out pre-stack depth migration process to prestack shot gather data, obtain common imaging gather, carry out again superposing the structure imaging result obtaining Depth Domain.The present invention is directed to the geological data had compared with macrorelief topographical features and carry out floating datum Kichhoff integral pre-stack depth migration, for the imaging of this class formation provides reliable basis.

Description

A kind of depth field complex earth surface seismic structure imaging method

Technical field

The present invention relates to the depth field complex earth surface seismic structure imaging technology in reflection wave seismic data process process, formation method is made in a kind of depth field complex earth surface 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, because of its can directly and well data set up contact thus discovery scale oil field in have very important effect.This technology is main target and then large-scale promotion application mainly for the oil-gas exploration of complex reservoir (hydrocarbon reservoir structure complicated) in actual production.Under a few cases, due to earth's surface relatively milder (as marine data and exploratory area, northeast), all shot points and geophone station can be corrected on same surface level, and complete pre-stack depth migration process on this surface level.But as a rule earth's surface very complicated (as exploratory area, south China, Gan Ning exploratory area, Shan and exploratory area, Xinjiang etc.), now in work area, the discrepancy in elevation of shot point and geophone station is very large, if cautious for all big guns being corrected on same surface level is carried out pre-stack depth migration process, the imaging results of its shallow-layer is very poor.So, the image error that complicated earth surface brings must be removed when pre-stack depth migration is carried out to the type data 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 famous foreign softwares such as GeoDepth and CGG, and realize suitability for industrialized production, but its treatment technology for relief surface is not open.There are some Kichhoff integral pre-stack depth migrations at present to the roadmap in 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 that improve on the basis of horizontal earth's surface Kichhoff integral pre-stack depth migration, applicable suitability for industrialized production, accurately depth field complex earth surface seismic structure imaging method.

The present invention is comprised by following concrete steps:

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

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

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

4) be that reference position calculates the whilst on tour of this position to underground any point with floating datum in each bin position;

5) floating datum low frequency component corresponding to every one sp location and geophone station position is determined;

And utilize the following formula scales 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 _sfor the vertical time difference, the Δ T of shot point _rfor the vertical time difference, the DACT of geophone station _cmpfor low frequency component, the DACT of point midway _cmpsfor low frequency component, the DACT of sp location _cmprfor the low frequency component of geophone station position;

6) according to step 4) whilst on tour and step 5) the vertical time difference with following formulae discovery imaging time, utilize imaging time to carry out pre-stack depth migration process to prestack shot gather data, obtain common imaging gather;

$\begin{array}{c}T\≈\sqrt{T_s^{\′2}+{\mathrm{\ΔT}}_s^2-2T_s^{\′}{\mathrm{\ΔT}}_s{\mathrm{cos\θ}}_s}+\sqrt{T_r^{\′2}+{\mathrm{\ΔT}}_r^2-2T_r^{\′}{\mathrm{\ΔT}}_r{\mathrm{cos\θ}}_r}\\ =T_s+T_r\end{array}$

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 _sfor the vertical time difference, the Δ T of shot point _rfor the vertical time difference, the θ of geophone station _sfor shot point is to angle, the θ of imaging point start ray direction and vertical direction _rfor geophone station is to the angle of imaging point start ray direction and vertical direction;

7) common imaging gather data are carried out to superpose the structure imaging result obtaining exploratory area Depth Domain and stratigraphic section image.

Depth field complex 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 owing to moving on in uniform reference surface when prestack seismogram is done vertical by needs, thus make the propagation path in seismologic record farther deviate from original travel path (as shown in Figure 1), so imaging effect is undesirable, the especially no good cake of the imaging effect of shallow-layer (as shown in Figure 3).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 the propagation trajectories that seismic event is original in underground 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 uniform reference surface, and right figure is floating datum Kichhoff integral pre-stack depth migration result.Can see from result, floating datum migration result of the present invention is better than the migration result of uniform reference surface, and the part especially in the drawings shown in circle, the migration result of floating datum is clearer and axle is more continuous in the same way.

Accompanying drawing explanation

The propagation path schematic diagram of Fig. 1 uniform reference surface;

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

The Kichhoff integral pre-stack depth migration imaging results of Fig. 3 uniform reference surface;

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 carrying out correction time difference schematic diagram calculation together;

Common imaging gather after Fig. 8 floating datum model offset of the present invention;

Seismic imaging section after Fig. 9 floating datum model offset of the present invention;

Uniform reference surface 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 field complex 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, data are utilized to ask for corresponding Depth Domain velocity field;

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

3) the floating datum elevation of each bin position, image space is specified to.

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

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

And utilize the following formula scales 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 _sfor the vertical time difference, the Δ T of shot point _rfor the vertical time difference, the DACT of geophone station _cmpfor low frequency component, the DACT of point midway _cmpsfor low frequency component, the DACT of sp location _cmprfor the low frequency component of geophone station position.

According to step 4) whilst on tour and rapid 5) the vertical time difference with following formulae discovery imaging time accurately, utilize imaging time to carry out pre-stack depth migration process to prestack shot gather data, obtain common imaging gather (as shown in Figure 8);

$\begin{array}{c}T\≈\sqrt{T_s^{\′2}+{\mathrm{\ΔT}}_s^2-2T_s^{\′}{\mathrm{\ΔT}}_s{\mathrm{cos\θ}}_s}+\sqrt{T_r^{\′2}+{\mathrm{\ΔT}}_r^2-2T_r^{\′}{\mathrm{\ΔT}}_r{\mathrm{cos\θ}}_r}\\ =T_s+T_r\end{array}$

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

6) common imaging gather data are carried out to superpose the structure imaging result obtaining exploratory area Depth Domain and stratigraphic section image (as shown in Figure 9).

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, the rough ground surface that this floating datum distance is actual is simultaneously very near, so the time error brought because of reference field time shift can be reduced as much as possible, and then open new thinking for solving the subsurface imaging problem of complicated rough ground.

(2) the present invention adopts point-device imaging whilst on tour computing formula, not only consider 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, thus the imaging results that can be satisfied with very much, this is core place of the present invention.

Claims (2)

1. a depth field complex earth surface seismic structure imaging method, feature is realized by following concrete steps:

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

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

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

4) be that reference position calculates the whilst on tour of this position to underground any point with floating datum in each bin position;

5) floating datum low frequency component corresponding to every one sp location and geophone station position is determined;

And utilize the following formula scales 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 _sfor the vertical time difference, the Δ T of shot point _rfor the vertical time difference, the DACT of geophone station _cmpfor low frequency component, the DACT of point midway _cmpsfor low frequency component, the DACT of sp location _cmprfor the low frequency component of geophone station position;

6) according to step 4) whilst on tour and step 5) the vertical time difference with following formulae discovery imaging time, utilize imaging time to carry out pre-stack depth migration process to prestack shot gather data, obtain common imaging gather;

$\begin{array}{c}T\≈\sqrt{T_s^{\′2}+{\mathrm{\ΔT}}_s^2-2T_s^{\′}{\mathrm{\ΔT}}_s{\mathrm{cos\θ}}_s}+\sqrt{T_r^{\′2}+{\mathrm{\ΔT}}_r^2-2T_r^{\′}{\mathrm{\ΔT}}_r{\mathrm{cos\θ}}_r}\\ =T_s+T_r\end{array}$

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 _sfor the vertical time difference, the Δ T of shot point _rfor the vertical time difference, the θ of geophone station _sfor shot point is to angle, the θ of imaging point start ray direction and vertical direction _rfor geophone station is to the angle of imaging point start ray direction and vertical direction;

7) common imaging gather data are carried out to superpose the structure imaging result obtaining exploratory area Depth Domain and stratigraphic section image.

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