CN102590860A - Seismic wave primary arrival information-based reflected wave modeling method - Google Patents

Abstract

The invention discloses a seismic wave primary arrival information-based reflected wave modeling method, which comprises the following steps of: (1) preparing seismic wave primary arrival data; (2) performing refraction method near-surface modeling by taking a primary pickup time as a basis, and calculating the speed and depth of a high-speed top interface; (3) smoothing the obtained speed and depth of the high-speed top interface; (4) loading the smoothed speed and depth information of the high-speed top interface, and adding the speed and depth information of the high-speed top interface into a prestack depth migration speed interface model to obtain an integral and refined underground shallow depth-speed structure; (5) performing deep speed modeling on the underground shallow depth-speed structure; and (6) performing prestack depth migration operation to obtain a prestack depth migration result profile. According to the method, the refraction method near-surface modeling is realized, a near-surface model is established by reflected primary waves, and a result in a static correction process is calculated for subsequent prestack depth migration speed modeling, so that the integration of the refraction method modeling and the depth migration speed modeling is realized as shown in figure 6, and the accuracy of the prestack depth migration modeling and migration imaging quality are improved.

Description

Reflection wave modeling method based on seismic event first arrival information

Technical field

The invention belongs in the oil seismic exploration; Seismic data is carried out the technical field that technical finesse is explained; Be particularly related to and a kind ofly ask for underground velocity interface and speed, and be used for the reflection wave modeling method among the pre-stack depth migration modeling to the result based on seismic event first arrival information according to the refraction static correction method.

Background technology

Usually all there is low velocity layer in the landform in the seismic exploration, and the low velocity layer interface when geophone offset reaches certain distance, just is easy to receive the refraction first arrival from refracting interface because the difference of speed and density has formed a good refracting interface; The physical message that has comprised low velocity layer time of arrival of refraction first arrival, speed and thickness etc.; In the computation process of first arrival refraction process calculating static correction, need ask for and push up the interface at a high speed, it has represented actual underground velocity variations interface.

In geological data was handled, refraction wave has been cut away as interference wave but the signal to noise ratio (S/N ratio) of refraction wave first arrival is the highest, and in complicated earth surface condition and low signal-to-noise ratio area, the refraction wave first arrival is an effective information of asking for top layer speed.And in the depth shift process, need set up accurate underground rate pattern, still owing to the excision reason of doubling ejected wave first arrival, caused the road that is used for pre-stack depth migration to concentrate this velocity surface information that lacked.

Summary of the invention

Weak point in view of prior art; The purpose of this invention is to provide and a kind ofly utilize the refraction primary wave to set up near-surface model to calculate result in the static correction process and be used for follow-up pre-stack depth migration speed modeling and solve the image quality problem of seismic data in handling; To improve the modeling accuracy in the complex area seismic data pre-stack depth migration speed modeling process; Make the underground velocity variations of the true reflection of rate pattern; Recover underground real stratum and velocity structure, thereby improve the pre-stack depth migration modeling precision and improve the migration imaging quality.

The technical scheme that realizes the technical solution problem is: a kind of reflection wave modeling method based on seismic event first arrival information, this method comprises the steps:

1), the production big gun primary wave data-preparing in seismic prospecting work area;

2), be the basis with the primary wave time of accurately picking up, carry out the modeling of refraction process near surface with optimum parameters, excite from a point, the b point receives, and can confirm the high speed top interface depth H that g is ordered through refraction process _g, be formulated:

$H_g=\frac{T_g\·v_0\·v_1}{\sqrt{v_1^2-v_0^2}}---\left(1\right)$

T in the formula _gFor the time depth that g is ordered, v can be confirmed by the first break time of picking up ₀Be the speed of low velocity layer (LVL), given in advance or definite through scanning, v ₁Be the speed of refractor, can confirm through the slope of match primary wave;

3), the high speed top interfacial velocity and the degree of depth that obtain in the birefringence method modeling process smoothly edit, and obtains rational variation tendency; According to the design spread length of field acquisition construction, according to the form size of underground structure, confirm the level and smooth radius of low frequency, 1/2nd of the level and smooth radius of structure radius≤low frequency≤design spread length;

4), concentrate the information on top at a high speed that lacked owing to be used for the road of pre-stack depth migration; A step is calculated high speed top speed and the depth information that obtains in the refraction first arrival modeling process in prestack depth speed modeling process, loading; Join the velocity interface model that is used for pre-stack depth migration to it as a key-course position; Thereby recover the variation of real velocity interface, obtain the underground shallow-layer velocity structure of complete and fine;

5), the modeling of depth shift speed is a process from shallow to deep, the whether accurate precision that determines deep layer speed of shallow-layer speed is being carried out the rate pattern of setting up mid-deep strata on the basis of shallow velocity model;

6), on the basis of setting up accurate pre-stack depth migration rate pattern, carry out the pre-stack depth migration computing, obtain pre-stack depth migration achievement section.

The remarkable result that the present invention compares prior art is: be attached to the near-surface model of asking in the near surface modeling process in the earthquake processing procedure in the middle of the follow-up pre-stack depth migration modeling, remedied the disappearance of the high speed top speed that causes owing to reasons such as excisions; And through the modeling of refraction process near surface, obtained under the sinking band high speed top velocity magnitude with push up the spatial depth at interface at a high speed, it has reflected the variation of ground next part velocity structure, and this high-velocity bed velocity interface is necessary being, and is as shown in Figure 1; For this reason, this information of pushing up at a high speed is attached in the modeling of pre-stack depth migration speed goes, can realize that refraction process modeling and the modeling of depth shift speed are integrated; Simultaneously, obtain the complete real underground degree of depth-velocity structure model, thereby improved the precision and raising image quality of pre-stack depth migration.

Description of drawings

Fig. 1 is that the present invention pushes up the interface synoptic diagram at a high speed

Fig. 2 is that the present invention asks for the refraction principle schematic on top at a high speed through refraction process

Fig. 3 is the refraction that obtains of refraction process of the present invention planimetric map when postponing

Fig. 4 is the high speed top velocity plane figure that refraction process of the present invention obtains

Fig. 5 is the high speed top depth plane figure that refraction process of the present invention obtains

Fig. 6 is the velocity boundary layer bitmap in area, the present invention crow south

Fig. 7 a is that the present invention does not add high speed backform type migration result synoptic diagram

Fig. 7 b is that the present invention adds high speed backform type migration result synoptic diagram

Embodiment

Below in conjunction with accompanying drawing and embodiment this technical scheme is further described

Embodiment 1

The present invention is applied to the black southern three-dimensional work area that the work area is positioned at western South Area, the Caidamu Basin, and the face of land, this area, underground structure are all comparatively complicated, and velocity variations is bigger, and pre-stack depth migration interval velocity modeling accurately is the basis that guarantees the Depth Domain imaging; We have carried out the application based on the reflection wave speed modeling method of primary wave for this reason, and the step that concrete grammar is implemented is following:

(1), the picking up of earthquake refraction wave first break time, be ready to the first arrival data and be used for follow-up calculating; The primary wave time accurately to pick up is the basis, carries out the modeling of refraction process near surface with optimum parameters, and its principle is as shown in Figure 2.

(2), ask for the time depth T on top at a high speed according to first break time _g, as shown in Figure 3; Ask for the speed v on top at a high speed through the slope method ₁, as shown in Figure 4; Ask for high speed top depth H according to formula (1) _g, as shown in Figure 5.

(3), the high speed top interfacial velocity and the degree of depth that obtain in the birefringence method modeling process smoothly edit, and obtains rational variation tendency.

(4), loaded a lasted step and calculate and reflect high speed top speed and the depth information that obtains in the first arrival modeling process, join the velocity interface model that is used for pre-stack depth migration to it as a key-course position, as shown in Figure 6; Thereby recover the variation of real velocity interface, obtain the underground shallow-layer velocity structure of complete and fine.

(5), the interface, high speed top that added a last step is as the key-course of shallow-layer, and carrying out the rate pattern of setting up mid-deep strata on the basis of shallow velocity model.

(6), on the basis of setting up accurate pre-stack depth migration rate pattern, carry out the pre-stack depth migration computing, obtain pre-stack depth migration achievement section, the migration imaging quality is improved, shown in Fig. 7 a, Fig. 7 b contrast.

Except that the foregoing description, the present invention can also have other embodiment; All employings are equal to the technical scheme of replacement or equivalent transformation form, all drop on the protection domain of requirement of the present invention.

Claims (1)

1. reflection wave modeling method based on seismic event first arrival information, it is characterized in that: this method comprises the steps:

1), the production big gun primary wave data-preparing in seismic prospecting work area;

2), be the basis with the primary wave time of accurately picking up, carry out the modeling of refraction process near surface with optimum parameters, excite from a point, the b point receives, and can confirm the high speed top interface depth H that g is ordered through refraction process _g, be formulated:

$H_g=\frac{T_g\·v_0\·v_1}{\sqrt{v_1^2-v_0^2}}---\left(1\right)$

In the formula, T _gFor the time depth that g is ordered, v can be confirmed by the first break time of picking up ₀Be the speed of low velocity layer (LVL), given in advance or definite through scanning, v ₁Be the speed of refractor, can confirm through the slope of match primary wave;

3), the high speed top interfacial velocity and the degree of depth that obtain in the birefringence method modeling process smoothly edit, and obtains rational variation tendency; According to the design spread length of field acquisition construction, according to the form size of underground structure, confirm the level and smooth radius of low frequency, 1/2nd of the level and smooth radius of structure radius≤low frequency≤design spread length;

4), concentrate the information on top at a high speed that lacked owing to be used for the road of pre-stack depth migration; A step is calculated high speed top speed and the depth information that obtains in the refraction first arrival modeling process in prestack depth speed modeling process, loading; Join the velocity interface model that is used for pre-stack depth migration to it as a key-course position; Thereby recover the variation of real velocity interface, obtain the underground shallow-layer velocity structure of complete and fine;

5), the modeling of depth shift speed is a process from shallow to deep, the whether accurate precision that determines deep layer speed of shallow-layer speed is being carried out the rate pattern of setting up mid-deep strata on the basis of shallow velocity model;

6), on the basis of setting up accurate pre-stack depth migration rate pattern, carry out the pre-stack depth migration computing, obtain pre-stack depth migration achievement section.

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