CN102590860B - 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 break information

Technical field

The invention belongs to the technical field of in oil seismic exploration, seismic data being carried out technical finesse and explanation, be particularly related to one and ask for underground high speed top interface depth and speed according to refraction statics normal operation method, and result is used for to the reflection wave modeling method based on seismic event first break information among pre-stack depth migration modeling.

Background technology

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

In geological data is processed, refraction wave as interference wave cut fall, but the signal to noise ratio (S/N ratio) of refraction wave first arrival is the highest, in complex near surface conditions and low signal-to-noise ratio area, refraction wave first arrival is the effective information of asking for top layer speed.And in depth shift process, need to set up accurate underground rate pattern, still due to the excision reason of doubling ejected wave first arrival, cause for the road of pre-stack depth migration and concentrated this velocity surface information that lacked.

Summary of the invention

In view of the weak point of prior art, the object of this invention is to provide a kind of result of utilizing refraction wave first arrival to set up in near-surface model calculating static correction process and solve the image quality problem in seismic data processing for follow-up pre-stack depth migration velocity modeling, to improve the modeling accuracy in the seismic data pre-stack depth migration velocity modeling process of complex area, make the underground velocity variations of the true reflection of rate pattern, recover underground real stratum and velocity structure, thereby improve the precision of pre-stack depth migration velocity modeling and improve migration imaging quality.

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

1), taking the first break time of accurately picking up as basis, carry out the modeling of refraction process near surface by the parameter of optimizing, excite from a point, the reception of b point, can determine by refraction process the high speed top interface depth H that g is ordered _g, be formulated:

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

T in formula _gfor the time depth that g is ordered, can be determined by the first break time of picking up v ₀for the speed of low velocity layer (LVL), in advance given or determine v by scanning ₁for pushing up at a high speed the speed at interface, can determine by the slope of matching first arrival;

2), the high speed top interfacial velocity and the high speed top interface depth that obtain in birefringence method near surface 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, determine the level and smooth radius of low frequency, 1/2nd of the level and smooth radius≤design of structure radius≤low frequency spread length;

3), because the information of pushing up at a high speed interface that lacked is concentrated in the road for pre-stack depth migration speed, in pre-stack depth migration velocity modeling process, load previous step by the high speed top interfacial velocity and the high speed top interface depth information that obtain in refraction wave first arrival near surface modeling process, it is joined to the INTERFACE MODEL for pre-stack depth migration speed as a key-course position, thereby recover the variation of real velocity interface, obtain complete meticulous underground shallow layer velocity structure;

4), pre-stack depth migration velocity modeling is a process from shallow to deep, the whether accurate precision that determines deep layer speed of shallow-layer speed is set up the rate pattern of mid-deep strata on the basis of carrying out shallow velocity model.

The present invention's remarkable result is compared to existing technology: the near-surface model of asking in the near surface modeling process in seismic processing process is attached in the middle of follow-up pre-stack depth migration velocity modeling, has made up the disappearance of the high speed top interfacial velocity causing due to reasons such as excisions; And by the modeling of refraction process near surface, obtain the high speed top interfacial velocity size under sinking band and pushed up at a high speed the spatial depth at interface, it has reflected the variation of ground next part velocity structure, and this high-velocity bed velocity interface is necessary being, as shown in Figure 1; For this reason, the information that this is pushed up at a high speed to interface is attached in pre-stack depth migration velocity modeling goes, and can realize the modeling of refraction process near surface and depth shift velocity modeling is integrated; Meanwhile, obtain the complete real underground degree of depth-velocity structure model, thereby improved the precision of pre-stack depth migration speed and improve image quality.

Brief description of the drawings

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

Fig. 2 is that the present invention is asked for and reflected the principle schematic of pushing up at a high speed interface by refraction process

Fig. 3 be refraction process of the present invention obtain Refraction Delay time planimetric map

Fig. 4 is the high speed top interfacial velocity planimetric map that refraction process of the present invention obtains

Fig. 5 is the high speed top interface depth planimetric map 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 top INTERFACE MODEL migration result schematic diagram

Fig. 7 b is that the present invention adds high speed top INTERFACE MODEL migration result schematic diagram

Embodiment

Below in conjunction with drawings and Examples, this technical scheme is further described

Embodiment 1

The present invention is applied to work area and is positioned at the three-dimensional work area, crow south of Southwest Area of Qaidam Basin, and earth's surface, this area, underground structure are all comparatively complicated, and velocity variations is larger, and prestack depth migration interval velocity modeling is accurately the basis that ensures Depth Domain imaging; We have carried out the application of the reflection wave velocity modeling method based on first arrival for this reason, and the step that concrete grammar is implemented is as follows:

(1), the picking up of earthquake refraction wave first break time, be ready to first arrival data for follow-up calculating; Taking the first break time of accurately picking up as basis, carry out the modeling of refraction process near surface by the parameter of optimization, its principle is as shown in Figure 2.

(2), ask for and push up at a high speed the time depth T at interface according to first break time _g, as shown in Figure 3; Ask for the speed v of pushing up at a high speed interface by Slope Method ₁, as shown in Figure 4; Ask for the depth H of pushing up at a high speed interface according to formula (1) _g, as shown in Figure 5.

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

(4), load previous step by the high speed top interfacial velocity and the high speed top interface depth information that obtain in refraction wave first arrival near surface modeling process, it is joined to the INTERFACE MODEL for pre-stack depth migration speed as a key-course position, as shown in Figure 6; Thereby recover the variation of real velocity interface, obtain complete meticulous underground shallow layer velocity structure.

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

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

In addition to the implementation, 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. the reflection wave modeling method based on seismic event first break information, is characterized in that: the method comprises the steps:

1), taking the first break time of accurately picking up as basis, carry out the modeling of refraction process near surface by the parameter of optimizing, excite from a point, the reception of b point, can determine by refraction process the high speed top interface depth H that g is ordered _g, be formulated:

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

In formula, T _gfor the time depth that g is ordered, can be determined by the first break time of picking up v ₀for the speed of low velocity layer (LVL), in advance given or determine v by scanning ₁for pushing up at a high speed the speed at interface, can determine by the slope of matching first arrival;

2), the high speed top interfacial velocity and the high speed top interface depth that obtain in birefringence method near surface 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, determine the level and smooth radius of low frequency, 1/2nd of the level and smooth radius≤design of structure radius≤low frequency spread length;

3), because the information of pushing up at a high speed interface that lacked is concentrated in the road for pre-stack depth migration, in pre-stack depth migration velocity modeling process, load previous step by the high speed top interfacial velocity and the high speed top interface depth information that obtain in refraction wave first arrival near surface modeling process, it is joined to the INTERFACE MODEL for pre-stack depth migration speed as a key-course position, thereby recover the variation of real velocity interface, obtain complete meticulous underground shallow layer velocity structure;

4), pre-stack depth migration velocity modeling is a process from shallow to deep, the whether accurate precision that determines deep layer speed of shallow-layer speed is set up the rate pattern of mid-deep strata on the basis of carrying out shallow velocity model.

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