CN102495426B - Kirchhoff integral seismic imaging method - Google Patents

Abstract

A Kirchhoff integral seismic imaging method comprises the following procedures: procedure 101, defining a same-phase superimposed maximum energy point on a diffraction track; procedure 102, adopting a bell-shaped window with the maximum energy point as the center as a weighting function; and procedure 103, adding the weighting function into a diffraction Kirchhoff integral seismic imaging formula as an integral item for seismic imaging. The Kirchhoff integral seismic imaging method takes the situation of opposite phases of diffracted waves into account, adopts the method for imaging the main energy, namely the energy in the range of the bell-shaped window which is arranged close to the maximum energy point on the diffraction track, can eliminate the influence of the diffracted waves of opposite phases and can judge the condition of underground media more accurately.

Description

A kind of Kirchhoff integral seismic imaging method

Technical field

The present invention relates to a kind of seismic imaging method, particularly relate to a kind of Kirchhoff integral seismic imaging method.

Background technology

For Study of The Underground geological interface, the physics law that the seismic event of surface seismic records need to be propagated by ripple is put back into underground, and this process is offset exactly, or seismic imaging.Kirchhoff (Kirchhoff) integral method speed is fast, adaptability good, is that current petroleum prospecting circle is used the most general Prestack depth migration.Current Kirchhoff earthquake prestack migration can be classified as two large classes, and a class is only to consider the imaging technique of reflection wave, and another kind of is imaging technique based on diffraction theory, and this two class is all to draw from the different angles of ripple propagation law.

Specifically, prestack catoptric imaging technology is a kind of the imaging technique of considering reflection wave, shown in Fig. 1, when after focal point S (Shot) earthquake-wave-exciting, propagate into reflection spot R (Reflect) after reflection a received some G (Geophone) be recorded to.Seismic reflection imaging is exactly that the seismic event of same reflection point, the different acceptance points of different focus is put back into reflection spot.Reflection Kirchhoff integral seismic imaging formula can be expressed as:

$R=\underset{s}{\mathrm{\Σ}}\underset{g}{\mathrm{\Σ}}{W}_{\mathrm{sg}}{G}_{\mathrm{sg}}(t_r+t_s)$

Wherein t _sfor seismic event is propagated into time of reflection spot R, t by focal point S _rfor seismic event is propagated into time of acceptance point G, W by reflection spot R _sgrepresent weighting coefficient, G _sgrepresent geological data, the data after the R representative skew on the equation left side.The shortcoming of the method clearly, is exactly only to have considered reflection wave, does not consider the impact of diffracted wave, and the area of growing at diffracted wave can reduce the signal to noise ratio (S/N ratio) of imaging results.And diffracted wave etc. also usually exists in seismologic record.

Another prestack migration based on diffraction, it draws from Huygens' principle.Shown in Fig. 2, according to Huygens' principle, the each point of underground medium can be regarded secondary focus as, and in the time that seismic event runs into this, Propagation of Energy towards periphery, is not only reflection.According to this, single focus is produced to record and be put back into underground Diffraction Point position and complete imaging.Diffraction Kirchhoff integral seismic imaging formula can be expressed as:

$R_s=\underset{G}{\mathrm{\Σ}}{W}_{G}G(t_r+t_s)$

Wherein t _sfor seismic event is propagated into time of reflection spot R, t by focal point S _rfor seismic event is propagated into time of acceptance point G by reflection spot R; W _grepresent a kind of weighting factor, it is relevant to seismic wave propagation; Rs represents the data after skew.This kind of method not only considered that reflection wave also considered the impact of diffracted wave.But, in the time running into breakpoint, section in seismic wave propagation process, can produce more intense diffracted wave.At this moment diffracted wave can produce the phenomenon of phase reversal.Shown in Fig. 3, when the central point O in the middle of focal point S and acceptance point G is just in time positioned at Diffraction Point, the diffracted wave on acceptance point G both sides has the phase differential of 180 °, i.e. single spin-echo.The current imaging technique based on diffraction is not considered the single spin-echo of diffracted wave, is about to along diffraction track, the seismic signal being recorded to directly be sued for peace.Due to positive and negative the offseting of diffracted wave seismic signal of single spin-echo, the result of this direct summation will reduce the signal to noise ratio (S/N ratio) of seismic signal.The area of growing at diffracted wave, does not solve into this problem and will be lowered into image quality, even can not get the good image of underground medium, affects oil-gas exploration.

Summary of the invention

Object of the present invention is exactly to solve now with the problems referred to above that exist in technology, a kind of single spin-echo situation of having considered diffracted wave existence is provided, and can judge more accurately underground medium situation, Kirchhoff integral seismic imaging method.

For solving the problems of the technologies described above, technical scheme of the present invention is:

A kind of Kirchhoff integral seismic imaging method, comprises the following steps:

Step 101: determine on diffraction track with superimposed energy maximum point;

Step 102: the bell window centered by described energy maximum point is as weighting function;

Step 103: join diffraction Kirchhoff integral seismic imaging formula using described weighting function as integration item and carry out seismic imaging.

In technique scheme, described energy maximum point is x _max, described weighting function is e (x _g-x _max) ², the end that wherein e is natural logarithm, x _grepresent.

In technique scheme, described diffraction Kirchhoff integral seismic imaging formula is wherein t _sfor seismic event is propagated into time of reflection spot, t by focal point _rfor seismic event is propagated into time of acceptance point by reflection spot; W _gfor with the seismic wave propagation related weighing factor, Rs represent skew after data.

Technique scheme of the present invention has the following advantages compared to existing technology:

Kirchhoff integral seismic imaging method of the present invention; consider single spin-echo situation that diffracted wave exists; adopt main energy; it is near the method that on diffraction track, energy maximum point, the energy within the scope of a bell window carries out imaging; can get rid of the impact of the diffracted wave of single spin-echo, judge more accurately underground medium situation.

Brief description of the drawings

For content of the present invention is more likely to be clearly understood, below according to a particular embodiment of the invention and by reference to the accompanying drawings, the present invention is further detailed explanation, wherein

Fig. 1 is the principle schematic that in prior art, reflection wave forms;

Fig. 2 is the principle schematic that in prior art, diffracted wave forms;

Fig. 3 is the principle schematic of diffracted wave single spin-echo phenomenon in prior art;

Fig. 4 is the step schematic diagram of Kirchhoff integral seismic imaging method of the present invention;

Fig. 5 application Kirchhoff integral seismic imaging method of the prior art obtains, and has not considered single spin-echo situation that diffracted wave exists, somewhere seismic event imaging results partial schematic diagram;

Fig. 6 application Kirchhoff integral seismic imaging method of the present invention obtains, and has considered single spin-echo situation that diffracted wave exists, somewhere seismic event imaging results partial schematic diagram.

Embodiment

Fig. 4 and Fig. 6 have shown a kind of concrete embodiment of Kirchhoff integral seismic imaging method of the present invention; in the time that diffraction anti-phase (single spin-echo) situation occurs; due to the existence of reflection wave; the two interference; make the energy of certain section of ripple on diffraction track the strongest, this section strong energy diffraction has identical phase place with reflection wave.In order to solve the anti-phase problem in Diffraction Imaging, only need be by main energy (energy on diffraction track within the scope of near the bell window of energy maximum point) imaging.Concrete steps are as follows:

Step 101: determine on diffraction track with superimposed energy maximum point.A given spatial window, slides and calculates the stack power in described spatial window along diffraction track, and near seismic event is defined as to energy maximum point x with the maximum point of the number of phases _max.Along diffraction track along the seismic travel time (Tr+Ts) of calculating, the point of the reception data in certain spatial dimension is got geological data.In this step, need for seismic event is maximum with the number of phases near determining energy maximum point xmax, this is the interference in order to prevent local maximum noise.

Step 102: the bell window centered by described energy maximum point is as weighting function.At energy maximum point x _maxboth sides add bell window, or other window function, choose bell window as weighting function: e (x _g-x _max) ², the end that wherein e is natural logarithm, x _grepresent other each geological data point coordinate.Due to the clock that the curve shape picture of above-mentioned weighting function beats, therefore, people are commonly called as bell shaped function.Described bell window with for determine ceiling capacity point x _maxand the above-mentioned spatial window providing is different, the object that adds this bell window is to make energy maximum point x _maxthe data on both sides decay gradually, do not occur the phenomenon of blocking.

Step 103: weighting function is joined to kirchhoff integration imaging formula and carry out seismic imaging.By above-mentioned weighting function e (x _g-x _max) ²join kirchhoff integration imaging formula, the Kirchhoff integral seismic imaging formula of the present invention obtaining is:

$R_s=\underset{G}{\mathrm{\Σ}}{W}_G{e}^{{(x_G-x_{\max })}^2}G(t_r+t_s)$

Wherein G represents acceptance point; W _grepresent to propagate relevant weighting factor to ripple; E (x _g-x _max) ²for weighting function; t _sfor seismic event is propagated into time of reflection spot by focal point; t _rfor seismic event is propagated into time of acceptance point by reflection spot; Rs represents the data after skew.

From Fig. 5 and Fig. 6, can find out the subsurface image better effects if that obtains in Fig. 6 (black in figure, horizontal continuous lineups that are called are strata interface).Especially in Fig. 5 and 6, enclose the part contrast effect drawing in order to contrast more obvious.In Fig. 6, can find out that lineups horizontal change is continuous, traceable, a kind of spatial shape of stratigraphic fluctuation has been described, more be conducive to the variation of people's Study of The Underground geologic structure.And the lateral continuity of lineups is very poor in Fig. 5, more mixed and disorderly, people almost cannot be along the variation of Event tracking layer position, variation that also just cannot geologize structure.

Obviously, above-described embodiment is only for example is clearly described, and the not restriction to embodiment.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here without also giving exhaustive to all embodiments.And the apparent variation of being extended out thus or variation are still among the protection domain in the invention.

Claims (1)

1. a Kirchhoff integral seismic imaging method, is characterized in that, comprises the following steps:

Step 101: determine on diffraction track with superimposed energy maximum point; A given spatial window, slides and calculates the stack power in described spatial window along diffraction track, and near seismic event is defined as to energy maximum point x with the maximum point of the number of phases _max; Along diffraction track along the seismic travel time (Tr+Ts) of calculating, the point of the reception data in certain spatial dimension is got geological data;

Step 102: the bell window centered by described energy maximum point is as weighting function; At energy maximum point x _maxboth sides add bell window, or other window function, choose bell window as weighting function: , the end that wherein e is natural logarithm, x _grepresent other each geological data point coordinate;

Step 103: join diffraction Kirchhoff integral seismic imaging formula using described weighting function as integration item and carry out seismic imaging; By above-mentioned weighting function join kirchhoff integration imaging formula, the Kirchhoff integral seismic imaging formula obtaining is:

$R_s=\underset{G}{\mathrm{\Σ}}{W}_G{e}^{{(x_G-x_{\max })}^2}G(t_r+t_s)$

Wherein G represents acceptance point; W _grepresent to propagate relevant weighting factor to ripple; for weighting function; t _sfor seismic event is propagated into time of reflection spot by focal point; t _rfor seismic event is propagated into time of acceptance point by reflection spot; Rs represents the data after skew.