CN110858003A - Non-earth surface consistency static correction method based on equivalent speed - Google Patents
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Abstract
The invention discloses a static correction method for non-earth surface consistency based on equivalent velocity, which relates to the field of seismic exploration and comprises the following steps: calculating the equivalent velocity of the seismic waves from the earth surface to the static correction surface H according to the near-earth surface model; constructing an offset mapping relation between the offset distance before static correction and the offset distance after static correction when the seismic waves are propagated along the actual propagation path according to the equivalent velocity, and constructing a travel time mapping relation between travel time before static correction and travel time after static correction when the seismic waves are propagated along the actual propagation path according to the equivalent velocity; and calculating the offset distance and the travel time after the seismic waves are propagated along the actual propagation path and are statically corrected according to the offset distance mapping relation and the travel time mapping relation. According to the method, the precision error caused by the fact that the conventional static correction assumes the vertical propagation of seismic waves is avoided, and compared with the conventional static correction, the method has the advantages that the technical precision is higher, the accurate space-time distance relation can be kept better, and meanwhile, the subsequent imaging precision can be guaranteed better.
Description
Technical Field
The invention relates to the field of seismic exploration, in particular to a non-earth surface consistency static correction method based on equivalent velocity, which can be applied to seismic data processing in petroleum geophysical exploration.
Background
The static correction method is a commonly used mode for processing complex surface seismic data, and generally comprises refraction chromatography static correction, elevation static correction, first-arrival wave chromatography static correction and the like, wherein the difference mainly lies in that methods for inverting the near-surface velocity are different, and the static correction processing after obtaining the velocity is vertical time shift based on the assumption of surface consistency. The conventional static correction processing is based on the assumption of surface consistency, namely, the seismic waves are supposed to vertically propagate on the near surface, and the static correction is carried out in a vertical time shifting mode during the processing.
But the fact is that most complex earth surfaces do not have obvious low-speed-drop zones or even high-speed layer exposure, and seismic waves do not propagate perpendicular to the earth surface; even if a low-deceleration zone occurs in the transmission process of seismic waves, the velocity of the seismic waves in the low-deceleration zone is high or the thickness of the seismic waves is large, and a large error can be caused by conventional static correction processing based on the ground surface consistency assumption, so that the subsequent accurate imaging is influenced.
In order to more reasonably correct along the actual propagation path of the seismic wave, a static correction method of non-surface consistency is needed.
Disclosure of Invention
The invention aims to solve the technical problem that the existing static correction method based on the ground surface consistency assumption is used for processing the seismic data, and the method has larger error and can influence the subsequent accurate imaging of the seismic data processing.
In order to solve the technical problem, the invention provides a non-earth surface consistency static correction method based on equivalent speed, which comprises the following steps:
calculating the equivalent velocity of the seismic waves from the earth surface to the static correction surface according to the near-earth surface model;
constructing an offset mapping relation between the offset distance before the seismic waves are propagated along the actual propagation path for static correction and the offset distance after the static correction according to the equivalent velocity, and constructing a travel time mapping relation between travel time before the seismic waves are propagated along the actual propagation path for static correction and travel time after the static correction according to the equivalent velocity;
and calculating the offset distance and the travel time of the seismic waves after the seismic waves are propagated along the actual propagation path and are subjected to static correction according to the preset offset distance before the static correction, the preset travel time before the static correction, the offset distance mapping relation and the travel time mapping relation.
Preferably, before calculating the equivalent velocity of the seismic waves from the surface to the static correction surface according to the near-surface model, the method further comprises the following steps:
the near-surface model comprises a regolith and a high-speed layer below the regolith; and setting a static correction surface in the high-speed layer, wherein the static correction surface is parallel to the horizontal plane.
Preferably, the step of calculating the equivalent velocity of the surface to the static correction surface from the near-surface model according to the near-surface model comprises:
calculating the equivalent velocity V of the seismic wave from the shot point to the static correction surfacets；
Calculating the equivalent velocity V of the seismic wave from the static correction surface to the wave detection pointtg。
Preferably, said equivalent speed VtsAnd said equivalent speed VtgIs formulated as:
wherein, V0Representing the propagation velocity, V, of said seismic waves in said regolith1Representing the propagation velocity, Z, of said seismic waves in said high-velocity zoneSRepresenting the distance of said shot from said static correction surface,ZWSindicating the thickness, Z, of the weathering layer corresponding to the location of the shotMSRepresenting the thickness, T, of the high-velocity layer corresponding to the shot locationSRepresenting travel time of the seismic waves from the shot point vertical to the static correction surface; zgRepresenting the distance, Z, of the demodulator probe from the static correction surfaceWgIndicating the thickness, Z, of the weathering layer corresponding to the location of the detection pointMgIndicating the thickness, T, of the high-speed layer corresponding to the position of the pickup pointgRepresenting the travel time of the seismic waves from the static correction surface to the geophone point.
Preferably, the step of constructing a travel time mapping relationship between travel times of the seismic waves before and after the static correction along the actual propagation path according to the equivalent velocity includes:
according to the equivalent speed VtsAnd a ray parameter p of said shotsCalculating the travel time T of the seismic waves transmitted from the shot point to the static correction surface along the actual propagation pathWS；
According to the equivalent speed VtgAnd a ray parameter p of the detection pointgCalculating the travel time T of the seismic wave transmitted from the static correction surface to the wave detection point along the actual propagation pathWg；
The travel time before static correction is carried out based on the seismic wave propagating along the actual propagation path is equal to the travel time TWSThe travel time TWgAnd the sum of travel time of the seismic waves after static correction is carried out along the actual propagation path, and the travel time mapping relation between the travel time of the seismic waves before static correction is carried out along the actual propagation path and the travel time after static correction is constructed.
Preferably, the travel time mapping relationship between the travel time before the static correction and the travel time after the static correction when the seismic wave is propagated along the actual propagation path is expressed by a formula:
Tt＝Td+TWS+TWg
wherein, TtRepresenting the travel time, T, of the seismic wave before the seismic wave is propagated along the actual propagation path for static correctiondRepresenting said seismic edges in realityThe travel time after the propagation path is statically corrected is propagated.
Preferably, the step of constructing an offset mapping relationship between the offset before the seismic wave is propagated along the actual propagation path and statically corrected and the offset after the seismic wave is statically corrected according to the equivalent velocity includes:
according to the equivalent speed VtsAnd a ray parameter p of said shotsCalculating the shot offset distance of the shot on the static correction surface;
according to the equivalent speed VtgAnd a ray parameter p of the detection pointgCalculating the offset distance of the wave detection point on the static correction surface;
and constructing an offset mapping relation between the offset before the seismic wave is propagated along the actual propagation path for static correction and the offset after the static correction on the basis that the offset before the seismic wave is propagated along the actual propagation path for static correction is equal to the sum of the shot point offset, the geophone point offset and the offset after the seismic wave is propagated along the actual propagation path for static correction.
Preferably, the offset mapping relationship between the offset before the seismic wave propagates along the actual propagation path and the offset after the seismic wave propagates along the actual propagation path and is represented by a formula:
Ht＝TWSVts 2*ps-TWgVtg 2*pg+Hd
wherein HtOffset distance, H, before static correction for propagation of said seismic waves along an actual propagation pathdAnd (4) performing static correction on the seismic waves propagating along the actual propagation path.
Preferably, the step of calculating the offset distance and the travel time after the seismic waves are propagated along the actual propagation path and are statically corrected according to the offset distance mapping relation and the travel time mapping relation comprises the following steps:
constructing a ray parameter p for the shotsAnd a ray parameter p of the detection pointgThe ray parameter mapping relation between the two;
and calculating the offset distance and the travel time of the seismic waves after the seismic waves are propagated along the actual propagation path and are subjected to static correction according to the ray parameter mapping relation, the preset offset distance before static correction, the preset travel time before static correction, the offset distance mapping relation and the travel time mapping relation.
Preferably, the ray parameter p of the shot pointsAnd a ray parameter p of the detection pointgThe ray parameter mapping relation between the two is formulated as:
where v represents the velocity of the seismic waves below the statics surface.
Compared with the prior art, one or more embodiments in the above scheme can have the following advantages or beneficial effects:
by applying the equivalent-velocity-based non-earth-surface consistency static correction method provided by the embodiment of the invention, by calculating the equivalent velocity of seismic waves from the earth surface to the static correction surface, the distance from the shot point to the static correction surface is equivalent to the path from the shot point to the static correction surface along the actual propagation path of the seismic waves, the distance from the demodulator probe to the static correction surface is equivalent to the path from the static correction surface to the demodulator probe along the actual propagation path of the seismic waves, thereby establishing the offset mapping relation before and after the seismic waves are propagated along the actual propagation path and are statically corrected, and establishing a travel time mapping relation before and after seismic waves are propagated along an actual propagation path and statically corrected, so that the precision error caused by the vertical propagation of the seismic waves assumed by the conventional static correction is avoided, the technology has higher precision, can better keep accurate space-time distance relation and simultaneously can better ensure the subsequent imaging precision.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of the path followed by seismic waves of the present invention;
FIG. 2 is a schematic representation of a near-surface model of the present invention;
FIG. 3 is a schematic diagram illustrating the steps of a non-surface consistent static correction method based on equivalent speed according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of an equivalent velocity model according to an embodiment of the present invention;
FIG. 5 is a schematic illustration of a single shot record being conducted on a relief surface;
FIG. 6 is a schematic diagram of a conventional statically corrected single shot record based on a surface consistency assumption;
FIG. 7 is a schematic diagram of a single shot record after equivalent velocity-based non-surface-consistent static correction;
fig. 8 is a schematic diagram of a single shot record being performed at a static correction surface 2000m according to a first embodiment of the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
The static correction method is a commonly used mode for processing complex surface seismic data, and is also one of the main difficulties for processing the complex surface seismic data. But the fact is that most complex earth surfaces do not have obvious low-speed-drop zones or even high-speed layer exposure, and seismic waves do not propagate perpendicular to the earth surface; even if a low-deceleration zone occurs in the transmission process of seismic waves, the velocity of the seismic waves in the low-deceleration zone is high or the thickness of the seismic waves is large, and a large error can be caused by conventional static correction processing based on the ground surface consistency assumption, so that the subsequent accurate imaging is influenced.
Example one
In order to solve the technical problems in the prior art, the embodiment of the invention provides a non-surface consistency static correction method based on equivalent speed.
FIG. 1 is a schematic diagram of a path of seismic waves propagating along an actual path according to an embodiment of the present invention, and FIG. 3 is a schematic diagram of a step of a non-surface-consistent static correction method based on equivalent velocity according to an embodiment of the present invention; referring to fig. 1 and 3, the non-surface consistent static correction method based on the equivalent speed of the embodiment comprises the following steps.
S101, the near-surface model comprises a weathered layer and a high-speed layer located below the weathered layer; a static correction surface H is set in the high-speed layer, and the static correction surface H is parallel to the horizontal plane.
Specifically, FIG. 2 is a schematic diagram of a near-surface model of the present invention; referring to fig. 2, the near-surface model includes a regolith and a high-speed layer, the high-speed layer being located below the regolith; a static correction surface H is set at the underground 2000m position in the weathered layer, and the set static correction surface H is parallel to the horizontal plane. It should be noted that the position of the static correction surface H (the depth on the ground) can be modified according to specific needs, and the invention of the present application is not limited thereto.
And S102, calculating the equivalent velocity of the seismic waves from the earth surface to the static correction surface H according to the near-earth model.
Specifically, fig. 4 is a schematic diagram of an equivalent velocity model according to an embodiment of the present invention; it should be noted that the propagation velocity of the seismic waves in the regolith in fig. 4 varies laterally, and the velocity variation is not too large, so that it is not too obvious in fig. 4. The equivalent velocity is an effective velocity defined between the earth surface and the static correction surface H, which is equivalent to the average velocity of the seismic waves from the earth surface to the static correction surface H, so that the velocity change of the seismic waves in the process of propagation from the earth surface to the static correction surface H is not considered in the application process, and thenAnd establishing a continuous mapping relation to lay a foundation. Further, the equivalent velocity includes the equivalent velocity V of the seismic waves from the shot S to the static correction surface HtsAnd the equivalent velocity V of the seismic wave from the static correction surface H to the demodulator probe Gtg。
Equivalent velocity V of the following pairstsAnd an equivalent speed VtgThe specific calculation process of (2) is explained in detail:
equivalent velocity V of seismic wave from shot point S to static correction surface HtsThe calculation process is as follows:
assuming that the seismic wave propagates in the earth surface vertically to the ground, taking shot point S as an example, the distance from shot point S to static correction surface H is the propagation path Z of the seismic waveS，TSRepresenting the travel time of the seismic wave from the shot S vertical to the static correction surface H, the equivalent velocity
The seismic wave propagation path Z is formed by a weathered layer and a high-speed layer between the shot point S and the static correction surface HSThickness Z of weathered layer corresponding to the position of shot point SWSHigh-velocity layer thickness Z corresponding to shot point S positionMSAnd (4) summing. Suppose V0Representing the propagation velocity, V, of seismic waves in the regolith1The propagation speed of the seismic wave in the high-speed layer is shown, and the time taken for the seismic wave to propagate in the weathered layer corresponding to the shot point S position is
The time for the seismic wave to propagate in the high-speed layer corresponding to the shot point S is
I.e. the travel time of the seismic waves from the shot point S sag to the static correction surface H
In summary, the equivalent speed V can be obtainedtsThe formula of (1) is:
equivalent speed V can be calculated by the same methodtsThe formula of (1) is:
wherein Z isgRepresenting the distance, Z, of the wave detection point G from the static correction surface HWgThickness of weathered layer corresponding to position G of wave detection point, ZMgHigh-speed layer thickness, T, corresponding to the position of the detection point GgRepresenting the travel time of the seismic waves from the normal to the geophone point G from the statics correction plane H.
Step S103, constructing an offset mapping relation between the offset distance before the seismic waves are propagated along the actual propagation path and statically corrected and the offset distance after the seismic waves are statically corrected according to the equivalent velocity; and constructing a travel time mapping relation between travel time before static correction and travel time after static correction of seismic waves propagated along the actual propagation path according to the equivalent velocity.
For ease of understanding, the steps for constructing the travel time mapping relationship and the offset mapping relationship are described in detail below.
The method for constructing the travel time mapping relation between the travel time before the seismic waves are propagated along the actual propagation path and statically corrected and the travel time after the seismic waves are statically corrected comprises the following steps.
Step S3011, according to the equivalent speed VtsAnd ray parameters p of the shot pointsCalculating the travel time T of the seismic wave transmitted from the shot point S to the static correction surface H along the actual propagation pathWS。
In particular, the travel time T of the seismic wave transmitted from the shot S to the static correction surface H propagates along the actual propagation pathWSThe equivalent velocity V and the path of the seismic wave transmitted from the shot point S to the static correction surface H along the actual propagation pathtsAnd the path of the seismic wave propagating along the actual propagation path from the shot S to the static correction surface H is:the travel time T of the seismic wave transmitted from the shot point S to the static correction surface H is propagated along the actual propagation pathWSIs formulated as:
wherein p issThe ray parameter is the ray parameter of a shot point, and in exploration seismology, the ray parameter is the ratio of the sine value of an incident angle at the same incident point to the velocity of a seismic wave.
Step S3012, according to the equivalent speed VtgAnd ray parameters p of the shot pointgCalculating the travel time T of the seismic wave transmitted from the static correction surface H to the wave detection point G along the actual propagation pathWg。
Specifically, the travel time T of the seismic wave from the static correction surface H to the demodulator probe G is propagated along the actual propagation pathWgEqual to the path equivalent velocity V of the seismic wave transmitted from the static correction surface H to the demodulator probe G along the actual propagation pathtgThe ratio of (A) to (B); and the path of the seismic wave from the static correction surface H to the demodulator probe G along the actual propagation path is as follows:
the travel time T of the seismic wave propagating along the actual propagation path from the static correction surface H to the demodulator probe GWgIs formulated as:
wherein p isgIs the ray parameter of the wave detection point.
Step S3013, the travel time before static correction is performed based on the propagation of the seismic wave along the actual propagation path is equal to the travel time TWSTime TWgAnd the sum of travel time of the seismic waves after the static correction is carried out along the propagation of the actual propagation path, and constructing a travel time mapping relation between the travel time of the seismic waves before the static correction is carried out along the propagation of the actual propagation path and the travel time after the static correction.
In particular, TtTravel time, T, before static correction for seismic wave propagation along actual propagation pathdStep S301 is combined to make travel time after static correction for seismic wave propagation along actual propagation path1 and the travel time T of the seismic wave obtained in the step S3012 from the shot point S to the static correction surface H along the actual propagation pathWSAnd the travel time T of the seismic wave transmitted from the static correction surface H to the wave detection point G along the actual propagation pathWgThe travel time mapping relationship between the travel time before the seismic wave is propagated along the actual propagation path for static correction and the travel time after the static correction can be expressed as:
Tt＝Td+TWS+TWg(5)。
the method for constructing the offset mapping relation between the offset before the seismic wave is propagated along the actual propagation path and statically corrected and the offset after the seismic wave is statically corrected according to the equivalent velocity comprises the following steps:
step S3021, according to the equivalent speed VtsAnd ray parameters p of the shot pointsAnd calculating the shot offset distance of the shot S on the static correction surface H.
Specifically, the shot offset of the shot S at the static correction surface H is the product of the path of the seismic wave propagating along the actual propagation path from the shot S to the static correction surface H and the sine of the angle of incidence of the seismic wave at the shot S. Wherein, the sine value of the incident angle of the seismic wave at the shot point S can be expressed as: vts*psThe path of the seismic wave transmitted from the shot point S to the static correction surface H along the actual propagation path is: t isWSVtsThen the shot offset of the shot S at the static correction surface H can be expressed as: t isWSVts 2*ps。
Step S3022, according to the equivalent speed VtgAnd ray parameters p of the detection pointgAnd calculating the offset of the wave detection point G on the static correction surface H.
Specifically, the offset of the demodulator probe at the demodulator probe point G on the static correction surface H is the product of the path of the seismic wave propagating along the actual propagation path from the static correction surface H to the demodulator probe point G and the sine value of the angle of incidence of the seismic wave at the demodulator probe point G. Wherein, the sine value of the incidence angle of the seismic wave at the wave detection point G can be expressed as: vtg*pgThe path of the seismic wave transmitted from the static correction surface H to the demodulator probe G along the actual propagation path is as follows: t isWgVtgDue to seismic waves from the shot point S to the statics correction surface HThe propagation direction is opposite to the propagation direction from the static correction surface H to the demodulator probe G, and if the direction from the shot point S to the static correction surface H is set to be positive, the offset distance of the demodulator probe G in the static correction surface H can be expressed as: -TWgVtg 2*pg。
And step S3023, constructing an offset mapping relation between the offset distance before the seismic wave is propagated along the actual propagation path and the offset distance after the seismic wave is propagated along the actual propagation path and is statically corrected based on the fact that the offset distance before the seismic wave is propagated along the actual propagation path and is statically corrected is equal to the sum of the shot point offset distance, the geophone point offset distance and the offset distance after the seismic wave is propagated along the actual propagation path and is statically corrected.
In particular, HtOffset distance, H, before static correction for seismic wave propagation along actual propagation pathdCombining the shot offset T of the shot S on the static correction surface H obtained in the step S3021 and the step S3022 for the offset after the static correction of the seismic waves along the actual propagation pathWSVts 2*psoffset-T of demodulator probe from demodulator probe G on static correction surface HWgVtg 2*pgThen, the offset mapping relationship between the offset before the seismic wave propagates along the actual propagation path and the offset after the seismic wave propagates along the actual propagation path and is represented as:
Ht＝TWSVts 2*ps-TWgVtg 2*pg+Hd(6)。
and step S104, calculating the offset distance and the travel time after the seismic waves are propagated along the actual propagation path and are statically corrected according to the offset distance mapping relation and the travel time mapping relation.
The method specifically comprises the following two small steps:
step S4011, constructing ray parameter p of shot pointsAnd ray parameters p of the detection pointgThe ray parameter mapping relation between the two.
Specifically, the seismic waves encounter the reflection surface R under the static correction surface H and are reflected, and the reflected seismic waves are statically corrected by the static correction surface H and then emitted from the wave detection point G. Based on the property that the distance from the point on the static correction surface H to the reflecting layer after the shot point S is statically corrected is equal to the distance from the point on the static correction surface H to the reflecting layer after the demodulator probe G is statically corrected, it can be obtained that:
wherein, TgdAnd v is the speed of the seismic wave under the static correction surface H when the travel time from the demodulator probe G behind the static correction surface H to the reflecting surface R.
And deducing the offset distance H after the seismic waves are statically corrected after being propagated along the actual propagation path based on the propagation path of the seismic waves under the static correction surface HdComprises the following steps:
Hd＝v2*ps*(Td-Tgd)+v2*pg*Tgd(8)。
the ray parameter p for constructing the shot point can be deduced according to the formula (7) and the formula (8)sRay parameters p of sum-and-detection point GgThe ray parameter mapping relationship between the two can be expressed by the formula:
and S4012, calculating the offset distance and the travel time of the seismic waves after the seismic waves are propagated along the actual propagation path and are statically corrected according to the ray parameter mapping relation, the offset distance before the preset static correction, the travel time before the preset static correction, the offset distance mapping relation and the travel time mapping relation.
Specifically, in a specific implementation process, the offset distance and travel time after the seismic waves are propagated along the actual propagation path and are statically corrected can be deduced according to the preset static correction travel time and the preset static correction offset distance and by combining the formulas (5), (6) and (9). Wherein it is applied to the equivalent speed VtsAnd said equivalent speed VtgThe calculation is performed in combination of equations (1) and (2).
It should be noted that the propagation velocity V of seismic waves in the weathered layer is measured by using the prior art before the seismic data processing is actually performed0The propagation velocity V of seismic waves in a high-speed layer1Thickness Z of weathered layer corresponding to the location of shot point SWSHigh-speed layer thickness Z corresponding to shot point S positionMS(ii) a Weathered layer thickness Z corresponding to position of wave detection point GWgThickness Z of high-speed layer corresponding to position of wave-detecting point GMgOther parameters are reduced in the calculation process.
In order to further embody the non-surface consistency static correction method based on the equivalent velocity in the embodiment, the embodiment shows the seismic data before and after the non-surface consistency static correction based on the equivalent velocity and the single shot record after the conventional static correction. Wherein, fig. 5 is a schematic diagram of a single shot record being played on a relief surface; FIG. 6 is a schematic diagram of a conventional statically corrected single shot record based on a surface consistency assumption; FIG. 7 is a schematic diagram of a single shot record after equivalent velocity-based non-surface-consistent static correction; fig. 8 is a schematic diagram of a single shot record being performed at a static correction surface 2000m according to a first embodiment of the present invention.
As shown in fig. 5, the shot record is a shot record based on the forward modeling of the undulating surface model, the shot point S position is 2500m on the abscissa, the time sampling interval is 4ms, and the record length is 2.2S; FIG. 6 shows the results of conventional static correction of the single shot record, with the same parameters as FIG. 5; comparing fig. 5 and 6, it can be seen that the seismic data differs before and after conventional statics. FIG. 7 shows the results of the single shot record after non-surface consistent static correction of the present invention, with the parameters shown in FIG. 5; as shown in fig. 8, a shot record is being played at a static correction surface of 2000m for comparing the static correction effect of the present invention; comparing fig. 7 and fig. 8, it can be seen that the time distance relationship after the static correction of the present invention is more consistent with the forward result, and more conforms to the actual situation.
It should be noted that x in all the drawings indicates a horizontal direction, and z indicates a vertical direction.
By applying the equivalent-velocity-based non-earth-surface consistency static correction method provided by the embodiment of the invention, by calculating the equivalent velocity of seismic waves from the earth surface to the static correction surface, the distance from the shot point to the static correction surface is equivalent to the path from the shot point to the static correction surface along the actual propagation path of the seismic waves, the distance from the demodulator probe to the static correction surface is equivalent to the path from the static correction surface to the demodulator probe along the actual propagation path of the seismic waves, thereby establishing the offset mapping relation before and after the seismic waves are propagated along the actual propagation path and are statically corrected, and establishing a travel time mapping relation before and after seismic waves are propagated along an actual propagation path and statically corrected, so that the precision error caused by the vertical propagation of the seismic waves assumed by the conventional static correction is avoided, the technology has higher precision, can better keep accurate space-time distance relation and simultaneously can better ensure the subsequent imaging precision.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A static correction method for non-surface consistency based on equivalent speed comprises the following steps:
calculating the equivalent velocity of the seismic waves from the earth surface to the static correction surface according to the near-earth surface model;
constructing an offset mapping relation between the offset distance before the seismic waves are propagated along the actual propagation path for static correction and the offset distance after the static correction according to the equivalent velocity, and constructing a travel time mapping relation between travel time before the seismic waves are propagated along the actual propagation path for static correction and travel time after the static correction according to the equivalent velocity;
and calculating the offset distance and the travel time of the seismic waves after the seismic waves are propagated along the actual propagation path and are subjected to static correction according to the preset offset distance before the static correction, the preset travel time before the static correction, the offset distance mapping relation and the travel time mapping relation.
2. The method of claim 1, wherein calculating the equivalent velocity of the seismic waves from the surface to the statics correction surface based on the near-surface model further comprises the steps of:
the near-surface model comprises a regolith and a high-speed layer below the regolith; and setting a static correction surface in the high-speed layer, wherein the static correction surface is parallel to the horizontal plane.
3. The method of claim 2, wherein the step of calculating the surface-to-stationary correction surface equivalent velocity from the near-surface model comprises:
calculating the equivalent velocity V of the seismic wave from the shot point to the static correction surfacets；
Calculating the equivalent velocity V of the seismic wave from the static correction surface to the wave detection pointtg。
4. Method according to claim 3, characterized in that said equivalent speed VtsAnd said equivalent speed VtgIs formulated as:
wherein, V0Representing the propagation velocity, V, of said seismic waves in said regolith1Representing the propagation velocity, Z, of said seismic waves in said high-velocity zoneSRepresenting the distance, Z, of said shot from said static correction surfaceWSIndicating the thickness, Z, of the weathering layer corresponding to the location of the shotMSRepresenting the thickness, T, of the high-velocity layer corresponding to the shot locationSRepresenting travel time of the seismic waves from the shot point vertical to the static correction surface; zgRepresenting the distance, Z, of the demodulator probe from the static correction surfaceWgIndicating the thickness, Z, of the weathering layer corresponding to the location of the detection pointMgIndicating the thickness, T, of the high-speed layer corresponding to the position of the pickup pointgRepresenting the seismic waves as vertical to the seismic waves from the static correction surfaceAnd (5) describing the travel time of the wave detection point.
5. The method according to claim 3 or 4, wherein the step of constructing a travel time mapping relation between travel times of the seismic waves before and after the seismic waves are statically corrected and propagated along the actual propagation path according to the equivalent velocity comprises the following steps:
according to the equivalent speed VtsAnd a ray parameter p of said shotsCalculating the travel time T of the seismic waves transmitted from the shot point to the static correction surface along the actual propagation pathWS；
According to the equivalent speed VtgAnd a ray parameter p of the detection pointgCalculating the travel time T of the seismic wave transmitted from the static correction surface to the wave detection point along the actual propagation pathWg；
The travel time before static correction is carried out based on the seismic wave propagating along the actual propagation path is equal to the travel time TWsThe travel time TWgAnd the sum of travel time of the seismic waves after static correction is carried out along the actual propagation path, and the travel time mapping relation between the travel time of the seismic waves before static correction is carried out along the actual propagation path and the travel time after static correction is constructed.
6. The method of claim 5, wherein the travel time mapping relationship between the travel time before and after statics of the seismic waves propagating along the actual propagation path is formulated as:
Tt＝Td+TWS+TWg
wherein, TtRepresenting the travel time, T, of the seismic wave before the seismic wave is propagated along the actual propagation path for static correctiondAnd representing the travel time of the seismic wave after static correction along the actual propagation path.
7. The method of claim 6, wherein the step of constructing a migration distance mapping relationship between the migration distance before the seismic wave is propagated along the actual propagation path for static correction and the migration distance after the seismic wave is propagated along the actual propagation path according to the equivalent velocity comprises:
according to the equivalent speed VtsAnd a ray parameter p of said shotsCalculating the shot offset distance of the shot on the static correction surface;
according to the equivalent speed VtgAnd a ray parameter p of the detection pointgCalculating the offset distance of the wave detection point on the static correction surface;
and constructing an offset mapping relation between the offset before the seismic wave is propagated along the actual propagation path for static correction and the offset after the static correction on the basis that the offset before the seismic wave is propagated along the actual propagation path for static correction is equal to the sum of the shot point offset, the geophone point offset and the offset after the seismic wave is propagated along the actual propagation path for static correction.
8. The method of claim 7, wherein the offset mapping relationship between the pre-statics offset and the post-statics offset for seismic waves propagating along the actual propagation path is formulated as:
Ht＝TWSVts 2*ps-TWgVtg 2*pg+Hd
wherein HtOffset distance, H, before static correction for propagation of said seismic waves along an actual propagation pathdAnd (4) performing static correction on the seismic waves propagating along the actual propagation path.
9. The method of claim 8, wherein the step of calculating the offset and travel time of the seismic waves after statics correction along the actual propagation path according to the offset mapping relationship and the travel time mapping relationship comprises:
constructing a ray parameter p for the shotsAnd a ray parameter p of the detection pointgThe ray parameter mapping relation between the two;
and calculating the offset distance and the travel time of the seismic waves after the seismic waves are propagated along the actual propagation path and are subjected to static correction according to the ray parameter mapping relation, the preset offset distance before static correction, the preset travel time before static correction, the offset distance mapping relation and the travel time mapping relation.
10. Method according to claim 9, characterized in that the ray parameter p of the shot point issAnd a ray parameter p of the detection pointgThe ray parameter mapping relation between the two is formulated as:
where v represents the velocity of the seismic waves below the statics surface.
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