CN112305595B - Method for analyzing geologic body structure based on refraction wave and storage medium - Google Patents
Method for analyzing geologic body structure based on refraction wave and storage medium Download PDFInfo
- Publication number
- CN112305595B CN112305595B CN201910670854.3A CN201910670854A CN112305595B CN 112305595 B CN112305595 B CN 112305595B CN 201910670854 A CN201910670854 A CN 201910670854A CN 112305595 B CN112305595 B CN 112305595B
- Authority
- CN
- China
- Prior art keywords
- geological
- seismic
- grid point
- underground
- seismic refraction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims abstract description 58
- 238000012937 correction Methods 0.000 claims abstract description 34
- 238000010521 absorption reaction Methods 0.000 claims abstract description 17
- 230000001902 propagating effect Effects 0.000 claims abstract description 10
- 238000001228 spectrum Methods 0.000 claims description 15
- 239000011159 matrix material Substances 0.000 claims description 7
- 238000004590 computer program Methods 0.000 claims description 3
- 238000003325 tomography Methods 0.000 description 13
- 230000005540 biological transmission Effects 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 3
- 239000013598 vector Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000012916 structural analysis Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/28—Processing seismic data, e.g. for interpretation or for event detection
- G01V1/30—Analysis
- G01V1/306—Analysis for determining physical properties of the subsurface, e.g. impedance, porosity or attenuation profiles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V2210/00—Details of seismic processing or analysis
- G01V2210/60—Analysis
- G01V2210/62—Physical property of subsurface
- G01V2210/624—Reservoir parameters
Landscapes
- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Acoustics & Sound (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The invention discloses a method and a storage medium for analyzing a geologic body structure based on refracted waves, wherein the method comprises the following steps: setting an initial value of the underground propagation speed of the seismic refraction wave at each geological grid point, constructing a ray path of the seismic refraction wave from the seismic source to each geological grid point, and correcting the initial value of the underground propagation speed according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along the ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point; and determining the geological quality factor of each geological grid point according to the corrected value of the underground propagation speed and the geological absorption characteristic time of each ray path based on the geological quality factor inversion model. The seismic refraction wavelets analyzed by the method are easy to distinguish from other waves, so that the seismic refraction wavelets can be accurately extracted, first arrival can be conveniently and reliably picked up, and the reliability of the inversion of the subsequent geologic body structure is improved.
Description
Technical Field
The invention belongs to the field of seismic data processing, and particularly relates to a method for analyzing a geologic structure based on refracted waves and a storage medium internally storing the method for analyzing the geologic structure based on refracted waves.
Background
Currently, in geophysical exploration, seismic data are mostly processed and interpreted using ground seismic reflection waves, transmission waves between wells, up-going and down-going waves of VSP (VERTICAL SEISMIC Profiling, vertical seismic profile), and the like.
However, the following problems exist in the process interpretation using surface seismic reflection waves, transmission waves between wells, VSP up-going and down-going waves, etc.:
firstly, because the seismic information reflected by the shallow layer is distributed in the near road and is seriously influenced by nearby surface waves, accurate seismic reflection wavelets are difficult to extract; the up-going and down-going waves of the VSP are not easy to separate; the cross-well transmitted wave is typically an auxiliary reference for the surface seismic reflected wave.
Secondly, exploration for deep basement structural morphology by using seismic reflection waves can be extremely weak due to deep reflection energy, reliability of effective information is also deteriorated, and small-scale geological structures such as underground thin layers and cracks cannot be well identified.
Third, most of the seismic reflected wave energy is concentrated only at the near offset distance, and information collection and imaging at the far offset distance cannot be performed.
The quality factor Q is an important parameter for reflecting the absorption and attenuation of the underground medium to the seismic wave energy, can represent the characteristic attribute of the stratum, and can be used for identifying and explaining the rock property, fault and fluid distribution, so that the accurate estimation of the Q value has important significance for researching the lithology, physical property, structure, fluid-containing property and the like of the underground medium. The geological quality factor may be calculated by Q tomography.
There is a need for a method for analyzing a geologic structure based on refracted waves and a storage medium having stored therein a method for analyzing a geologic structure based on refracted waves.
Disclosure of Invention
The invention aims to solve the technical problem that the analysis result of a geologic body structure is inaccurate due to the fact that seismic wavelets cannot be accurately acquired.
In order to solve the technical problems, the invention provides a method for analyzing a geologic structure based on refracted waves, which comprises the following steps:
S100, dividing a geologic body profile of a target reservoir into a plurality of geologic grids to form a plurality of geologic grid points;
S200, setting an initial value of the underground propagation speed of the seismic refraction wave at each geological grid point, constructing a ray path of the seismic refraction wave from the seismic source to each geological grid point, and correcting the initial value of the underground propagation speed according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagation along the ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
S300, determining the geological quality factor of each geological grid point according to the corrected value of the underground propagation speed of the seismic refraction wave at each geological grid point and the geological absorption characteristic time of each ray path based on the geological quality factor inversion model;
S400, analyzing the geologic body structure of the target reservoir according to the distribution of the geologic quality factors of each geologic grid point.
Preferably, the step S200 includes the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
S230, correcting the initial value of the underground propagation velocity according to the difference between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along the ray path based on the underground velocity inversion model, so as to obtain the corrected value of the underground propagation velocity of the seismic refraction wave at each geological grid point.
Preferably, the step S200 includes the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
s230, correcting an initial value of the underground propagation speed based on an underground speed inversion model according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along a ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
S240, judging whether the difference between the theoretical first-arrival travel time and the actual first-arrival travel time corresponding to the correction value of the current underground propagation speed is smaller than a preset threshold value:
If yes, go to step S300;
If not, the initial value of the subsurface propagation velocity is made equal to the correction value of the current subsurface propagation velocity, and the process returns to step S220 to correct the subsurface propagation velocity of the seismic refraction wave at each geological grid point again.
Preferably, in the step S200, an initial value of the underground propagation velocity of the seismic refraction wave at each geological grid point is set so as to conform to a two-dimensional velocity distribution of a uniform gradient; ray paths of seismic refracted waves from the seismic source to each geological grid point are constructed through a ray tracing method.
Preferably, in the step S200, the actual first-arrival travel time of the seismic refraction wave from the seismic source to each geological grid point is the actual first-arrival travel time of the seismic refraction wave at the geological grid point picked up on the non-superimposed single shot seismic record section.
Preferably, the step S400 includes the steps of:
s410, correspondingly filling the geological quality factors of each geological grid point into the geological profile to obtain the structural distribution of the geological quality factors;
s420, analyzing the geologic structure of the target reservoir according to the distribution of the geologic quality factors in the geologic body profile.
Preferably, the subsurface velocity inversion model is as follows:
Bδv＝δt
Wherein B is an underground speed inversion coefficient matrix, δv is a difference value between a correction value and an initial value of an underground propagation speed of the seismic refraction wave of each geological grid point, and δt is a difference value between an actual first arrival travel time and a theoretical first arrival travel time of the seismic refraction wave of each geological grid point.
Preferably, in the step S300, the geological absorption characteristic time of each ray path is obtained by the following expression:
Wherein t * is the characteristic time of geological absorption, C (f) is the stratum response spectrum, and f is the seismic refraction wavelet frequency.
Preferably, in the step S300, the geological quality factor inversion model is:
Where Q (x, z) is a geological quality factor of a geological grid point, v k (x, z) is a correction value of an underground propagation speed of a seismic refraction wave of the geological grid point on the kth ray, w k (x, z) is a weight factor of the kth ray, t * k is a geological absorption characteristic time of the kth ray, and L k is a ray path of the kth ray.
According to another aspect of the present invention there is provided a storage medium having stored thereon a computer program, characterized in that the program when executed by a processor implements the steps of the method as described above.
One or more embodiments of the above-described solution may have the following advantages or benefits compared to the prior art:
1) The analyzed seismic refraction wavelets are easy to distinguish from other waves and avoid near-road interference, so that the seismic refraction wavelets can be accurately extracted, first arrivals can be conveniently and reliably picked up, and the reliability of the inversion of the subsequent geologic body structure is improved;
2) According to the method, the propagation process of the seismic refraction wavelets in a plurality of geological grids is analyzed, and as the coaxial energy of the seismic refraction wavelets is strong and the traceability is good, the method can perform speed imaging on small-scale geological structures such as underground thin layers and cracks, conveniently and reliably identify the small-scale geological structures, and further provide explanation for the details of the geological structures;
3) The propagation process of the seismic refraction wavelet in a plurality of geological grids has the characteristic of wide angle, can acquire and image information at a far offset distance, and provides more complete explanation for inversion of a geological structure.
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 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 are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention, without limitation to the invention. In the drawings:
FIG. 1 shows a flow chart of a method of analyzing a geologic volume structure based on refracted waves, according to an embodiment of the invention;
FIG. 2 is a flowchart showing specific steps of a method for analyzing a geologic structure based on refracted waves according to an embodiment of the invention;
FIG. 3 is a flowchart showing another specific steps of a method for analyzing a geologic volume structure based on refracted waves according to a second embodiment of the invention;
FIG. 4 shows a data morphology of a test site in a fourth embodiment of the present invention;
figure 5 shows a layered initial velocity model established by travel time tomography in a fourth embodiment of the invention,
The reference numerals in the drawings are: 1-refracted wave, 2-reflected wave, 3-water wave.
Detailed Description
The following will describe embodiments of the present invention in detail with reference to the drawings and examples, thereby solving the technical problems by applying technical means to the present invention, and realizing the technical effects can be fully understood and implemented accordingly. It should be noted that, as long as no conflict is formed, each embodiment of the present invention and each feature of each embodiment may be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.
The invention acquires the underground propagation speed of each geological grid point according to the travel time tomography principle, wherein the travel time tomography principle is a process of establishing an underground medium speed structure by taking travel time as a starting point. The inversion process of the speed belongs to the nonlinear inversion problem, and the nonlinear problem can be linearized by solving the nonlinear problem by adopting an iterative method. After the conversion to linearization, an initial velocity model is first provided, and the path length and theoretical first arrival time can be calculated by the shortest path ray tracing method. Secondly, the residual error of the speed model is obtained from the difference of the travel time according to the selected regularization criterion. And finally, gradually updating the speed structure model by the residual error of the speed until the residual error is in an acceptable enough range, so as to obtain a real underground speed model, and further obtain the underground propagation speed of each geological grid point. And obtaining the Q value of each geological grid point according to the underground propagation speed of each geological grid point and the Q tomography principle. The Q tomography principle requires two-dimensional or three-dimensional ray tracing. The Q tomography principle is divided into two steps: in the first step, the waveform and amplitude spectrum ratio of the relevant wave is used to find the travel time t related to Q. And step two, carrying out Q value inversion by the t value obtained in the step one. The inversion requires gridding the model, and after the velocity model is obtained, the value of v at each grid point corresponds to a Q value to be obtained.
Specifically, the invention adopts a spectral ratio method in a frequency domain to carry out Q value estimation and tomography on a refraction wave ray propagation region.
Example 1
In order to solve the technical problems in the prior art, the embodiment of the invention provides a method for analyzing a geologic structure based on refracted waves.
Referring to fig. 2, the method for analyzing a geologic structure based on refracted waves according to the embodiment includes the following steps:
S100, dividing a geologic body profile of a target reservoir into a plurality of geologic grids to form a plurality of geologic grid points;
S200, setting an initial value of the underground propagation speed of the seismic refraction wave at each geological grid point, constructing a ray path of the seismic refraction wave from the seismic source to each geological grid point, and correcting the initial value of the underground propagation speed according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagation along the ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
specifically, the step S200 includes the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
S230, correcting the initial value of the underground propagation velocity according to the difference between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along the ray path based on the underground velocity inversion model, so as to obtain the corrected value of the underground propagation velocity of the seismic refraction wave at each geological grid point.
S300, determining the geological quality factor of each geological grid point according to the corrected value of the underground propagation speed of the seismic refraction wave at each geological grid point and the geological absorption characteristic time of each ray path based on the geological quality factor inversion model;
S400, analyzing the geologic body structure of the target reservoir according to the distribution of the geologic quality factors of each geologic grid point.
Example two
In order to solve the technical problems in the prior art, the embodiment of the invention also provides another specific implementation mode of the method for analyzing the geologic structure based on the refraction waves.
Referring to fig. 3, the method for analyzing a geologic structure based on refracted waves according to the embodiment includes the following steps:
S100, dividing a geologic body profile of a target reservoir into a plurality of geologic grids to form a plurality of geologic grid points;
Here, the geologic volume profile may be drawn from a target reservoir, which is the geologic volume to be analyzed. The geologic volume profile is parameterized by a uniform grid of constant size in all directions.
S200, setting an initial value of the underground propagation speed of the seismic refraction wave at each geological grid point, constructing a ray path of the seismic refraction wave from the seismic source to each geological grid point, and correcting the initial value of the underground propagation speed according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagation along the ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
specifically, the step S200 includes the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
Specifically, an initial velocity model of seismic refraction wave propagation in a target reservoir is obtained, and initial values of underground propagation velocities of the seismic refraction waves at each geological grid point are extracted from the initial velocity model; the initial velocity model is a two-dimensional velocity distribution of uniform variation gradients, so as to set initial values of underground propagation velocities of seismic refraction waves at each geological grid point, and enable the initial values to conform to the two-dimensional velocity distribution of the uniform variation gradients. The initial velocity model is obtained from empirical data and is related to the properties of the geologic volume. For example, a two-dimensional velocity profile of uniformly varying gradients may be given according to known parameters such as measured seafloor terrain depth, acquisition range, etc., from a preliminary estimate of the actual first arrival travel of the seismic refraction wave at each geological grid point.
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
Specifically, ray paths of seismic refracted waves from the seismic source to each geological grid point are constructed by a ray tracing method. In particular, the forward process of travel and ray paths employs the ray tracing forward method of Vidale (1988,1990), which is not described in detail herein.
S230, correcting the initial value of the underground propagation velocity according to the difference between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along the ray path based on the underground velocity inversion model, so as to obtain the corrected value of the underground propagation velocity of the seismic refraction wave at each geological grid point.
Specifically, the subsurface velocity inversion model is as follows:
Bδv＝δt
Wherein B is an underground velocity inversion coefficient matrix, δv is the difference between the underground propagation velocity and the initial velocity of each geological grid point, and δt is the difference between the actual first arrival travel time and the theoretical first arrival travel time of the seismic refraction wave of each geological grid point. Here, B is a matrix of subsurface velocity inversion coefficients, and is applied to a specific matrix in which δv is obtained from δt column vectors, and when δt and δv are both n×1 column vectors, B is an n×n matrix.
Specifically, the actual first arrival travel time of the seismic refraction wave at the geological grid point is picked up on the non-superimposed single shot seismic record section. Here, based on the artificial source wide-angle seismic data collected by the nius island in the suger answer area, picking up the first-arrival refraction wave travel is performed, a time window with a proper width is selected to completely intercept the required waveform, the process can be performed manually, and the quality of intercepted data in the step determines the reliability of the subsequent inversion step.
S240, judging whether the difference between the theoretical first-arrival travel time and the actual first-arrival travel time corresponding to the correction value of the current underground propagation speed is smaller than a preset threshold value:
If yes, go to step S300;
If not, the initial value of the subsurface propagation velocity is made equal to the correction value of the current subsurface propagation velocity, and the process returns to step S220 to correct the subsurface propagation velocity of the seismic refraction wave at each geological grid point again.
Here, the correction value of the current subsurface propagation velocity is a correction value of the subsurface propagation velocity of the seismic refraction wave at each geological grid point in step S230.
The following illustrates the process of multiple corrections for the subsurface propagation velocity of seismic refraction waves at each geological grid point:
setting the actual first arrival travel time of the seismic refraction wave from a seismic source to each geological grid point as T, setting the first constructed ray path as s0, and setting the initial value of the underground propagation speed as v0;
Secondly, forward modeling a theoretical first arrival travel time T0 of the seismic refraction wave propagating along s0 according to the first constructed ray path s0 and an initial value v0 of the underground propagation speed, and obtaining a first correction value v1 of the underground propagation speed according to the initial value v0 of the underground propagation speed, the theoretical first arrival travel time T0 and the actual first arrival travel time T;
Thirdly, judging whether the difference value between the theoretical first arrival travel time and the actual first arrival travel time T of the forward seismic refraction wave propagating along the s0 according to the ray path s0 and the first correction value v1 of the underground propagation speed meets the precision; if so, the first correction v1 of the underground propagation velocity is the final correction of the underground propagation velocity, and step S300 is performed; if not, returning to the step S200, reconstructing a ray path S1, forward modeling a theoretical first-arrival travel time T1 of the seismic refraction wave propagating along the S1 according to the ray path S1 and a first correction value v1 of the underground propagation speed, and obtaining a second correction value v2 of the underground propagation speed according to an initial value v1 of the underground propagation speed, the theoretical first-arrival travel time T1 and the actual first-arrival travel time T;
Fourth, according to the ray path s1 and the second correction value v2 of the underground propagation speed, whether the difference value between the theoretical first arrival travel time and the actual first arrival travel time T of the forward seismic refraction wave propagated along the s1 meets the precision or not; if so, the second correction v2 of the subsurface propagation velocity is the final correction of the subsurface propagation velocity; if the first-pass travel time is not longer than the first-pass travel time, reconstructing a ray path s2, forward modeling the theoretical first-pass travel time T2 of the seismic refraction wave transmitted along the s2 according to the ray path s2 and a second correction value v2 of the underground transmission speed, and obtaining a third correction value v3 of the underground transmission speed according to an initial value v2 of the underground transmission speed, the theoretical first-pass travel time T2 and the actual first-pass travel time T;
And so on until the difference between the theoretical first-arrival travel time and the actual first-arrival travel time corresponding to the correction value of the current underground propagation speed meets the precision.
Along with the continuous decrease of the δt value of multiple iterations, the underground propagation speed is updated until δt reaches a specified accuracy range, for example, the ratio of δt to the actual first arrival travel time is less than 0.1%, and the obtained underground propagation speed is the final inversion result.
Furthermore, in this embodiment, inversion iterations are performed from theoretical travel time and picked up actual travel time, and after the iterations are completed, the formation velocity structure is drawn by GMT (THE GENERIC MAPPING tools, general drawing tool) drawing script.
Further, in steps S100 to S240, the formation velocity structure and the ray path of the local region are preferably obtained using refracted wave first arrival travel time tomography.
S300, determining the geological quality factor of each geological grid point according to the corrected value of the underground propagation speed of the seismic refraction wave at each geological grid point and the geological absorption characteristic time of each ray path based on the geological quality factor inversion model;
Specifically, the determination of the time t of the geologic absorption characteristic of each ray path uses the method proposed by Wilcock (1995). In the time domain, the seismic signals may be represented in convolution:
x(t)＝s(t)*c(t)*i(t)
Where t is time, s (t) is the source signal, c (t) is the formation response, and i (t) is the instrument response.
Accordingly, in the frequency domain, the frequency spectrum C of the formation response may be obtained by dividing the spectrum X of the seismic signal by the spectrum S of the source signal and the spectrum I of the instrument response:
Wherein C (f) is the stratum response spectrum, X (f) is the received seismic signal spectrum, S (f) is the source signal spectrum, I (f) is the instrument response spectrum, and f is the frequency.
Assuming that the time window used for the spectral measurement has only one phase and that the only frequency dependent attenuation in the propagation component of the seismic refraction sub-wave is only, then C can be expressed as:
C(f,s)＝G(s)exp[-2πft(s)]
Where s is the path of the wave, G is the divergence of the wave, and is a constant.
The value of t can be obtained by plotting ln C (f) and linearizing it again in the frequency domain.
Wherein t * is the characteristic time of geological absorption, C (f) is the stratum response spectrum, and f is the seismic refraction wavelet frequency.
Thus, the geologic absorption feature time is obtained by the following expression:
Wherein t * is the characteristic time of geological absorption, C (f) is the stratum response spectrum, and f is the seismic refraction wavelet frequency.
Specifically, the Q tomography principle, i.e., the relationship of t * to Q, can be expressed specifically as:
Where Q (x, z) is the geological quality factor of the geological grid point and v (x, z) is the subsurface propagation velocity of the geological grid point.
With the velocity v (x, z) known, the inversion of Q (x, z) can be performed using the travel time t.
This process of finding Q can be expressed by the following expression:
wherein A is the coefficient matrix is the quantity related to the intersection of the ray path with the grid; lambda is a constraint parameter; l is the Laplace operator; t is the column vector of the obtained t.
The discrete geological quality factor inversion model is as follows:
Where Q (x, z) is a geological quality factor of the geological grid point, v k (x, z) is a subsurface propagation velocity of the geological grid point on the kth ray, w k (x, z) is a weight factor of the kth ray, t * k is a geological absorption characteristic time of the kth ray, and L k is a ray path of the kth ray.
The above is a linear equation set established based on the linear relationship between the t-x values corresponding to all the rays and the Q-value model, and the Q-value is solved by using a least square method.
S400, analyzing the geologic body structure of the target reservoir according to the distribution of the geologic quality factors of each geologic grid point.
In the second embodiment, the accuracy of the correction value of the current underground propagation speed is ensured by controlling the accuracy of the difference between the theoretical first-arrival travel time and the actual first-arrival travel time corresponding to the correction value of the current underground propagation speed in an iterative manner.
Example III
To solve the above technical problems in the prior art, a third embodiment of the present invention further provides a storage medium having a computer program stored thereon, where the program when executed by a processor implements the steps of the method as described above.
It should be noted that, the method for implementing the program stored on the storage medium by execution is the same as the method for analyzing the geologic structure based on the refracted wave in the first embodiment, so the method for implementing the program stored on the storage medium in this embodiment will not be described herein again.
Example IV
The method for analyzing geologic structures based on refracted waves of the invention is used for carrying out structural analysis on geologic structures with the X-axis range of 0-120km and the Z-axis range of 0-20km so as to show the longitudinal and transverse changes of Q values of a sedimentary layer and the crust below the sedimentary layer. Fig. 4 shows the data morphology of the test work area in the fourth embodiment of the present invention, in which the morphology of the refracted wave 1, reflected wave 2, and direct water wave 3 of the data can be clearly seen. As can be seen from fig. 4, the seismic refraction wavelet analyzed by the invention is easy to distinguish from other waves and avoid near-road interference, so that the seismic refraction wavelet can be accurately extracted, the first arrival can be conveniently and reliably picked up, the reliability of the inversion of the subsequent geologic structure is improved, and the propagation process of the seismic refraction wavelet in a plurality of geologic grids has the characteristic of wide angle, can acquire and image information at a far offset distance, and provides more complete explanation for the inversion of the geologic structure. Fig. 5 shows a layered initial velocity model established by travel time tomography in the fourth embodiment of the present invention, and an arrow in fig. 5 indicates a direction in which the layered initial velocity is changed from small to large.
Firstly, obtaining an initial velocity model and a ray path of seismic refraction waves of a selected test work area by adopting a refraction wave first arrival travel time tomography method; secondly, obtaining a t-value related to the Q value by utilizing the slope of the spectrum ratio of the refraction wave first arrival and the water layer direct wave (namely the frequency spectrum of the seismic source signal); and finally, based on the linear relation between the t-value and the Q-value model corresponding to all rays, establishing a linear equation set, and solving the Q-value model by using a least square method.
Q tomography results showed longitudinal and lateral changes in Q values present for the sedimentary layer and its underlying crust at depths of 5-12 km. In the range from x=0 km to x=120 km, Q -1 decreases overall in the vertical direction, especially below 10km (marine crust region) showing lower Q -1 values, showing that the seismic attenuation of the marine crust is much less than that of the sedimentary layer. In the range of x=120 km to x=200 km, both the sedimentary and marine crust exhibit lower Q -1 values, in sharp contrast to the X <120km region in the transverse direction. Therefore, the Q value distribution of the underground structure can be effectively and reliably inverted by the method for analyzing the geologic body structure based on the refraction waves, so that a powerful scientific basis is provided for subsequent geologic interpretation.
Although the embodiments of the present invention are disclosed above, the embodiments are only used for the convenience of understanding the present invention, and are not intended to limit the present invention. Any person skilled in the art can make any modification and variation in form and detail without departing from the spirit and scope of the present disclosure, but the scope of the present disclosure is still subject to the scope of the present disclosure as defined by the appended claims.
Claims (8)
1. A method for analyzing a geologic structure based on refracted waves, comprising:
S100, dividing a geologic body profile of a target reservoir into a plurality of geologic grids to form a plurality of geologic grid points;
S200, setting an initial value of the underground propagation speed of the seismic refraction wave at each geological grid point, constructing a ray path of the seismic refraction wave from the seismic source to each geological grid point, and correcting the initial value of the underground propagation speed according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagation along the ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
S300, determining the geological quality factor of each geological grid point according to the corrected value of the underground propagation speed of the seismic refraction wave at each geological grid point and the geological absorption characteristic time of each ray path based on the geological quality factor inversion model;
S400, analyzing the geologic body structure of the target reservoir according to the distribution of the geologic quality factors of each geologic grid point;
In the step S300, the geological absorption characteristic time of each ray path is obtained by the following expression:
Wherein t * is the geological absorption characteristic time, C (f) is the stratum response spectrum, and f is the earthquake refraction wavelet frequency;
In the step S300, the geological quality factor inversion model is:
Where Q (x, z) is a geological quality factor of a geological grid point, v k (x, z) is a correction value of an underground propagation speed of a seismic refraction wave of the geological grid point on the kth ray, w k (x, z) is a weight factor of the kth ray, t * k is a geological absorption characteristic time of the kth ray, and L k is a ray path of the kth ray.
2. The method according to claim 1, wherein said step S200 comprises the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
S230, correcting the initial value of the underground propagation velocity according to the difference between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along the ray path based on the underground velocity inversion model, so as to obtain the corrected value of the underground propagation velocity of the seismic refraction wave at each geological grid point.
3. The method according to claim 1, wherein said step S200 comprises the steps of:
s210, setting initial values of underground propagation speeds of seismic refraction waves at each geological grid point;
S220, constructing ray paths of the seismic refraction waves from the seismic source to each geological grid point, and determining theoretical first arrival travel time of the seismic refraction waves along the ray paths according to the initial value of the underground propagation speed;
s230, correcting an initial value of the underground propagation speed based on an underground speed inversion model according to a difference value between the actual first arrival travel time of the seismic refraction wave from the seismic source to each geological grid point and the theoretical first arrival travel time of the seismic refraction wave propagating along a ray path so as to obtain a correction value of the underground propagation speed of the seismic refraction wave at each geological grid point;
S240, judging whether the difference between the theoretical first-arrival travel time and the actual first-arrival travel time corresponding to the correction value of the current underground propagation speed is smaller than a preset threshold value:
If yes, go to step S300;
If not, the initial value of the subsurface propagation velocity is made equal to the correction value of the current subsurface propagation velocity, and the process returns to step S220 to correct the subsurface propagation velocity of the seismic refraction wave at each geological grid point again.
4. A method according to any one of claims 1 to 3, wherein in step S200, initial values of subsurface propagation velocities of seismic refraction waves at each geological grid point are set so as to conform to a two-dimensional velocity distribution of uniform gradient; ray paths of seismic refracted waves from the seismic source to each geological grid point are constructed through a ray tracing method.
5. A method according to any one of claims 1 to 3, wherein in step S200, the actual first arrival travel of the seismic refraction wave from the source to each geological grid point is the actual first arrival travel of the seismic refraction wave at the geological grid point picked up on an unstacked single shot seismic record section.
6. A method according to any one of claims 1 to 3, wherein said step S400 comprises the steps of:
s410, correspondingly filling the geological quality factors of each geological grid point into the geological profile to obtain the structural distribution of the geological quality factors;
s420, analyzing the geologic structure of the target reservoir according to the distribution of the geologic quality factors in the geologic body profile.
7. A method according to claim 2 or 3, wherein the subsurface velocity inversion model is as follows:
Bδv＝δt
Wherein B is an underground speed inversion coefficient matrix, δv is a difference value between a correction value and an initial value of an underground propagation speed of the seismic refraction wave of each geological grid point, and δt is a difference value between an actual first arrival travel time and a theoretical first arrival travel time of the seismic refraction wave of each geological grid point.
8. A storage medium having stored thereon a computer program, which when executed by a processor performs the steps of the method according to any of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910670854.3A CN112305595B (en) | 2019-07-24 | 2019-07-24 | Method for analyzing geologic body structure based on refraction wave and storage medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910670854.3A CN112305595B (en) | 2019-07-24 | 2019-07-24 | Method for analyzing geologic body structure based on refraction wave and storage medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112305595A CN112305595A (en) | 2021-02-02 |
| CN112305595B true CN112305595B (en) | 2024-05-17 |
Family
ID=74328777
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910670854.3A Active CN112305595B (en) | 2019-07-24 | 2019-07-24 | Method for analyzing geologic body structure based on refraction wave and storage medium |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112305595B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116698141B (en) * | 2023-07-28 | 2023-10-27 | 山东大学 | Speed measurement error correction method and system for ultrasonic flowmeter under different working conditions |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1308240A (en) * | 2001-01-21 | 2001-08-15 | 周熙襄 | Short wavelength static correction method of seismic prospecting data with preliminary refraction wave |
| GB0119245D0 (en) * | 2001-08-07 | 2001-10-03 | Statoil Asa | Method and apparatus for determining the nature of subterranean reservoirs |
| US6864684B2 (en) * | 2001-08-07 | 2005-03-08 | Statoil Asa | Electromagnetic methods and apparatus for determining the content of subterranean reservoirs |
| CN101980054A (en) * | 2010-10-22 | 2011-02-23 | 中国石油化工股份有限公司 | Method for establishing near-surface velocity model in high-density seismic static correction processing |
| CN102096099A (en) * | 2009-12-14 | 2011-06-15 | 武侯区巅峰机电科技研发中心 | Ray chromatography imaging method for refracted waves |
| CN104570057A (en) * | 2015-01-28 | 2015-04-29 | 中国电建集团昆明勘测设计研究院有限公司 | Water seismic refraction data acquisition method based on manual rammer seismic source |
| CN105277975A (en) * | 2014-07-23 | 2016-01-27 | 中国石油化工股份有限公司 | Harmonic-wave removing method in multi-seismic-source seismic data processing |
| CN105301639A (en) * | 2015-10-21 | 2016-02-03 | 中国石油天然气集团公司 | Speed field inversion method and device based on VSP double-weight travel time tomography |
| CN105445789A (en) * | 2014-09-04 | 2016-03-30 | 中国石油化工股份有限公司 | Three-dimensional Fresnel volume travel-time tomographic method based on multiple reflected refraction wave constraint |
| WO2017024536A1 (en) * | 2015-08-11 | 2017-02-16 | 深圳朝伟达科技有限公司 | Method for automatically removing wave arrival of seismic wave |
| CN107843922A (en) * | 2017-12-25 | 2018-03-27 | 中国海洋大学 | One kind is based on seismic first break and the united chromatography imaging method of Travel time |
| CN107942372A (en) * | 2016-10-12 | 2018-04-20 | 中国石油化工股份有限公司 | Between well and well combine seismic CT imaging method and device |
| WO2019071504A1 (en) * | 2017-10-12 | 2019-04-18 | 南方科技大学 | Two-point ray tracing based seismic travel time tomography inversion method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9291733B2 (en) * | 2011-01-31 | 2016-03-22 | Cggveritas Services Sa | Device and method for determining S-wave attenuation in near-surface condition |
-
2019
- 2019-07-24 CN CN201910670854.3A patent/CN112305595B/en active Active
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1308240A (en) * | 2001-01-21 | 2001-08-15 | 周熙襄 | Short wavelength static correction method of seismic prospecting data with preliminary refraction wave |
| GB0119245D0 (en) * | 2001-08-07 | 2001-10-03 | Statoil Asa | Method and apparatus for determining the nature of subterranean reservoirs |
| US6864684B2 (en) * | 2001-08-07 | 2005-03-08 | Statoil Asa | Electromagnetic methods and apparatus for determining the content of subterranean reservoirs |
| CN102096099A (en) * | 2009-12-14 | 2011-06-15 | 武侯区巅峰机电科技研发中心 | Ray chromatography imaging method for refracted waves |
| CN101980054A (en) * | 2010-10-22 | 2011-02-23 | 中国石油化工股份有限公司 | Method for establishing near-surface velocity model in high-density seismic static correction processing |
| CN105277975A (en) * | 2014-07-23 | 2016-01-27 | 中国石油化工股份有限公司 | Harmonic-wave removing method in multi-seismic-source seismic data processing |
| CN105445789A (en) * | 2014-09-04 | 2016-03-30 | 中国石油化工股份有限公司 | Three-dimensional Fresnel volume travel-time tomographic method based on multiple reflected refraction wave constraint |
| CN104570057A (en) * | 2015-01-28 | 2015-04-29 | 中国电建集团昆明勘测设计研究院有限公司 | Water seismic refraction data acquisition method based on manual rammer seismic source |
| WO2017024536A1 (en) * | 2015-08-11 | 2017-02-16 | 深圳朝伟达科技有限公司 | Method for automatically removing wave arrival of seismic wave |
| CN105301639A (en) * | 2015-10-21 | 2016-02-03 | 中国石油天然气集团公司 | Speed field inversion method and device based on VSP double-weight travel time tomography |
| CN107942372A (en) * | 2016-10-12 | 2018-04-20 | 中国石油化工股份有限公司 | Between well and well combine seismic CT imaging method and device |
| WO2019071504A1 (en) * | 2017-10-12 | 2019-04-18 | 南方科技大学 | Two-point ray tracing based seismic travel time tomography inversion method |
| CN107843922A (en) * | 2017-12-25 | 2018-03-27 | 中国海洋大学 | One kind is based on seismic first break and the united chromatography imaging method of Travel time |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112305595A (en) | 2021-02-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8352190B2 (en) | Method for analyzing multiple geophysical data sets | |
| EP2093591B1 (en) | Method for Three Dimensional Seismic Travel Time Tomography in Transversely Isotropic Media | |
| CN101086535B (en) | A process and program for characterising evolution of an oil reservoir over time | |
| Tang et al. | Processing array acoustic-logging data to image near-borehole geologic structures | |
| EP2491428B1 (en) | Full-waveform inversion in the traveltime domain | |
| EP3028071B1 (en) | Method and device for the generation and application of anisotropic elastic parameters in horizontal transverse isotropic (hti) media | |
| CN102937721B (en) | Limited frequency tomography method for utilizing preliminary wave travel time | |
| CN108139499A (en) | The full wave field inversion of Q- compensation | |
| CN102937720B (en) | Well control improves the method for seismic data resolution | |
| US7768870B2 (en) | Method for adjusting a seismic wave velocity model according to information recorded in wells | |
| WO2017035104A1 (en) | Velocity model seismic static correction | |
| CN102841376A (en) | Retrieval method for chromatography speed based on undulating surface | |
| MX2013000343A (en) | Methods and Devices for Transformation of Collected Data for Improved Visualization Capability. | |
| Bradford et al. | Reverse-time migration from rugged topography to image ground-penetrating radar data in complex environments | |
| US20140081577A1 (en) | Method For Calibrating Seismic Imaging Velocities | |
| CN111025387B (en) | Pre-stack earthquake multi-parameter inversion method for shale reservoir | |
| CN111123359B (en) | Logging while drilling and stratum grid constrained well periphery seismic imaging detection method and device | |
| CN115877449B (en) | Computer-implemented method for obtaining subsurface superimposed images within a survey area | |
| US10379244B2 (en) | Method for obtaining estimates of a model parameter so as to characterise the evolution of a subsurface volume over a time period | |
| CN104199088B (en) | Incident angle gather extraction method and system | |
| Guo et al. | Topography-dependent eikonal tomography based on the fast-sweeping scheme and the adjoint-state technique | |
| Gong et al. | Combined migration velocity model-building and its application in tunnel seismic prediction | |
| CN112379462B (en) | Electromagnetic seismic data joint processing method and device | |
| CN112305595B (en) | Method for analyzing geologic body structure based on refraction wave and storage medium | |
| Gibson Jr et al. | Modeling and velocity analysis with a wavefront-construction algorithm for anisotropic media |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |