CN108983290B - It is a kind of three-dimensional Method in Transverse Isotropic Medium in travel when determine method and system - Google Patents
It is a kind of three-dimensional Method in Transverse Isotropic Medium in travel when determine method and system Download PDFInfo
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Abstract
The invention discloses determine method and system when travelling in a kind of three-dimensional Method in Transverse Isotropic Medium.The determination method includes: to obtain three layers of radiation relationship change matrix；6 different incident orientations in 24 kinds of face when determining three-dimensional Method in Transverse Isotropic Medium travelling according to described three layers radiation relationship change matrix；Radiation coordinate system is determined according to described 24 kinds different incident orientations；Under the radiation coordinate system, known mesh point coordinate is obtained；The minimum traveltimes of three-dimensional Method in Transverse Isotropic Medium are updated according to the known mesh point coordinate；According to the minimum traveltimes, geological structure is determined using offset imaging method.It can reduce the complexity that travel time table shows in three-dimensional Method in Transverse Isotropic Medium using determining method and system provided by the present invention, facilitate Parallel Design, improve computational efficiency.
Description
Technical Field
The invention relates to the field of seismic data processing of petroleum geophysical exploration, in particular to a travel time determining method and system in a three-dimensional transverse isotropic medium.
Background
In seismic exploration, the general existence of anisotropy has become a common recognition in academia and industry, and Transverse Isotropic (TI) Media include Transverse Isotropic (VTI) Media having a horizontal symmetry axis, Transverse Isotropic (HTI) Media having a vertical symmetry axis, and Transverse Isotropic (TTI) Media having an inclined symmetry axis, and these seismic anisotropic Media models have become conventional targets for seismic interpretation and processing, and the field of seismic data processing, and the processing method of TI Media involves a square surface, which have been widely studied.
The calculation during travel of the TI medium is the basis of TI medium integration method offset imaging, and the traditional methods mainly comprise several types of methods: firstly, a ray tracing method; the finite difference method of the engineering function equation; and thirdly, a Fermat principle method. Schneiderel at (1992) and Wang et al (1999) proposed Fermat-based travel-time dynamic programming computation methods in 2D and 3D isotropic Media, respectively, and Liu et al (2014) and Hu et al (2017) developed dynamic programming travel-time computation methods in TTI Media and ORT (orthogonal anisotropic Media) based on Wang et al (1999). The dynamic programming method needs to solve a nonlinear equation system to determine the incident orientation of the ray in a regular grid, a Newton iteration method is usually used, a Jacobian matrix of the Newton method can be analyzed and expressed in isotropy, and a local minimum value cannot occur in the solving process; in an anisotropic medium, the group velocity changes along with the position, the nonlinearity is strong, the group velocity is easy to fall into a local minimum point, the iteration times are more, and the efficiency is lower; the method proposed by Liu et al (2014) is that a jacobian matrix representing a newton method can be approximately analyzed by using an approximate group velocity formula, and the efficiency is lower than that of the newton iterative method by using an iterative method of conjugate gradients in Hu et al (2017). In an isotropic medium, the speed does not change along with the change of the direction, and a Jacobian matrix of the incident direction of the relative ray is easy to represent when traveling; however, in the anisotropic medium, the velocity is changed along with the change of the direction, and the direction of the ray is changed along with the change of the possible incident orientation, so that the velocity itself is also an implicit function of the incident orientation in the nonlinear relation of the traveling relative to the incident orientation of the ray, and thus, 24 group velocity expression formulas under different conditions consisting of 6 surfaces of the velocity profile grid need to be considered, and then the Jacobian matrix of Newton iteration of the incident orientation under different group velocities is determined, the complexity of the expression of the TI medium during traveling is high, and the calculation efficiency is low.
Disclosure of Invention
The invention aims to provide a method and a system for determining travel time in a three-dimensional transverse isotropic medium, which aim to solve the problems of high complexity and low computational efficiency of the prior art in determining TI medium travel time.
In order to achieve the purpose, the invention provides the following scheme:
a method for travel time determination in a three-dimensional transversely isotropic medium, comprising:
acquiring a three-layer radiation relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix;
determining 24 different incidence directions of 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radioactive relation change matrix;
determining a radial coordinate system according to the 24 different incidence orientations;
acquiring coordinates of known grid points under the radiation coordinate system; the known grid point coordinates comprise 4 and the known grid point coordinates at the next moment are obtained when the minimum travel time is updated again;
updating a minimum travel time of the three-dimensional transversely isotropic medium according to the known grid point coordinates;
and determining the geological structure by adopting an offset imaging method according to the minimum travel time.
Optionally, the acquiring a three-layer radiation relation change matrix specifically includes:
according to a matrixAnd a matrixDetermining a first conversion matrix; the first transformation matrix comprises two transformation matrices, namely a matrix CXYZ_ZXYAnd CXYZ_YZX；
According to a matrixDetermining a second transformation matrix; the second transformation matrix comprises a transformation matrix, matrix BXYZ_XY—Z；
According to a matrixMatrix arrayAnddetermining a third transformation matrix; the third transformation matrix comprises three transformation matrices, namely a matrix AXYZ_—XYZMatrix, matrixAnd matrix AXYZ—X—YZ。
Optionally, the determining a radiation coordinate system according to the 24 different incidence orientations specifically includes:
according to the formulaDetermining a radial coordinate system;coordinates in a radial coordinate system;coordinates for any of the 24 orientations; c is a third conversion matrix; b is a second conversion matrix; a is a first transformation matrix.
Optionally, the updating the minimum travel time of the three-dimensional transversely isotropic medium according to the coordinates of the known grid points specifically includes:
acquiring a gradient equation set;
determining the coordinates of the incident square point according to the gradient equation set;
determining z-direction intervals and ray direction vectors in the z-axis direction according to the incident square point coordinates;
acquiring the direction of a symmetry axis of a three-dimensional transverse isotropic medium; the directions of the three-dimensional transverse isotropic medium symmetry axis comprise an inclination angle and an azimuth angle;
determining a direction vector of a symmetry axis of the three-dimensional transverse isotropic medium according to the inclination angle and the azimuth angle;
determining a group velocity angle according to the ray direction vector and the direction vector of the symmetry axis of the three-dimensional transverse isotropic medium;
determining a full slowness according to the group velocity angle;
updating a minimum travel time of a three-dimensional transversely isotropic medium according to the incident azimuth point coordinates, the z-direction spacing, and the full slowness.
A travel-time determination system in a three-dimensional transversely isotropic medium, comprising:
the three-layer radiation relation change matrix acquisition module is used for acquiring a three-layer radiation relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix;
24 different incidence direction determining modules, which are used for determining 24 different incidence directions of 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radioactive relation change matrix;
a radiation coordinate system determining module for determining a radiation coordinate system according to the 24 different incidence orientations;
a known grid point coordinate acquisition module, configured to acquire coordinates of a known grid point in the radial coordinate system; the known grid point coordinates comprise 4 and the known grid point coordinates at the next moment are obtained when the minimum travel time is updated again;
a minimum travel time updating module for updating the minimum travel time of the three-dimensional transversely isotropic medium according to the known grid point coordinates;
and the geological structure determining module is used for determining the geological structure by adopting an offset imaging method according to the minimum travel time.
Optionally, the three-layer radial relationship change matrix obtaining module specifically includes:
a first conversion matrix determination unit for determining a first conversion matrix based on the matrixAnd a matrixDetermining a first conversion matrix; the first transformation matrix comprises two transformation matrices, namely a matrix CXYZ_ZXYAnd CXYZ_YZX；
A second conversion matrix determination unit for determining a conversion matrix based on the matrixDetermining a second transformation matrix; the second transformation matrix comprises a transformation matrix, matrix BXYZ_XY—Z；
A third conversion matrix determination unit for determining a conversion matrix based on the matrixMatrix arrayAnddetermining a third transformation matrix; the third transformation matrix comprises three transformation matrices, namely a matrix AXYZ_—XYZMatrix, matrixAnd matrix AXYZ—X—YZ。
Optionally, the radiation coordinate system determining module specifically includes:
a radiation coordinate system determination unit for determining the radiation coordinate system according to the formulaDetermining a radial coordinate system;coordinates in a radial coordinate system;coordinates for any of the 24 orientations; c is a third conversion matrix; b is a second conversion matrix; a is a first transformation matrix.
Optionally, the minimum travel time updating module specifically includes:
the gradient equation set acquisition unit is used for acquiring a gradient equation set;
the incidence square point coordinate determination unit is used for determining the coordinates of the incidence square point according to the gradient equation set;
a z-direction interval and ray direction vector determining unit, configured to determine a z-direction interval and a ray direction vector in the z-axis direction according to the incident square point coordinate;
the direction acquisition unit of the three-dimensional transverse isotropic medium symmetry axis is used for acquiring the direction of the three-dimensional transverse isotropic medium symmetry axis; the directions of the three-dimensional transverse isotropic medium symmetry axis comprise an inclination angle and an azimuth angle;
the direction vector determining unit of the three-dimensional transverse isotropic medium symmetry axis is used for determining the direction vector of the three-dimensional transverse isotropic medium symmetry axis according to the inclination angle and the azimuth angle;
the group velocity angle determining unit is used for determining a group velocity angle according to the ray direction vector and the direction vector of the symmetry axis of the three-dimensional transverse isotropic medium;
a full slowness determination unit for determining a full slowness according to the group velocity angle;
a minimum travel time determination unit to update a minimum travel time of the three-dimensional transversely isotropic medium according to the cube point coordinates, the z-direction spacing, and the full slowness.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention provides a method and a system for determining travel time in a three-dimensional transverse isotropic medium, which are used for unifying 24 different incident directions of 6 surfaces into a radial coordinate system and updating the minimum travel time of the three-dimensional transverse isotropic medium according to known grid point coordinates. The determining method and the determining system provided by the invention can adapt to the incident condition in any direction by using the direction vector as a variable, do not need to consider the change of the direction in a classified manner, and do not need to consider a group velocity expression formula under 24 different conditions formed by 6 surfaces of the velocity profile grid in a classified manner, thereby reducing the complexity of the expression of the TI medium during traveling, facilitating the parallel design and improving the calculation efficiency.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of travel time calculations in a three-dimensional TI medium provided by the present invention; FIG. 1a is a schematic diagram of a three-dimensional velocity network model provided by the present invention; FIG. 1b is a schematic diagram of the first arrival travel time of all grids in the XY plane where the seismic source is located according to the velocity field and the seismic source position; FIG. 1c is a schematic diagram of the present invention providing a first arrival travel time for calculating all grids above the source plane, starting from the source XY plane, recursively in the Z direction; FIG. 1d is a schematic diagram of the first arrival travel time for calculating all grids recursively along the Z direction from the surface XY plane according to the present invention; FIG. 1e is a schematic diagram of the first arrival travel time for calculating all grids recursively in the Z direction starting from the deepest XY plane according to the present invention.
FIG. 2 is a flow chart of a travel time calculation in a two-dimensional TI medium provided by the present invention; FIG. 2a is a schematic diagram of a two-dimensional velocity mesh model provided by the present invention; FIG. 2b is a schematic diagram of the first arrival travel time of all grids of X-axis direction where the seismic source is located according to the velocity field and the seismic source position; FIG. 2c is a schematic diagram of the first arrival travel time of all grids above the X-axis line calculated by recursion from the X-axis line of the seismic source along the Y-direction 0 direction according to the present invention; fig. 2d is a schematic diagram of calculating the first-arrival travel of all grids by recursion from the X-axis direction line where Y is 0 to the maximum direction; FIG. 2e is a schematic diagram of calculating the first arrival travel of all grids from the X-direction line where the maximum Y value is located and by recursion along the Y-direction 0 value provided by the present invention.
FIG. 3 is a schematic diagram of 8 different directions of incidence during the calculation of two-dimensional grid point (center point position) travel according to the present invention;
FIG. 4 is a schematic diagram of 24 different directions of incident orientations when the three-dimensional grid point (central point position) provided by the present invention is calculated during traveling;
FIG. 5 is a flow chart of a method for determining travel time in a three-dimensional transversely isotropic medium according to the present invention;
FIG. 6 is a schematic diagram of a grid point travel update provided by the present invention;
FIG. 7 is a diagram of the correspondence between incident radiation and the TI medium provided by the present invention;
FIG. 8 is a schematic representation of a travel time slice of the homogeneous three-dimensional bulk Isotropy (ISO), anisotropic VTI and anisotropic TTI provided by the present invention; FIG. 8a is a schematic view of an XZ-plane slice of three media provided by the present invention; FIG. 8b is a schematic YX-plane slice of three media provided by the present invention; FIG. 8c is a schematic YZ-plane slice of three media provided by the present invention;
FIG. 9 is a schematic section of the XZ plane of the three-dimensional TTI salt dome model provided in the present invention; FIG. 9a is a schematic diagram of a velocity model provided by the present invention; FIG. 9b is a schematic diagram of an anisotropy parameter ε model provided in accordance with the present invention; FIG. 9c is a schematic view of an anisotropy parameter model provided in accordance with the present invention;
FIG. 10 is a schematic view of a traveling time slice of a three-dimensional TTI salt dome model-cannon (6900m,5100m, 0m) provided by the present invention; FIG. 10a is a schematic view of an XZ slice provided by the present invention; FIG. 10b is a schematic YX-plane slice provided by the present invention; FIG. 10c is a schematic YZ-plane slice provided by the present invention;
FIG. 11 is a block diagram of a three-dimensional transversely isotropic medium travel time determination system provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for determining travel time in a three-dimensional transverse isotropic medium, which can improve the calculation efficiency.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The travel time dynamic planning method based on the fermat principle calculates a travel time calculation flow in a three-dimensional TI medium, as shown in fig. 1, based on a three-dimensional velocity network model schematic diagram shown in fig. 1 a:
the first step is as follows: as shown in fig. 1b, the first-arrival travel time of all the grids of the XY plane where the source is located is calculated from the velocity field and the source location.
The first step is a travel-time computation process in a two-dimensional TI medium, as shown in FIG. 2, based on the two-dimensional velocity mesh model shown in FIG. 2 a:
1) as shown in fig. 2b, calculating the first arrival travel time of all grids of the X-axis direction line where the seismic source is located according to the velocity field and the seismic source position; 2) as shown in fig. 2c, calculating the first arrival travel time of all grids above the X-axis line in a recursive manner along the Y-direction 0 from the X-axis line where the seismic source is located; 3) as shown in fig. 2d, calculating the first arrival travel time of all the grids by recursion from the X-axis direction line where Y is 0 to the maximum direction along Y; 4) as shown in fig. 2e, the first-arrival travel time of all grids is calculated from the X-direction line where the maximum Y value is located, and recurrently from the Y-direction 0 value.
The second step is that: as shown in FIG. 1c, the first arrival travel times for all the grids above the source plane are calculated recursively in the Z direction starting from the source XY plane.
The third step: as shown in FIG. 1d, the first arrival travel times for all grids are calculated recursively down Z from the surface XY plane.
The fourth step: the first arrival travel times for all grids are calculated recursively in the Z-direction starting from the deepest XY plane, as shown in fig. 1 e.
The key of the dynamic planning method is to dynamically determine the incidence direction in the calculation process, which is an optimization problem when the minimum travel is solved according to the Fermat principle, and the incidence conditions in different directions need to be considered for the calculation points of the regular grid section.
Two-dimensional media problem: as shown in fig. 3, the calculation process for the two-dimensional grid point travel of fig. 2 c-2 d includes the case of ray incidence from 8 different directions.
Three-dimensional media problem: as shown in fig. 4, the calculation process for traveling the three-dimensional grid points of fig. 1c to 1d includes the case of ray incidence from 24 different directions: each face has 4 directions: the light source is characterized in that the light source is incident on four planes of the upper 01, 02, 03 and 04 at a certain position, is incident on four planes of the lower 05, 06, 07 and 08 at a certain position, is incident on four planes of the left 09, 10, 11 and 12 at a certain position, is incident on four planes of the right 13, 14, 15 and 16 at a certain position, is incident on four planes of the front 17, 18, 19 and 20 at a certain position, and is incident on four planes of the rear 21, 22, 23 and 24 at a certain position.
In two-dimensional TI media, the grid point update in fig. 3 replaces the X and Y order in different ways each time, and then considers the scalar angle consistency into two groups:
the incident directions 1, 2, 3 and 4 form a first group, the first group is consistent with a calculation formula of absolute values of included angles in the vertical direction, and the signs of the included angles under different incident conditions are further considered; the incidence directions 5, 6, 7 and 8 form a second group, the second group is consistent with a calculation formula of the included angle in the horizontal direction, and the signs of the included angles under different incidence conditions are further considered.
In the three-dimensional TI medium, the X, Y and Z sequences are replaced in different modes each time when the grid points in the graph 4 are updated, and then the angle consistency is considered to be divided into three groups:
the incident directions 01, 02, 03, 04, 05, 06, 07 and 08 form a first group, the calculation formula of the included angle is consistent with that of the vertical direction, and the signs of the included angles under different incident conditions are further considered; the incidence directions 09, 10, 11, 12, 13, 14, 15 and 16 form a second group, the calculation formula of the included angle is consistent with the calculation formula of the included angle in the X-axis direction, and the signs of the included angles under different incidence conditions are further considered; the incidence directions 17, 18, 19, 20, 21, 22, 23 and 24 form a third group, the third group is consistent with the calculation formula of the included angle in the Y-axis direction, and the signs of the included angles under different incidence conditions are further considered.
Since the speed (or slowness) in the TI medium changes along with the direction (different incident directions at different positions), the first-arrival travel time calculation is related to the speed (or slowness), and the existing calculation method needs to consider all travel time calculation formulas with 24 three-dimensional and 8 two-dimensional incident directions through grouping, mechanical coordinate replacement and consideration of the signs of angle calculation formulas, so that the expression, implementation and industrial application of the algorithm are not facilitated.
Fig. 5 is a flowchart of a method for determining travel time in a three-dimensional transversely isotropic medium according to the present invention, as shown in fig. 5, including:
step 501: acquiring a three-layer radiation relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix.
Step 502: and determining 24 different incidence directions of the 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radioactive relation change matrix.
Step 503: and determining a radial coordinate system according to the 24 different incidence orientations.
There are 24 incident cases in the travel time calculation under the radiation coordinate, and the relationship between them is unified by three layers of radiation relationship change matrixes:
the first step is as follows: four planes at the left 09, 10, 11, 12 and four planes at the right 13, 14, 15, 16, four planes at the front 17, 18, 19, 20 and four planes at the back 21, 22, 23, 24, two groups (left and right and front and back) are transformed into corresponding four planes at the upper 01, 02, 03, 04 and four planes at the lower 05, 06, 07, 08.
The second step is that: 05, 06, 07, 08 into corresponding four planes 01, 02, 03, 04.
The third step: the 02, 03, 04 plane is transformed into the 01 plane.
Thus, the radial coordinate system is expressed as:
where C is the transformation matrix of the first step, B is the transformation matrix of the second step, and A is the transformation matrix of the third step.
The transformation matrix of C includes two cases:and
the transformation matrix of B includes one case:
the transformation matrix of a includes three cases:and and
let T be A.B.C.
Then
Final radial coordinate system:
step 504: acquiring coordinates of known grid points under the radiation coordinate system; the known grid point coordinates include 4 and the known grid point coordinates for the next time instance are acquired while updating the minimum travel time again.
Step 505: updating a minimum travel time of the three-dimensional transversely isotropic medium according to the known grid point coordinates.
Obtaining a gradient equation set:
cube corner point coordinates (x0, y0) are determined from the system of gradient equations.
Fig. 6 is a schematic diagram of grid point travel time update provided by the present invention, as shown in fig. 6, the (x, y) grid travel time is updated from known 4 grid points (x1, y1), (x2, y1), (x1, y2), (x2, y2), dz is a z-direction interval, (x0, y0) is a position point to be obtained, and the optimization problem is that t is minimum when (x, y) travels; the minimum travel time t of (x, y) is updated from the travel times t1, t2, t3, and t4 of the grid points (x1, y1), (x2, y1), (x1, y2), (x2, y 2).
The formula is as follows:
wherein, is the Ray direction (incident direction of Ray), directionWith different incidence orientations (x) in fig. 40，y0) Expressed as different formulas:
as shown in FIG. 7, the included angle φ between the Symmetry Axis (Symmetry Axis of TI) perpendicular to the transverse isotropic surface and the incident Ray (Ray) is the group velocity angle, and the directionAnd the direction of the symmetry axis of the TI mediumThe included angle is phi; according to the formula s2(φ)＝a1+a2cos2φ-a3cos4φ determines the relationship of group slowness (inverse of group velocity) to group angle φ;
where φ is the group velocity angle (see FIG. 7), s is the full slowness, a1，a2And a3Is related to 45-degree group velocity, phase velocity of vertical symmetry axis incidence and anisotropy parameter epsilon, and is approximately constant when the grid is calculated during traveling at a certain point, so that a in the invention1，a2And a3When solving the travel of the anisotropic medium, the parameters (known) required to be input comprise the velocity Vp0 vertical to the isotropic surface, the anisotropic parameters epsilon and delta, and the directions of the symmetry axis of the TI medium, namely the inclination angle α and the azimuth angle β, the direction of the symmetry axis of the TI medium can be expressed by a vector as follows:
further extracting the parameters a needed for obtaining the following calculation1，a2And a3Andaccording toAnddetermining
Therefore, the temperature of the molten metal is controlled,
in summary, the minimum travel time of the three-dimensional transversely isotropic medium is updated based on the cube-corner point coordinates, the z-direction spacing, and the full slowness.
Slowness s (phi) and coordinate point location (x)0，y0) The implicit functional relationship of the variables is determined by the intermediate variables of phi, whose signs are determined in the prior art disclosure by the incident direction of the ray, so solving the above-mentioned system of gradient nonlinear equations involves the slowness s (phi) versus (x)0，y0) And when the derivative is in a high order, positive and negative problems of phi need to be considered, so that the method is very complicated. By passingSubstitute cos phi in s (phi) to obtain s (x)0，y0) The slowness and coordinate point position (x)0，y0) Implicit functional relationship of variables throughThe intermediate variable is determined, the vectorization conversion does not need to consider the sign problem of the intermediate variable, and derivation and implementation become direct and simple.
Step 506: and determining the geological structure by adopting an offset imaging method according to the minimum travel time.
The invention uses the expression s The direction vector is used as a variable, the incident condition in any direction is adapted, the change of the direction is not required to be considered in a classification mode, the direction vector and a related derivative value are only required to be input when a program is written, and only one expression is required for a Jacobian matrix of a nonlinear equation set.
Meanwhile, the parallel computation provided by the invention is the process plus thread level parallel; the travel time required by the offset imaging module comprises a plurality of cannon numbers which are independent from each other and can be designed to be parallel in a process level; and the calculation of each cannon during travel is recurrently dependent, namely the solution of the next layer of travel depends on the value of the previous layer, and all travel values are updated in a recurrently way layer by layer, so that the parallel of the calculation of one cannon during travel can only be performed in a thread level parallel way between one layer. The radiation coordinate system unifies all 24 incident ray directions, so that a thread pool can be uniformly arranged on the outer layer, the thread pool does not need to be destroyed and reestablished among different conditions, and the parallel implementation of thread levels can be facilitated.
Based on the travel time determination method and system in the three-dimensional transverse isotropic medium provided by the invention, a uniform three-dimensional medium test and a non-uniform TTI medium test are taken as examples.
The uniform medium speed is 3000m/s, the anisotropy parameters of the VTI medium are epsilon-0.195 and delta-0.22, and the anisotropy parameters of the TTI medium are that the inclination angle alpha is 45 degrees and the azimuth angle beta is 0 degrees. The sampling interval in the X-axis direction is 40m, and a total of 101 sampling points, the sampling interval in the Y-axis direction is 40m, and a total of 61 sampling points, and the sampling interval in the Z-axis direction is 40m, and a total of 100 sampling points. The travel time result obtained by the calculation method is shown in fig. 8, the anisotropic TTI medium and the VTI medium belong to TI medium types, and slices in different directions in the graph show expected characteristics compared with isotropy.
The heterogeneous TTI medium test is shown in FIG. 9, a standard three-dimensional TTI salt dome model, a velocity model (FIG. 9a), an anisotropy parameter epsilon model (FIG. 9b) and an anisotropy parameter delta model (FIG. 9c), and an inclination angle, azimuth and interface reference standard model, which are mainly used as the reference of travel time pictures. The shot position is set, X is 6900m, Y is 5100m, Z is 0m, the calculated travel time result of the invention is shown in fig. 10, and the XZ plane slice (fig. 10a), the YX plane slice (fig. 10b) and the YZ plane slice (fig. 10c) are compared with the model, so that the result is reasonable, the invention does not cause any error, and the invention is more convenient and effective in program implementation.
Fig. 11 is a structural diagram of a travel time determination system in a three-dimensional transversely isotropic medium provided by the present invention, and as shown in fig. 11, the travel time determination system in a three-dimensional transversely isotropic medium includes:
a three-layer radial relation change matrix obtaining module 1101, configured to obtain a three-layer radial relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix.
The three-layer radial relationship change matrix obtaining module 1101 specifically includes:
a first conversion matrix determination unit for determining a first conversion matrix based on the matrixAnd a matrixDetermining a first conversion matrix; the first transformation matrix comprises two transformation matrices,i.e. matrix CXYZ_ZXYAnd CXYZ_YZX；
A second conversion matrix determination unit for determining a conversion matrix based on the matrixDetermining a second transformation matrix; the second transformation matrix comprises a transformation matrix, matrix BXYZ_XY-Z；
A third conversion matrix determination unit for determining a conversion matrix based on the matrixMatrix arrayAnddetermining a third transformation matrix; the third transformation matrix comprises three transformation matrices, namely a matrix AXYZ_-XYZMatrix, matrixAnd matrix AXYZ-X-YZ。
And the 24 different incidence orientation determining modules 1102 are used for determining 24 different incidence orientations of the 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radial relation change matrix.
A radial coordinate system determining module 1103, configured to determine a radial coordinate system according to the 24 different incident orientations.
The radiation coordinate system determining module 1103 specifically includes: a radiation coordinate system determination unit for determining the radiation coordinate system according to the formulaDetermining a radial coordinate system;is a radiationCoordinates within a coordinate system;coordinates for any of the 24 orientations; c is a third conversion matrix; b is a second conversion matrix; a is a first transformation matrix.
A known grid point coordinate acquiring module 1104, configured to acquire coordinates of a known grid point in the radial coordinate system; the known grid point coordinates include 4 and the known grid point coordinates for the next time instance are acquired while updating the minimum travel time again.
A minimum travel time update module 1105 for updating the minimum travel time of the three dimensional transversely isotropic media according to the known grid point coordinates.
The minimum travel time update module 1105 specifically includes:
the gradient equation set acquisition unit is used for acquiring a gradient equation set;
the incidence square point coordinate determination unit is used for determining the coordinates of the incidence square point according to the gradient equation set;
a z-direction interval and ray direction vector determining unit, configured to determine a z-direction interval and a ray direction vector in the z-axis direction according to the incident square point coordinate;
the direction acquisition unit of the three-dimensional transverse isotropic medium symmetry axis is used for acquiring the direction of the three-dimensional transverse isotropic medium symmetry axis; the directions of the three-dimensional transverse isotropic medium symmetry axis comprise an inclination angle and an azimuth angle;
the direction vector determining unit of the three-dimensional transverse isotropic medium symmetry axis is used for determining the direction vector of the three-dimensional transverse isotropic medium symmetry axis according to the inclination angle and the azimuth angle;
the group velocity angle determining unit is used for determining a group velocity angle according to the ray direction vector and the direction vector of the symmetry axis of the three-dimensional transverse isotropic medium;
a full slowness determination unit for determining a full slowness according to the group velocity angle;
a minimum travel time determination unit to update a minimum travel time of the three-dimensional transversely isotropic medium according to the cube point coordinates, the z-direction spacing, and the full slowness.
A geological structure determination module 1106 configured to determine a geological structure using an offset imaging method according to the minimum travel time.
The invention provides a method and a system for determining travel time in a three-dimensional transverse isotropic medium, wherein the determination method is a method for rapidly obtaining travel time in a three-dimensional TI medium based on a radioactive coordinate system. The nonlinear solving Newton iteration method of the dynamic planning travel time solving method in the three-dimensional TI medium in the industry at present is mainly used for improving the processing capacity of the group velocity changing along with the direction (actually along with the target parameter, namely the incident direction), the nonlinear relation between the travel time and the incident direction is uniformly expressed by using vectorization parameters under a radiation coordinate system, and 24 different conditions of 6 surfaces of a grid do not need to be considered respectively, so that the purpose of quickly implementing an algorithm is achieved.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A method for determining travel time in a three-dimensional transversely isotropic medium, comprising:
acquiring a three-layer radiation relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix;
determining 24 different incidence directions of 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radioactive relation change matrix;
determining a radial coordinate system according to the 24 different incidence orientations;
acquiring coordinates of known grid points under the radiation coordinate system; the known grid point coordinates comprise 4 known grid point coordinates which can be updated again at the next moment when the minimum travel time is obtained;
updating a minimum travel time of the three-dimensional transversely isotropic medium according to the known grid point coordinates;
and determining the geological structure by adopting an offset imaging method according to the minimum travel time.
2. The determination method according to claim 1, wherein the acquiring the three-layer radial relationship change matrix specifically includes:
according to a matrixAnd a matrixDetermining a first conversion matrix; the first transformation matrix comprises two transformation matrices, namely a matrix CXYZ_ZXYAnd CXYZ_YZX；
According to a matrixDetermining a second transformation matrix; the second transformation matrix comprises a transformation matrix, matrix BXYZ_XY—Z；
According to a matrixMatrix arrayAnddetermining a third transformation matrix; the third transformation matrix comprises three transformation matrices, namely a matrix AXYZ_—XYZMatrix AXYZ_X—YZAnd matrix AXYZ_—X—YZ。
3. The method according to claim 1, wherein the determining a radial coordinate system from the 24 different incident orientations includes:
according to the formulaDetermining a radial coordinate system;coordinates in a radial coordinate system;coordinates for any of the 24 orientations; c is a third conversion matrix; b is a second conversion matrix; a is a first transformation matrix.
4. The method according to claim 1, wherein the updating of the minimum travel time of the three-dimensional transversely isotropic medium according to the coordinates of the known grid points specifically comprises:
acquiring a gradient equation set;
determining the coordinates of the incident square point according to the gradient equation set;
determining z-direction intervals and ray direction vectors in the z-axis direction according to the incident square point coordinates;
acquiring the direction of a symmetry axis of a three-dimensional transverse isotropic medium; the directions of the three-dimensional transverse isotropic medium symmetry axis comprise an inclination angle and an azimuth angle;
determining a direction vector of a symmetry axis of the three-dimensional transverse isotropic medium according to the inclination angle and the azimuth angle;
determining a group velocity angle according to the ray direction vector and the direction vector of the symmetry axis of the three-dimensional transverse isotropic medium;
determining a full slowness according to the group velocity angle;
updating a minimum travel time of a three-dimensional transversely isotropic medium according to the incident azimuth point coordinates, the z-direction spacing, and the full slowness.
5. A travel time determination system in a three-dimensional transversely isotropic medium, comprising:
the three-layer radiation relation change matrix acquisition module is used for acquiring a three-layer radiation relation change matrix; the three layers of radiation relation change matrixes comprise a first conversion matrix, a second conversion matrix and a third conversion matrix;
24 different incidence direction determining modules, which are used for determining 24 different incidence directions of 6 surfaces when the three-dimensional transverse isotropic medium travels according to the three-layer radioactive relation change matrix;
a radiation coordinate system determining module for determining a radiation coordinate system according to the 24 different incidence orientations;
a known grid point coordinate acquisition module, configured to acquire coordinates of a known grid point in the radial coordinate system; the known grid point coordinates comprise 4 known grid point coordinates which can be updated again at the next moment when the minimum travel time is obtained;
a minimum travel time updating module for updating the minimum travel time of the three-dimensional transversely isotropic medium according to the known grid point coordinates;
and the geological structure determining module is used for determining the geological structure by adopting an offset imaging method according to the minimum travel time.
6. The system according to claim 5, wherein the three-tier radial relationship change matrix acquisition module specifically includes:
a first conversion matrix determination unit for determining a first conversion matrix based on the matrixAnd a matrixDetermining a first conversion matrix; the first transformation matrix comprises two transformation matrices, namely a matrix CXYZ_ZXYAnd CXYZ_YZX；
A second conversion matrix determination unit for determining a conversion matrix based on the matrixDetermining a second transformation matrix; the second transformation matrix comprises a transformation matrix, matrix BXYZ_XY_Z；
A third conversion matrix determination unit for determining a conversion matrix based on the matrixMatrix arrayAnddetermining a third transformation matrix; the third transformation matrix comprises three transformation matrices, namely a matrix AXYZ_—XYZMatrix AXYZ_X—YZAnd matrix AXYZ_—X—YZ。
7. The determination system according to claim 5, wherein the radial coordinate system determination module comprises:
a radiation coordinate system determination unit for determining the radiation coordinate system according to the formulaDetermining a radial coordinate system;coordinates in a radial coordinate system;is any one of the 24 incidence orientationsThe coordinates of (a); c is a third conversion matrix; b is a second conversion matrix; a is a first transformation matrix.
8. The determination system according to claim 5, wherein the minimum travel time update module specifically comprises:
the gradient equation set acquisition unit is used for acquiring a gradient equation set;
the incidence square point coordinate determination unit is used for determining the coordinates of the incidence square point according to the gradient equation set;
a z-direction interval and ray direction vector determining unit, configured to determine a z-direction interval and a ray direction vector in the z-axis direction according to the incident square point coordinate;
the direction acquisition unit of the three-dimensional transverse isotropic medium symmetry axis is used for acquiring the direction of the three-dimensional transverse isotropic medium symmetry axis; the directions of the three-dimensional transverse isotropic medium symmetry axis comprise an inclination angle and an azimuth angle;
the direction vector determining unit of the three-dimensional transverse isotropic medium symmetry axis is used for determining the direction vector of the three-dimensional transverse isotropic medium symmetry axis according to the inclination angle and the azimuth angle;
the group velocity angle determining unit is used for determining a group velocity angle according to the ray direction vector and the direction vector of the symmetry axis of the three-dimensional transverse isotropic medium;
a full slowness determination unit for determining a full slowness according to the group velocity angle;
a minimum travel time determination unit to update a minimum travel time of the three-dimensional transversely isotropic medium according to the cube point coordinates, the z-direction spacing, and the full slowness.
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