CN115201899A - High-precision mixed speed modeling method - Google Patents
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Abstract
The application provides a high-precision mixed speed modeling method, which comprises the following steps: s1: acquiring basic data of a geological region to be modeled; s2: establishing a geological frame model for each fault and each horizon according to the fault data and the horizon data; defining an intersection relation among all faults and a contact relation among all horizons, and associating all geological framework models through the intersection relation and the contact relation to obtain a three-dimensional closed structure grid model; s3: combining a plurality of speed sources obtained according to basic data with a three-dimensional closed structure lattice model to construct a three-dimensional fine mixing speed model; s4: explaining the time-depth conversion of each horizon in the three-dimensional fine hybrid velocity model; s5: calculating the depth error of the target horizon; s6: judging whether the calculated depth error is within a threshold range, if not, repeating the steps S2-S5; and if so, outputting the three-dimensional fine mixing speed model as a final speed model.
Description
Technical Field
The invention belongs to the technical field of high-precision speed modeling for time-depth conversion in petroleum exploration and development, and particularly relates to a high-precision mixed speed modeling technology utilizing a geological frame model and fault constraint.
Background
In order to realize the exploration and development process with uniform time and depth, the spatial domain conversion is required to be carried out through a speed model. Accurate velocity models are of vital importance in oil and gas exploration and development. With the continuous deepening of exploration degree, geological targets faced by oil and gas exploration are more and more complex, the exploration with structures is the main in the early exploration, but the structure trapping is increasingly deficient nowadays, the purpose of finding hidden oil and gas is more and more urgent, and the targets of oil and gas exploration and development are not oil and gas reservoirs with structures as the main, but rather types of oil and gas reservoirs with more hidden lithologic trapping and the like.
In the face of exploration target conversion, the traditional method is no longer applicable only by depending on seismic processing speed or single well drilling data, and as is well known, the seismic can provide good transverse resolution, the well drilling can provide high vertical resolution in a depth domain, and the target can be accurately predicted only by combining well seismic. The key of well-to-seismic integration is to build an accurate velocity model. Small differences in the velocity model may cause the trap area, the reservoir thickness, and the oil-gas-water interface to fluctuate, which may lead to uncertainty in the reserve evaluation. Therefore, establishing an accurate velocity model is very important for oil and gas exploration and development.
The existing industrialized software speed modeling still faces many challenges, for example, a model used in a modeling scheme is too simple and has insufficient precision, especially for a complex fault-tolerant basin, the speed transverse change is large under the influence of a complex fracture system, the conventional single-well deep fitting deepening method is difficult to meet and adapt to an area with large stratum occurrence fluctuation change or fault development, and the model scheme is not unique. Meanwhile, in a wider risk exploration area, under the condition of data shortage, a larger and more accurate speed model is required more and more to meet the actual exploration requirement.
Disclosure of Invention
The embodiment of the application aims to provide a high-precision mixed-velocity modeling method which can fuse a special geologic body fracture-containing system to realize high-precision velocity modeling so as to better meet production requirements.
According to an embodiment of the present application, there is provided a high-precision hybrid velocity modeling method including:
s1: acquiring basic data of a geological region to be modeled; the basic data at least comprises fault data, horizon data, well data and seismic data;
s2: establishing a geological frame model for each fault and each horizon according to the fault data and the horizon data; defining an intersection relation among all faults and a contact relation among all horizons, and associating all geological framework models through the intersection relation and the contact relation to obtain a three-dimensional closed structure lattice model capable of reflecting the fluctuation change of the underground strata and the spatial structure;
s3: obtaining velocity sources such as an aboveground time-depth relation, a construction interpretation result, a seismic processing speed, a geological stratification, a velocity analytic function, an interpolation mode and the like according to the basic data, and combining the obtained multiple velocity sources with the three-dimensional closed structure framework model to construct a three-dimensional fine mixing velocity model;
s4: interpreting a time-depth transition of each horizon in the three-dimensional fine hybrid velocity model;
s5: calculating the depth error of the target horizon;
s6: judging whether the calculated depth error is within a threshold range, if not, repeating the steps S2-S5; and if so, outputting the three-dimensional fine mixing speed model as a final speed model.
In one embodiment, the defining an intersection relationship or a contact relationship between the faults and the associating the geologic framework model corresponding to each fault by the intersection relationship or the contact relationship comprises:
carrying out combined interpretation on the longitudinal and transverse sections of the fault and the horizon on the seismic section to obtain the horizon and fault data with preset grid density and intervals;
and carrying out three-dimensional space grid interpolation on the picked horizon and fault data.
In one embodiment, after defining the intersection relationship type among the faults and before associating the geological framework model, defining the level structure of the faults; and establishing a fracture system according to the level structure of the fault and the intersection relation of the fault.
In one embodiment, the defining the intersection relationship between the faults comprises:
establishing a primary and secondary relation of faults according to the scale of each fault, wherein the fault with a larger scale is a primary fault and the fault with a smaller scale is a secondary fault;
if the secondary fault is too far away from the main fault, the secondary fault and the main fault are not connected with each other;
if the fault end points are close to the main fault and the distance between the fault end points is less than 5% of the total length, connecting the fault end points;
if a fault is automatically truncated to a cross-sectional area of more than 25%, the fault will be retained and may cross the main fault.
In one embodiment, the defining the contact relationship between the respective horizons comprises:
establishing a stratigraphic comparison grid, wherein the comparison is carried out on a geologic time synchronous interface which is parallel to or integrated with a seismic reflection interface;
and defaulting the sequence of the horizons from the shallow layer to the deep layer, wherein the shallow layer is defaulted to cut the deep layer.
In one embodiment, after obtaining the basic data of the region to be modeled, before establishing the geologic framework model for each fault, the method further comprises: interpreting the base data;
interpreting the data includes: adopting a method of firstly explaining the fault and then explaining the horizon; tracking the trend of the fault by explaining the fault of the main section of the region to be modeled and combining the time slices of the seismic data volume and the coherence analysis data volume, and analyzing the intersection relation of the fault; the horizons within each patch are then tracked from the well.
In one embodiment, the associating the respective geologic framework models by an intersection relationship and a contact relationship, resulting in the three-dimensional closed architecture lattice model comprises:
interpolating the interpreted horizon and fault, carrying out fault-free constrained meshing on the horizon, adding a fault plane, and cutting the horizon in a fault plane region;
independently gridding the horizon in each fault block area;
combining each interface with each fault by adopting a topological bottom algorithm, cutting horizon data by using fault planes, gridding the data among fault blocks, and independently modeling each fault block;
and splicing all the broken blocks to form the three-dimensional closed structure grid model.
In one embodiment, in the S3, the constructing the three-dimensional fine mixing velocity model includes:
analyzing the earthquake processing speed, eliminating unreasonable outliers and improving the speed reliability;
converting the average velocity, the stacking velocity or the root mean square velocity of seismic processing into layer velocity by using a Dix formula, and further gridding the layer velocity to be used as a background velocity field of the three-dimensional closed structure lattice model;
each horizon in the three-dimensional closed-structure grid model is given an initial seismic velocity after corresponding stratigraphic gridding to form the three-dimensional fine mixed velocity model.
In one embodiment, in the S4, interpreting a time-depth transform of each horizon in the three-dimensional fine hybrid velocity model comprises:
dispersing a plurality of well points at each layer by using data such as VSP (vertical seismic profiling), acoustic logging, well drilling layering and the like in the basic data;
calculating the initial velocity of the well point according to the initial seismic processing velocity of each horizon in the three-dimensional fine mixed velocity model and the well position;
and calculating the current velocity at the well point according to the depth of each horizon in the basic data, the seismic processing velocity and the well position.
In one embodiment, in S5, the calculating the depth error of the target horizon includes:
extracting the current speed at the well point from the target horizon in the three-dimensional fine mixed speed model, and comparing the current speed with the initial speed of the well point; meanwhile, the error value at the well point is used as a constraint condition of the three-dimensional fine mixed velocity model to solve the distribution condition of the velocity error in the whole model, the error distribution is analyzed to find out the error distribution rule, and the optimal mathematical expectation method is utilized to enable the error distribution to be closer to the reality.
The high-precision mixing speed modeling method has the beneficial effects that:
the high-precision mixed speed modeling method supports multi-condition constraint and multi-speed-source mixed refined speed modeling, not only considers the influence of geological result factors such as drilling curve data, seismic processing speed, horizon and drilling geological stratification on a speed model, but also fully considers complex conditions such as faults and rock masses. Actual work area data tests show that the speed modeling level and the section effect of the high-precision mixed speed modeling method are faithful to the real speed characteristics and the change rule of the underground stratum structure, the deep conversion effect and the error precision are superior to those of the conventional speed modeling method when a micro-scale structural plane is compared, and more accurate depth prediction can be provided for a target to be drilled.
Drawings
To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
FIG. 1 is a flow chart illustrating a high accuracy hybrid velocity modeling method according to an embodiment of the present application;
FIG. 2 is a schematic diagram illustrating a three-dimensional geological framework grid model built using horizon and fault interpretation data according to an embodiment of the present application;
FIG. 3 is a cross-sectional view of a geological structure of a field sinking certain oil from West lake of the east China sea according to an embodiment of the present application;
FIG. 4 is a development fault evolution law diagram of a sunken certain oil field in West lake of the east China sea according to the embodiment of the application;
FIG. 5 is an illustration of an original seismic profile of a local block section of a study area according to an embodiment of the present application;
FIG. 6 is a diagram illustrating a framework model and seismic processing velocity constraint building velocity model according to an embodiment of the present application;
FIG. 7 is a diagram illustrating a framework model and an uphole velocity constraint building velocity model according to an embodiment of the present application;
FIG. 8 is a velocity model graph generated by the high-precision hybrid fine velocity modeling method according to an embodiment of the present application;
FIG. 9 is a comparison graph of the structural features of a constant velocity map and the structural features of a velocity model map obtained by the modeling method of the present application, according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. 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 application.
The currently common methods for establishing the velocity field are roughly as follows:
(1) DIX method of formulation
The theoretical basis of the method is a DIX formula, the root mean square velocity is obtained through the stacking velocity, and then the layer velocity of each layer is calculated. Its advantages are simple operation, short time and convenient research. However, the method assumes that the stratum is level and even, and the underground structure is simpler.
(2) Horizon control method
The horizon control method is used under the conditions that the overall speed and structural performance are uniform, the dip angle of the stratum is relatively small, and some speed abnormality occurs in local areas. However, the accuracy of the velocity field obtained by the method is relatively low, and the method is generally carried out when the collected velocity spectrum data is poor and cannot be applied to field building work.
(3) Model chromatography
The model chromatography method solves the defect that the DIX formula has strict requirements on underground conditions, and can well solve the problems of speed reversal and the like in areas with complex and broken underground structures and fault development.
There are common problems in using the commonly used velocity modeling methods: (1) A velocity model is established mainly by using well velocity and seismic velocity through horizon constraint, the butt joint relation of faults, stratums and the faults is not considered, and finer constraint is not performed on the integral surface. (2) Only by the seismic processing speed, the picking speed spectrum grid is large, the multiple wave analysis in the processing process is not fine enough, the seismic processing speed is low in precision, and the error after the depth turning is large. (3) The requirements of speed modeling in areas with large transverse change of speed and fault development cannot be met by utilizing simple single-well speed and interval speed models. In the exploration, development and evaluation period, the traditional method has certain limitations.
Based on the method, the invention provides a high-precision velocity model building method, which is used for building a high-precision velocity model suitable for a complex structure by utilizing a geological frame model and adding a complex structure framework and fault constraint, is used for time-depth conversion and the like, and is suitable for an exploration area with less data and a wide area.
Fig. 1 is a flowchart illustrating a high-precision hybrid velocity modeling method according to an embodiment of the present application. Referring to fig. 1, the following process is included:
s1: acquiring basic data of a geological region to be modeled; the base data includes at least fault data, horizon data, well data, and seismic data.
The modeling of the geological region to be modeled needs to firstly collect information such as seismic data, well drilling data, whether faults exist, fault types, stratum positions and the like of the geological region to be modeled.
S2: establishing a geological frame model for each fault and each horizon according to the fault data and the horizon data; and defining an intersection relation among all faults and a contact relation among all horizons, and associating all geological framework models through the intersection relation and the contact relation to obtain the three-dimensional closed structure grid model. The three-dimensional closed-structure grid model is used for reflecting the fluctuation and the spatial structure of the underground stratum, and is shown in figure 2.
After various data of the geological area to be modeled are collected, the basic data are explained. A method of explaining fault firstly and then explaining horizon is adopted. The fault explanation adopts the idea of determining the trend of a section, determining the walking of a slice and determining the depth of a real drilling result. The horizons within each block are then automatically tracked from the well. By means of fault interpretation of a main section of a region to be modeled and time slicing of a seismic data body and a coherence analysis data body, the trend of a fault is tracked, and the cross-cutting relation of the fault is analyzed.
And after the fault and horizon interpretation is finished, establishing a geological frame model for each fault and each horizon according to fault data and horizon data.
Wherein, defining the intersection relation among all faults comprises:
and establishing a primary and secondary relation of faults according to the scale of each fault, wherein a primary fault with a larger scale and a secondary fault with a smaller scale are established. If the secondary fault is too far away from the main fault, the secondary faults are not connected with each other. Connecting fault end points which are closer to the main fault and are not more than 5% of the total length; if a fault is automatically truncated to a cross-sectional area of more than 25%, the fault will be retained and may cross the main fault. In addition to checking the relationship between faults, it is also necessary to check the displacement of individual faults to ensure that they are consistent with the true geological structure of the subsurface and do not move about during the modeling process.
It should be noted that, due to the complex underground stratum structure, the development of fracture systems and faults, before the closed three-dimensional closed structure grid model is established, the level structure of the fault needs to be defined, and the fracture system needs to be established according to the intersection relationship between the level structure of the fault and the fault. And (3) checking or editing the intersection relation by adjusting the parameter extension fault plane so as to match the intersection relation with a reasonable geological model.
Defining contact relationships between the respective horizons includes:
and establishing a stratum contrast framework, wherein the contrast is carried out on a geologic time synchronous interface which is parallel to or integrated with the seismic reflection interface.
And defaulting the sequence of the horizons from the shallow layer to the deep layer, wherein the shallow layer is defaulted to cut the deep layer. When the stratum is overthrown or degraded, the proper contact relation can be adjusted and selected according to the actual contact relation of the underground stratum reflected by the seismic section.
Associating each geological framework model through the acquired intersection relation and contact relation to obtain a three-dimensional closed structure grid model, wherein the three-dimensional closed structure grid model comprises the following steps:
and performing longitudinal and transverse section joint interpretation on the fault and the horizon on the seismic section to obtain the horizon and fault data with preset grid density and interval. And performing three-dimensional spatial grid interpolation on the picked layer position and fault data, performing non-fault constraint gridding on the layer position, adding a fault surface, and cutting the layer position in a fault surface region. And independently gridding the horizon in each fault block area. And combining each interface with each fault by adopting a topological bottom algorithm, cutting horizon data by using the fault plane, gridding the data among all fault blocks, and independently modeling each fault block. And splicing all the broken blocks to form a three-dimensional closed structure grid model.
When three-dimensional space grid interpolation is carried out on the layer position and fault data, the adopted difference method is a least square interpolation or a Krigin interpolation algorithm.
In the method, accurate well-seismic calibration and horizon and fault picking are crucial to correct geological frame model building, and the precision of high-precision speed model building is influenced finally.
S3: and obtaining velocity sources such as an aboveground time-depth relation, a construction interpretation result, a seismic processing speed, a geological stratification, a velocity analytic function, an interpolation mode and the like according to the basic data, and combining the obtained multiple velocity sources with a three-dimensional closed structure framework model to construct a three-dimensional fine mixed velocity model.
In the step, for each horizon in the three-dimensional closed structure grid model, under the condition of comprehensively considering at least one of factors such as an uphole time-depth relation, a structure interpretation result, a seismic processing speed, geological stratification, a speed analytic function, an interpolation mode and the like, calculating a corresponding initial speed for each horizon or fault block to form a background velocity field of each horizon or fault block.
And endowing each horizon in the three-dimensional closed structure grid model with the initial speed after corresponding stratum gridding so as to form a three-dimensional fine mixed speed model.
S4: the time-depth transition of each horizon in the three-dimensional fine hybrid velocity model is explained.
And dispersing a plurality of well points at each layer by using VSP (Vertical Seismic Profiling) well logging, acoustic logging, well drilling layering and other data in the basic data.
And calculating the initial velocity at the well point according to the initial seismic processing velocity of each horizon in the three-dimensional fine mixed velocity model and the position of the well.
And calculating the current velocity at the well point according to the depth of each horizon, the seismic processing velocity and the well position in the basic data.
S5: the depth error of the destination horizon is calculated.
Extracting the current speed at the well point from the target horizon in the three-dimensional fine mixed speed model, and comparing the current speed with the initial speed of the well point; meanwhile, the error value at the well point is used as a constraint condition of the three-dimensional fine mixed velocity model to solve the distribution condition of the velocity error in the whole model, the error distribution is analyzed to find out the error distribution rule, and the optimal mathematical expectation method is utilized to enable the error distribution to be closer to the reality.
S6: judging whether the calculated depth error is within a threshold range, if not, repeating the steps S2-S5; and if so, outputting the three-dimensional fine mixing speed model as a final speed model.
In order to further verify the feasibility and applicability of the modeling method disclosed by the application. The modeling method is used for carrying out comprehensive speed modeling on the actual test block of a certain oil field sunk in West lake of the east China sea, realizes high-precision time-depth conversion and variable-speed imaging, and provides effective support for subsequent well position target deployment and accurate drilling of the oil field.
Example (b):
and selecting a certain oil field sunk in the West lake of the east China sea as an example, and carrying out high-precision speed modeling data test on the actual complex geological structure of the certain oil field sunk in the West lake of the east China sea. The research area region structure mainly takes an extension structure pattern and a torsion structure pattern, and is represented by a tilting block and a multi-level y-shaped combination. The NE trend and SE inclination of the fault in the area on the plane are mainly the main faults and the development arc faults; the plane is mainly parallel and oblique; the section of the block is a forward tilting block, a multi-stage y-shaped block and a reverse tilting block (see figure 3). Research area fracture evolution law: the first new generation is characterized by the development of a forward fault, which is associated with a series of small reverse faults. The fault plays a certain control role in the thickness of the stratum, and the stratum falls downwards gradually to the east to form a slope structure. The inherited activity of the forward fault with larger scale of the gradual generation is always moved to the stratum deposition period at the upper part of the hong Kong group, but the activity is obviously weakened; the accompanying minor faults mostly cease to be active during the period of stratum deposition at the bottom of the flower harbor group (see fig. 4).
The research stratum lithology is mainly clastic rock and contains thin coal seams (sandstone and mudstone, and the velocity zone is 1500-5000m \). At present, there are many drilled wells, the data quality of logging curve is reliable, and the data of past earthquake collecting and processing result, speed, etc. are available. Due to the fact that the fault development of a research area is large in transverse and longitudinal changes of speed, the staggered distance between fault blocks is large, and a conventional speed modeling method is difficult, the trap area, the reservoir thickness and the reserve volume of the area are not estimated correctly. Therefore, how to build a high-precision velocity model for the complex fault block (in-phase fault order) geological structure of the research area is the key of research.
Aiming at the characteristics of a research area, the specific speed modeling realization process is as follows:
(1) And preparing basic data, including fault, horizon data, well logging curves, time-depth relation on the well, well layering, seismic processing speed and other data.
(2) And establishing a geological framework model by utilizing fault and horizon data, defining the grid size of a grid speed model, and defining the intersection relation and the contact relation of horizons of all faults so as to obtain a three-dimensional closed structure grid model.
(3) And analyzing the seismic processing speed, eliminating unreasonable outliers and improving the speed reliability. The average velocity, stacking velocity or root mean square velocity of seismic processing is converted into interval velocity by utilizing a Dix formula, and further gridding is carried out to construct a three-dimensional fine mixed velocity model, and each interval in the model is initially endowed with the seismic velocity after corresponding stratum gridding.
(4) And discretizing well points in each layer by using data such as VSP (vertical seismic profiling), acoustic logging, well drilling layering and the like. And for each extracted well point, acquiring an initial speed at the well point, and calculating the current speed at the well point. Comparing the current speed of the well point with the initial speed of the well point, solving the distribution condition of the speed error in the whole model by taking the error value at the well point as the constraint condition of the three-dimensional fine mixed speed model, analyzing the error distribution, finding out the error distribution rule, and making the error distribution closer to the reality by using an optimal mathematical expectation method.
(5) The velocity grid update iteration is performed from shallow to deep. And combining the error distribution into the three-dimensional fine mixed speed model, correcting the speed field, and circulating the steps until the error at the well point is minimum and the distribution rule of the three-dimensional fine mixed speed model is maximally consistent with the actual geological condition. Three-dimensional fine mixing speed model meeting error requirements as final speed model
In the embodiment, according to the geological conditions and the data conditions of the research area, a certain speed source can be independently utilized to establish a model, and the quality of modeling basic data is tested to determine whether the modeling basic data accords with the underground real speed trend characteristics; deterministic speed models can also be built in combination. For the horizontal interpolation during the combination, the data application has a certain priority, and the upward priority is higher, which is specifically shown in the following table:
TABLE 1 data application priority
Focusing on local fault blocks and wells aiming at researching structural characteristic features and basic data conditions. Referring to fig. 5, specifically: three faults (one left incline and two right inclines) are developed, the terrain is west high and east low, the whole fault block slope stratum structure is presented, a drilled well is respectively arranged in the east and west regions, and a prediction well (to be drilled) is arranged in the middle. Fig. 6 shows the effect of the velocity model established by using the frame model and the seismic processing velocity constraint, and it can be seen from the figure that the velocity established by using the seismic processing velocity has a correct trend (influenced by formation compaction) of gradually increasing the velocity from shallow to deep as a whole, the local formation and the basement exhibit high-velocity characteristics (the lower left part in the figure), but the characteristics of the velocity changing along with the fault and the formation fluctuation (the velocity of the same set of formation should be kept consistent regardless of the local compaction difference) are not obvious, the velocity accuracy is poor, and the whole reflects only the large velocity trend. FIG. 7 is a velocity model effect established by using a frame model and an uphole velocity constraint, and it can be seen from the figure that the velocity effect established by using the depth during logging completely depends on the well, and the velocity is relatively accurate and has high velocity precision in the interval controlled by the well curve by performing lateral interpolation through the uphole velocity, and the characteristic that the velocity changes with the fault and the formation fluctuation (the same set of formation velocity should be kept consistent regardless of local compaction difference) is not obvious, and an abnormal value is easy to occur in the interval not controlled by the well curve. FIG. 8 is a comprehensive velocity model established by utilizing geological frame model, seismic processing velocity and aboveground velocity constraints, the seismic processing velocity can provide good transverse resolution, and well drilling can provide good vertical resolution.
In a research area, the three-dimensional space velocity field is established under the constraint of a geological model by adopting the velocity analysis method, and then the To map is converted into a structural map by utilizing the three-dimensional velocity field. The left graph in fig. 9 is a plot of the top T24 of the hong kong group plotted by time-depth transformation in the research area at a conventional speed, and the right graph in fig. 9 is a plot of the top T24 of the hong kong group plotted by time-depth transformation in the research area at a speed produced by the modeling method described in the present application. Comparing and analyzing the two graphs, the speed model manufactured by the modeling method of the application can accurately reflect the slight change of the nasal structure of the research area, the B68 well and the B130 well are positioned on the shaft part of the nasal structure on the time To graph and the conventional speed graph, and the speed graph manufactured by the modeling method of the application is positioned on the saddle part or a small platform of the structure. This is consistent with the drilling results. The comparison with the drilling data shows that the absolute error of the gear diagram is within 8m, see table 2.
TABLE 2 study area Huagang group Top bound T24 real drilling depth and mapping depth
According to the scheme, the high-precision mixed velocity modeling method supports multi-condition constraint and multi-velocity-source mixed refined velocity modeling, not only considers the influence of geological result factors such as drilling curve data, seismic processing speed, horizon and drilling geological stratification on a velocity model, but also fully considers complex conditions such as faults and rock masses. The speed established by the modeling method is high in precision, reasonable in longitudinal and transverse trends, remarkable in effect of changing along with faults and stratum fluctuation, capable of achieving the same speed of different fault blocks of the isochronous stratum and meeting the requirement of fine speed modeling of complex structures.
Actual work area data tests show that the speed modeling level and the section effect of the high-precision mixed speed modeling method are faithful to the real speed characteristics and the change rule of the underground stratum structure, the deep conversion effect and the error precision are superior to those of the conventional speed modeling method when a micro-width structural plane is compared, and more accurate depth prediction can be provided for a target to be drilled.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. A high-precision hybrid velocity modeling method is characterized by comprising the following steps:
s1: acquiring basic data of a geological region to be modeled; the basic data at least comprises fault data, horizon data, well data and seismic data;
s2: establishing a geological frame model for each fault and each horizon according to the fault data and the horizon data; defining an intersection relation among all faults and a contact relation among all horizons, and associating all geological framework models through the intersection relation and the contact relation to obtain a three-dimensional closed structure grid model capable of reflecting the fluctuation change of the underground stratum and the spatial structure;
s3: obtaining velocity sources such as an aboveground time-depth relation, a construction interpretation result, a seismic processing speed, a geological stratification, a velocity analytic function, an interpolation mode and the like according to the basic data, and combining the obtained multiple velocity sources with the three-dimensional closed structure framework model to construct a three-dimensional fine mixing velocity model;
s4: interpreting a time-depth transition of each horizon in the three-dimensional fine hybrid velocity model;
s5: calculating the depth error of the target horizon;
s6: judging whether the calculated depth error is within a threshold range, if not, repeating the steps S2-S5; and if so, outputting the three-dimensional fine mixing speed model as a final speed model.
2. The modeling method of claim 1, wherein the defining of the intersection or contact relationship between the faults and the associating of the geologic framework model corresponding to each fault by the intersection or contact relationship comprises:
carrying out combined interpretation on longitudinal and transverse sections of faults and horizons on the seismic section to obtain horizons and fault data with preset grid density and intervals;
and carrying out three-dimensional space grid interpolation on the picked horizon and fault data.
3. The modeling method of claim 1, further comprising, after defining the cross-correlation between each fault and before correlating the geologic framework model, defining a hierarchical structure of the faults; and establishing a fracture system according to the level structure of the fault and the intersection relation of the fault.
4. The modeling method of claim 1, wherein the defining the intersection relationship between the faults comprises:
establishing a primary and secondary relation of faults according to the scale of each fault, wherein the fault with a larger scale is a primary fault and the fault with a smaller scale is a secondary fault;
if the secondary fault is too far away from the main fault, the secondary fault and the main fault are not connected with each other;
if the fault end points are close to the main fault and the distance between the fault end points is less than 5% of the total length, connecting the fault end points;
if a fault is automatically clipped to a cross-sectional area of more than 25%, the fault will be retained and may cross the main fault.
5. The modeling method of claim 1, wherein the defining contact relationships between respective horizons comprises:
establishing a stratigraphic comparison framework, wherein the comparison is carried out on a geologic time synchronous interface, and the interface is parallel to or integrated with a seismic reflection interface;
and defaulting the sequence of the horizons from the shallow layer to the deep layer, wherein the shallow layer is defaulted to cut the deep layer.
6. The modeling method of claim 1, after obtaining the base data of the region to be modeled, before building a geological framework model for each fault, further comprising: interpreting the base data;
interpreting the data includes: adopting a method of firstly explaining the fault and then explaining the horizon; tracking the trend of the fault by explaining the fault of the main section of the region to be modeled and combining the time slices of the seismic data volume and the coherence analysis data volume, and analyzing the intersection relation of the fault; the horizons within each patch are then tracked from the well.
7. The modeling method of claim 6, wherein said associating each geologic frame model by an intersection relationship and a contact relationship, resulting in the three-dimensional closed architecture lattice model comprises:
interpolating the interpreted horizon and fault, carrying out fault-free constrained meshing on the horizon, adding a fault plane, and cutting the horizon in a fault plane region;
independently gridding the horizon in each fault block area;
combining each interface with each fault by adopting a topological bottom algorithm, cutting horizon data by using the fault plane, gridding the data among each fault block, and modeling each fault block independently;
and splicing all the broken blocks to form the three-dimensional closed structure grid model.
8. The modeling method according to claim 1, wherein in the S3, the constructing the three-dimensional fine mixing velocity model includes:
analyzing the earthquake processing speed, eliminating unreasonable outliers and improving the speed reliability;
converting the average velocity, stacking velocity or root-mean-square velocity of seismic processing into layer velocity by using a Dix formula, and further gridding the layer velocity to be used as a background velocity field of the three-dimensional closed structure lattice model;
each horizon in the three-dimensional closed-structure grid model is given an initial seismic velocity after corresponding stratigraphic gridding to form the three-dimensional fine mixed velocity model.
9. The modeling method of claim 8, wherein in the S4, interpreting the time-depth transform of each horizon in the three-dimensional fine hybrid velocity model comprises:
dispersing a plurality of well points at each layer by using data such as VSP (vertical seismic profiling), acoustic logging, well drilling layering and the like in the basic data;
calculating the initial velocity of the well point according to the initial seismic processing velocity of each horizon in the three-dimensional fine mixed velocity model and the well position;
and calculating the current velocity at the well point according to the depth of each horizon in the basic data, the seismic processing velocity and the well position.
10. The modeling method of claim 9, wherein in S5, said calculating a depth error of the destination horizon comprises:
extracting the current speed at the well point from the target horizon in the three-dimensional fine mixed speed model, and comparing the current speed with the initial speed of the well point; meanwhile, the error value at the well point is used as a constraint condition of the three-dimensional fine mixed velocity model to solve the distribution condition of the velocity error in the whole model, the error distribution is analyzed to find out the error distribution rule, and the optimal mathematical expectation method is utilized to enable the error distribution to be closer to the reality.
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