Fine synthetic recording horizon calibration method for searching marker bed based on average speed

Abstract

The invention relates to the technical field of structural interpretation, and provides a fine synthetic record horizon calibration method for searching a marker bed based on average speed. Comprising the steps of performing waveform matching calibration on a well with a complete stratum in a research area by using an area average speed; determining the earthquake and geologic horizon with the matched waveform as a marker bed; the average speed and the marker bed are used for conducting up-down offset waveform matching calibration on the well with the stratum missing area; according to the method, the problem of inaccurate calibration caused by short curve and no starting from zero in horizon calibration merely relying on synthesis recording is solved, the corresponding relation between each geologic horizon and the seismic horizon is established, and the horizon calibration precision is improved.

Description

Technical Field

[0001] This invention relates to the field of structural interpretation technology, and provides a method for fine synthetic record layer calibration based on average velocity to find marker layers. Background Technology

[0002] Stratigraphic calibration assigns geological meaning to seismic reflection layers. It serves as a bridge connecting seismic profiles in the time domain with geological, drilling, and logging information in the depth domain. It is fundamental to structural interpretation and reservoir prediction, and the accuracy of its results significantly impacts subsequent development work. Conventional stratigraphic calibration methods mainly include three categories: synthetic record calibration, VSP record calibration, and mean velocity calibration.

[0003] Synthetic record calibration mainly involves generating a synthetic record by convolving the reflection coefficient obtained from the acoustic curve with the wavelet, and then performing waveform matching calibration with the seismic traces near the well. When there is no actual filling velocity between the starting point of the logging curve and the ground, it is difficult to accurately calibrate by relying solely on the correspondence of waveform characteristics. Furthermore, the quality of the acoustic curve, the wavelet, and the length of the logging curve will also affect the calibration results.

[0004] VSP record calibration is the most accurate, but because the detector position of VSP record is different from that of seismic acquisition detector, there is no half loss, and VSP record is negative polarity, the waveform characteristics corresponding to the same time value will be significantly different. It can only be correctly calibrated for the marker layer with strong energy and obvious characteristics in the work area, and it is relatively difficult to calibrate the next level layer.

[0005] Average velocity calibration uses the average velocity of the region or the average velocity obtained from the superimposed velocity to establish the time-depth relationship for calibration. This method has a large error and requires manual adjustment.

[0006] Under varying geological conditions, a single method is insufficient for accurate calibration. Therefore, researchers have proposed multi-information integrated calibration techniques to address different exploration objectives and data conditions. For example:

[0007] In blocks with few wells and no acoustic logging curves, Ding Jianqiang et al. used time-depth analysis and acoustic fitting method, well-seismic combined forward modeling method, and seismic-geological multi-attribute fusion comprehensive calibration to improve calibration accuracy; Yang Zhanlong achieved reservoir fine calibration by first coarsely calibrating the target layer and then finely calibrating the reservoir; Zhao Haiying et al. addressed the problems of multiple solutions and limitations in the stratigraphic calibration process of VSP data by using a seismic stratigraphic comprehensive calibration method based on VSP data to improve calibration accuracy.

[0008] Some patent documents are also based on the above ideas, for example:

[0009] Chinese invention patent CN104656142B discloses a seismic horizon calibration method using a combination of vertical seismic profiling and well logging. This invention utilizes a combined vertical seismic profiling and well logging method to measure and obtain the P-wave time-depth relationship and corridor stacking profile based on zero-source distance data, and obtains sonic logging and density logging data. The time difference is calculated by determining the sonic time-depth relationship and the VSP time-depth relationship, and the sonic curve is corrected. The corrected well logging curve is convolved with the seismic wavelet to obtain a synthetic record. After determining the time shift and correct polarity of the VSP corridor, a horizon calibration map is created. The surface seismic profile is then calibrated based on known well geological stratification. This invention eliminates sonic logging errors and dispersion effects, improves the accuracy of synthetic record creation, reduces human factors in calibration, and improves calibration accuracy.

[0010] The aforementioned patents involve seismic horizon calibration methods that combine vertical seismic profiles with well logging, and VSP-based precise horizon calibration methods that improve calibration accuracy. However, these methods are difficult to implement due to the limited availability of zero-well source data and VSP data.

[0011] Chinese invention patent CN111045085A discloses a method and apparatus for stratigraphic calibration, belonging to the field of stratigraphic calibration technology. The method includes: obtaining the reflection coefficient based on well logging data of a target well within a target area; determining initial synthetic seismic data based on the reflection coefficient and the Ricker wavelet; performing preliminary stratigraphic calibration on the target well based on the initial synthetic seismic data; determining secondary synthetic seismic data based on the reflection coefficient and the amplitude spectral wavelet; performing secondary stratigraphic calibration on the target well based on the secondary synthetic seismic data, building upon the preliminary stratigraphic calibration; determining tertiary synthetic seismic data based on the reflection coefficient and the amplitude phase spectral wavelet; performing tertiary stratigraphic calibration based on the tertiary synthetic seismic data, building upon the secondary stratigraphic calibration; and if the first offset between the time-depth curve of the tertiary stratigraphic calibration and the average time-depth curve is less than a first preset threshold, then the tertiary stratigraphic calibration is considered the final stratigraphic calibration. This method can improve the accuracy and precision of stratigraphic calibration.

[0012] The above-mentioned three-stage synthetic record layer calibration based on reflection coefficient and amplitude phase spectral wavelet does not solve the problems of actual filling rate, short logging curves, and lack of marker layers in synthetic record layer calibration, making it difficult to achieve precise calibration.

[0013] Invention patent CN114428320A discloses a method and system for accurate VSP (Very Seismic Spatial Perimeter) calibration based on ray theory. This invention provides a method and system for accurate VSP calibration based on ray theory, belonging to the field of seismic data processing and interpretation in oil and gas exploration and development. This method establishes a seismic forward model using seismic data observation systems and well logging data. Through the seismic forward model and first-arrival travel time (FAT) picking, it obtains the VSP up-traveling wave travel time error and the FAT error. Then, through VSP up-traveling wave FAT error correction and FAT correction, it obtains the accurate two-way travel time of the VSP, determines the time-depth relationship, and thus achieves accurate VSP calibration. This invention is more consistent with the actual situation of underground strata, laying the foundation for accurate calibration. Based on ray theory, it can accurately calculate the VSP up-traveling wave travel time error with high computational efficiency. Combined with FAT picking, it can obtain the accurate VSP two-way travel time through travel time correction, determine the correct time-depth relationship, and then perform accurate stratigraphic calibration to obtain accurate layer velocities.

[0014] The method of rapidly verifying the accuracy of seismic horizon calibration using horizontal isochronous surfaces can effectively improve calibration accuracy when obvious marker layers are missing, but it is not applicable when seismic data contains velocity anomalies in the plane or has few well controls.

[0015] Invention CN112558180A discloses a method for rapidly verifying the accuracy of seismic horizon calibration using horizontal isochronous surfaces. This invention relates to a method for rapidly verifying the accuracy of seismic horizon calibration using horizontal isochronous surfaces, comprising: 1. Preliminary horizon calibration of all wells in the study area, i.e., the spatial velocity field of the study area, based on the similarity between synthetic records and well-side seismic data; 2. Establishing horizontal isochronous surfaces distributed throughout the entire study area within the seismic data volume; 3. Performing time-depth conversion on the horizontal isochronous surfaces using the spatial velocity field obtained after horizon calibration, obtaining the depth surface of the isochronous surfaces under this velocity field; 4. Compiling a planar contour map of this depth surface, where the positions of anomalies reflect velocity anomalies, and the positions of the anomalies are the locations of wells with inaccurate horizon calibration; 5. Establishing profiles through the anomaly wells, and re-matching the wells with inaccurate horizon calibration with well-seismic synthetic records; 6. Repeating steps 3 to 5 until the depth surface reflecting velocity changes shows a natural trend with no anomalies. This invention improves the calibration accuracy in areas lacking obvious marker layers.

[0016] The integrated calibration of multiple seismic and geological attributes can effectively improve the accuracy of stratigraphic calibration, but it can mislead the calibration when well data is incorrect.

[0017] In summary, when the thickness of sedimentary strata changes rapidly, faults are well-developed, there are no high-energy seismic marker layers, and there are velocity variations in the seismic data plane, existing stratigraphic calibration methods are difficult to achieve accurate calibration.

[0018] To address these challenges, this invention provides a method for finely synthesized stratigraphic mapping of complex sedimentary strata based on average velocity marker layers, thus resolving the aforementioned difficulties. Summary of the Invention

[0019] The purpose of this invention is to address the shortcomings of existing technologies by proposing a fine synthetic recording layer calibration method based on average velocity to find marker layers.

[0020] It is suitable for complex sedimentary strata and solves the problems of rapid changes in sedimentary thickness, differences in planar velocity, lack of seismic marker layers, and difficulty in stratigraphic calibration in fault-developed areas.

[0021] To achieve the above objectives, the present invention adopts the following technical solution:

[0022] A refined synthetic record layer calibration method based on average velocity to find marker layers includes:

[0023] Waveform matching calibration was performed on wells with intact strata in the study area using regional average velocity.

[0024] The earthquake and geological strata with well-matched waveforms are identified as marker layers;

[0025] The average velocity and marker layers are used to perform vertical offset waveform matching calibration on wells in areas with missing formations.

[0026] Furthermore, it also includes:

[0027] By calibrating seismic profiles through wells, we can check whether the seismic reflection characteristics, stratigraphic sedimentary characteristics and seismic stratigraphic sedimentary characteristics of various geological strata on the well are consistent. Wells with anomalies can be returned to check whether the geological stratification is correct.

[0028] The time and depth of the wells on the well profile are superimposed and analyzed to check for any wells with abnormal time and depth. If there is an abnormality, the calibration is returned. If the calibration is fine, the time and depth of the adjacent wells are used for calibration. If it is suitable, the time and depth of the adjacent wells are used. If it is not suitable, check whether the overall time and depth of the layers is too low. If they are all too low, consider the well inclination error and do not use the well.

[0029] Given an initial velocity, the synthetic record is used to perform fine synthetic record layer calibration by means of the correspondence between the geological layers and the seismic layers.

[0030] Furthermore, step S1 includes: selecting the well with the most complete stratum deposition in the work area, establishing the initial time depth using the regional average velocity, creating a synthetic record using the initial time depth, the reflection coefficient formed by the sonic curve, and the wavelet extracted from the wellside trace, combining geological stratification, and performing up-and-down movement to match and calibrate the synthetic record with the waveform characteristics of the wellside seismic trace, and determining the seismic and geological strata with the matched waveforms as marker layers.

[0031] Furthermore, step S3 includes: establishing an initial time depth using the average velocity; creating a synthetic record using the initial time depth, the reflection coefficient formed by the acoustic curve, and the wavelet extracted from the wellside trace; and, in conjunction with geological stratification, performing synthetic record matching and calibration with the wellside seismic trace waveform for wells in areas with missing strata through the marker layer in step 1.

[0032] Furthermore, the initial time depth is established using the regional average velocity.

[0033] Furthermore, the layer calibration includes the following steps:

[0034] Establish the initial time depth using average velocity;

[0035] The synthetic record was created using the initial time depth, the reflection coefficient formed by the acoustic curve, and the wavelet extracted from the wellside trace. The waveform of the wellside seismic trace was matched and calibrated.

[0036] Furthermore, the stratigraphic calibration involves combining geological strata and marker layers with the synthetic record and matching the waveform of the seismic traces near the well for wells in areas with missing strata.

[0037] Furthermore, step three also includes identifying abnormal wells, which is handled through the following steps:

[0038] If a well is found to be abnormal, it should be returned to the geology department to check whether the geological stratification is correct. At the same time, the time-depth curves of the wells on the well-connected profile should be overlaid to check for wells with abnormal time-depth. If any abnormality is found, the well should be returned for calibration.

[0039] If the calibration is successful, use the time depth of the adjacent well for calibration; if it is suitable, use the time depth of the adjacent well.

[0040] If it is not suitable, check if the overall stratification is too low. If all strata are too low, consider the well inclination error and do not use the well.

[0041] Furthermore, the abnormal well judgment is made by checking whether the seismic reflection characteristics of various geological strata above the well are consistent by calibrating seismic profiles through longitudinal and transverse well connections, and whether the sedimentary characteristics of the strata are consistent with the sedimentary characteristics of the seismic strata.

[0042] Furthermore, the fine synthesis record calibration includes creating an acoustic synthesis record using the reflection coefficient formed by the acoustic wave curve and the wavelet extracted from the wellbore.

[0043] The beneficial effects of this invention are as follows:

[0044] This invention determines seismic geological marker layers through average velocity offset calibration and obtains the initial velocity of a single well. It then verifies the drilling and geological stratification through well-to-well calibration, establishing a correspondence between geological strata and seismic horizons. Based on this, it performs refined synthetic record horizon calibration, achieving waveform matching calibration across the entire stratigraphic segment. This method solves the inaccuracies caused by short curves and non-zero starting points in synthetic record horizon calibration alone. It establishes a correspondence between various geological horizons and seismic horizons, improving the accuracy of horizon calibration. Attached Figure Description

[0045] Figure 1 Flowchart of a specific embodiment of the present invention;

[0046] Figure 2 A calibration map of a single-well synthetic record based on average velocity from the well with the most complete formation sedimentation in a specific embodiment of the present invention;

[0047] Figure 3 A specific embodiment of the present invention provides a well profile diagram for synthetic record stratigraphic calibration based on average velocity.

[0048] Figure 4 Specific embodiments of the present invention include time-depth overlay diagrams of individual wells;

[0049] Figure 5 A specific embodiment of the present invention includes a calibration diagram of a single-well fine acoustic synthesis record.

[0050] Figure 6 Specific embodiments of the present invention provide finely synthesized records of well calibration profiles.

[0051] Figure 7 Cross-sectional view of the calibration effect of the method of the present invention in a specific embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0053] Example 1:

[0054] The Chengdao East Slope region is structurally located at the southeastern end of the Chengbei Low Uplift, where the Jiyang Depression and the Bozhong Depression intersect. It is divided into an overlap zone, a first slope break zone, a second slope break zone, a depression zone, and a fault step zone. This study covers the fault step zone (CB32, 325, 326) and the gentle slope zone (G4-812 well area), with the strata generally dipping towards the northwest valley. Four sets of Paleozoic, Lower Tertiary Shahejie Formation, Dongying Formation, and Upper Tertiary Guantao Formation were discovered in the Chengdao East Slope region. The study area contains oil and gas reservoirs, with the Dongying Formation being the main oil and gas-bearing strata. The study section is the Dongying Formation ED6-ED9. The sedimentary thickness of each sandstone group varies considerably. Faults are developed in the eastern step zone, and a large syn-sedimentary fault is developed in the southeast direction. In the western gentle slope zone, the study section overlaps the Mesozoic and Paleozoic strata. The study area is large, and the well control is low in some areas. The plane velocity varies greatly, making stratigraphic calibration difficult.

[0055] The calibration is performed using the fine synthetic record layer calibration method based on average velocity to find marker layers in this invention. The specific steps are as follows:

[0056] Step 1: Select wells 327, 323, and 804 in the valley. Establish initial time depth using the average velocity of the ridge island. Create a synthetic record using the initial time depth, the reflection coefficient formed by the sonic curve, and the wavelet extracted from the wellside trace. Combined with geological stratification, the synthetic record is matched and calibrated with the waveform characteristics of the wellside seismic trace by moving it up and down. By calibrating the weak wave peak reflection corresponding to ED9, the entire area is relatively stable, and this layer is determined as the marker layer. Proceed to Step 2.

[0057] Step 2: Using the average velocity as the initial time depth, a synthetic record is created using the initial time depth, the reflection coefficient formed by the acoustic curve, and the wavelet extracted from the wellbore. Using ED9 as the marker layer, the synthetic record is matched and calibrated with the waveform characteristics of the wellbore seismic trace. Proceed to Step 3.

[0058] Step 3: By calibrating the seismic profile through the Lalian well, the seismic reflection characteristics of each geological stratum (ED6-ED9) are examined. The profile shows that the seismic reflection characteristics of each geological stratum are relatively uniform. However, due to the variation in reservoir thickness, facies transitions occur locally in ED8. At the same time, the time-depth overlay maps of each individual well show that the time-depth variation trend is relatively uniform throughout the area. The well data and stratification are appropriate and there are no problems. Furthermore, by calibrating the areas near the weak wave peaks corresponding to ED6, ED7, and ED9, the local energy weakens. ED8 corresponds to a wave trough in the north and a weak wave peak in the southeast. Proceed to Step 4.

[0059] Step 4: Using the initial velocity of each well determined in Step 2 and the seismic characteristics of each geological stratum determined in Step 3, the acoustic synthesis record is made using the reflection coefficient formed by the acoustic curve and the wavelet extracted from the wellbore. Referring to the correspondence between each sand group (ED6-ED9) and the seismic stratum in Step 4, the stratum of the refined synthesis record is calibrated. By calibrating the seismic reflection characteristics of each geological stratum, the waveform characteristics of the entire stratum are more uniform, and the process ends.

[0060] The method of this invention is used to determine the stratigraphic position, match the well seismic wave groups, unify the seismic reflection characteristics of each geological stratum, and match the faults of the well surface comparison faults with the seismic profile faults. Based on this, structural interpretation is carried out, and the fault positions of the three oil-controlling faults are finely characterized, providing a reliable basic guidance for the next step of tapping the remaining oil potential and well location deployment.

[0061] This invention locates auxiliary marker layers under average velocity control, then uses these auxiliary marker layers to perform synthetic record layer calibration, and utilizes multiple seismic and geological attributes for well-to-well calibration, ultimately achieving accurate calibration. This method first uses regional average velocity to perform waveform matching calibration on wells with intact strata in the study area through vertical offset, identifying the wells with well-matched seismic and geological strata as marker layers. Then, using average velocity and marker layers, it performs vertical offset waveform matching calibration on wells in areas with missing strata. Next, it uses vertical and horizontal well-to-well calibration to examine the consistency of seismic reflection characteristics across different geological strata, checking for consistency between stratigraphic and seismic sedimentary characteristics. Wells with anomalies are returned to the geology department for verification of geological stratification. Simultaneously, the time-depth overlay analysis of the well-calibrated wells on the interconnected well profiles is performed to check for wells with abnormal time-depth. If anomalies are found, the wells are returned for calibration. If the calibration is successful, the time-depth of adjacent wells is used; if suitable, it is used; otherwise, it is checked whether the overall strata are too low. If all are too low, the well inclination is considered incorrect, and the well is discarded. Finally, given an initial velocity, it uses acoustic synthesis recording to perform fine-grained synthetic record strata calibration based on the correspondence between different geological strata and seismic strata, thus achieving the goal of full-stratum waveform matching calibration.

[0062] Example 2:

[0063] This invention addresses the challenges of rapid changes in stratigraphic thickness, variations in planar velocities, the lack of seismic marker layers, and difficulties in stratigraphic calibration in fault-developed areas. It proposes a method to locate auxiliary marker layers under average velocity control, then use these auxiliary marker layers for synthetic record stratigraphic calibration, and finally utilize multiple seismic and geological attributes for well-to-well calibration, ultimately achieving accurate calibration. This method first uses regional average velocity to perform waveform matching calibration on wells with intact strata in the study area through vertical offset, identifying the wells with well-matched seismic and geological strata as marker layers. Then, using average velocity and marker layers, it performs vertical offset waveform matching calibration on wells in areas with missing strata. Next, it uses vertical and horizontal well-to-well calibration to examine the consistency of seismic reflection characteristics across different geological strata, checking for consistency between stratigraphic and seismic sedimentary characteristics. Wells with anomalies are returned to the geology department for verification of geological stratification. Simultaneously, the time-depth overlay analysis of the well-calibrated wells on the interconnected well profiles is performed to check for wells with abnormal time-depth. If anomalies are found, the wells are returned for calibration. If the calibration is successful, the time-depth of adjacent wells is used; if suitable, it is used; otherwise, it is checked whether the overall strata are too low. If all are too low, the well inclination is considered incorrect, and the well is discarded. Finally, given an initial velocity, it uses acoustic synthesis recording to perform fine-grained synthetic record strata calibration based on the correspondence between different geological strata and seismic strata, thus achieving the goal of full-stratum waveform matching calibration.

[0064] The method of this invention can be achieved through the following steps:

[0065] Step 1: Select the well with the most complete stratigraphic deposition within the work area, establish the initial time depth using the regional average velocity, and create a synthetic record using the initial time depth, the reflection coefficient formed by the sonic curve, and the wavelet extracted from the wellside trace. Combined with geological stratification, the synthetic record is matched and calibrated with the waveform characteristics of the wellside seismic trace by moving it up and down. The seismic and geological strata with well-matched waveforms are identified as marker layers, and then proceed to Step 2.

[0066] Step 2: Establish initial time depth using average velocity. Use the initial time depth, reflection coefficient formed by acoustic curve, and wavelet extracted from the wellbore trace to create a synthetic record. Combined with geological stratification, for wells with missing strata, perform synthetic record matching and calibration with the wellbore seismic trace waveform through the marker layer in Step 1. Proceed to Step 3.

[0067] Step 3: By calibrating the seismic profiles through longitudinal and transverse well connections, check whether the seismic reflection characteristics of various geological strata on the wells are consistent, and check whether the stratigraphic sedimentary characteristics are consistent with the seismic stratigraphic sedimentary characteristics. Wells with anomalies are returned to the geology department to check whether the geological stratification is correct. At the same time, the time-depth curves of the wells on the well connections are overlaid to check for wells with abnormal time depths. If there are anomalies, they are returned for calibration. If the calibration is fine, the time-depth of the adjacent well is used for calibration. If it is suitable, the time-depth of the adjacent well is used. If it is not suitable, check whether the overall stratification is too low. If it is too low, consider the well deviation to be incorrect and do not use the well. Proceed to Step 4.

[0068] Step 4: Determine the initial surface velocity using the stratigraphic calibration in Step 2, then use the reflection coefficient formed by the acoustic curve and the wavelet extracted from the wellbore to create an acoustic synthesis record. Refer to the correspondence between the geological strata and seismic stratigraphic levels in Step 3 to perform fine synthesis record stratigraphic calibration, thereby achieving the purpose of full-system wave group matching calibration. The process ends.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for fine synthetic record layer calibration based on average velocity to find marker layers, characterized in that, include: S1. Use regional average velocity to perform waveform matching calibration on wells with intact strata in the study area; S2. Identify the well-matched seismic and geological strata as marker layers; S3. Use the average velocity and marker layers to perform vertical offset waveform matching calibration on wells in areas with missing strata.

2. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 1, characterized in that, Also includes: S4. By calibrating seismic profiles across wells, check whether the seismic reflection characteristics, stratigraphic sedimentary characteristics, and seismic stratigraphic sedimentary characteristics of various geological strata are consistent. For wells with anomalies, return to check whether the geological stratification is correct. S5. Perform time-depth overlay analysis on the well-calibrated profiles across wells to check for wells with abnormal time depths. If anomalies are found, return to calibration. If the calibration is correct, use the time depth of adjacent wells for calibration. If it is suitable, use the time depth of adjacent wells. If it is not suitable, check whether the overall stratification is too low. If all are too low, consider the well inclination error and do not use that well. S6. Given an initial velocity, use acoustic synthesis recording to perform fine synthesis recording stratification based on the correspondence between various geological strata and seismic strata.

3. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 2, characterized in that, Step S1 includes: selecting the well with the most complete stratum deposition in the work area, establishing the initial time depth using the regional average velocity, creating a synthetic record using the initial time depth, the reflection coefficient formed by the sonic curve, and the wavelet extracted from the wellside trace, combining geological stratification, and performing up-and-down movement to match and calibrate the synthetic record with the waveform characteristics of the wellside seismic trace, and determining the seismic and geological strata with the matched waveforms as marker layers.

4. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 2, characterized in that, Step S3 includes: establishing an initial time depth using the average velocity; creating a synthetic record using the initial time depth, the reflection coefficient formed by the acoustic curve, and the wavelet extracted from the wellside trace; and, in conjunction with geological stratification, performing synthetic record matching and calibration with the wellside seismic trace waveform for wells in areas with missing strata through the marker layer in step 1.

5. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 3 or 4, characterized in that, The initial time depth is established using the regional average velocity.

6. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 3 or 4, characterized in that, The stratigraphic calibration includes the following steps: establishing an initial time depth using average velocity; and creating a synthetic record and matching the waveform of the wellbore seismic trace using the initial time depth, the reflection coefficient formed by the acoustic curve, and the wavelet extracted from the wellbore trace.

7. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 6, characterized in that, The stratigraphic calibration involves, for wells in areas with missing stratigraphic layers, combining geological strata and marker layers to create a synthetic record and matching it with the waveform of the seismic traces near the well.

8. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 7, characterized in that, Step three also includes the identification of abnormal wells, which is handled through the following steps: Abnormal wells are returned to the geology department to check whether the geological stratification is correct. At the same time, the time-depth curves of the wells on the well-connected profile are overlaid to check for wells with abnormal time-depth. If there is an abnormality, the well is returned for calibration. If the calibration is fine, the time-depth of the adjacent well is used for calibration. If it is suitable, the time-depth of the adjacent well is used. If it is not suitable, it is checked whether the overall stratification is too low. If it is too low, the well inclination is considered to be incorrect, and the well is not used.

9. The method for fine synthetic record layer calibration based on average velocity to find marker layers according to claim 8, characterized in that, The identification of abnormal wells is made by examining the seismic reflection characteristics of various geological strata above the wells through longitudinal and transverse well calibration seismic profiles, and by checking whether the sedimentary characteristics of the strata are consistent with the sedimentary characteristics of the seismic strata.

10. The method for fine synthetic record layer localization based on average velocity to find marker layers according to any one of claims 9, characterized in that, The fine synthetic record calibration includes creating a synthetic acoustic record using the reflection coefficient formed by the acoustic wave curve and the wavelet extracted from the wellbore.

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