Design method and device of in-well microseism monitoring and observing system of vertical monitoring well

Abstract

The invention provides a method and a device for designing a microseism monitoring and observing system in a vertical monitoring well. According to the method, the optimal layout parameters of the vertical monitoring well detector are determined by comprehensively considering the comprehensive evaluation of the wave field characteristics of different lowering depths in the target monitoring area, the monitoring field angle, the well cementation quality of the monitoring well and the positioning precision analysis and evaluation. According to the scheme, the influence of the speed change of the complex stratum on the micro seismic wave field is reduced, and the direct wave first arrival pickup precision is improved; the observation field angles of different near and far seismic sources of the ultra-long horizontal well are comprehensively analyzed and optimized, and the observation effect of the whole fractured well section observation system is improved; the well cementation quality and the positioning precision are comprehensively analyzed, the signal-to-noise ratio and the quality of data collected by the observation system of the vertical well are improved, and a decisive effect is achieved on subsequent processing and explaining work.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum geophysical exploration, and more specifically, to a design method and device for a microseismic monitoring and observation system in a vertical monitoring well. Background Art

[0002] Microseismic monitoring technology collects microseismic signals generated by rock rupture or fluid activity disturbance during engineering construction activities, analyzes the impact, effect and engineering status during engineering construction, and evaluates the construction effect, damage condition, safety condition, etc. of the monitored object, thereby providing a basis for engineering process optimization and adjustment and disaster warning.

[0003] Microseismic monitoring is divided into three collection methods: ground, well, and sparse stations. Different monitoring methods have different applicable conditions and technical advantages. The well microseismic monitoring method has the technical advantages of high precision and low cost, and is widely used in the oil and gas field development stage.

[0004] The in-well microseismic acquisition method deploys a string of geophones in the neighboring wells around the target well to monitor microseisms during the fracturing of the fractured well. The in-well geophones are placed in the well below the surface, close to the horizontal section of the fracturing, with little interference from environmental noise, and reduced energy attenuation of the signal by the formation. The acquired data has a high signal-to-noise ratio and a stronger signal receiving capability for weak shear fractures. However, due to the limited number and deployment range of geophones, the three-component geophone receives full wavefield records, and the wavefield is relatively complex, improving the quality of acquired data is the top priority of the in-well monitoring method. Therefore, the design of the observation system is the most critical content of in-well microseismic monitoring.

[0005] At present, the design of in-well microseismic monitoring uses the reservoir depth of the monitoring target to determine the lowering position of the detector, which is relatively simple. If the monitoring well is vertical or the detector can only be placed in the vertical section of the monitoring well, this single observation design method takes into account the influence of multiple factors such as the complex microseismic wave field characteristics caused by formation velocity changes, the small monitoring angle and the limited long-distance monitoring range, and the detector coupling problem caused by the cementing quality of the monitoring well. As a result, the wave field characteristics of the in-well microseismic monitoring signal are difficult to effectively identify weak signals, which increases the difficulty of subsequent in-well microseismic data processing and reduces the advantages of the in-well monitoring method.

[0006] Therefore, there is an urgent need for a design scheme for a microseismic monitoring and observation system in a vertical monitoring well that can effectively improve the quality of microseismic monitoring signals. Summary of the invention

[0007] In view of this, the present invention discloses a design scheme for a microseismic monitoring and observation system in a vertical monitoring well, which determines the optimal layout parameters of the vertical monitoring well detector by comprehensively considering the wave field characteristics of different lowering depths, monitoring angle, positioning accuracy analysis and evaluation, and cementing quality of the monitoring well.

[0008] According to one aspect of the present invention, a design method for a microseismic monitoring and observation system in a vertical monitoring well is proposed, comprising the following steps:

[0009] Step 1, obtaining a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information;

[0010] Step 2: Select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and place the range S of the detectors in the monitoring well. 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points;

[0011] Step 3, based on the multiple excitation sources and the multiple observation points, perform elastic wave forward simulation according to the formation velocity model:

[0012] Step 4: Analyze the wave field type characteristics based on the forward simulation records and select the range S of the optional placement of the geophone. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 :

[0013] Step 5: Calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 :

[0014] Step 6: Based on the determined second detector selectable area S 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 :

[0015] Step 7: Calculate the third detector placement area S according to the formation velocity model 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8Select the best placement depth range S for the geophone u ~S p .

[0016] In some embodiments, step 1 specifically includes:

[0017] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0018] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0019] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0020]

[0021] Where j is the grid number in the X direction, and Δx is the grid side length.

[0022] In some embodiments, step 4 specifically includes:

[0023] According to the forward simulation record analysis of wave field type characteristics, the range S of the optional placement of the geophone is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0024] In some embodiments, step 6 specifically includes:

[0025] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0026] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0027] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0028] In some implementations, step S7 specifically includes:

[0029] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0030] Conduct confidence space analysis and evaluation of positioning errors;

[0031] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0032] In some embodiments, the method further comprises:

[0033] After step 8, the placement interval between adjacent detectors is determined, and the placement interval does not exceed a preset interval threshold.

[0034] In some embodiments, the method further comprises:

[0035] Set the time sampling interval Δt according to the following formula:

[0036]

[0037] Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

[0038] According to another aspect of the present invention, a design device for a microseismic monitoring and observation system in a vertical monitoring well is also proposed, the device comprising:

[0039] A formation velocity model acquisition unit, used to obtain a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information;

[0040] The initial setting unit is used to select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and the range S of the optional placement of detectors in the monitoring well 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points;

[0041] A forward modeling unit is used to carry out elastic wave forward modeling based on the multiple excitation sources and the multiple observation points according to the formation velocity model:

[0042] The first preferred detector placement range determination unit is used to determine the range of the optional placement of the detector according to the forward simulation record analysis wave field type characteristics.1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 :

[0043] The second preferred detector placement range determination unit is used to calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 :

[0044] The third preferred detector placement range determination unit is used to determine the second detector optional area S based on the determined 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 :

[0045] The optimal detector placement range determination unit is used to calculate the third detector placement area S according to the formation velocity model. 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

[0046] In some implementations, the formation velocity model acquisition unit is specifically used to:

[0047] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0048] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0049] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0050]

[0051] Where j is the grid number in the X direction and Δx is the grid side length.

[0052] In some implementations, the first preferred detector placement range determination unit is specifically configured to:

[0053] According to the forward simulation record analysis of wave field type characteristics, the range S of optional placement of geophones is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0054] In some implementations, the third preferred detector placement range determination unit is specifically used to:

[0055] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0056] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0057] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0058] In some implementations, the optimal detector placement range determination unit is specifically used to:

[0059] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0060] Conduct confidence space analysis and evaluation of positioning errors;

[0061] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0062] In some embodiments, the device further comprises:

[0063] The placement spacing determination unit is used to determine the placement spacing of adjacent detectors, where the placement spacing does not exceed a preset spacing threshold.

[0064] In some embodiments, the device further comprises:

[0065] The sampling interval determination unit is used to set the time sampling interval Δt according to the following formula:

[0066]

[0067] Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

[0068] According to another aspect of the present invention, an electronic device is also provided, the electronic device comprising:

[0069] A memory storing executable instructions;

[0070] A processor runs the executable instructions in the memory to implement the design method of the microseismic monitoring observation system in the vertical monitoring well as described above.

[0071] According to another aspect of the present invention, a computer-readable storage medium is also proposed, which stores a computer program. When the computer program is executed by a processor, the design method of the microseismic monitoring observation system in the vertical monitoring well described above is implemented.

[0072] The present invention comprehensively considers the wave field characteristics at different lowering depths in the target monitoring area, the monitoring angle, the cementing quality of the monitoring well, and the positioning accuracy analysis and evaluation to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves. It comprehensively analyzes and optimizes the observation angles of different seismic sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system. It comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work. The advantages of this technical solution are further explained in detail below.

[0073] 1. Help optimize the layout parameters of the detector and improve the quality of monitoring data

[0074] The present invention comprehensively considers wave field characteristics, monitoring angle, cementing quality and positioning accuracy evaluation to determine the optimal placement range of vertical monitoring well geophones. It is beneficial to improve the recognition accuracy of direct waves and the signal-to-noise ratio of collected data, and provide high-quality and low-noise record files for subsequent processing and analysis.

[0075] 2. Improving the monitoring effect of ultra-long fracturing sections

[0076] The present invention optimizes the observation angles of different target points at near and far distances, strengthens the monitoring capability of the entire fracturing section, and makes the monitoring coverage wider.

[0077] 3. Reduce errors in the processing process and improve the accuracy of microseismic location

[0078] By constructing a velocity model, forward simulation and positioning error optimization calculation, the velocity simulation error transmission is reduced, and the ability to judge the location information of the microseismic source (wave source) area is enhanced, providing a more accurate reference for subsequent engineering evaluation.

[0079] 4. The method is systematic and has universal applicability and potential for transfer and use in other fields

[0080] The evaluation system and process of this method are highly robust, and the analytical identification ability of the preferred solution is strong. Through parameter fine-tuning, it can be migrated to other application scenarios with different well images. It is not limited to a single project and has good versatility and scalability.

[0081] The methods and apparatus of the present invention have other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and subsequent detailed descriptions incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0083] Figure 1 A flow chart showing a method for designing a microseismic monitoring and observation system in a vertical monitoring well according to an embodiment of the present invention is shown.

[0084] Figure 2 A schematic diagram of an initial formation velocity model of a work area established according to an embodiment of the present invention is shown.

[0085] Figure 3 A schematic diagram of selecting a suitable placement range for an observation well geophone according to an embodiment of the present invention is shown.

[0086] Figure 4 A schematic diagram of three earthquake source forward modeling according to an embodiment of the present invention is shown.

[0087] Figure 5A schematic diagram showing a first preferred detector placement depth range according to an embodiment of the present invention.

[0088] Figure 6 A schematic diagram of observation angle and well deviation corresponding to different lowering depths of a detector string according to an embodiment of the present invention is shown.

[0089] Figure 7 A schematic diagram of positioning confidence space analysis for different aperture angle ranges according to an embodiment of the present invention is shown.

[0090] Figure 8 A schematic diagram of microseismic records during fracturing collected by an observation system designed according to an embodiment of the present invention is shown.

[0091] Fig. 9 A conceptual schematic diagram of the present invention is shown. DETAILED DESCRIPTION

[0092] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0093] The concept of the present invention is briefly introduced below.

[0094] Fig. 9 The schematic diagram of the concept of the present invention is shown. Theoretically, the larger the observation angle of the detector in the well relative to the source position, the closer the detector is to the monitoring target layer, the stronger the ability to monitor weak signals, and the higher the positioning accuracy; in actual situations, due to the complexity of the formation, it is easy to cause the complexity of the microseismic wave field, which is not conducive to the first arrival of the direct wave caused by shear fracture. Picking and positioning, thereby reducing the processing accuracy. The present invention comprehensively considers the wave field type (i.e., wave field characteristics) of different lowering depths, the observation angle positioning, the positioning accuracy evaluation, the cementing quality of the monitoring well, and other aspects to determine the optimal layout range of the vertical monitoring well detector. The number of detectors to be laid is also determined based on the relationship between the positioning accuracy evaluation and the number of detectors (i.e., the number of detectors on the detector string). The more detectors there are, the higher the number of detector arrays formed, the stronger the ability to collect and analyze microseismic signals, the higher the positioning accuracy evaluation, and the corresponding cost and calculation amount. Finally, the sampling rate is determined.

[0095] Example 1

[0096] Figure 1A flow chart showing a method for designing a microseismic monitoring and observation system in a vertical monitoring well according to an embodiment of the present invention is shown. As shown in the figure, the method includes steps 1 to 7.

[0097] Step 1: Obtain a formation velocity model, wherein the formation velocity model includes logging velocity data and formation interface information.

[0098] The use of a velocity model that includes stratum interface information can make the simulation results more accurate and realistic when performing subsequent wave field simulations. This is because the complex velocity model takes into account the morphological characteristics of the strata and their interfaces, can better simulate the actual wave propagation environment, and can also reduce error transmission in the simulation, improve simulation accuracy, and improve the resolution of subsequent imaging.

[0099] In some embodiments, step 1 may specifically include:

[0100] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0101] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0102] After drawing the stratigraphic stratification and obtaining the data of the stratification interface, a smaller fit can be performed on the stratification interface data. When the interface morphology is complex and cannot be well approximated, the interface can be given by a segmented curve; then the velocity block boundary can be determined. When the velocity gradient is large, smoothing processing is performed to reduce the velocity, and then the stratigraphic velocity model is output.

[0103] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0104]

[0105] Where j is the grid number in the X direction and Δx is the grid side length.

[0106] For grid storage, the smaller the velocity gradient of each grid, the smaller the forward simulation error.

[0107] Step 2: Select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and place the range S of the detectors in the monitoring well. 1 ~S 2 Multiple groups of detector strings are placed inside as multiple observation points.

[0108] The three positions of the horizontal section of the fracturing, the target point B, the center point M of the horizontal section, and the target point A can be selected as the excitation source, and the range of the downhole detector (S 1 ~S 2 ) are placed between the two observation points (x 1 、x 2 、x 3 、x 4 …x n ).

[0109] Step 3: Based on the multiple excitation sources and the multiple observation points, perform elastic wave forward simulation according to the formation velocity model.

[0110] Elastic wave forward modeling can be performed using ray tracing techniques or wave equation simulation.

[0111] Step 4: Analyze the wave field type characteristics based on the forward simulation records and select the range S of the optional placement of the geophone. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 .

[0112] In some embodiments, the wave field type characteristics can be analyzed based on the forward simulation records, and the range S of the optional placement of the geophone can be selected. 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0113] The wave field type characteristics can be analyzed, and the location where the direct wave of the exciting source is least disturbed and easiest to identify is selected as the first preferred detector placement depth range S 3 ~S 4 .

[0114] Step 5: Calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 .

[0115] Step 6: Based on the determined second detector selectable area S 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 .

[0116] In some embodiments, it may specifically include:

[0117] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0118] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0119] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0120] In the determined second detector optional area S 5 ~S 6 If there is cementing quality data (including well deviation, etc.) in this area, the cementing quality data can be evaluated. If the cementing quality evaluation is relatively good, the second geophone optional area S can be determined. 5 ~S 6 That is, the third detector placement area S can be further selected 7 ~S 8 If the cementing quality evaluation is relatively poor, it can be appropriately moved up or down to select an area with a larger observation angle to avoid the coupling effect of the detector due to poor cementing quality, which will affect the acquisition effect.

[0121] Step 7: Calculate the third detector placement area S according to the formation velocity model 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

[0122] In some embodiments, it may specifically include:

[0123] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0124] Conduct confidence space analysis and evaluation of positioning errors;

[0125] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0126] Under the condition of known formation velocity model, the wave propagation characteristic imaging matrix from three seismic sources to each geophone can be calculated through numerical simulation of wave equation. Then the eigenvalue and eigenvector of the wave propagation characteristic imaging matrix are analyzed to judge the difference in positioning accuracy of the three seismic sources at different geophone placement depths. The larger the eigenvalue, the more sensitive the geophone position is to seismic source identification and positioning.

[0127] This embodiment comprehensively considers the wave field characteristics, monitoring angle, cementing quality of the monitoring well, and positioning accuracy analysis and evaluation at different lowering depths in the target monitoring area to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves; comprehensively analyzes and optimizes the observation angles of different sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system; comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work.

[0128] Example 2

[0129] According to one embodiment of the present invention, a design device for a microseismic monitoring and observation system in a vertical monitoring well is provided, the device comprising:

[0130] A formation velocity model acquisition unit, used to obtain a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information;

[0131] The initial setting unit is used to select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and the range S of the optional placement of detectors in the monitoring well 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points;

[0132] A forward modeling unit is used to carry out elastic wave forward modeling based on the multiple excitation sources and the multiple observation points according to the formation velocity model:

[0133] The first preferred detector placement range determination unit is used to determine the range of the optional placement of the detector according to the forward simulation record analysis wave field type characteristics. 1 ~S 2 Select the first preferred detector placement depth range S3 ~S 4 :

[0134] The second preferred detector placement range determination unit is used to calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 :

[0135] The third preferred detector placement range determination unit is used to determine the second detector optional area S based on the determined 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 :

[0136] The optimal detector placement range determination unit is used to calculate the third detector placement area S according to the formation velocity model. 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

[0137] In some implementations, the formation velocity model acquisition unit is specifically used to:

[0138] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0139] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0140] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0141]

[0142] Where j is the grid number in the X direction, and Δx is the grid side length.

[0143] In some implementations, the first preferred detector placement range determination unit is specifically configured to:

[0144] According to the forward simulation record analysis of wave field type characteristics, the range S of the optional placement of the geophone is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0145] In some implementations, the third preferred detector placement range determination unit is specifically used to:

[0146] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0147] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0148] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0149] In some implementations, the optimal detector placement range determination unit is specifically used to:

[0150] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0151] Conduct confidence space analysis and evaluation of positioning errors;

[0152] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0153] In some embodiments, the device further comprises:

[0154] The placement spacing determination unit is used to determine the placement spacing of adjacent detectors, where the placement spacing does not exceed a preset spacing threshold.

[0155] In some embodiments, the device further comprises:

[0156] The sampling interval determination unit is used to set the time sampling interval Δt according to the following formula:

[0157]

[0158] Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

[0159] This embodiment comprehensively considers the wave field characteristics, monitoring angle, cementing quality of the monitoring well, and positioning accuracy analysis and evaluation at different lowering depths in the target monitoring area to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves; comprehensively analyzes and optimizes the observation angles of different sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system; comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work.

[0160] For other detailed descriptions and advantages of this embodiment, reference may be made to the corresponding descriptions in the aforementioned embodiments, which will not be repeated here.

[0161] Example 3

[0162] According to another aspect of the present invention, an electronic device is provided. The electronic device comprises:

[0163] Memory, which stores executable instructions:

[0164] A processor runs the executable instructions in the memory to implement the design method of the microseismic monitoring observation system in the vertical monitoring well according to the present invention.

[0165] Specifically, the memory may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, a random access memory (RAM) and / or a cache memory (cache), etc. The non-volatile memory may include, for example, a read-only memory (ROM), a hard disk, a flash memory, etc.

[0166] The processor may be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In one embodiment of the present invention, the processor is used to run the computer-readable instructions stored in the memory.

[0167] The design method of the microseismic monitoring observation system in the vertical monitoring well comprises the following steps:

[0168] Step 1, obtaining a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information;

[0169] Step 2: Select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and place the range S of the detectors in the monitoring well. 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points;

[0170] Step 3, based on the multiple excitation sources and the multiple observation points, perform elastic wave forward simulation according to the formation velocity model:

[0171] Step 4: Analyze the wave field type characteristics based on the forward simulation records and select the range S of the optional placement of the geophone. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 :

[0172] Step 5: Calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 :

[0173] Step 6: Based on the determined second detector selectable area S 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 :

[0174] Step 7: Calculate the third detector placement area S according to the formation velocity model 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8Select the best placement depth range S for the geophone u ~S p .

[0175] In some embodiments, step 1 specifically includes:

[0176] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0177] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0178] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0179]

[0180] Where j is the grid number in the X direction and Δx is the grid side length.

[0181] In some embodiments, step 4 specifically includes:

[0182] According to the forward simulation record analysis of wave field type characteristics, the range S of optional placement of geophones is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0183] In some embodiments, step 6 specifically includes:

[0184] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0185] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0186] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0187] In some implementations, step S7 specifically includes:

[0188] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0189] Conduct confidence space analysis and evaluation of positioning errors;

[0190] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0191] In some embodiments, the method further comprises:

[0192] After step 8, the placement interval between adjacent detectors is determined, and the placement interval does not exceed a preset interval threshold.

[0193] In some embodiments, the method further comprises:

[0194] Set the time sampling interval Δt according to the following formula:

[0195]

[0196] Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

[0197] This embodiment comprehensively considers the wave field characteristics, monitoring angle, cementing quality of the monitoring well, and positioning accuracy analysis and evaluation at different lowering depths in the target monitoring area to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves; comprehensively analyzes and optimizes the observation angles of different sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system; comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work.

[0198] For detailed description of this embodiment, reference may be made to the corresponding descriptions in the aforementioned embodiments, which will not be repeated here.

[0199] Example 4

[0200] According to another aspect of the present invention, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, it implements the design method of the microseismic monitoring and observation system in the vertical monitoring well according to the present invention.

[0201] The computer-readable storage medium according to the embodiment of the present invention stores non-transitory computer-readable instructions, and when the non-transitory computer-readable instructions are executed by a processor, all or part of the steps of the above-mentioned methods of the embodiments of the present invention are executed.

[0202] The above-mentioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or mobile hard disk), media with built-in rewritable non-volatile memory (e.g., memory card) and media with built-in ROM (e.g., ROM box).

[0203] Those skilled in the art should be able to understand that in order to solve the technical problem of how to obtain a good user experience, the present embodiment may also include well-known structures such as a communication bus and an interface, and these well-known structures should also be included in the protection scope of the present invention.

[0204] The design method of the microseismic monitoring observation system in the vertical monitoring well comprises the following steps:

[0205] Step 1, obtaining a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information;

[0206] Step 2: Select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and place the range S of the detectors in the monitoring well. 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points;

[0207] Step 3, based on the multiple excitation sources and the multiple observation points, perform elastic wave forward simulation according to the formation velocity model:

[0208] Step 4: Analyze the wave field type characteristics based on the forward simulation records and select the range S of the optional placement of the geophone. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 :

[0209] Step 5: Calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3~S 4 Select the second detector selectable area S 5 ~S 6 :

[0210] Step 6: Based on the determined second detector selectable area S 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 :

[0211] Step 7: Calculate the third detector placement area S according to the formation velocity model 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

[0212] In some embodiments, step 1 specifically includes:

[0213] An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data:

[0214] According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

[0215] In some embodiments, the formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows:

[0216]

[0217] Where j is the grid number in the X direction and Δx is the grid side length.

[0218] In some embodiments, step 4 specifically includes:

[0219] According to the forward simulation record analysis of wave field type characteristics, the range S of optional placement of geophones is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

[0220] In some embodiments, step 6 specifically includes:

[0221] Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data;

[0222] If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ;

[0223] If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

[0224] In some implementations, step S7 specifically includes:

[0225] Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources;

[0226] Conduct confidence space analysis and evaluation of positioning errors;

[0227] Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

[0228] In some embodiments, the method further comprises:

[0229] After step 8, the placement interval between adjacent detectors is determined, and the placement interval does not exceed a preset interval threshold.

[0230] In some embodiments, the method further comprises:

[0231] Set the time sampling interval Δt according to the following formula:

[0232]

[0233] Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

[0234] This embodiment comprehensively considers the wave field characteristics, monitoring angle, cementing quality of the monitoring well, and positioning accuracy analysis and evaluation at different lowering depths in the target monitoring area to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves; comprehensively analyzes and optimizes the observation angles of different sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system; comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work.

[0235] For detailed description of this embodiment, reference may be made to the corresponding descriptions in the aforementioned embodiments, which will not be repeated here.

[0236] Example 5

[0237] The effect of the design scheme of the microseismic monitoring and observation system in a vertical monitoring well according to the present invention is verified and explained below with a specific exemplary embodiment.

[0238] Taking a horizontal well fracturing well and a monitoring well for in-well microseismic monitoring as an example, the initial formation velocity model of the work area is established based on the acoustic logging data of the two wells and the formation dip angle of the horizontal section of the fracturing well, such as Figure 2 As shown, there are 4 layers in total.

[0239] Figure 3 A schematic diagram of selecting a suitable placement range for an observation well geophone according to an embodiment of the present invention is shown. Figure 3 As shown in the figure, 111 geophones (in the green solid frame) are placed between the appropriate locations of the observation wells (measured depth 1500m to 2800m) to perform elastic wave forward simulation; and three target seismic sources are set from far to near (A, M, B) from the wellhead of the fracturing well, and the following are obtained. Figure 4 The three source records are shown. From the forward modeling records, it can be found that the wave fields of the two end detectors are crossed, especially the first arrival signal of the deep detector in the long-distance fracturing section decays quickly. This kind of complex wave field and low signal-to-noise ratio data are not conducive to microseismic positioning processing; the range of detectors that are really conducive to microseismic processing is Figure 5 The location marked in the box.

[0240] For this monitoring well, the detector range is Figure 5 In the marked area (measured depth is 1600m to 2500m), based on the trajectory data of the monitoring well, the corresponding observation angle and well deviation of the three seismic sources (A, M, B) at different lowering depths of the geophone string are calculated. Figure 6 The figure shows the corresponding observation angle and well inclination when the detector string is lowered to different depths. Figure 5The depth of the area in the box is (1600m~2500m). In the red dotted area, at 1958 meters (well inclination of about 30 degrees), the observed angles of the three sources (A, M, B) are all local maximums, and the cementing quality is relatively good.

[0241] exist Figure 5 The depth measurement of the area in the box is (1600m~2500m). In the red dotted area, the local maximum of the opening angle is selected to analyze the positioning error of the lowering depth of the detectors from the three sources (A, M, B). From the spatial analysis of the positioning information of different opening angle ranges, it can be obtained that Figure 7 A schematic diagram of spatial analysis of positioning information in different opening angle ranges according to an embodiment of the present invention is shown, verifying that the positioning accuracy of the detector at the maximum opening angle is higher than that at other positions.

[0242] The optimal layout parameters of vertical monitoring well geophones (1970 m - 1980 m) were determined by taking into account the wave field characteristics at different lowering depths in the target monitoring area, the monitoring angle, the cementing quality of the monitoring wells, and the comprehensive evaluation of the positioning accuracy analysis.

[0243] Figure 8 The microseismic records during fracturing at three locations (A, M, B) collected by the observation system based on the method are all clearly visible, verifying that the method of the present invention has certain feasibility and outstanding effect.

[0244] In summary, the various embodiments of the present invention comprehensively consider the wave field characteristics at different lowering depths in the target monitoring area, the monitoring angle, the cementing quality of the monitoring well, and the positioning accuracy analysis and evaluation to determine the optimal layout parameters of the vertical monitoring well detector. This solution reduces the impact of complex formation velocity changes on the microseismic wave field and improves the accuracy of the first arrival of direct waves; comprehensively analyzes and optimizes the observation angles of different seismic sources near and far in ultra-long horizontal wells, and improves the observation effect of the entire fracturing well section observation system; comprehensively analyzes the cementing quality and positioning accuracy, improves the signal-to-noise ratio and quality of the acquisition data of the vertical well observation system, and plays a decisive role in the subsequent processing and interpretation work. A detailed analysis of the beneficial effects of this technical solution is as follows.

[0245] 1. Help optimize the layout parameters of the detector and improve the quality of monitoring data

[0246] The present invention comprehensively considers wave field characteristics, monitoring angle, cementing quality and positioning accuracy evaluation to determine the optimal placement range of vertical monitoring well geophones. It is beneficial to improve the recognition accuracy of direct waves and the signal-to-noise ratio of collected data, and provide high-quality and low-noise record files for subsequent processing and analysis.

[0247] 2. Improving the monitoring effect of ultra-long fracturing sections

[0248] The present invention optimizes the observation angles of different target points at near and far distances, strengthens the monitoring capability of the entire fracturing section, and makes the monitoring coverage wider.

[0249] 3. Reduce errors in the processing process and improve the accuracy of microseismic location

[0250] By constructing a velocity model, forward simulation and positioning error optimization calculation, the velocity simulation error transmission is reduced, and the ability to judge the location information of the microseismic source (wave source) area is enhanced, providing a more accurate reference for subsequent engineering evaluation.

[0251] 4. The method is systematic and has universal applicability and potential for transfer and use in other fields

[0252] The evaluation system and process of this method are highly robust, and the analytical identification ability of the preferred solution is strong. Through parameter fine-tuning, it can be migrated to other application scenarios with different well images. It is not limited to a single project and has good versatility and scalability.

[0253] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications, or technical improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A design method for a microseismic monitoring and observation system in a vertical monitoring well. It is characterized in that The following steps are involved: Step 1, obtaining a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information; Step 2: Select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and place the range S of the detectors in the monitoring well. 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points; Step 3, based on the multiple excitation sources and the multiple observation points, perform elastic wave forward simulation according to the formation velocity model: Step 4: Analyze the wave field type characteristics based on the forward simulation records and select the range S of the optional placement of the geophone. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 : Step 5: Calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 : Step 6: Based on the determined second detector selectable area S 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 : Step 7: Calculate the third detector placement area S according to the formation velocity model 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

2. The method according to claim 1, It is characterized in that The step 1 specifically includes: An initial velocity model is established based on the acoustic logging data of the fracturing well and the monitoring well and the seismic geological data in the monitoring target area. The initial velocity model includes the logging velocity data: According to the initial velocity model, the formation stratification is plotted, the data of the stratification interface is obtained and fitted, and according to the fitted stratification interface data, the formation velocity model is output.

3. The method according to claim 1, It is characterized in that The formation velocity model is stored in a grid format, and the velocity gradient V in the grid is calculated using the central difference method. x , the formula is as follows: Where j is the grid number in the X direction, and Δx is the grid side length.

4. The method according to claim 1, It is characterized in that Step 4 specifically includes: According to the forward simulation record analysis of wave field type characteristics, the range S of the optional placement of the geophone is 1 ~S 2 Select the area with the clearest direct wave from the excitation source as the first preferred depth range S for geophone placement 3 ~S 4 .

5. The method according to claim 1, It is characterized in that Step 6 specifically includes: Evaluation of the optional area S of the second detector 5 ~S 6 Cementing quality data; If the cementing quality data meets the requirements, the second detector optional area S is determined. 5 ~S 6 Place area S for the third detector 7 ~S 8 ; If the cementing quality data does not meet the requirements, select the second detector optional area S according to the observed opening angle 5 ~S 6 The area moved up or down is used as the third detector placement area S 7 ~S 8 .

6. The method according to claim 1, It is characterized in that Step S7 specifically includes: Based on the formation velocity model, an inversion is performed and the eigenvalue and eigenvector of the matrix are used to calculate the third geophone placement area S 7 ~S 8 Positioning errors from multiple observation points within the range to the multiple excitation sources; Conduct confidence space analysis and evaluation of positioning errors; Select the best placement depth range S of the geophone based on the evaluation results u ~S p .

7. The method according to claim 1, It is characterized in that The method further comprises: After step 8, the placement interval between adjacent detectors is determined, and the placement interval does not exceed a preset interval threshold.

8. The method according to claim 1, It is characterized in that The method further comprises: Set the time sampling interval Δt according to the following formula: Among them, the unit of time sampling interval Δt is milliseconds (ms), f max Indicates the highest frequency of the signal that needs protection, in Hertz (Hz).

9. A design device for a microseismic monitoring and observation system in a vertical monitoring well. It is characterized in that The device comprises: A formation velocity model acquisition unit, used to obtain a formation velocity model, wherein the formation velocity model includes logging velocity data and formation layer interface information; The initial setting unit is used to select multiple locations in the horizontal section of the fracturing as multiple excitation sources, and the range S of the optional placement of detectors in the monitoring well 1 ~S 2 Multiple groups of geophone strings are placed inside as multiple observation points; A forward modeling unit is used to carry out elastic wave forward modeling based on the multiple excitation sources and the multiple observation points according to the formation velocity model: The first preferred detector placement range determination unit is used to determine the range of the optional placement of the detector according to the forward simulation record analysis wave field type characteristics. 1 ~S 2 Select the first preferred detector placement depth range S 3 ~S 4 : The second preferred detector placement range determination unit is used to calculate the determined detector placement depth range S 3 ~S 4 The first preferred geophone placement depth range S is selected based on the local maximum of the observed opening angle. 3 ~S 4 Select the second detector selectable area S 5 ~S 6 : The third preferred detector placement range determination unit is used to determine the second detector optional area S based on the determined 5 ~S 6 The cementing quality data is used to determine the third geophone placement area S 7 ~S 8 : The optimal detector placement range determination unit is used to calculate the third detector placement area S according to the formation velocity model. 7 ~S 8 The positioning accuracy of each observation point within the plurality of excitation sources is determined, and the positioning accuracy is calculated from the third detector placement area S 7 ~S 8 Select the best placement depth range S for the geophone u ~S p .

10. An electronic device, It is characterized in that The electronic device comprises: A memory storing executable instructions; A processor, wherein the processor runs the executable instructions in the memory to implement the method according to any one of claims 1 to 8.

11. A computer-readable storage medium storing a computer program, wherein the computer program implements the method according to any one of claims 1 to 8 when executed by a processor.

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