Method and device for ocean drilling wellbore acoustic velocity imaging based on multi-scale tomography

Abstract

This application relates to the field of marine geophysical exploration technology, and specifically provides a method and device for acoustic velocity imaging around an ocean drilling well based on multi-scale tomography. The method includes: obtaining acoustic logging data and a borehole diameter curve; performing velocity extraction or slowness extraction on the acoustic logging data, and combining the borehole diameter curve to construct a velocity model around the well as an initial inversion model; performing travel time extraction on the acoustic logging data; using the multi-scale tomography method to invert the initial inversion model to obtain an acoustic velocity imaging profile around the well. The present invention first applies the multi-scale tomography method to the acoustic velocity imaging around an ocean drilling well, and uses the background velocity and path length to quickly invert the velocity perturbation, realizing fast imaging of the small-scale velocity around the well, overcoming the situation of low resolution between the sound source and the receiver in the traditional imaging method, effectively improving the imaging accuracy, and providing a new idea for optimizing logging technology and improving subsurface imaging, etc.

Description

Technical Field

[0001] This application relates to the technical field of marine geophysical exploration, and specifically to a method and device for ocean drilling wellbore acoustic velocity imaging based on multi-scale tomography. Background Art

[0002] Wellbore velocity imaging technology is one of the important technologies in the fields of oil and gas exploration, underground engineering, geological survey, etc. In oil and gas exploration, wellbore velocity imaging is used to infer the velocity structure of underground formations, help study the distribution characteristics of underground media, and thus provide reliable reference information for drilling, reservoir evaluation, and oil production plan formulation. The wellbore velocity field reflects the physical properties of the formation and is one of the important parameters in seismic exploration and downhole measurement. Therefore, accurate wellbore velocity imaging can greatly improve the efficiency of underground resource exploration and development.

[0003] Traditional wellbore velocity imaging methods (such as single-scale tomography) often rely on a specified scale and are difficult to balance between large and small ranges. At the same time, under complex geological conditions such as faults or abnormal media, traditional imaging methods may be difficult to effectively distinguish different velocity structures, and in high-resolution imaging, the computational complexity and data processing difficulty of traditional imaging methods are relatively large, often requiring high computing resources.

[0004] At the same time, the cost of offshore drilling is high. In the prior art, complex inversion is required when converting travel-time perturbations into velocity perturbations, which requires high computing resources, prolongs the computing time, and increases the drilling cost. In summary, there is an urgent need to provide a fast and accurate method, device, and equipment for ocean drilling wellbore acoustic velocity imaging to evaluate wellbore stability, formation stress, and optimize oil and gas production. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, this application provides a method and device for ocean drilling wellbore acoustic velocity imaging based on multi-scale tomography, which combines the multi-scale tomography method for wellbore velocity imaging. The multi-scale tomography method is known for its stability and high precision in complex geophysical structures, but it is currently mainly applied to surface seismic research. The present invention innovatively applies the multi-scale tomography method to the wellbore environment of ocean drilling. By combining numerical analysis, the effectiveness of this method in imaging inversion is explored, providing valuable reference value for wellbore imaging.

[0006] In a first aspect, an embodiment of this application provides a method for ocean drilling wellbore acoustic velocity imaging based on multi-scale tomography, including:

[0007] Obtain acoustic logging data and well diameter curves;

[0008] Extract the velocity or slowness from the acoustic logging data, and construct a velocity model around the wellbore in combination with the well diameter curve as the initial inversion model;

[0009] Extract the travel time from the acoustic logging data;

[0010] Invert the initial inversion model using the multi-scale tomography method to obtain a velocity imaging profile around the wellbore.

[0011] In a possible implementation, the acoustic logging data includes a slowness curve and a travel time curve.

[0012] In a possible implementation, the step of inverting the initial inversion model using the multi-scale tomography method to obtain a velocity imaging profile around the wellbore includes:

[0013] Decompose the initial inversion model into sub-models of multiple different scales;

[0014] Invert the sub-models of multiple different scales simultaneously;

[0015] Superimpose the inversion results of all sub-models to obtain a velocity imaging profile around the wellbore.

[0016] In a possible implementation, the calculation formula for inverting the sub-models of multiple different scales is:

[0017] ,

[0018] where, represents the velocity perturbation of the k th scale sub-model; represents the background velocity of the k th scale sub-model; represents the ray path length of the k th scale sub-model; J represents the total number of grids of the k th scale sub-model; represents the first arrival time at the k th grid of the j th scale sub-model; represents the theoretical arrival time at the k th grid of the j th scale sub-model.

[0019] In a possible implementation, the calculation formula for the ray path length k of the th scale sub-model is:

[0020] ,

[0021] Among them, J represents the total number of grids of the sub-model at the k th scale; I represents the total number of acoustic wave rays in the k th grid in the sub-model at the j th scale; represents the path length of the k th acoustic wave ray in the j th grid in the sub-model at the i th scale.

[0022] In a possible implementation, the calculation formula for superimposing the inversion results of all sub-models is:

[0023] ,

[0024] Among them, represents the velocity perturbation; K represents the total number of sub-models; represents the weighting factor; represents the velocity perturbation of the sub-model at the k th scale.

[0025] In a possible implementation, the calculation formula for the weighting factor is:

[0026] ,

[0027] Among them, K represents the total number of sub-models.

[0028] In a second aspect, the embodiments of the present application provide an ocean drilling wellbore acoustic velocity imaging device based on multi-scale tomography, including:

[0029] A logging data acquisition module, configured to acquire acoustic logging data and a well diameter curve;

[0030] A model construction module, configured to extract velocity or slowness from the acoustic logging data, and construct a wellbore velocity model in combination with the well diameter curve as an initial inversion model;

[0031] A travel time extraction module, configured to extract travel time from the acoustic logging data;

[0032] An inversion module, configured to invert the initial inversion model by using a multi-scale tomography method to obtain a wellbore velocity imaging profile;

[0033] The inversion module includes:

[0034] A model decomposition module, configured to decompose the initial inversion model into multiple sub-models of different scales;

[0035] A sub - model inversion module, configured to invert multiple sub - models with different scales simultaneously;

[0036] An inversion superposition module, configured to superpose the inversion results of all sub - models to obtain a velocity imaging profile around the wellbore.

[0037] In a third aspect, an embodiment of the present application provides an electronic device, including:

[0038] A processor;

[0039] A memory;

[0040] And a computer program, where the computer program is stored in the memory, and the computer program includes instructions that, when executed by the processor, cause the electronic device to execute the method according to any one of the first aspect.

[0041] In a fourth aspect, an embodiment of the present application provides a computer - readable storage medium, where the computer - readable storage medium includes a stored program, and when the program runs, it controls the device where the computer - readable storage medium is located to execute the method according to any one of the first aspect.

[0042] Based on the above - mentioned invention content, compared with the prior art, the present invention first applies the multi - scale tomography method to the acoustic velocity imaging around the ocean - drilling wellbore, quickly inverts the velocity perturbation using the background velocity and path length, realizes fast imaging of small - scale velocity anomalies around the wellbore (such as perforations, fractures, fluid pockets, cement - bonding defects outside the casing), overcomes the situation of low resolution between the sound source and the receiver in the traditional imaging method, does not require complex inversion, directly calculates, has high real - time performance, and effectively improves the imaging accuracy, providing a new idea for optimizing logging technology, improving subsurface imaging, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0044] Figure 1 It is a schematic flowchart of the ocean - drilling wellbore acoustic velocity imaging method based on multi - scale tomography provided by the embodiment of the present application;

[0045] Figure 2 It is an effect diagram of processing and interpreting the on - site logging data of a perforated wellbore by the ocean - drilling wellbore acoustic velocity imaging method based on multi - scale tomography provided by the embodiment of the present application;

[0046] Figure 3 It is a structural block diagram of the ocean drilling wellbore acoustic velocity imaging device based on multi-scale tomography provided by the embodiment of the present application;

[0047] Figure 4 It is a schematic structural diagram of an electronic device provided by the embodiment of the present application. Specific embodiments

[0048] To better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0049] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0050] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0051] It should be understood that the term " / and / " used herein is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0052] Aiming at the defects of low accuracy and slow speed of the existing wellbore velocity imaging method, the present invention proposes an ocean drilling wellbore acoustic velocity imaging method and device based on multi-scale tomography, and analyzes it with the velocity profiles before and after perforation as an example, proving the reliability of the method. The borehole diameter information can be obtained by other logging methods, which provides constraints for the wellbore conditions in the acoustic velocity inversion process, so that the inversion process mainly focuses on the velocity imaging outside the wellbore. Numerical simulation and field experimental results show that the ocean drilling wellbore acoustic velocity imaging method based on multi-scale tomography disclosed by the present invention has high accuracy in matching the penetration depth and application potential in the fields of unconventional oil and gas, hydrogen, geothermal energy development and carbon dioxide sequestration.

[0053] See Figure 1 , which is a schematic flow chart of the ocean drilling wellbore acoustic velocity imaging method based on multi-scale tomography provided by the embodiment of the present application. As Figure 1 shown, it mainly includes the following steps.

[0054] Step S1, obtain acoustic logging data and borehole diameter curve.

[0055] The acoustic logging data includes slowness curve, travel time curve, etc.

[0056] The travel time curve is obtained by the shortest path method using Fermat's principle.

[0057] Step S2, perform velocity extraction or slowness extraction on the acoustic logging data, and construct a borehole wall velocity model in combination with the borehole diameter curve as the initial inversion model.

[0058] Step S3, perform travel time extraction on the acoustic logging data.

[0059] Step S4, use the multi-scale tomography method to invert the initial inversion model to obtain a borehole wall velocity imaging profile. Specifically:

[0060] Step S41, decompose the initial inversion model into multiple sub-models of different scales.

[0061] Step S42, simultaneously invert multiple sub-models of different scales.

[0062] The inversion calculation formula is:

[0063] ,

[0064] where, represents the velocity perturbation of the k th scale sub-model; represents the background velocity of the k th scale sub-model, in the embodiment of the present application comes from the ray average velocity of the k th scale sub-model; represents the ray path length of the k th scale sub-model; J represents the total number of grids of the k th scale sub-model; represents the first arrival time in the k th grid of the j th scale sub-model, represents the theoretical arrival time in the k th grid of the j th scale sub-model. In the present application, by combining the background velocity with the path length to invert the velocity perturbation, fast imaging of small-scale velocity anomalies around the borehole (such as perforations, fractures, fluid pockets, cement bonding defects outside the casing) is realized, without complex inversion, direct calculation, and high real-time performance.

[0065] Thek The ray path length of the sub-model at a certain scale The calculation formula is as follows:

[0066] ,

[0067] Wherein, J represents the total number of grids of the sub-model at the k th scale; I represents the total number of acoustic wave rays in the k th grid of the sub-model at the j th scale; represents the path length of the k th acoustic wave ray in the j th grid of the sub-model at the i th scale.

[0068] Step S23: Superimpose the inversion results of all sub-models to obtain the velocity imaging profile around the well.

[0069] The calculation formula for superimposing the inversion results of all sub-models is as follows:

[0070] ,

[0071] Wherein, represents the velocity perturbation; K represents the total number of sub-models; represents the weighting factor; represents the velocity perturbation of the sub-model at the k th scale.

[0072] The weighting factor The calculation formula is as follows:

[0073] ,

[0074] Wherein, K represents the total number of sub-models.

[0075] Taking the in-situ logging data of the perforated wellbore as an example, the method disclosed in the embodiments of the present application is used for acoustic velocity imaging around the well to prove the reliability of the method described in the present application.

[0076] See Figure 2 , which is the effect diagram of processing and interpreting the in-situ logging data of the perforated wellbore by the ocean drilling wellbore acoustic velocity imaging method based on multi-scale tomography provided by the embodiments of the present application. Figure 2The logging data of a perforated wellbore with a depth of 20 meters is shown, and the perforation depths vary from X148.5 to X158.5 (10 meters). Panel 1 and Panel 2 respectively show the gamma ray (GR) and slowness curves before and after perforation. The slowness curves before and after perforation in Panel 2 are nearly overlapping. The slowness curve before perforation is black, and the slowness curve after perforation is red, indicating that the perforation effect is mainly limited to the vicinity of the wellbore, and the change in the far-field properties is very small. Panel 3 shows the P-wave travel-time curve using 8 receivers. It can be seen from Panel 3 that there is a significant delay after perforation in the target interval.

[0077] Taking the acoustic logging data before and after perforation as the initial inversion model, the initial inversion model includes 385 grids in the depth direction and 131 grids in the radial direction, and the grid sizes are 0.0508m and 0.01m respectively. Using the method for ocean drilling wellbore circumferential sound velocity imaging based on multi-scale tomography provided by the embodiments of the present application for inversion, the model is divided into 131 sub-models to facilitate fine-scale analysis of the velocity change. Panel 4 and Panel 5 respectively show the velocity profiles before and after perforation. The standard deviations of the initial inversion model are 18.53µs and 18.32µs respectively, and are reduced to 1.32µs and 1.63µs respectively after iteration. The overall velocity change is not large, but the velocity change in a specific depth interval is obvious, which reflects the low-scale change in the formation properties after perforation. Panel 6 shows the velocity change in a specific depth interval before and after perforation. It can be seen from Panel 6 that the perforation spacing is significantly reduced, especially at X150, X151, X152, X155.8 and X157 meters, and the influence at X157 meters is the largest. The estimated penetration depth is about 17 cm, but due to limited receivers, the actual depth may be larger. This shows the ability of the method proposed by the embodiments of the present application to solve the velocity change caused by perforation.

[0078] To further illustrate the reliability of the processing results of the method proposed by the embodiments of the present application, Panel 7 shows the average time delay before and after perforation (the area to the left of the dashed line in Panel 7, from left to right) and the perforation penetration depth estimated according to the time delay (the area to the right of the dashed line in Panel 7, from right to left). It can be seen from Panel 7 that the maximum perforation depth is 19 cm, which is in good agreement with the inversion result of the method proposed by the embodiments of the present application, confirming the reliability of the method proposed by the embodiments of the present application. However, it should be noted that the deviation between the depth estimation area and the actual perforation area is about 1.5 meters, and this deviation is mainly caused by the influence of the size of the transceiver device on the time delay. Although the depth deviation is relatively small, this reminds those skilled in the art to carefully consider the design parameters of the instrument when evaluating the perforation area.

[0079] Corresponding to the above embodiments, the present application also provides an ocean drilling wellbore circumferential sound velocity imaging device based on multi-scale tomography.

[0080] SeeFigure 3 , which is a structural block diagram of the ocean drilling borehole acoustic velocity imaging device based on multi-scale tomography provided by the embodiment of the present application. As Figure 3 shown, it mainly includes the following modules.

[0081] The logging data acquisition module is used to acquire acoustic logging data and borehole diameter curves;

[0082] The model construction module is used to extract velocity or slowness from the acoustic logging data, and construct a borehole velocity model in combination with the borehole diameter curve as the initial inversion model;

[0083] The travel time extraction module is used to extract travel time from the acoustic logging data;

[0084] The inversion module is used to invert the initial inversion model by using the multi-scale tomography method to obtain a borehole velocity imaging profile.

[0085] The inversion module further includes:

[0086] The model decomposition module is used to decompose the initial inversion model into multiple sub-models of different scales.

[0087] The sub-model inversion module is used to invert multiple sub-models of different scales simultaneously.

[0088] The inversion superposition module is used to superpose the inversion results of all sub-models to obtain a borehole velocity imaging profile.

[0089] It should be noted that the specific content involved in the embodiment of the present application can be referred to the description of the above method embodiment. For the sake of brevity of expression, it will not be repeated here.

[0090] Corresponding to the above embodiment, the embodiment of the present application also provides an electronic device.

[0091] See Figure 4 , which is a structural schematic diagram of an electronic device provided by the embodiment of the present application. As Figure 4 shown, the electronic device 400 may include: a processor 401, a memory 402, and a communication unit 403. These components communicate through one or more buses. Those skilled in the art can understand that the structure of the electronic device shown in the figure does not constitute a limitation on the embodiment of the present application. It can be a bus structure, a star structure, and may also include more or fewer components than shown in the figure, or combine certain components, or different component arrangements.

[0092] Among them, the communication unit 403 is used to establish a communication channel so that the electronic device can communicate with other devices.

[0093] The processor 401 is the control center of the electronic device. It connects various parts of the entire electronic device through various interfaces and circuits. By running or executing software programs and / or modules stored in the memory 402, and by invoking the data stored in the memory, it executes various functions of the electronic device and / or processes data. The processor may be composed of an integrated circuit (IC). For example, it may be composed of a single packaged IC, or may be composed of multiple packaged ICs with the same or different functions connected together. For example, the processor 401 may include only a central processing unit (CPU). In the embodiments of the present application, the CPU may be a single-core processor or may include multiple cores.

[0094] The memory 402 is used to store the execution instructions of the processor 401. The memory 402 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, a magnetic disk, or an optical disc.

[0095] When the execution instructions in the memory 402 are executed by the processor 401, the electronic device 400 is enabled to execute some or all of the steps in the above method embodiments.

[0096] Corresponding to the above embodiments, the embodiments of the present application further provide a computer-readable storage medium. The computer-readable storage medium may store a program. When the program runs, it can control the device where the computer-readable storage medium is located to execute some or all of the steps in the above method embodiments. Specifically, the computer-readable storage medium may be a magnetic disk, an optical disc, a read-only memory (ROM), or a random access memory (RAM), etc.

[0097] Corresponding to the above embodiments, the embodiments of the present application further provide a computer program product. The computer program product contains executable instructions. When the executable instructions are executed on a computer, the computer is enabled to execute some or all of the steps in the above method embodiments.

[0098] In the embodiments of the present application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the relationship between associated objects and indicates that three relationships may exist. For example, A and / or B may represent the cases of A existing alone, A and B existing simultaneously, and B existing alone. Here, A and B may be singular or plural. The character " / " generally indicates an "or" relationship between the associated objects before and after. "At least one of the following" and its similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c may represent: a, b, c, a - b, a - c, b - c, or a - b - c, where a, b, and c may be single or multiple.

[0099] Those of ordinary skill in the art can realize that the various units and algorithm steps described in the embodiments disclosed herein can be implemented by a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered to exceed the scope of the present application.

[0100] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0101] In several embodiments provided by the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM for short), random access memory (RAM for short), magnetic disks, or optical discs that can store program codes.

[0102] The above is only the specific implementation manner of the present application. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application and should be covered by the protection scope of the present application. The protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography, characterized in that: include: Obtain sonic logging data and wellbore curves; Extracting velocity or slowness from the acoustic logging data, and building a wellbore velocity model in combination with the wellbore curve as an initial inversion model; Extracting travel time from the sonic logging data; The initial inversion model is inverted using a multi-scale tomography method to obtain a wellbore velocity imaging section.

2. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 1, characterized in that: The sonic logging data include a slowness curve and a travel time curve.

3. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 1, characterized in that: The method of inverting the initial inversion model by using a multi-scale tomography method to obtain a wellbore velocity imaging profile includes: Decomposing the initial inversion model into a plurality of sub-models of different scales; Invert multiple sub-models of different scales simultaneously; The inversion results of all sub-models are superimposed to obtain the wellbore velocity imaging profile.

4. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 3, characterized in that: The calculation formula for inversion of multiple sub-models of different scales is: ， in, Indicates k The velocity perturbation of the sub-model at each scale; Indicates k The background velocity of the sub-model at each scale; Indicates k The ray path length of the sub-model at each scale; J Indicates k The total number of grids in the sub-model of each scale; Indicates k The sub-model of the scale j The first arrival time in the grid; Indicates k The sub-model of the scale j The theory in the grid arrives.

5. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 4, characterized in that: No. k The ray path length of the submodel at each scale The calculation formula is: ， in, J Indicates k The total number of grids in the sub-model of each scale; I Indicates k In the sub-model of the scale j The total number of sound rays in a grid; Indicates k In the sub-model of the scale j In the grid i The path length of a sound wave ray.

6. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 3, characterized in that: The calculation formula for superimposing the inversion results of all sub-models is: ， in, represents the velocity disturbance; K Indicates the total number of sub-models; represents the weighting factor; Indicates k The velocity perturbation of the sub-model at each scale.

7. The method for imaging the acoustic velocity of ocean drilling wells based on multi-scale tomography according to claim 6, characterized in that: Weighting Factor The calculation formula is: ， in, K Indicates the total number of submodels.

8. An ocean drilling well perimeter sonic velocity imaging device based on multi-scale tomography, characterized in that: include: Well logging data acquisition module, used to obtain acoustic well logging data and well diameter curve; A model building module, used for extracting velocity or slowness from the acoustic logging data, and building a wellbore velocity model in combination with the wellbore curve as an initial inversion model; A travel time extraction module, used for extracting travel time from the acoustic logging data; An inversion module, used to invert the initial inversion model using a multi-scale tomography method to obtain a wellbore velocity imaging profile; The inversion module comprises: A model decomposition module, used for decomposing the initial inversion model into a plurality of sub-models of different scales; Sub-model inversion module, used to invert multiple sub-models of different scales simultaneously; The inversion stacking module is used to stack the inversion results of all sub-models to obtain the wellbore velocity imaging profile.

9. An electronic device, characterized in that: include: processor; Memory; And a computer program, wherein the computer program is stored in the memory, and the computer program includes instructions, and when the instructions are executed by the processor, the electronic device executes the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method according to any one of claims 1 to 7.

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