A hydraulic fracturing fracture monitoring method and device based on Krauklis wave full waveform inversion

Abstract

The application discloses a hydraulic fracturing fracture monitoring method and device based on Krauklis wave full waveform inversion, and comprises the following steps: obtaining a forward data set containing Krauklis wave and an actual data set of Krauklis wave; using full waveform inversion to invert the hydraulic fracturing fracture; periodically using full waveform inversion to image the fracturing fracture and periodically monitoring the hydraulic fracturing fracture. The application fully utilizes the relationship between the waveform characteristics of Krauklis wave, such as propagation along the fluid layer in the fracture, strong amplitude, strong frequency dispersion and low frequency propagation speed, and the fracture geometry, is based on the numerical solution of the elastic wave equation, adopts full wave field information, and thus provides a high-resolution and high-precision fracture fine structure image, so as to serve quantitative fracturing monitoring and fracture effect evaluation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of exploration technology, in particular to a hydraulic fracturing fracture monitoring method and device based on Krauklis wave full waveform inversion. BACKGROUND

[0002] Microseismic monitoring technology is currently the main means of monitoring the hydraulic fracturing process and evaluating the fracturing effect. It takes a series of microseisms formed by shear sliding along the fracture surface during the expansion of the fracturing fracture as the research object, and locates the microseismic source through the microseismic events recorded on the ground or in the well, and describes the development of the fracture through the spatial distribution of the microseismic source. Therefore, this technology is an indirect monitoring method, although it can determine the spatial position of the fracture development, but it is difficult to accurately describe the geometric parameters such as the length, width and height of the fracture. In addition, the recorded microseismic signals are often weak in energy and mixed in noise, and there is a certain difficulty in identifying and picking up the microseismic signals, and the accuracy of identification will directly affect the accuracy of the source location. SUMMARY

[0003] The purpose of the present application is to provide a hydraulic fracturing fracture monitoring method and device based on Krauklis wave full waveform inversion to solve the problems raised in the background technology.

[0004] To achieve the above purpose, the present application provides the following technical scheme:

[0005] A hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion, comprising the following steps:

[0006] S1, obtaining a forward data set containing Krauklis wave and an actual data set of Krauklis wave;

[0007] S2, using full waveform inversion to invert the hydraulic fracturing fracture;

[0008] S3, periodically using full waveform inversion to image the fracturing fracture, and periodically monitoring the hydraulic fracturing fracture.

[0009] Further, obtaining the (difference) forward data set containing Krauklis wave comprises:

[0010] Obtaining forward data u0 using a reference model m0;

[0011] Obtaining forward data u1 using a fracture model m1;

[0012] The forward data set u is the difference between the forward data u0 and the forward data u1.

[0013] Further, using the wellbore before hydraulic fracturing as a reference model m0, numerical simulation is performed to obtain forward data u0, and an initial model m1 containing fractures is constructed to perform numerical simulation to obtain forward data u1.

[0014] Further, the (difference) actual data set containing Krauklis waves includes:

[0015] Actual data d0 is obtained before hydraulic fracturing;

[0016] Actual data d1 is obtained after hydraulic fracturing;

[0017] The difference between the actual data d0 and the actual data d1 is taken as the difference actual data d.

[0018] Further, the actual data d0 of the wellbore is recorded by the observation system before fracturing, and the actual data d1 recorded after fracturing is obtained after fracturing.

[0019] Further, the difference between the actual data d0 obtained before hydraulic fracturing and the actual data d1 obtained after hydraulic fracturing is taken as the difference actual data d.

[0020] Further, the initial model m1 is updated by using a multi-scale full waveform inversion strategy based on envelope calculation and wavelet transform until the error of full waveform inversion is less than a certain threshold or no longer increases, and the final fracture model m is obtained.

[0021] To achieve the above object, the present application further provides the following technical scheme:

[0022] A hydraulic fracturing fracture monitoring device based on Krauklis wave full waveform inversion, characterized in that it comprises:

[0023] An acquisition module for acquiring a forward data set containing Krauklis waves and an actual data set of Krauklis waves;

[0024] An inversion module for inverting hydraulic fracturing fractures by using full waveform inversion;

[0025] A monitoring module for periodically imaging the fracturing fractures by using full waveform inversion and periodically monitoring the hydraulic fracturing fractures.

[0026] To achieve the above object, the present application further provides the following technical scheme:

[0027] A computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method according to any one of the above embodiments when executing the computer program.

[0028] To achieve the above object, the present application further provides the following technical scheme:

[0029] A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the method of any one of the preceding claims.

[0030] Compared with the prior art, the present application has the beneficial effects that:

[0031] The relationship between the wave shape characteristics of Krauklis wave, such as propagation along the fluid layer in the fracture, strong amplitude, strong dispersion, and low frequency propagation speed, and the fracture geometry is fully utilized; high-resolution imaging of the fine structure of the fracture is performed in the theoretical framework of full waveform inversion of the elastic wave field; in combination with the non-uniform grid finite difference method, the development of fractures of different scales can be accurately depicted, and the calculation cost can be saved, and the imaging efficiency can be improved; through the design of a double-difference objective function and a multi-scale strategy based on envelope and wavelet decomposition, Krauklis wave full wave data which are most sensitive to changes in the shape and structure of the fracture are inversed in a targeted manner; the algorithm is easy to extend to different inversion objective functions, and is not limited to L2 norm waveform fitting, and thus specific properties in matching data with different signal-to-noise ratios can be realized and applied. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a schematic diagram of the model comparison of the present application before (a) and after (b) hydraulic fracturing.

[0033] Figure 2 It is a schematic diagram of the vertical component of displacement recorded by the well wall, in which (a) is the pre-fracturing record, (b) is the post-fracturing record, and (c) is the result of subtracting the pre-fracturing record from the post-fracturing record.

[0034] Figure 3 It is a synthetic data test based on Krauklis wave hydraulic fracturing fracture monitoring of the present application, in which (a) is the actual structure of the underground before fracturing, (b) is the actual structure of the underground after fracturing, and (c) is the Krauklis wave inversion result based on a double-difference objective function.

[0035] Figure 4 It is a hierarchical flowchart of the method of the present application.

[0036] Figure 5 It is a flowchart of the steps of the hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion of the present application.

[0037] Figure 6 It is a structure block diagram of the hydraulic fracturing fracture monitoring device based on Krauklis wave full waveform inversion of the present application.

[0038] Figure 7 It is an internal structure diagram of the computer equipment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0040] In the description of the present application, it should be noted that the terms "upper end", "lower end", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0041] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "provided with", "provided with", "sleeved", "connected" and the like should be broadly understood, for example, "connected" can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be internal communication of two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0042] Please refer to Figures 1-7 The present application provides a technical solution:

[0043] With the increasing decrease of conventional oil and gas resources and the increasing demand for energy, shale gas has been widely researched and concerned all over the world. Shale gas refers to the unconventional natural gas stored in organic matter-rich shale and interbeds in the form of free state and adsorbed state, and the gas reservoir itself has the characteristics of low porosity and low permeability. Hydraulic fracturing as a main technology in shale gas exploitation can transform shale reservoirs to improve the flow performance of the reservoirs and establish fluid channels between the reservoirs and the wellbore. The post-fracturing effect can be evaluated by parameters such as spatial expansion law, length, width and height of the fracturing cracks, so as to guide the fracturing model correction, sand addition amount determination and sand addition process in the fracturing construction process.

[0044] Krauklis wave is a kind of slow wave that propagates in fluid-filled fractures. Because it is very sensitive to the morphological structure of the fracture and has strong energy, it provides the possibility for its application in hydraulic fracture monitoring. Existing research shows that the geometric morphology of the fracture will directly affect the resonance frequency and attenuation of Krauklis wave and other waveform characteristics, so it can be considered to obtain the fracture morphology from the waveform inversion, so as to provide high-resolution and high-precision fracture fine structure images to serve quantitative fracture monitoring and fracture effect evaluation.

[0045] The Krauklis wave full waveform inversion-based hydraulic fracture monitoring method of the application:

[0046] Based on the direct correlation between the resonance frequency and attenuation of Krauklis wave and the geometric morphology of the fracture, the full waveform inversion method based on Krauklis wave is proposed to quantitatively estimate the spatial distribution and geometric morphology of the fracture generated after hydraulic fracturing. Since the method is based on the numerical solution of the elastic wave equation and uses full wave field information, it is expected to provide high-resolution and high-precision fracture fine structure images to serve quantitative fracture monitoring and fracture effect evaluation.

[0047] Method flow:

[0048] Obtain numerical simulation results:

[0049] Step one: numerical simulation results of the wellbore model without fractures: use the wellbore before hydraulic fracturing as the reference model m0, as shown in Figure 1 (a), perform numerical simulation to obtain forward data u0( Figure 2 (a));

[0050] Reference the structure of the vertical well during actual fracturing, establish the reference model m0 without hydraulic fracturing;

[0051] Step two: construct the initial model m1 containing fractures (as shown in Figure 1 (b)) to perform numerical simulation to obtain forward data u1( Figure 2 b);

[0052] On the basis of the reference model m0, add a fracture model to form the initial model m1 containing fractures;

[0053] u0 and u1 are the particle velocity information recorded by the detector, which are the forward simulation data recorded by using the m0 model and the m1 model respectively;

[0054] Similarly, d0 and d1 are also the particle velocity information recorded by the detector, but they are the actual obtained data;

[0055] Obtain actual data:

[0056] Step three: record the actual data d0 of the wellbore before fracturing by using the observation system;

[0057] Step four: record again after fracturing to obtain the actual data d1 recorded after fracturing;

[0058] Invert the hydraulic fracture by using the full waveform inversion technology:

[0059] Step five: take u0-u1 as the difference forward data u in the full waveform inversion (c) ; and take d0-d1 as the difference actual data d; Figure 2

[0060] Step six: update the initial model m1 by using the multi-scale full waveform inversion strategy based on envelope calculation and wavelet transformation until the error of the full waveform inversion is less than a certain threshold value or no longer increases, and the final fracture model m is obtained.

[0061] After envelope calculation and wavelet transformation are performed on the actual data and the forward data, the two-norm error of the two is calculated, and the gradient of the error is obtained. The gradient optimization method (such as the L-BFGS method) can obtain the model update direction, and combined with the model update step, the model update amount can be obtained, so as to realize the update of the model.

[0062] This threshold value means that the update amount of the new model is less than 1% of the model updated last time.

[0063] Fracture monitoring:

[0064] Step seven: periodically use the full waveform inversion technology to image the fracture, so as to achieve the purpose of periodic monitoring of the hydraulic fracture.

[0065] Wherein, Figure 3 A result figure of our method is shown, wherein Figure 3 (a) is the initial model, Figure 3 (b) is the actual model, Figure 3 (c) is the final inversion result, and it can be seen that the proposed method successfully inverts the hydraulic fracture.

[0066] In the present application:

[0067] 1) fully utilize the relationship between the waveform characteristics of Krauklis wave, such as propagation along the fluid layer in the crack, strong amplitude, strong dispersion, and slow propagation velocity of low frequency, and the crack geometry;

[0068] 2) perform high-resolution imaging of the fine structure of the crack in the theoretical framework of full waveform inversion of the elastic wave field;

[0069] ​3) Combined with non-uniform grid finite difference method, the development of fractures of different scales can be accurately described and the calculation cost can be saved, and the imaging efficiency can be improved;

[0070] Combined with non-uniform grid finite difference method: when discretizing the model, the conventional finite difference method adopts the same grid spacing, which will lead to a very large amount of calculation when describing the fracture. Therefore, we adopt non-uniform grid to discretize the fracture, that is, the grid spacing is small near the fracture and the grid spacing is large in the surrounding area.

[0071] 4) By designing a double-difference objective function and a multi-scale strategy based on envelope and wavelet decomposition, the Krauklis wave full-wave data most sensitive to the change of fracture shape structure is inversed;

[0072] 5) The algorithm is easy to extend to different inversion objective functions, not limited to L2 norm waveform fitting, and further applied to match specific attributes in different signal-to-noise ratio data.

[0073] As shown in Figure 6 , a hydraulic fracturing fracture monitoring device 100 based on Krauklis wave full waveform inversion is provided, comprising:

[0074] An acquisition module 200 is configured to acquire a forward data set containing Krauklis wave and an actual data set of Krauklis wave;

[0075] An inversion module 300 is configured to invert the hydraulic fracturing fracture by using full waveform inversion;

[0076] A monitoring module 400 is configured to periodically image the fracturing fracture by using full waveform inversion, and periodically monitor the hydraulic fracturing fracture.

[0077] The computer equipment provided by the application can be a server, and its internal structure diagram can be as shown in Figure 7 . The computer equipment includes a processor, a memory and a network interface connected through a system bus. The processor of the computer equipment is used to provide computing and control capabilities. The memory of the computer equipment includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer equipment is used to store data. The network interface of the computer equipment is used to communicate with the external terminal through the network connection. The computer program is executed by the processor to implement the above-mentioned optimization method.

[0078] Those skilled in the art can understand, Figure 7The structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0079] The present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps in each method embodiment.

[0080] Meanwhile, a computer program product is provided, which includes a computer program, and the computer program is executed by a processor to implement the steps in each method embodiment.

[0081] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties.

[0082] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0083] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for monitoring hydraulic fracturing fractures based on Krauklis wave full waveform inversion, characterized in that, Includes the following steps: Obtain the forward modeling dataset containing Krauklis waves and the actual dataset of Krauklis waves; Inversion of hydraulic fracturing fractures was performed using full waveform inversion. Periodically use full waveform inversion to image hydraulic fracturing fractures and periodically monitor hydraulic fracturing fractures; Obtaining a forward modeling dataset containing Krauklis waves includes: Obtain forward modeling data u0 using the baseline model m0; Forward modeling data u1 is obtained using crack model m1; The forward dataset u is the difference between the forward data u0 and the forward data u1; The initial model m1 is updated using a multi-scale full waveform inversion strategy based on envelope calculation and wavelet transform until the error of the full waveform inversion is less than a certain threshold or no longer increases, thus obtaining the final crack model m.

2. The hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion as described in claim 1, characterized in that, Using the pre-fracturing wellbore as the baseline model m0, numerical simulation was performed to obtain forward modeling data u0. An initial model m1 containing fractures was then constructed for numerical simulation to obtain forward modeling data u1.

3. The hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion as described in claim 1, characterized in that, Obtaining the actual dataset containing Krauklis waves includes: Acquire actual data d0 before hydraulic fracturing; Obtain actual data d1 after hydraulic fracturing; The difference between the actual data d0 and the actual data d1 is taken as the difference actual data d.

4. The hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion as described in claim 3, characterized in that, Before fracturing, the actual data d0 of the wellbore is recorded using an observation system. After fracturing, the data is recorded again to obtain the actual data d1 recorded after fracturing.

5. The hydraulic fracturing fracture monitoring method based on Krauklis wave full waveform inversion as described in claim 1, characterized in that, The difference between the actual data d0 obtained before hydraulic fracturing and the actual data d1 obtained after hydraulic fracturing is taken as the difference actual data d.

6. A hydraulic fracturing fracture monitoring device based on Krauklis wave full waveform inversion, characterized in that, include: The acquisition module is used to acquire forward modeling datasets containing Krauklis waves and actual datasets containing Krauklis waves; The inversion module is used to invert hydraulic fracturing fractures using full waveform inversion. The monitoring module is used to periodically image the hydraulic fracturing fractures using full waveform inversion, and to periodically monitor the hydraulic fracturing fractures. Obtaining a forward modeling dataset containing Krauklis waves includes: Obtain forward modeling data u0 using the baseline model m0; Forward modeling data u1 is obtained using crack model m1; The forward dataset u is the difference between the forward data u0 and the forward data u1; The initial model m1 is updated using a multi-scale full waveform inversion strategy based on envelope calculation and wavelet transform until the error of the full waveform inversion is less than a certain threshold or no longer increases, thus obtaining the final crack model m.

7. A computer device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, It stores a computer program thereon, which, when executed by a processor, implements the steps of the method as described in any one of claims 1 to 5.

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