Light cement well cementation formation wave signal processing method and system based on sound wave variable density logging

Abstract

The invention discloses a light cement well cementation formation wave signal processing method and system based on sound wave variable density logging, and the method comprises the steps: carrying out the logging based on a sound wave variable density cement cementing instrument, and obtaining CBL / VDL logging data; according to the well body structure, a light cement well cementation well section is determined; fourier transform is carried out on the 5-foot full wave train of the light cement well cementation well section, and a frequency domain waveform is obtained; filtering the transformed frequency domain waveform frequency spectrum to filter casing wave components; and performing Fourier inversion on the filtered frequency spectrum to obtain a time domain waveform, and performing variable density processing on a time domain wave train after Fourier inversion to obtain a processed CBL / VDL evaluation graph. According to the method, the problem of accurate evaluation of the light cement well cementation quality is solved, and well logging engineering information capable of truly reflecting the light cement well cementation quality is ensured to be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of geophysical logging engineering, and relates to a method and system for processing formation wave signals of lightweight cementing in well cementing based on acoustic variable density logging. Background Technique

[0002] The quality of well cementing is the key to making full use of oil wells, and the evaluation of well cementing quality is the key to correctly using oil wells and taking measures to protect oil wells. Cement bond logging technology represented by CBL / VDL has become a basic method and means for detecting and evaluating well cementing quality for many years, and has played an important role in the production of detecting the cement bond quality of cased wells.

[0003] When well cementing in oil fields, high-density cement with a density of 1.9 g / cm 3 is usually used. However, in actual well cementing, due to the existence of low-pressure and easily lost formations, lightweight cement slurry cementing technology is widely used. Lightweight cementing is to reduce the annular liquid column pressure during cement injection by applying lightweight cement slurry, ensure that the cement slurry returns to the designed well depth, protect the oil and gas layers, and thus reduce the pollution of the reservoir by the cement slurry. However, due to the addition of lightening agents in the lightweight cement slurry, the original acoustic properties of the cement slurry and cement stone are changed, resulting in the inability of acoustic amplitude logging to accurately evaluate its cementing quality. In view of this situation, there has been research on the correction of the 3-foot amplitude method in the past, but the correction method for the 5-foot full wave train is missing, resulting in the inability of the 5-foot full wave train logging curve to truly reflect the actual cementing quality status. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the prior art that due to the addition of lightening agents in the lightweight cement slurry, the original acoustic properties of the cement slurry and cement stone are changed, resulting in the inability of acoustic amplitude logging to accurately evaluate its cementing quality; and the correction method for the 5-foot full wave train is missing, resulting in the inability of the 5-foot full wave train logging curve to truly reflect the actual cementing quality status, and to provide a method and system for processing formation wave signals of lightweight cementing in well cementing based on acoustic variable density logging.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for processing formation wave signals of lightweight cementing in well cementing based on acoustic variable density logging includes:

[0007] Logging with an acoustic variable density cement bond logging tool to obtain CBL / VDL logging data;

[0008] Determine the lightweight cementing well section according to the wellbore structure;

[0009] Perform Fourier transform on the 5-foot full wave train of the lightweight cementing well section to obtain the frequency domain waveform;

[0010] Filter the spectrum of the transformed frequency-domain waveform to filter out the casing wave component;

[0011] Perform an inverse Fourier transform on the filtered spectrum to obtain a time-domain waveform, and perform variable density processing on the time-domain wave train after the inverse Fourier transform to obtain a processed CBL / VDL evaluation graph.

[0012] A further improvement of the present invention lies in:

[0013] Further, determine the light cement cementing section according to the wellbore structure, specifically: based on the wellbore structure parameters on the actual construction sheet of the construction unit, determine the light cement cementing section.

[0014] Further, perform a Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain a frequency-domain waveform, specifically: assume a finite-length waveform data sequence x(n), n = 0, 1, 2,..., N - 1, and its discrete Fourier transform is

[0015]

[0016] Further, filter the spectrum of the transformed frequency-domain waveform to filter out the casing wave component, specifically: set a filter window in the frequency domain range to filter out the main components of the casing wave signal; the filter window is 20KHz - 25KHz.

[0017] Further, perform an inverse Fourier transform on the filtered spectrum, specifically:

[0018]

[0019] Further, the time-domain form of the acoustic logging signal X(k) includes a rectangular coordinate representation form in the complex plane and a polar coordinate representation form in the complex plane; the rectangular coordinate representation form in the complex plane includes a real part and an imaginary part, specifically:

[0020] X(k) = X R (k) + jX I (k) (3)

[0021] The polar coordinate representation form in the complex plane includes amplitude and phase, specifically:

[0022]

[0023] Among them, the amplitude X(k) is called the amplitude spectrum of the sequence x(n), and the phase is called the phase spectrum of the sequence x(n); the amplitude spectrum and the phase spectrum are respectively:

[0024]

[0025]

[0026] Further, perform variable density processing on the time-domain wave train after inverse Fourier transform, specifically: take the positive half-cycle of the full wave train of the time-domain wave train, and display it according to different gray levels according to the amplitude size.

[0027] A light cement cementing formation wave signal processing system based on acoustic variable density logging includes:

[0028] An acquisition module, which performs logging based on an acoustic variable density cement bond logging tool to acquire CBL / VDL logging data;

[0029] A determination module, which determines the light cement cementing interval according to the wellbore structure;

[0030] A Fourier transform module, which performs Fourier transform on the 5-foot full wave train of the light cement cementing interval to obtain a frequency-domain waveform;

[0031] A filtering processing module, which filters the spectrum of the transformed frequency-domain waveform to filter out the casing wave component;

[0032] An inverse Fourier transform module, which performs inverse Fourier transform on the filtered spectrum to obtain a time-domain waveform, and performs variable density processing on the time-domain wave train after inverse Fourier transform to obtain a processed CBL / VDL evaluation map.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention performs Fourier transform on the 5-foot full wave train data, converts it into frequency-domain data, then filters the casing wave frequency band in the transformed spectrum to filter out the casing wave component of 20 - 25 KHz, performs inverse Fourier transform on the filtered data, converts it into a time-domain waveform, so that the formation wave in the processed full wave train data is less affected by the casing wave, performs variable density processing on it, and obtains a variable density map. The present invention solves the problem of accurately evaluating the quality of light cement cementing, and ensures that logging engineering information that can truly reflect the quality of light cement cementing is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0036] Figure 1Schematic flow chart of the method for processing formation wave signals of lightweight cementing based on acoustic variable density logging according to the present invention;

[0037] Figure 2 Schematic structural diagram of the system for processing formation wave signals of lightweight cementing based on acoustic variable density logging according to the present invention;

[0038] Figure 3 Schematic diagram of theoretical simulation of cement bonding with different densities;

[0039] Figure 4 (a) Schematic diagram of time-domain simulation of 3ft full waveform and 5ft full waveform in the case of a free casing;

[0040] Figure 4 (b) Schematic diagram of frequency-domain numerical simulation of 3ft full waveform and 5ft full waveform in the case of a free casing;

[0041] Figure 5 (a) Schematic diagram of time-domain waveform simulation of 3ft full waveform and 5ft full waveform in the case of lightweight cement;

[0042] Figure 5 (b) Schematic diagram of domain waveform simulation of 3ft full waveform and 5ft full waveform in the case of lightweight cement;

[0043] Figure 6 (a) Schematic diagram of time-domain waveform simulation of 3ft full waveform and 5ft full waveform after correction;

[0044] Figure 6 (b) Schematic diagram of frequency-domain waveform simulation of 3ft full waveform and 5ft full waveform after correction;

[0045] Figure 7 (a) Measured diagram of CBL / VDL for lightweight cementing and cementing;

[0046] Figure 7 (b) Evaluation diagram of CBL / VDL after variable density processing. Specific embodiments

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0048] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0049] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0050] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0051] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0052] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] The present invention will be further described in detail below with reference to the accompanying drawings:

[0054] See Figure 1 , the present invention discloses a method for processing formation wave signals of light - weight cementing based on acoustic variable - density logging, including:

[0055] S101, perform logging based on an acoustic variable - density cement bond logging tool to obtain CBL / VDL logging data.

[0056] S102, determine the light - weight cementing interval according to the wellbore structure.

[0057] Determine the light - weight cement cementing interval based on the wellbore structure parameters on the actual construction sheet of the construction unit.

[0058] S103. Perform Fourier transform on the 5 - foot full - wave train of the light - weight cement cementing interval to obtain the waveform in the frequency domain.

[0059] Let the finite - length waveform data sequence be x(n), where n = 0, 1, 2, …, N - 1, and its discrete Fourier transform is

[0060]

[0061] S104. Filter the spectrum of the transformed waveform in the frequency domain to filter out the casing wave component.

[0062] Set a filter window in the frequency domain range to filter out the main components of the casing wave signal; the filter window is 20KHz - 25KHz.

[0063] S105. Perform inverse Fourier transform on the filtered spectrum to obtain the waveform in the time domain, and perform variable - density processing on the time - domain wave train after inverse Fourier transform to obtain the processed CBL / VDL evaluation diagram.

[0064] Performing inverse Fourier transform on the filtered spectrum specifically is:

[0065]

[0066] The time - domain form of the acoustic logging signal X(k) includes the rectangular - coordinate representation form in the complex plane and the polar - coordinate representation form in the complex plane; the rectangular - coordinate representation form in the complex plane includes a real part and an imaginary part, specifically:

[0067] X(k)=X R (k)+jX I (k)(3)

[0068] The polar - coordinate representation form in the complex plane includes amplitude and phase, specifically:

[0069]

[0070] Among them, the amplitude |X(k)| is called the amplitude spectrum of the sequence x(n), and the phase is called the phase spectrum of the sequence x(n); the amplitude spectrum and the phase spectrum are respectively:

[0071]

[0072]

[0073] Perform variable density processing on the time-domain wave train after inverse Fourier transform, specifically: take the positive half-cycle of the entire wave train of the time-domain wave train and display it according to different gray levels according to the amplitude size.

[0074] See Figure 2 , the present invention discloses a light cement cementing formation wave signal processing system based on acoustic variable density logging, including:

[0075] An acquisition module, which performs logging based on an acoustic variable density cement bond logging tool to acquire CBL / VDL logging data;

[0076] A determination module, which determines the light cement cementing section according to the wellbore structure;

[0077] A Fourier transform module, which performs Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain a frequency-domain waveform;

[0078] A filtering processing module, which performs filtering processing on the spectrum of the transformed frequency-domain waveform to filter out the casing wave component;

[0079] An inverse Fourier transform module, which performs inverse Fourier transform on the filtered spectrum to obtain a time-domain waveform, and performs variable density processing on the time-domain wave train after inverse Fourier transform to obtain a processed CBL / VDL evaluation diagram.

[0080] Embodiment:

[0081] See Figures 3 to 7 (b), the present invention discloses a light cement cementing formation wave signal processing method based on acoustic variable density logging, including the following steps:

[0082] Step 1: Perform logging with an acoustic variable density cement bond logging tool to obtain CBL / VDL logging data;

[0083] Step 2: Determine the light cement cementing section according to the wellbore structure parameters;

[0084] Step 3: Perform Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain a frequency-domain waveform;

[0085] Step 4: Perform filtering processing on the transformed spectrum to filter out the casing wave component of 20 - 25 KHz;

[0086] Step 5: Perform inverse Fourier transform on the filtered spectrum, and perform variable density processing and display on the wave train after inverse transform to finally obtain a processed CBL / VDL evaluation diagram.

[0087] As Figure 3 shown, Figure 3From top to bottom, they respectively represent the CBL / VDL responses under the conditions of cement density of 1.4 g / cm 3 , 1.7 g / cm 3 and 1.9 g / cm 3 . It can be seen from Figure 3 that in the case of complete cementation, the lower the density of the cementing cement, the greater the amplitude of the casing wave, which masks the formation wave information and affects the accuracy of the evaluation of the cementing quality of the second interface.

[0088] As Figure 4 (a) and Figure 4 (b) show, in the case of free casing, since there is no cementation between the casing and the formation at all, it is shown in the time-domain waveform that the amplitude of the casing wave is the strongest and the formation wave signal is invisible; the time-domain signal is Fourier-transformed to obtain the frequency-domain waveform, and the frequency band of the casing wave is located concentratedly at 20 - 25 KHz.

[0089] As Figure 5 (a) and Figure 5 (b) show, since lightening agents are often added to light cement to reduce the cement density, the acoustic coupling ability of light cement is poorer than that of conventional density cement. In the time-domain waveform, it often shows that in the case of high-quality cementation, the numerical simulation shows that the amplitude of the casing wave is larger and the formation wave signal is masked by the casing wave.

[0090] As Figure 6 (a) and Figure 6 (b) show, the casing wave signal is well processed and shows a good cementation state in the time-domain waveform, that is, the amplitude of the casing wave is a small value and the amplitude of the formation wave is obvious, which can truly reflect the cementation situation of the cement.

[0091] It can be seen from Figure 7 (a) that due to using light cement for cementing, the measured value of the amplitude of the casing wave is relatively large, and the calculated bonding index BI values are all below 0.8. In the variable density diagram, the formation wave is relatively seriously masked by the casing wave. If evaluated according to the conventional cementing quality, there is no well section with good cementation. By performing Fourier transform on the 5-foot full wave train data of the present invention, converting it into frequency-domain data, then filtering the frequency band of the casing wave in the transformed spectrum, filtering out the casing wave component of 20 - 25 KHz, performing inverse Fourier transform on the filtered data, converting it into a time-domain waveform, the formation wave in the processed full wave train data obtained in this way is less affected by the casing wave. Performing variable density processing on it to obtain a variable density diagram. As Figure 7 (b) shows, it can be seen from the variable density diagram that after being processed by the present invention, part of the information of the casing wave is basically filtered out, and the formation wave information can be used to more intuitively judge the cementing quality of the second interface.

[0092] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for processing formation wave signals in light cement cementing based on acoustic variable density logging, characterized in that Including: Logging is carried out based on an acoustic variable density cement bond logging tool to obtain CBL / VDL logging data; Determine the light cement cementing section according to the wellbore structure; Perform Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain the frequency-domain waveform; Perform filtering processing on the spectrum of the transformed frequency-domain waveform to filter out the casing wave component; Perform inverse Fourier transform on the filtered spectrum to obtain the time-domain waveform, and perform variable density processing on the time-domain wave train after the inverse Fourier transform to obtain the processed CBL / VDL evaluation diagram.

2. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 1, characterized in that The step of determining the light cement cementing section according to the wellbore structure is specifically: determining the light cement cementing section based on the wellbore structure parameters on the actual construction sheet of the construction unit.

3. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 2, characterized in that The step of performing Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain the frequency-domain waveform is specifically: assuming a finite-length waveform data sequence x(n), n = 0, 1, 2, …, N - 1, and its discrete Fourier transform is 4. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 3, characterized in that The step of performing filtering processing on the spectrum of the transformed frequency-domain waveform to filter out the casing wave component is specifically: setting a filtering window in the frequency domain range to filter out the main components of the casing wave signal; where the filtering window is 20KHz - 25KHz.

5. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 4, characterized in that The step of performing inverse Fourier transform on the filtered spectrum is specifically:

6. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 5, characterized in that The time-domain form of the acoustic logging signal X(k) includes the rectangular coordinate representation form in the complex plane and the polar coordinate representation form in the complex plane; the rectangular coordinate representation form in the complex plane includes a real part and an imaginary part, specifically: X(k) = X R (k) + jX I (k) (3) The polar coordinate representation form in the complex plane includes an amplitude and a phase, specifically: Among them, the amplitude |X(k)| is called the amplitude spectrum of the sequence x(n), and the phase is called the phase spectrum of the sequence x(n); the amplitude spectrum and the phase spectrum are respectively:

7. The method for processing formation wave signals in light cement cementing based on acoustic variable density logging according to claim 6, characterized in that The step of performing variable density processing on the time-domain wave train after the inverse Fourier transform is specifically: taking the positive half cycle of the full wave train of the time-domain wave train and displaying it according to different gray levels according to the amplitude size.

8. A system for processing formation wave signals in light cement cementing based on acoustic variable density logging, characterized in that Including: An acquisition module, which performs logging based on an acoustic variable density cement bond logging tool to obtain CBL / VDL logging data; A determination module, which determines the light cement cementing section according to the wellbore structure; A Fourier transform module, which performs Fourier transform on the 5-foot full wave train of the light cement cementing section to obtain the frequency-domain waveform; A filtering processing module, which performs filtering processing on the spectrum of the transformed frequency-domain waveform to filter out the casing wave component; An inverse Fourier transform module, which performs inverse Fourier transform on the filtered spectrum to obtain the time-domain waveform, and performs variable density processing on the time-domain wave train after the inverse Fourier transform to obtain the processed CBL / VDL evaluation diagram.

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