Time-lapse seismic energy difference calculation method based on oil and gas sensitive frequency band

Abstract

This invention relates to the field of seismic exploration and development technology for oil and gas, specifically to a method for calculating time-lapse seismic energy differences based on oil and gas sensitive frequency bands. By identifying sensitive frequency bands in the baseline and monitoring earthquakes where amplitude anomalies occur due to oil and gas extraction, new sensitive frequency band seismic bodies are extracted, obtaining the sensitive frequency band amplitude and frequency of two periods of seismic data. Based on the sensitive frequency band amplitude and frequency of the two periods of data, the energy difference of the sensitive frequency band in time-lapse seismic data is calculated. This method improves the interpretability of time-lapse seismic data and can better represent the differential response patterns of time-lapse seismic data caused by oil-water displacement. Even under conditions of poor repeatability of time-lapse seismic data, it can effectively guide the prediction of remaining oil and gas.

Description

Technical Field

[0001] This invention relates to the field of seismic exploration and development technology for oil and gas, and in particular to a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands, which falls within the application scope of geophysical methods in four-dimensional seismic reservoir monitoring. Background Technology

[0002] Most domestic and international research on time-lapse seismic interpretation techniques is based on analyzing oil-water replacement patterns through amplitude differences in full-band seismic data. Existing methods primarily obtain the amplitude difference of time-lapse seismic events by subtracting the amplitude energy of the baseline seismic event from that of the monitoring seismic event. Current research shows that these methods are effective in high-porosity, high-permeability reservoirs and exploration areas with good seismic repeatability. However, they are less effective in areas with non-repeatable time-lapse seismic events and medium-to-low porosity, low-permeability reservoirs. To address this issue, a method based on calculating the energy difference of time-lapse seismic events in oil and gas sensitive frequency bands is proposed. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention provides a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands. This method yields good results, effectively obtaining time-shifted seismic energy differences even under non-repetitive time-shifted seismic conditions.

[0004] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0005] In a first aspect, in one embodiment of the present invention, a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands is provided, the method comprising the following steps:

[0006] a. Use the earlier acquired seismic data as the basic data and the latest acquired seismic data as the monitoring data; input the basic data and monitoring data respectively, and determine the analysis time window based on the reservoir thickness;

[0007] b. Basic data represents the period before oil and gas extraction, while monitoring data represents the period after oil and gas extraction. In the analysis window, oil-producing wells are selected to conduct spectral characteristic difference analysis of basic data (before oil and gas extraction) and monitoring data (after oil and gas extraction) to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction.

[0008] c. Apply the spectral decomposition method to extract new sensitive frequency band seismic bodies, and obtain the basic earthquakes and monitoring earthquakes in the sensitive frequency bands.

[0009] d. Extract the amplitude A1 and frequency F1 of the basic earthquake in the sensitive frequency band, and extract the amplitude A2 and frequency F2 of the monitored earthquake in the sensitive frequency band.

[0010] e. Based on the amplitude and frequency of the sensitive frequency band in the two data periods, the energy difference of the sensitive frequency band of time-lapsed earthquakes is calculated. The ratio of the amplitude to frequency of the sensitive frequency band in the basic data and the monitoring data are calculated separately, and then the difference in the ratio of the amplitude to frequency of the sensitive frequency band in the two data periods is calculated to further amplify the energy difference of time-lapsed earthquakes.

[0011] f. Based on the calculated energy differences in time-shifted seismic sensitive frequency bands, extract planar properties from oil-bearing strata. Analyze the oil-water replacement patterns based on these planar properties to guide the prediction of remaining oil and gas.

[0012] As a further aspect of the present invention, determining the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction includes:

[0013] Taking advantage of the characteristics of low-frequency energy reduction and high-frequency energy increase after oil and gas extraction, the spectral characteristics of basic data (before oil and gas extraction) and monitoring data (after oil and gas extraction) of oil-producing wells were analyzed to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction.

[0014] As a further aspect of the present invention, a new sensitive frequency band seismic body is extracted using a spectral decomposition method, including:

[0015] Based on the sensitive frequency band, the two earthquakes were subjected to spectral decomposition to obtain the basic earthquake and the monitored earthquake in the sensitive frequency band.

[0016] As a further aspect of the present invention, the amplitudes of two earthquake-sensitive frequency bands are obtained, wherein the amplitudes of the two earthquake-sensitive frequency bands include the basic earthquake-sensitive frequency band amplitude A1 and the monitoring earthquake-sensitive frequency band amplitude A2.

[0017] As a further aspect of the present invention, two earthquake-sensitive frequency bands are obtained, wherein the two earthquake-sensitive frequency bands include: a basic earthquake-sensitive frequency band F1 and a monitoring earthquake-sensitive frequency band F2.

[0018] As a further aspect of the present invention, the energy difference of the time-shifted seismic sensitive frequency band is calculated based on the amplitude and frequency of the sensitive frequency band from two periods of data, including:

[0019] First, the amplitude-to-frequency ratio of the sensitive frequency bands for the two data periods is calculated separately. Then, the difference in the amplitude-to-frequency ratio of the sensitive frequency bands for the two data periods is calculated to obtain the energy difference of the time-shifted earthquake sensitive frequency bands, thereby achieving the purpose of further amplifying the energy difference of time-shifted earthquakes.

[0020] As a further aspect of the present invention, the energy difference of the time-shifted seismic sensitive frequency band is obtained by calculation using the following formula:

[0021]

[0022] In the formula, ΔE represents the energy difference of the time-shifted seismic sensitive frequency band. A1 is the amplitude of the basic seismic sensitive frequency band, A2 is the amplitude of the monitored seismic sensitive frequency band, F1 is the frequency of the basic seismic sensitive frequency band, and F2 is the frequency of the monitored seismic sensitive frequency band.

[0023] The technical solution provided by this invention has the following beneficial effects:

[0024] This invention can significantly amplify time-shifted seismic difference information, providing an effective technical means for interpreting time-shifted earthquakes, especially non-repeating time-shifted earthquakes. By replacing full-band amplitude differences with energy differences in sensitive frequency bands, the consistency rate between seismic difference information and oil and gas production capacity can be improved, enabling a better understanding of the response patterns of time-shifted earthquake differences caused by oil-water replacement. Even under conditions of poor repeatability of time-shifted earthquakes, it can effectively guide the prediction of remaining oil and gas.

[0025] These or other aspects of the invention will become more apparent from the following description of embodiments. It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands, according to an embodiment of the present invention.

[0028] Figure 2 This is a spectrum characteristic difference analysis diagram of the target layer of oil-producing wells with high oil-water replacement rate in the study area of ​​this invention.

[0029] Figure 3 This is a spectrum characteristic difference analysis diagram of the target layer of oil-producing wells with low oil-water replacement rate in the study area of ​​this invention.

[0030] Figure 4 The amplitude of the basic earthquake-sensitive frequency band is A1.

[0031] Figure 5 To monitor the amplitude of the earthquake-sensitive frequency band A2.

[0032] Figure 6 The basic earthquake-sensitive frequency band is F1.

[0033] Figure 7 To monitor the earthquake-sensitive frequency band, frequency F2.

[0034] Figure 8 This is a planar diagram showing the superimposed oil-water replacement rate based on the amplitude difference attributes across the entire frequency band of the main oil layer.

[0035] Figure 9 This is a planar diagram showing the superposition of oil-water displacement rate based on the energy difference attributes of the sensitive frequency band of the main oil layer. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0038] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] The existing technology uses the following formula to calculate the energy difference of time-shifted earthquakes:

[0040] ΔA=A2-A1

[0041] In the formula, ΔA represents the time-shifted seismic energy difference, A1 represents the basic seismic amplitude energy, and A2 represents the monitoring seismic amplitude energy.

[0042] To address the issue that existing technologies are ineffective for non-repetitive time-shifted seismic exploration areas with low to medium porosity and permeability, this invention provides a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands.

[0043] Specifically, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0044] Please see Figure 1 , Figure 1 This is a flowchart of a method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands, provided by an embodiment of the present invention.

[0045] like Figure 1As shown, the earlier acquired seismic data is used as the basic data, and the latest acquired seismic data is used as the monitoring data; the basic data and monitoring data are input separately, and the analysis time window is determined according to the reservoir thickness.

[0046] The basic data represents the period before oil and gas extraction, while the monitoring data represents the period after oil and gas extraction. In the analysis window, oil-producing wells are selected to conduct spectral characteristic difference analysis of the basic data (before oil and gas extraction) and the monitoring data (after oil and gas extraction) to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction.

[0047] It should be noted that determining the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction includes:

[0048] Taking advantage of the characteristics of low-frequency energy reduction and high-frequency energy increase after oil and gas extraction, the spectral characteristics of basic data and monitoring data of oil-producing wells were analyzed to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction.

[0049] like Figure 2 and Figure 3 As shown, in an embodiment of the present invention, two oil wells with high and low oil-gas replacement rates are selected. Based on the spectral characteristic differences between basic data and monitoring data, the sensitive frequency bands where amplitude anomalies occur due to oil and gas extraction are analyzed. In an embodiment of the present invention, the sensitive frequency band is 3-25Hz.

[0050] Next, refer to Figure 1 New sensitive frequency band seismic bodies were extracted using the spectral decomposition method, resulting in the acquisition of basic sensitive frequency band seismic bodies (3-25Hz) and sensitive frequency band monitoring seismic bodies (3-25Hz).

[0051] It should be noted that the application of spectral decomposition methods to extract new sensitive frequency band seismic bodies includes:

[0052] Based on the sensitive frequency band, the two earthquakes were subjected to spectral decomposition to obtain the basic earthquake and the monitored earthquake in the sensitive frequency band.

[0053] Then, the amplitude A1 and frequency F1 of the basic earthquake in the sensitive frequency band are extracted, and the amplitude A2 and frequency F2 of the monitored earthquake in the sensitive frequency band are extracted.

[0054] like Figure 4 and 5 In an embodiment of the present invention, the amplitudes of the two earthquake-sensitive frequency bands include the amplitude A1 of the basic earthquake-sensitive frequency band (3-25Hz) and the amplitude A2 of the monitoring earthquake-sensitive frequency band (3-25Hz).

[0055] like Figure 6 and 7The two earthquake-sensitive frequency bands include: the basic earthquake-sensitive frequency band (3-25Hz) frequency F1 and the monitoring earthquake-sensitive frequency band (3-25Hz) frequency F2.

[0056] Based on the amplitude and frequency of the sensitive frequency bands from two data periods, the energy difference of the sensitive frequency bands during time-lapse earthquakes is calculated. First, the amplitude-to-frequency ratio of the sensitive frequency bands is calculated for both the basic data and the monitoring data. Then, the difference in the amplitude-to-frequency ratio of the sensitive frequency bands between the two data periods is calculated to further amplify the energy difference of time-lapse earthquakes.

[0057] It should be noted that, based on the amplitude and frequency of the sensitive frequency band from the two data periods, the energy difference of the time-shifted seismic sensitive frequency band is calculated, including:

[0058] First, the ratio of amplitude to frequency of the sensitive frequency band in the two data periods is calculated. Then, the difference in the ratio of amplitude to frequency of the sensitive frequency band in the two data periods is calculated to obtain the energy difference of the time-shifted earthquake sensitive frequency band, so as to further amplify the energy difference of the time-shifted earthquake.

[0059] In an embodiment of the present invention, the energy difference of the time-shifted seismic sensitive frequency band is obtained by calculation using the following formula:

[0060]

[0061] In the formula, ΔE represents the energy difference of the time-shifted seismic sensitive frequency band. A1 is the amplitude of the basic seismic sensitive frequency band, A2 is the amplitude of the monitored seismic sensitive frequency band, F1 is the frequency of the basic seismic sensitive frequency band, and F2 is the frequency of the monitored seismic sensitive frequency band.

[0062] Based on the calculated energy differences in time-shifted seismic sensitive frequency bands, planar properties are extracted from oil-bearing strata.

[0063] like Figure 8 and 9 Compared with the time-shift amplitude difference across the entire frequency band, the planar agreement rate between the energy difference in the sensitive frequency band and the oil and gas replacement rate is significantly improved, increasing from 71% to 93%.

[0064] It should be noted that using energy differences in sensitive frequency bands instead of amplitude differences across the entire frequency band improves the consistency between seismic difference information and oil and gas production capacity. By comprehensively applying energy and frequency information, the 4D seismic differences caused by geological factors are effectively amplified, while the influence of non-geological factors is reduced, thus improving the interpretability of 4D seismic data. This allows for a better understanding of the response patterns of time-lapsed seismic differences caused by oil-water replacement. Even under conditions of poor repeatability of time-lapsed seismic data, it can effectively guide the prediction of remaining oil and gas.

[0065] This invention utilizes the principle that seismic reflections from oil and gas reservoirs exhibit enhanced low-frequency energy and absorbed high-frequency energy, while low-frequency energy decreases and high-frequency energy increases after oil and gas extraction. It proposes a method based on energy differences in sensitive frequency bands. Since the amplitude, energy, and frequency of base earthquakes and monitoring earthquakes differ, comprehensively applying these energy and frequency differences to calculate the energy differences in the sensitive frequency bands of time-shifted seismic earthquakes can effectively amplify these energy differences, providing better guidance for predicting remaining oil and gas reserves.

[0066] It should be understood that, as used herein, the singular form "a" is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations of one or more of the associatedly listed items. The embodiment numbers disclosed above are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0067] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands, characterized in that, The method includes: a. Use the earlier acquired seismic data as the basic data and the latest acquired seismic data as the monitoring data; input the basic data and monitoring data respectively, and determine the analysis time window based on the reservoir thickness; b. Basic data represents the period before oil and gas extraction, while monitoring data represents the period after oil and gas extraction. In the analysis window, oil-producing wells are selected to conduct spectral characteristic difference analysis of basic data and monitoring data to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction. c. Apply the spectral decomposition method to extract new sensitive frequency band seismic bodies, and obtain the basic earthquakes and monitored earthquakes in the sensitive frequency bands; d. Extract the amplitude A1 and frequency F1 of the basic earthquake in the sensitive frequency band, and extract the amplitude A2 and frequency F2 of the monitored earthquake in the sensitive frequency band; e. Calculate the amplitude-to-frequency ratio of the sensitive frequency band for the basic data and the monitoring data respectively, and then calculate the difference in the amplitude-to-frequency ratio of the sensitive frequency band between the two periods of data to obtain the energy difference of the sensitive frequency band of time-shifted earthquakes, so as to further amplify the energy difference of time-shifted earthquakes; f. Based on the calculated energy differences in time-shifted seismic sensitive frequency bands, extract planar properties of oil-bearing strata; analyze the oil-water replacement patterns based on the planar property maps to guide the prediction of remaining oil and gas.

2. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 1, characterized in that, Determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction, including: Taking advantage of the characteristics of low-frequency energy reduction and high-frequency energy increase after oil and gas extraction, the spectral characteristics of basic data and monitoring data of oil-producing wells were analyzed to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas extraction.

3. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 2, characterized in that, New sensitive frequency band seismic bodies are extracted using spectral decomposition methods, including: Based on the sensitive frequency band, the two earthquakes were subjected to spectral decomposition to obtain the basic earthquake and the monitored earthquake in the sensitive frequency band.

4. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 3, characterized in that, Two periods of earthquake-sensitive frequency band amplitudes are obtained, including the basic earthquake-sensitive frequency band amplitude A1 and the monitoring earthquake-sensitive frequency band amplitude A2.

5. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 4, characterized in that, Two earthquake-sensitive frequency bands are obtained, including: the basic earthquake-sensitive frequency band F1 and the monitoring earthquake-sensitive frequency band F2.

6. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 5, characterized in that, Based on the amplitude and frequency of the sensitive frequency band from the two data periods, the energy difference of the time-shifted seismic sensitive frequency band was calculated, including: The amplitude-to-frequency ratio of the sensitive frequency band is calculated separately for the basic data and the monitoring data. Then, the difference in the amplitude-to-frequency ratio of the sensitive frequency band between the two periods of data is calculated to obtain the energy difference of the sensitive frequency band of time-shifted earthquakes, thereby achieving the purpose of further amplifying the energy difference of time-shifted earthquakes.

7. The method for calculating time-shifted seismic energy differences based on oil and gas sensitive frequency bands as described in claim 6, characterized in that, The energy difference in the time-shifted seismic sensitive frequency band is obtained by calculation using the following formula: In the formula, ΔE represents the energy difference of the time-shifted seismic sensitive band; A1 is the amplitude of the basic seismic sensitive band; A2 is the amplitude of the monitored seismic sensitive band; F1 is the frequency of the basic seismic sensitive band; and F2 is the frequency of the monitored seismic sensitive band.

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