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

Abstract

The invention relates to the technical field of oil and gas seismic exploration and development, in particular to a time-lapse seismic energy difference calculation method based on an oil and gas sensitive frequency band. The method comprises the following steps: extracting a new sensitive frequency band seismic body by searching a sensitive frequency band of a basic earthquake and a monitoring earthquake with abnormal amplitude due to oil and gas exploitation, and obtaining sensitive frequency band amplitude and sensitive frequency band frequency of two-stage seismic data; and calculating to obtain the time-lapse seismic sensitive frequency band energy difference based on the two-stage data sensitive frequency band amplitudes and frequencies. According to the method, the interpretability of the time-lapse earthquake is improved, and a time-lapse earthquake difference response rule caused by representative oil-water replacement can be better obtained. Even under the condition of poor time-lapse seismic repeatability, residual oil and gas prediction can be effectively guided.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas seismic exploration and development, and particularly to a method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band, belonging to the application scope of geophysical methods in four-dimensional seismic reservoir monitoring. Background Art

[0002] Most of the domestic and foreign research on time-lapse seismic interpretation technology analyzes the law of oil-water displacement based on the amplitude difference of full-band seismic data. The existing technical methods mainly obtain the amplitude difference of time-lapse seismic by subtracting the energy of the amplitude of the basic seismic from the energy of the amplitude of the monitoring seismic. From the current research situation at home and abroad, the above methods have achieved good results in high-porosity and high-permeability oil reservoirs and exploration areas with good seismic repeatability. However, for non-repetitive time-lapse seismic and medium-low porosity and permeability exploration areas, the effect of this method is not ideal. In order to solve this technical problem, a calculation of the time-lapse seismic energy difference based on the oil and gas sensitive frequency band is proposed. Summary of the Invention

[0003] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band. This method has good effect, and can effectively obtain the time-lapse seismic energy difference even under non-repetitive time-lapse seismic conditions.

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

[0005] In the first aspect, in an embodiment provided by the present invention, a method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band is provided, and the method includes the following steps:

[0006] a. Take the seismic data collected earlier as the basic data, and the seismic data collected most recently as the monitoring data; input the basic data and the monitoring data respectively, and determine the analysis time window according to the reservoir thickness;

[0007] b. The basic data represents before the oil and gas are produced, and the monitoring data represents after the oil and gas are produced; select the production wells in the analysis time window to perform the spectral characteristic difference analysis of the basic data (before the oil and gas are produced) and the monitoring data (after the oil and gas are produced), and determine the sensitive frequency band corresponding to the amplitude difference before and after the oil and gas are produced;

[0008] c. Apply the spectral decomposition method to extract a new seismic body of the sensitive frequency band, and obtain the basic seismic of the sensitive frequency band and the monitoring seismic of the sensitive frequency band.

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

[0010] e. Calculate the energy difference of the time-lapse seismic sensitive frequency band based on the amplitudes and frequencies of the sensitive frequency bands in two periods of data. Calculate the ratios of the amplitudes and frequencies of the sensitive frequency bands of the basic data and the monitoring data respectively, and then calculate the differences in the ratios of the amplitudes and frequencies of the sensitive frequency bands in the two periods of data, so as to further amplify the energy difference of the time-lapse seismic.

[0011] f. Extract the planar attributes of the oil-bearing formation sections according to the calculated energy difference of the time-lapse seismic sensitive frequency band. Analyze the law of oil-water displacement based on the planar attributes to guide the prediction of remaining oil and gas.

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

[0013] Utilize the characteristics that after oil and gas production, the low-frequency energy decreases and the high-frequency energy increases. Select production wells to conduct differential analysis of the spectral characteristics of the basic data (before oil and gas production) and the monitoring data (after oil and gas production), and determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production.

[0014] As a further solution of the present invention, applying the spectral decomposition method to extract a new sensitive frequency band seismic volume includes:

[0015] Based on the sensitive frequency band, perform spectral decomposition processing on the two periods of seismic data to obtain the basic seismic data of the sensitive frequency band and the monitoring seismic data of the sensitive frequency band.

[0016] As a further solution of the present invention, obtaining the amplitudes of the sensitive frequency bands of the two periods of seismic data, the amplitudes of the sensitive frequency bands of the two periods of seismic data include the amplitude A1 of the sensitive frequency band of the basic seismic data and the amplitude A2 of the sensitive frequency band of the monitoring seismic data.

[0017] As a further solution of the present invention, obtaining the frequencies of the sensitive frequency bands of the two periods of seismic data, the frequencies of the sensitive frequency bands of the two periods of seismic data include: the frequency F1 of the sensitive frequency band of the basic seismic data and the frequency F2 of the sensitive frequency band of the monitoring seismic data.

[0018] As a further solution of the present invention, calculating the energy difference of the time-lapse seismic sensitive frequency band based on the amplitudes and frequencies of the sensitive frequency bands in two periods of data includes:

[0019] First, calculate the ratios of the amplitudes and frequencies of the sensitive frequency bands in the two periods of data respectively, and then calculate the differences in the ratios of the amplitudes and frequencies of the sensitive frequency bands in the two periods of data to obtain the energy difference of the time-lapse seismic sensitive frequency band, so as to further amplify the energy difference of the time-lapse seismic.

[0020] As a further solution of the present invention, the energy difference of the time-lapse seismic sensitive frequency band is obtained by calculating through the following formula:

[0021]

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

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

[0024] The present invention can significantly amplify the time-lapse seismic difference information, providing an effective technical means for time-lapse seismic interpretation, especially for non-repeated time-lapse seismic interpretation. Using the energy difference of the sensitive frequency band instead of the amplitude difference of the full frequency band can improve the coincidence rate of seismic difference information and oil and gas production capacity, and can better obtain the time-lapse seismic difference response law representing the oil-water displacement. Even under the condition of poor repeatability of time-lapse seismic, it can effectively guide the prediction of remaining oil and gas.

[0025] These aspects or other aspects of the present invention will be more clearly understood in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of the time-lapse seismic energy difference calculation method based on the oil and gas sensitive frequency band according to an embodiment of the present invention.

[0028] Figure 2 It is an analysis diagram of the spectral feature differences of the target layer sections of the oil-producing wells with a relatively high oil-water displacement rate in the study area of the present invention.

[0029] Figure 3 It is an analysis diagram of the spectral feature differences of the target layer sections of the oil-producing wells with a relatively low oil-water displacement rate in the study area of the present invention.

[0030] Figure 4 It is the amplitude A1 of the base seismic sensitive frequency band.

[0031] Figure 5 It is the amplitude A2 of the monitored seismic sensitive frequency band.

[0032] Figure 6 It is the frequency F1 of the base seismic sensitive frequency band.

[0033] Figure 7 It is the frequency F2 of the monitored seismic sensitive frequency band.

[0034] Figure 8 It is a superimposed oil-water displacement rate plan view of the full-frequency band amplitude difference attribute of the main pay zone.

[0035] Figure 9 It is a superimposed oil-water displacement rate plan view of the energy difference attribute of the sensitive frequency band of the main pay zone. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] The flowcharts shown in the accompanying drawings are only illustrative examples, which do not necessarily include all contents and operations / steps, nor do they necessarily need to be executed in the described order. For example, some operations / steps can be decomposed, combined, or partially merged, so the actual execution order may change according to the actual situation.

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

[0039] The prior art calculates the time-lapse seismic energy difference using the following formula:

[0040] ΔA = A2 - A1

[0041] In the formula, ΔA is the time-lapse seismic energy difference, A1 is the basic seismic amplitude energy, and A2 is the monitored seismic amplitude energy.

[0042] To solve the problem that the prior art has poor effects on non-repetitive time-lapse seismic and exploration areas with medium and low porosity and permeability, the present invention provides a method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band.

[0043] Specifically, the embodiments of the present invention will be further elaborated below in conjunction with the accompanying drawings.

[0044] Please refer to Figure 1 , Figure 1 which is a flowchart of a method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band provided by the embodiments of the present invention.

[0045] As Figure 1As shown, the early 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 the monitoring data are respectively input, and the analysis time window is determined according to the reservoir thickness.

[0046] The basic data represents before oil and gas production, while the monitoring data represents after oil and gas production; production wells are selected in the analysis time window for the differential analysis of the spectral characteristics of the basic data (before oil and gas production) and the monitoring data (after oil and gas production) to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production.

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

[0048] Utilizing the characteristics of the reduction of low-frequency energy and the increase of high-frequency energy after oil and gas production, production wells are selected for the differential analysis of the spectral characteristics of the basic data and the monitoring data to determine the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production.

[0049] As Figure 2 and Figure 3 shown, in the embodiments of the present invention, two production wells with relatively high and relatively low oil and gas replacement rates are selected, and the sensitive frequency bands with abnormal amplitudes due to oil and gas production are analyzed according to the differential analysis of the spectral characteristics of the basic data and the monitoring data. In the embodiments of the present invention, the sensitive frequency band is 3 - 25 Hz.

[0050] Then referring to Figure 1 , the spectral decomposition method is applied to extract new seismic bodies in the sensitive frequency band to obtain the basic seismic in the sensitive frequency band (3 - 25 Hz) and the monitoring seismic in the sensitive frequency band (3 - 25 Hz).

[0051] It should be noted that applying the spectral decomposition method to extract new seismic bodies in the sensitive frequency band includes:

[0052] Based on the sensitive frequency band, spectral decomposition processing is performed on two-phase seismic data to obtain the basic seismic in the sensitive frequency band and the monitoring seismic in the sensitive frequency band.

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

[0054] As Figure 4 and 5 shown, in the embodiments of the present invention, among them, the amplitudes of the two-phase seismic sensitive frequency band include the amplitude A1 of the basic seismic sensitive frequency band (3 - 25 Hz) and the amplitude A2 of the monitoring seismic sensitive frequency band (3 - 25 Hz).

[0055] As Figure 6 and 7, wherein the frequencies of the two-phase seismic sensitive frequency bands include: the frequency F1 of the basic seismic sensitive frequency band (3 - 25 Hz) and the frequency F2 of the monitoring seismic sensitive frequency band (3 - 25 Hz).

[0056] Based on the amplitudes and frequencies of the sensitive frequency bands of the two-phase data, calculate the energy difference of the time-lapse seismic sensitive frequency band. First, calculate the ratios of the amplitudes and frequencies of the sensitive frequency bands of the basic data and the monitoring data respectively, and then calculate the differences in the ratios of the amplitudes and frequencies of the sensitive frequency bands of the two-phase data, so as to further amplify the energy difference of the time-lapse seismic.

[0057] It should be noted that calculating the energy difference of the time-lapse seismic sensitive frequency band based on the amplitudes and frequencies of the sensitive frequency bands of the two-phase data includes:

[0058] First, calculate the ratios of the amplitudes and frequencies of the sensitive frequency bands of the two-phase data, and then calculate the differences in the ratios of the amplitudes and frequencies of the sensitive frequency bands of the two-phase data to obtain the energy difference of the time-lapse seismic sensitive frequency band, so as to further amplify the energy difference of the time-lapse seismic.

[0059] In the embodiment of the present invention, the energy difference of the time-lapse seismic sensitive frequency band is obtained by calculating through the following formula:

[0060]

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

[0062] Extract the plane attributes of the oil-bearing interval according to the calculated energy difference of the time-lapse seismic sensitive frequency band.

[0063] Such as Figure 8 and 9 , compared with the time-lapse amplitude difference of the full frequency band, the plane coincidence rate of the energy difference of the sensitive frequency band and the oil-gas replacement rate has been significantly improved, and the coincidence rate has increased from 71% to 93%.

[0064] It should be noted that using the energy difference of the sensitive frequency band instead of the amplitude difference of the full frequency band improves the coincidence rate of the seismic difference information and the oil-gas production capacity, comprehensively applies the energy and frequency information, effectively amplifies the 4D seismic difference caused by geological factors, reduces the influence of non-geological factors, improves the interpretability of 4D seismic, and can better obtain the time-lapse seismic difference response law representing the oil-water replacement. Even under the condition of poor repeatability of time-lapse seismic, it can effectively guide the prediction of remaining oil and gas.

[0065] The present invention utilizes the principle that seismic reflections from oil and gas reservoirs have enhanced low-frequency energy and absorbed high-frequency energy, while after oil and gas production, the low-frequency energy decreases and the high-frequency energy increases, and proposes a method for the energy difference in the sensitive frequency band. There are differences in both the amplitude energy and frequency between the baseline seismic and the monitored seismic. By comprehensively applying the differences in energy and frequency and calculating the energy difference in the oil and gas sensitive frequency band of time-lapse seismic, the energy difference of time-lapse seismic can be effectively amplified, better guiding the prediction of remaining oil and gas.

[0066] It should be understood that, as used herein, unless the context clearly supports the exception, the singular form "a" is also intended to include the plural form. It should also be understood that the "and / or" used herein refers to any and all possible combinations of one or more of the associated listed items. The serial numbers of the disclosed embodiments of the present invention above are only for description and do not represent the advantages or disadvantages of the embodiments.

[0067] Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope (including the claims) of the disclosed embodiments of the present invention is limited to these examples; under the concept of the embodiments of the present invention, the technical features between the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band, characterized in that The method includes: a. Using the seismic data collected earlier as the basic data and the most recently collected seismic data as the monitoring data; inputting the basic data and the monitoring data respectively, and determining the analysis time window according to the reservoir thickness; b. The basic data represents the situation before oil and gas production, while the monitoring data represents the situation after oil and gas production; Selecting production wells in the analysis time window to conduct a differential analysis of the spectral characteristics of the basic data and the monitoring data, and determining the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production; c. Applying the spectral decomposition method to extract a new seismic body in the sensitive frequency band, obtaining the basic seismic data in the sensitive frequency band and the monitoring seismic data in the sensitive frequency band; d. Extracting the amplitude A1 and frequency F1 of the basic seismic data in the sensitive frequency band, and extracting the amplitude A2 and frequency F2 of the monitoring seismic data in the sensitive frequency band; e. Calculating the ratios of the amplitudes and frequencies of the sensitive frequency bands of the basic data and the monitoring data respectively, and then calculating the difference in the ratios of the amplitudes and frequencies of the sensitive frequency bands of the two periods of data to obtain the energy difference of the time-lapse seismic sensitive frequency band, so as to further amplify the energy difference of the time-lapse seismic; f. Extracting the planar attributes of the oil-bearing formation section according to the calculated energy difference of the time-lapse seismic sensitive frequency band. Analyzing the law of oil-water displacement according to the planar attribute map to guide the prediction of remaining oil and gas.

2. The method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band according to claim 1, wherein Determining the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production includes: Utilizing the characteristics that after oil and gas production, the low-frequency energy decreases and the high-frequency energy increases, selecting production wells to conduct a differential analysis of the spectral characteristics of the basic data and the monitoring data, and determining the sensitive frequency band corresponding to the amplitude difference before and after oil and gas production.

3. The time-lapse seismic energy difference calculation method based on the oil and gas sensitive frequency band according to claim 2, wherein Applying the spectral decomposition method to extract a new seismic body in the sensitive frequency band includes: Based on the sensitive frequency band, performing spectral decomposition processing on the two periods of seismic data to obtain the basic seismic data in the sensitive frequency band and the monitoring seismic data in the sensitive frequency band.

4. The method for calculating time-lapse seismic energy difference based on the oil and gas sensitive frequency band according to claim 3, wherein Obtaining the amplitudes of the sensitive frequency bands of the two periods of seismic data, and the amplitudes of the sensitive frequency bands of the two periods of seismic data include the amplitude A1 of the basic seismic data in the sensitive frequency band and the amplitude A2 of the monitoring seismic data in the sensitive frequency band.

5. The method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band according to claim 4, wherein Obtaining the frequencies of the sensitive frequency bands of the two periods of seismic data, and the frequencies of the sensitive frequency bands of the two periods of seismic data include: the frequency F1 of the basic seismic data in the sensitive frequency band and the frequency F2 of the monitoring seismic data in the sensitive frequency band.

6. The time-lapse seismic energy difference calculation method based on the oil and gas sensitive frequency band according to claim 5, wherein Calculating the energy difference of the time-lapse seismic sensitive frequency band based on the amplitudes and frequencies of the sensitive frequency bands of the two periods of data includes: Calculating the ratios of the amplitudes and frequencies of the sensitive frequency bands of the basic data and the monitoring data respectively, and then calculating the difference in the ratios of the amplitudes and frequencies of the sensitive frequency bands of the two periods of data to obtain the energy difference of the time-lapse seismic sensitive frequency band, so as to further amplify the energy difference of the time-lapse seismic.

7. The method for calculating the time-lapse seismic energy difference based on the oil and gas sensitive frequency band according to claim 6, wherein The energy difference of the time-lapse seismic sensitive frequency band is obtained through the following formula: In the formula, ΔE is the energy difference of the time-lapse seismic sensitive frequency band. A1 is the amplitude of the basic seismic data in the sensitive frequency band, A2 is the amplitude of the monitoring seismic data in the sensitive frequency band, F1 is the frequency of the basic seismic data in the sensitive frequency band, and F2 is the frequency of the monitoring seismic data in the sensitive frequency band.

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