A method for estimating flux of bubble plumes based on seismic oceanography

Abstract

The application discloses a seabed bubble plume flux estimation method based on seismic oceanology, and is characterized in that: based on a seabed bubble plume parameter model, numerical simulation and attribute analysis are mainly used as research means to accurately identify and analyze the seismic response of the seabed bubble plume, a function equation is used to quantitatively analyze the relationship between the bubble volume fraction and the seismic response characteristics (instantaneous amplitude, instantaneous frequency and instantaneous phase); the bubble volume fraction is obtained by combining the function equation and the parameters such as the width, height and shape of the seabed bubble plume in the actual seismic data to further obtain the quantitative index of the seabed bubble plume flux, which provides important theoretical reference and technical support for the identification and analysis of the seabed bubble plume in the actual seismic data, the positioning of the seabed cold spring activity, the research on the enrichment rule and the occurrence area of the seabed resources and the climate change of the greenhouse gas.

Description

Technical Field

[0001] This invention belongs to the field of marine exploration technology, and in particular relates to a method for estimating seabed bubble plume flow based on seismic oceanography. Background Technology

[0002] Submarine bubble plumes develop above active cold seep areas, formed by numerous free bubbles continuously moving upwards through seawater, providing the most direct evidence of active cold seeps. Extensive observations have revealed that numerous continuously developing submarine bubble plumes are often closely related to the decomposition of natural gas hydrates, indirectly indicating the possible presence of natural gas hydrates in seabed sediments and potentially accelerating global warming. Their potential resource and environmental effects have made submarine bubble plumes and related research of great interest, holding significant importance in studies of natural gas hydrates, conventional oil and gas exploration, seabed tectonics and fluid geology, global climate change, carbon cycles, and extreme biota. Therefore, studying the leakage and dissipation of submarine bubble plumes in seawater and the atmosphere, and estimating their flux, is crucial.

[0003] Due to the high cost, significant risk, and low efficiency of direct seabed observation (in-situ observation), geophysical exploration methods are crucial for observing seabed bubble plumes. Currently, high-frequency acoustic methods such as seabed visualization technology, side-scan sonar, shallow seismic profilers, high-frequency seismic recordings, single-beam echo sounders, and multi-beam bathymetry systems have all captured and detected the morphological characteristics of plumes. These high-frequency acoustic methods have high detection frequencies; theoretically, higher sound frequencies result in higher resolution, allowing for imaging of seabed bubble plumes with smaller areas and bubble diameters. However, because detection depth is negatively correlated with detection frequency, high-frequency acoustic methods struggle to obtain effective signals from seabed bubble plumes when detecting deep-sea plumes. Therefore, they are difficult to use for estimating seabed bubble plume flow and typically cannot provide acoustic response characteristics of subsea sedimentary layers.

[0004] Seismic oceanography is an emerging interdisciplinary field combining reflection seismology and physical oceanography. Utilizing traditional multichannel reflection seismic methods to study physical oceanographic problems, its advantages of high lateral resolution and rapid imaging of small-to-medium scale processes will undoubtedly lead to widespread application in the field and profound impact on oceanographic development. Unlike high-frequency acoustic methods, conventional multichannel reflection seismic methods typically use lower seismic wave frequencies, distributed in the tens of hertz range. Their main principle is based on the difference in wave impedance between the target object and surrounding materials. Recent research indicates that seismic oceanography methods can not only study physical oceanographic phenomena (internal ocean waves, eddies, etc.) and processes within the ocean layer, but also image important boundary processes between the hydrosphere and lithosphere, thereby exploring related processes such as marine sedimentary dynamics, cold seeps, and hydrothermal activity. This helps to reveal various complex interactions / processes near the seafloor boundaries.

[0005] To date, the seismic response generated by submarine bubble plumes has attracted widespread attention, but only a simple qualitative analysis and explanation of its seismic reflection characteristics has been conducted. There has been no detailed quantitative modeling, and no further technical support to quantify the bubble volume fraction of submarine plumes, making it impossible to estimate their flux and thus impossible to explore scientific questions related to natural gas hydrates.

[0006] Compared to other acoustic methods, quantitative research is a significant advantage of seismic oceanography, and it represents its research focus and a crucial direction for breakthroughs. However, there are currently no effective examples of using seismic oceanography methods to estimate the flow of seafloor bubble plumes, nor has a corresponding theoretical research system been established. Therefore, studying the dynamic processes of seafloor bubble plumes, and consequently identifying cold seeps and the natural gas hydrates they contain, remains a significant challenge. Summary of the Invention

[0007] To address the shortcomings of existing technologies in estimating submarine bubble plume flow using seismic oceanography methods, this invention proposes a method for estimating submarine bubble plume flow based on seismic oceanography. This method estimates submarine bubble plume flow by analyzing seismic attributes based on seismic profile response characteristics, providing a new, simple, and effective method for studying and capturing submarine bubble plume flow parameters.

[0008] This invention is achieved using the following technical solution: a method for estimating seafloor bubble plume flux based on seismic oceanography, characterized by comprising the following steps:

[0009] Step S1: Establish a parameter model for submarine bubble plumes that matches the characteristics and intrinsic properties of actual plume records;

[0010] Step S2: Based on the submarine bubble plume parameter model described in Step S1, obtain seismic data through numerical simulation and determine the seismic response characteristics of the submarine bubble plume.

[0011] Step S3: Perform seismic attribute analysis on the seismic data obtained in step S2 to obtain a seismic attribute profile, which includes an instantaneous phase profile, an instantaneous frequency profile, and an instantaneous amplitude profile;

[0012] Step S4: Quantitatively analyze the relationship between the seismic attributes and bubble volume fraction described in Step S3 using a functional equation. The specific functional equation is as follows:

[0013]

[0014] Where φ is the bubble volume fraction, IA is the instantaneous amplitude, IFr is the instantaneous frequency, IPh is the instantaneous phase information entropy, and a IA b IA c IA a IFr b IFr c IFr a IPh b IPh c IPh and d IPh For parameters of the function equation;

[0015] Step S5: Fit the parameters of the function equation under different seismic wavelet dominant frequencies to obtain the mathematical relationship model between the parameters of the function equation in step S4 and the seismic wavelet dominant frequency;

[0016] Step S6: Process the actual multichannel reflection seismic data based on seismic oceanography data processing methods to obtain a reflection seismic profile containing seafloor bubble plumes;

[0017] Step S7: Perform seismic attribute analysis on the seafloor bubble plume reflection seismic profile described in Step S6 to obtain the actual seismic attribute (instantaneous amplitude, instantaneous frequency, and instantaneous phase) profile;

[0018] Step S8: Invert and estimate the volume fraction profile of the seafloor bubble plume by integrating multiple seismic attributes (instantaneous amplitude, instantaneous frequency, and instantaneous phase);

[0019] Step S9: Quantitative study of the velocity field of the seabed bubble plume: Using particle image velocimetry technology, quantitative analysis of the flow field is performed on video data of the seabed bubble plume to obtain the velocity field of the seabed bubble plume.

[0020] Step S10: Based on the volume fraction profile of the submarine bubble plume described in Step S8 and the velocity field of the submarine bubble plume described in Step S9, estimate the flux of the submarine bubble plume.

[0021] Furthermore, step S1, establishing the parameter model for the seabed bubble plume flow, specifically includes the following steps:

[0022] Step S11: Design the scale of the parameter model for the submarine bubble plume flow;

[0023] Step S12: Based on physical oceanography data, and combining the seawater state equation and empirical formula for sound speed, establish an initial seawater model;

[0024] Step S13: Based on the bubble dissolution model and stochastic medium theory, simulate and calculate the evolution process and distribution state of bubbles, and combine different bubble number models to calculate multiple bubble volume fraction models;

[0025] The bubble volume fraction model is represented as follows:

[0026]

[0027] Where r is the bubble radius, and [] denotes the floor function, δN b The model represents the random perturbation of the bubble quantity in a bubble-containing medium region, where σ(x,y) is a second-order stationary spatial random process with a certain mean and variance derived from random medium theory, and φ... j To divide a spherical region of radius Rs into n The radius of the part is The volume fraction of bubbles within the small spherical region;

[0028] Step S14: Based on the modified gas law and the gas density-velocity of sound function relationship, calculate the gas density (ρ). Bubble ) and the speed of sound in gas (v Bubble Establish a gas density sound velocity model;

[0029] The gas density, derived from the modified gas law, is as follows:

[0030]

[0031] Where, ρ Bubble Where is the gas density, M is the molar mass, R is the universal gas constant, T is the absolute temperature, Z is the compressibility factor, and k1, k2, and p0 are temperature-dependent parameters.

[0032] The specific relationship between gas density and speed of sound is as follows:

[0033]

[0034] Where γ = 1.314 is the adiabatic index of methane gas, and P is the pressure;

[0035] Step S15: Based on the calculation formula of acoustic properties of bubble-containing medium, establish a bubble model by combining the bubble volume fraction model described in step S13 and the gas density sound velocity model described in step S14;

[0036] The formula for calculating the acoustic properties of the bubble-containing medium is as follows:

[0037]

[0038] Where, ρ Plume v is the density of the bubble-containing medium. Plume K represents the speed of sound in a bubble-containing medium. ω For bulk modulus, μ ω Let ρ' be the shear modulus, k be the wave number, and ρ' be the wave number. Plume and K Plume Let be the density and equivalent elastic modulus of the bubble-containing medium, respectively, and ||, Re, and Im be the modulus, real part, and imaginary part, respectively.

[0039] Step S16: Couple the initial seawater model described in step S12 and the bubble model described in step S15 to establish a parameter model for the seabed bubble plume.

[0040] Furthermore, step S2, determining the seismic response characteristics of the seafloor bubble plume, specifically includes the following steps:

[0041] Step S21: Forward modeling to obtain shot gather seismic record data of submarine bubble plumes;

[0042] Different dominant frequencies of the Rake wavelet were selected to simulate the seismic wavelet. The finite difference method was used to decompose the acoustic wave equation to perform forward modeling of the parameter model of the seabed bubble plume with different bubble volume fractions, and the seismic record data of the seabed bubble plume shot gather were obtained.

[0043] Step S22: Based on the above shot gather seismic record data, a depth-domain seismic oceanographic simulation profile reflecting the seismic response characteristics of seafloor bubble plumes is obtained using the reverse time migration imaging method.

[0044] Furthermore, the specific operations for step S3, seismic attribute analysis, include:

[0045] Step S31: Perform a depth-time transformation on the depth-domain seismic oceanographic simulation profile to obtain a time-domain seismic oceanographic simulation profile, and perform a Hilbert transform on it to obtain an analytical signal;

[0046] Step S32: Calculate the time-domain earthquake instantaneous attribute profile using the analytical signal described in step S31. The earthquake instantaneous attributes include instantaneous amplitude, instantaneous phase, and instantaneous frequency. The instantaneous amplitude is the root mean square of the real and imaginary parts of the analytical signal. The instantaneous phase is the arctangent value obtained by dividing the imaginary and real parts. The instantaneous frequency is the derivative of the phase with respect to time.

[0047] Step S33: Perform time-depth conversion on the time-domain instantaneous seismic attribute profile obtained in step S32 to obtain the seismic attribute profile.

[0048] Furthermore, step S4, the specific operations for quantitatively analyzing the relationship between seismic attributes and the bubble volume fraction function, include:

[0049] Step S41: For the seismic attribute profile described in step S3, calculate the mean value of the seismic attribute at different rectangular locations within the submarine bubble plume, and the bubble volume fraction at the same location in the submarine bubble plume parameter model described in step S1.

[0050] Step S42: Plot the paired seismic attribute values ​​and bubble volume fraction values, where the horizontal axis represents the bubble volume fraction and the vertical axis represents the seismic attribute values. The instantaneous amplitude and instantaneous frequency are plotted directly using the seismic attribute values ​​described in step S41 to plot their relationship curve with the bubble volume fraction, while the instantaneous phase is plotted by introducing information entropy as an intermediate variable to plot its relationship curve with the bubble volume fraction.

[0051] Step S43: Then, through quantitative research, regression fitting is used to obtain the functional equation between seismic attributes and bubble volume fraction.

[0052] Furthermore, step S5, which establishes the mathematical relationship model between the parameters of the function equation and the dominant frequency of the seismic wavelet, includes the following specific steps:

[0053] Step S51: The functional relationship described in step S4 has different function equation parameters under different seismic wavelet dominant frequencies. Pairs of seismic wavelet dominant frequencies and function equation parameters are plotted in a two-dimensional coordinate system, where the horizontal coordinate is the seismic wavelet dominant frequency and the vertical coordinate is the function equation parameters.

[0054] Step S52: Through quantitative fitting analysis, establish a mathematical relationship model between the parameters of the function equation and the dominant frequency of the seismic wavelet.

[0055] Furthermore, in step S6, when obtaining the seismic profile containing seafloor bubble plume reflections according to the seismic oceanographic data processing method, minimum phase filtering is used during the filtering process to avoid artificial noise caused by strong low-frequency noise; in terms of direct wave processing, direct wave suppression is achieved by combining horizontal median filtering with matched subtraction.

[0056] Furthermore, step S8 is implemented in the following way:

[0057] Step S81: Based on the source frequency information of the actual earthquake data and the mathematical relationship model established in step S5, calculate the parameters of the function equation, and then obtain the functional relationship equation between the earthquake attributes and the bubble volume fraction at the source frequency of the actual earthquake data.

[0058] Step S82: Based on the actual seismic attribute profile described in step S7 and the functional relationship equation described in step S81, the volume fraction profile of the seafloor bubble plume is estimated by calculation and inversion.

[0059] Furthermore, the specific operations for estimating the flow rate of seabed bubble plumes in step S10 include:

[0060] Step S101: Design a rectangular window of appropriate size, and based on the seismic profile containing the seafloor bubble plume reflection described in step S6, obtain the physical meaning information contained in the rectangular window, including horizontal distance (d) and two-way travel time (t).

[0061] Step S102: Based on the sound velocity-bubble volume fraction function relationship between the sound velocity model and the bubble volume fraction model of the seabed bubble plume described in Step S1, and the bubble volume fraction profile of the seabed bubble plume described in Step S8, calculate the sound velocity of the rectangular window region described in Step S101, and then convert the two-way travel time (t) of the rectangular window described in Step S101 into depth (h).

[0062] Step S103: Derive and calculate the bubble volume based on the bubble volume fraction formula, wherein the bubble volume fraction formula is as follows:

[0063]

[0064] Where φ is the bubble volume fraction, V Bubble V is the volume of the bubble. Seawater The volume of seawater;

[0065] Step S104: Based on the rectangular window described in step S101 and the bubble volume (V) described in step S103 Bubble Combining the velocity field of the seabed bubble plume described in step S9, the volumetric flux of the bubbles in this region is calculated.

[0066] Step S105: Perform statistical analysis on the bubble volume flux described in step S104 to finally estimate the flow flux of seabed bubble plumes.

[0067] Furthermore, the specific steps for calculating the bubble volume using the bubble volume fraction formula in step S103 include:

[0068] Step S1031: The two-dimensional profile of the seabed bubble plume is the projection of its three-dimensional fluid structure onto a plane;

[0069] Step S1032: Based on the rectangular window described in step S101, and combined with the seabed bubble plume bubble volume fraction profile and seawater volume formula described in step S8, the bubble volume is calculated.

[0070] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0071] This scheme first analyzes the seismic attribute profile at the theoretical level, then combines actual multichannel reflection seismic data to analyze the seismic attributes, and then combines the theoretical and actual seismic attributes to invert and estimate the bubble volume fraction profile of the submarine bubble plume to obtain the bubble volume fraction of the submarine bubble plume; finally, it combines the bubble volume fraction profile and the velocity field of the submarine bubble plume to estimate the flux of the submarine bubble plume.

[0072] When conducting seismic attribute profile analysis, the proposed submarine bubble plume parameter model is studied and analyzed from multiple perspectives (phase, frequency, amplitude). This provides a more realistic numerical model for further in-depth research on seismic oceanographic imaging and flux estimation, and provides an important basic reference for identifying and analyzing such features in actual seismic data.

[0073] Finally, numerical simulations and comprehensive examples were used to verify the feasibility of using seismic oceanography methods to study the dynamics of seafloor bubble plumes. This provides a new detection method and research perspective for the past inability to effectively observe various complex ocean processes near the seafloor boundary. Attached Figure Description

[0074] Figure 1 This is a flowchart of the seabed bubble plume flow estimation method based on seismic oceanography as described in an embodiment of the present invention. Detailed Implementation

[0075] To better understand the above-described objects, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may be practiced in other ways than those described herein, and therefore, the present invention is not limited to the specific embodiments disclosed below.

[0076] Traditional physical oceanography methods cannot provide effective flux calculation methods, and quantitative relationships using high-frequency acoustics are difficult to establish. Furthermore, high-frequency acoustics struggles to obtain effective signals from deep-sea plumes, while in-situ measurements suffer from high costs and low efficiency, making them unsuitable for estimating seafloor bubble plume flux. This invention proposes a seafloor bubble plume flux estimation method based on seismic oceanography, effectively overcoming these shortcomings and providing crucial technical support for further joint seismic oceanographic exploration.

[0077] Specifically, this embodiment proposes a method for estimating seafloor bubble plume flux based on seismic oceanography, such as... Figure 1 As shown, the method includes the following steps:

[0078] Step S1: Establish a seafloor bubble plume parameter model that matches the actual plume record characteristics and intrinsic properties. The seafloor bubble plume parameter model includes a seafloor bubble plume bubble volume fraction model, a seafloor bubble plume sound velocity model, and a seafloor bubble plume density model.

[0079] Step S11: Design the scale of the parameter model for the submarine bubble plume flow:

[0080] Submarine bubble plumes exhibit a "flame-like" gas-liquid mixing characteristic surrounded by seawater. Based on this, this embodiment designs a "flame-like" submarine bubble plume parameter model. The model has a horizontal width of 2000m and a vertical height of 1000m, with the bubble plume located between 400m and 1000m below sea level.

[0081] Step S12: Based on physical oceanography data, and combining the seawater state equation and empirical formula for sound speed, establish an initial seawater model;

[0082] Based on physical oceanography data, namely seawater temperature (T), seawater salinity (S), and seawater depth (or pressure, P) obtained by conventional physical oceanography measurement equipment (CTD (Conductivity-Temperature-Depth), XBT (Expendable Bathy Thermograph System), XCTD (Expendable Conductivity-Temperature-Depth)), combined with the seawater state equation (ρ = f ρ (S,T,P)) and the empirical formula for the speed of sound (v=f) v (S,T,P)) is used to calculate the speed of sound in the seawater (v). Seawater ) and seawater density (ρ Seawater ), establish an initial seawater model;

[0083] Step S13: Based on the bubble dissolution model and stochastic medium theory, simulate and calculate the evolution process and distribution state of bubbles, and combine different bubble number models to calculate multiple bubble volume fraction models;

[0084] In this embodiment, the seabed bubble plume can be considered as being composed of many spherical regions (R... s The spherical region is composed of a gas-containing medium and can be further divided into smaller regions containing a large number of bubbles. Therefore, a bubble number model (N) needs to be given. Bubble To calculate the bubble volume fraction model (φ);

[0085] The bubble volume fraction model is represented as follows:

[0086]

[0087] Where r is the bubble radius, and [] denotes the floor function, δN b The model represents the random perturbation of the bubble quantity in a bubble-containing medium region, where σ(x,y) is a second-order stationary spatial random process with a certain mean and variance derived from random medium theory, and φ... j To make the radius R s The spherical region is divided into n The radius of the part is The volume fraction of bubbles within the small spherical region;

[0088] In this embodiment, a total of 20 bubble volume fraction models with varying bubble volume fractions were established, and their specific information is shown in Table 1.

[0089] Table 1. Model of bubble volume fraction in submarine bubble plume flow.

[0090]

[0091] Step S14: Calculate the gas density (ρ) based on the modified gas law and the gas density-velocity of sound function. Bubble ) and the speed of sound in gas (v Bubble Establish a gas density sound velocity model;

[0092] The gas density, derived from the modified gas law, is as follows:

[0093]

[0094] Where, ρ Bubble Where is the gas density, M is the molar mass, R is the universal gas constant (≈8.314 J / (mol·K)), T is the absolute temperature, Z is the compressibility factor, which can be derived from the Peng-Robinson equation of state, and k1, k2 and p0 are temperature-dependent parameters.

[0095] The specific relationship between gas density and speed of sound is as follows:

[0096]

[0097] Where γ = 1.314 is the adiabatic index of methane gas;

[0098] Step S15: Combine the acoustic property calculation formula of the bubble-containing medium, the bubble volume fraction model described in step S13 and the gas density sound velocity model described in step S14 to establish a bubble model;

[0099] The specific formula for calculating the acoustic properties of the bubble-containing medium (bubble plume flow) is as follows:

[0100]

[0101] Where, ρ Plume v is the density of the bubble-containing medium. Plume K represents the speed of sound in a bubble-containing medium. ω For bulk modulus, μ ω Let ρ' be the shear modulus, k be the wave number, and ρ' be the wave number. Plume and K Plume Let be the density and equivalent elastic modulus of the bubble-containing medium, respectively, and ||, Re, and Im be the modulus, real part, and imaginary part, respectively.

[0102] Step S16: Couple the initial seawater model described in step S12 and the bubble model described in step S15, that is, place the bubble model in the initial seawater model, and keep the boundary of the bubble model and the surrounding seawater in a gradual state to match the reality, and establish the seabed bubble plume parameter model.

[0103] Step S2: Based on the sound velocity model and density model of the submarine bubble plume described in Step S1, numerical simulation is used to obtain seismic data and determine the seismic response characteristics of the submarine bubble plume; specifically, this includes the following steps:

[0104] Step S21: Forward modeling to acquire seismic record data from submarine bubble plume shot gauging;

[0105] Different dominant frequencies of the Rake wavelet were selected to simulate the seismic wavelet. The finite difference method was used to decompose the acoustic equation to perform forward modeling of the sound velocity model and the density model of the seabed bubble plume flow, and the seismic record data of the seabed bubble plume flow shot gather were obtained.

[0106] The specific parameters required for the numerical simulation are shown in Table 2.

[0107] Table 2. Parameters required for numerical simulation.

[0108]

[0109]

[0110] Step S22: Apply the reverse time migration imaging method to the shot gathering seismic record data described in step S21 to obtain a depth-domain seismic oceanographic simulation profile that reflects the seismic response characteristics of seafloor bubble plumes.

[0111] Step S3: Perform seismic attribute analysis on the seismic data obtained in step S2 to obtain a seismic attribute profile; specifically including:

[0112] Step S31: Perform a depth-time transformation on the depth-domain seismic oceanographic simulation profile to obtain a time-domain seismic oceanographic simulation profile, and perform a Hilbert transform on it to obtain an analytical signal;

[0113] Step S32: Calculate the time-domain seismic instantaneous attribute profile using the analytical signal described in step S31. The instantaneous amplitude (IA) is the root mean square of the real and imaginary parts of the analytical signal. The instantaneous phase (IPh) is the arctangent value obtained by dividing the imaginary and real parts. The instantaneous frequency (IFr) is obtained by differentiating the phase with respect to time.

[0114] Step S33: Perform time-depth conversion on the time-domain instantaneous seismic attribute profile obtained in step S32 to obtain the seismic attribute profile.

[0115] Step S4: Quantitatively analyze the relationship between the seismic attributes described in Step S3 and the bubble volume fraction using functional equations; specifically including:

[0116] Step S41: For the seismic attribute profile described in step S3 and the seafloor bubble plume bubble volume fraction model described in step S1, the “flame-shaped” position of the seafloor bubble plume is scanned by setting the size of the rectangular window (e.g., 40×40 grid), and the mean value within the rectangular window is calculated for each movement, so as to obtain the seismic attribute value and bubble volume fraction value required for quantitative analysis.

[0117] Step S42: Plot pairs of seismic attribute values ​​and bubble volume fraction values ​​in a two-dimensional coordinate system, where the horizontal coordinate represents the bubble volume fraction value and the vertical coordinate represents the values ​​of each seismic attribute parameter. A scatter plot of the relationship between seismic attribute values ​​and bubble volume fraction can be obtained. The instantaneous amplitude and instantaneous frequency can be plotted directly using the seismic attribute values ​​described in step S41 to plot their relationship curve with the bubble volume fraction. However, the instantaneous phase needs to introduce information entropy as an intermediate variable to plot its relationship curve with the bubble volume fraction. Furthermore, the data within the rectangular window described in step S41 needs to be horizontally differencing first.

[0118] Qualitative analysis of the relationship curves revealed that the instantaneous amplitude increases with the increase of bubble volume fraction, while the instantaneous frequency decreases with the increase of bubble volume fraction. There is an "inflection point" between the instantaneous phase information entropy and the bubble volume fraction. As the bubble volume fraction increases, the instantaneous phase information entropy value first increases rapidly, then shows a slight upward trend, and finally reaches a stable state.

[0119] Step S43: Based on the seismic attribute values ​​and bubble volume fraction values ​​described in Step S41, and combined with the method described in Step S42, a functional equation between seismic attributes and bubble volume fraction is obtained through quantitative research and regression fitting.

[0120] The specific function equation is as follows:

[0121]

[0122] Where φ is the bubble volume fraction, IA is the instantaneous amplitude, IFr is the instantaneous frequency, IPh is the instantaneous phase information entropy, and a IA b IA c IA a IFr b IFr c IFr a IPh b IPh c IPh and d IPh The parameters of the function equation are shown in Tables 3-5.

[0123] Table 3. Parameters of the function equation ① described in step S43 under different seismic wavelet dominant frequencies.

[0124]

[0125] Table 4. Parameters of the function equation ② described in step S43 under different seismic wavelet dominant frequencies.

[0126]

[0127] Table 5. Parameters of the function equation ③ described in step S43 under different seismic wavelet dominant frequencies.

[0128]

[0129] Step S5: Fit the parameters of the function equation under different seismic wavelet dominant frequencies to obtain the mathematical relationship model between the parameters of the function equation in step S4 and the seismic wavelet dominant frequency; specifically including:

[0130] Step S51: The parameters of the function equation described in step S4 differ under different seismic wavelet dominant frequencies. Pairs of seismic wavelet dominant frequencies and function equation parameters described in step S4 are plotted in a two-dimensional coordinate system, where the horizontal coordinate represents the seismic wavelet dominant frequency and the vertical coordinate represents the function equation parameters, to obtain a scatter plot between the seismic wavelet dominant frequency and the function equation parameters described in step S4.

[0131] Step S52: Based on the data (function equation parameters and seismic wavelet dominant frequency) method described in Step S51, a mathematical relationship model between the function equation parameters described in Step S4 and the seismic wavelet dominant frequency is established through quantitative fitting analysis; the specific mathematical relationship model is shown in Table 6:

[0132] Table 6 shows the mathematical relationship between the parameters of the function equation and the dominant frequency of the seismic wavelet.

[0133]

[0134] Step S6: Process the actual multichannel reflection seismic data according to the seismic oceanography data processing method to obtain a reflection seismic profile containing seafloor bubble plumes.

[0135] The main processing flow for multichannel reflection seismic data from the sea surface and shallow strata below the seabed is as follows: defining the observation system → direct wave suppression and amplitude recovery → high-pass filtering → common midpoint gathering → constant velocity horizontal stacking (seawater sound speed ≈ 1500 m / s), and post-stack FK filtering for some sea surface profiles. The overall processing flow for seismic oceanographic data is largely the same as that for conventional reflection seismic data, but due to differences in research objectives, there are significant differences in the filtering process and direct wave processing: during the filtering process, minimum phase filtering is used to avoid artificial noise caused by strong low-frequency noise; in terms of direct wave processing, direct wave suppression is achieved by combining horizontal median filtering with matched subtraction.

[0136] Step S7: Perform seismic attribute analysis on the seafloor bubble plume reflection seismic profile described in Step S6 to obtain the actual seismic attribute (instantaneous amplitude, instantaneous frequency, and instantaneous phase) profile;

[0137] In this step, the method for obtaining the actual seismic attribute profile is operated according to the principle described in step S3, and will not be elaborated in detail here.

[0138] Step S8: The volume fraction profile of the submarine bubble plume is estimated by inverting multiple seismic attributes (instantaneous amplitude, instantaneous frequency, and instantaneous phase), specifically;

[0139] Step S81: Substitute the source frequency information (f) of the actual earthquake data into the mathematical relationship model described in step S5, calculate the function equation parameters described in step S4, and then obtain the functional relationship equation between the earthquake attributes and the bubble volume fraction under the source frequency (f) of the actual earthquake data.

[0140] Step S82: Substitute the seismic attribute values ​​(instantaneous amplitude, instantaneous frequency, and instantaneous phase) of the actual seismic attribute profile described in Step S7 into the functional relationship equation described in Step S81, and the volume fraction profile of the seafloor bubble plume can be estimated by calculation.

[0141] In addition, to reduce the uncertainty in estimating the bubble volume fraction, a weighted average is applied to the bubble volume fractions at the same location estimated based on different seismic attributes as described in step S82.

[0142] Step S9: Quantitatively study the velocity field of the seabed bubble plume;

[0143] Particle Image Velocimetry (PIV) technology is used to perform quantitative flow field analysis on video data of seabed bubble plumes, obtaining the flow velocity field of seabed bubble plumes. PIV technology records the movement information of tracer particles in the fluid through images, and the particle velocity is obtained after image processing. The particle velocity reflects the velocity of the carrier, i.e., the fluid.

[0144] Specifically, the particle image velocimetry technology is as follows:

[0145] Step S911: Use ffmpeg software to extract images from the video data and save them in bmp format. The image resolution should be the same as the corresponding video (e.g., 1980×1080).

[0146] Step S912: The PIV analysis uses a cross-correlation algorithm to process the image described in step S911. During the analysis, a window of appropriate size (such as a 32×32 grid) is selected, and the step size is a certain proportion of the window size (such as 50%).

[0147] Step S913: Post-process the calculation results described in step S912 to eliminate various interferences, obtain the flow velocity field, and then perform appropriate statistical analysis to obtain the final velocity measurement value (v).

[0148] Step S10: Combining the volume fraction profile of the submarine bubble plume described in Step S8 and the velocity field of the submarine bubble plume described in Step S9, the flux of the submarine bubble plume is estimated, specifically:

[0149] Step S101: Design a rectangular window of appropriate size (grid number such as 50×50). Based on the seismic profile of the seafloor bubble plume reflection described in Step S6, obtain the physical meaning information (horizontal distance (d) and round-trip travel time (t), etc.) contained in this rectangular window. The physical meaning can be directly obtained from the horizontal and vertical coordinates of the seismic profile of the seafloor bubble plume reflection.

[0150] Step S102: Based on the sound velocity-bubble volume fraction function relationship between the sound velocity model and the bubble volume fraction model of the seabed bubble plume described in Step S1, and the bubble volume fraction profile of the seabed bubble plume described in Step S8, calculate the sound velocity of the rectangular window region described in Step S101, and then convert the two-way travel time (t) of the rectangular window described in Step S101 into depth (h).

[0151] The specific relationship between the sound velocity and the bubble volume fraction function is as follows:

[0152] As can be seen from the calculation formula of the acoustic properties of the bubble-containing medium in step S15, there is a functional relationship between the sound velocity of the seabed bubble plume and the bubble volume fraction. Therefore, the correspondence between the sound velocity and the bubble volume fraction in the parameter model of the seabed bubble plume can be directly established. By substituting the bubble volume fraction profile in step S8 into the above correspondence, the corresponding sound velocity can be obtained. Then, the sound velocity of the rectangular window region in step S101 can be calculated. Then, the two-way travel time (t) of the rectangular window in step S101 can be converted into depth (h).

[0153] Step S103: Derive and calculate the bubble volume based on the bubble volume fraction formula, wherein the bubble volume fraction formula is as follows:

[0154]

[0155] Where φ is the bubble volume fraction, V Bubble V is the volume of the bubble. Seawater The volume of seawater;

[0156] The specific steps for calculating the bubble volume are as follows:

[0157] Step S1031: The two-dimensional profile of the seabed bubble plume is the projection of its three-dimensional fluid structure onto a plane;

[0158] Step S1032: Using the rectangular window described in step S101, scan the bubble volume fraction profile described in step S8, calculate the bubble volume fraction within the rectangular window area, and combine it with the seawater volume formula. Substituting the above parameter values ​​into the bubble volume fraction formula described in step S103 yields the bubble volume (V). Bubble );

[0159] Step S104: Using the rectangular window described in step S101, scan the velocity field (v) of the submarine bubble plume described in step S9 to obtain the velocity at the corresponding position described in step S1032, and combine it with the bubble volume (V) described in step S103. Bubble The volumetric flux of bubbles in that region can then be calculated.

[0160] Step S105: Perform appropriate statistical analysis on the bubble volume flux described in step S104 to finally estimate the flow flux of seabed bubble plumes.

[0161] In this scheme, a functional equation is used to quantitatively analyze the relationship between seismic properties and bubble volume fraction. Changes in the bubble volume fraction of submarine bubble plumes will cause significant changes in seismic response, and there is a strong correlation between the two. Therefore, under optimal noise conditions, seismic property analysis based on seismic profile response characteristics can be used to estimate submarine bubble plume flow rates. This further demonstrates that seismic oceanography provides a new, simple, and effective method for studying and capturing parameters of submarine bubble plumes.

[0162] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for estimating seafloor bubble plume flow based on seismic oceanography, characterized in that, Includes the following steps: Step S1: Establish a parameter model for submarine bubble plumes that matches the characteristics and intrinsic properties of actual plume records; Step S2: Based on the parameter model of the submarine bubble plume described in Step S1, numerical simulation is used to obtain seismic data and determine the seismic response characteristics of the submarine bubble plume. Step S3: Perform seismic attribute analysis on the seismic data obtained in step S2 to obtain a seismic attribute profile, which includes an instantaneous amplitude profile, an instantaneous frequency profile, and an instantaneous phase profile; Step S4: Quantitatively analyze the relationship between the seismic attributes and bubble volume fraction described in Step S3 using a functional equation. The specific functional equation is as follows: ， in, Let denoted as bubble volume fraction, IA as instantaneous amplitude, IFr as instantaneous frequency, and IPh as instantaneous phase information entropy. , , , , , , , , and For parameters of the function equation; Step S5: Fit the parameters of the function equation under different seismic wavelet dominant frequencies to obtain the mathematical relationship model between the parameters of the function equation in step S4 and the seismic wavelet dominant frequency; Step S6: Process the actual multichannel reflection seismic data based on seismic oceanography data processing methods to obtain a reflection seismic profile containing seafloor bubble plumes; Step S7: Perform seismic attribute analysis on the seabed bubble plume reflection seismic profile described in Step S6 to obtain the actual seismic attribute profile. Step S8: The volume fraction profile of the submarine bubble plume is estimated by inverting multiple seismic attributes, including instantaneous amplitude, instantaneous frequency, and instantaneous phase. Step S9: Quantitative study of the velocity field of the seabed bubble plume: Using particle image velocimetry technology, quantitative analysis of the flow field is performed on video data of the seabed bubble plume to obtain the velocity field of the seabed bubble plume. Step S10: Based on the volume fraction profile of the submarine bubble plume described in Step S8 and the velocity field of the submarine bubble plume described in Step S9, estimate the flux of the submarine bubble plume.

2. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 1, characterized in that, Step S1, establishing the parameter model for the submarine bubble plume flow, specifically includes the following steps: Step S11: Design the scale of the parameter model for the submarine bubble plume flow; Step S12: Based on physical oceanography data, and combining the seawater state equation and empirical formula for sound speed, establish an initial seawater model; Step S13: Based on the bubble dissolution model and stochastic medium theory, simulate and calculate the evolution process and distribution state of bubbles, and combine different bubble number models to calculate multiple bubble volume fraction models; The bubble volume fraction model is represented as follows: ， Where r is the bubble radius, and [] denotes the floor function. For the random perturbation of the bubble quantity model in the bubble-containing medium region, It is a second-order stationary spatial random process with a certain mean and variance, derived from the theory of random media. To make the radius of The spherical region is divided into ( (radius) The volume fraction of bubbles within the small spherical region; Step S14: Based on the modified gas equation of state and the gas density-velocity of sound function relationship, calculate the gas density and gas velocity of sound, and establish a gas density-velocity of sound model; The gas density, derived from the modified gas law, is as follows: ， in, For gas density, Where is the speed of sound in the gas, M is the molar mass, R is the universal gas constant, T is the absolute temperature, Z is the compressibility factor, and k1, k2, and p0 are temperature-dependent parameters. The specific relationship between gas density and speed of sound is as follows: ， Where γ = 1.314 is the adiabatic index of methane gas, and P is the pressure; Step S15: Based on the calculation formula of acoustic properties of bubble-containing medium, establish a bubble model by combining the bubble volume fraction model described in step S13 and the gas density sound velocity model described in step S14; The formula for calculating the acoustic properties of the bubble-containing medium is as follows: ， in, The density of the bubble-containing medium. The density of seawater, The velocity of sound in a bubble-containing medium. Bulk modulus Shear modulus For wave number, and These represent the density and equivalent elastic modulus of the bubble-containing medium, respectively. , and These are the modulus, the real part, and the imaginary part, respectively. Step S16: Couple the initial seawater model described in step S12 and the bubble model described in step S15 to establish a parameter model for the seabed bubble plume.

3. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 2, characterized in that, Step S2, determining the seismic response characteristics of submarine bubble plumes, specifically includes the following steps: Step S21: Forward modeling to acquire seismic record data from submarine bubble plume shot gauging; Different dominant frequencies of the Rake wavelet were selected to simulate the seismic wavelet. The finite difference method was used to decompose the acoustic wave equation to perform forward modeling of the parameter model of the seabed bubble plume with different bubble volume fractions, and the seismic record data of the seabed bubble plume shot gather were obtained. Step S22: Based on the above shot gather seismic record data, a depth-domain seismic oceanographic simulation profile reflecting the seismic response characteristics of seafloor bubble plumes is obtained using the reverse time migration imaging method.

4. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 3, characterized in that, The specific operations for step S3, seismic attribute analysis, include: Step S31: Perform a depth-time transformation on the depth-domain seismic oceanographic simulation profile to obtain a time-domain seismic oceanographic simulation profile, and perform a Hilbert transform on it to obtain an analytical signal; Step S32: Calculate the time-domain earthquake instantaneous attribute profile using the analytical signal described in step S31. The earthquake instantaneous attributes include instantaneous amplitude, instantaneous phase, and instantaneous frequency. The instantaneous amplitude is the root mean square of the real and imaginary parts of the analytical signal. The instantaneous phase is the arctangent value obtained by dividing the imaginary and real parts. The instantaneous frequency is the derivative of the phase with respect to time. Step S33: Perform time-depth conversion on the time-domain instantaneous seismic attribute profile obtained in step S32 to obtain the seismic attribute profile.

5. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 4, characterized in that, Step S4, the specific operations for quantitatively analyzing the relationship between seismic attributes and the bubble volume fraction function, include: Step S41: For the seismic attribute profile described in step S3, calculate the mean value of the seismic attribute at different rectangular locations within the submarine bubble plume, and the bubble volume fraction at the same location in the submarine bubble plume parameter model described in step S1. Step S42: Plot the paired seismic attribute values ​​and bubble volume fraction values, where the horizontal axis represents the bubble volume fraction and the vertical axis represents the seismic attribute values. The instantaneous amplitude and instantaneous frequency are plotted directly using the seismic attribute values ​​described in step S41 to plot their relationship curve with the bubble volume fraction, while the instantaneous phase is plotted by introducing information entropy as an intermediate variable to plot its relationship curve with the bubble volume fraction. Step S43: Then, through quantitative research, regression fitting is used to obtain the functional equation between seismic attributes and bubble volume fraction.

6. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 5, characterized in that, Step S5, establishing the mathematical relationship model between the parameters of the function equation and the dominant frequency of the seismic wavelet, includes the following steps: Step S51: The function equation parameters described in step S4 differ under different seismic wavelet dominant frequencies. Pairs of seismic wavelet dominant frequencies and function equation parameters are plotted in a two-dimensional coordinate system, where the horizontal coordinate represents the seismic wavelet dominant frequency and the vertical coordinate represents the function equation parameters. Step S52: Through quantitative fitting analysis, establish a mathematical relationship model between the parameters of the function equation and the dominant frequency of the seismic wavelet.

7. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 1, characterized in that, In step S6, when obtaining the seismic profile containing seafloor bubble plume reflections according to the seismic oceanographic data processing method, minimum phase filtering is used during the filtering process to avoid artificial noise caused by strong low-frequency noise; in terms of direct wave processing, direct wave suppression is achieved by combining horizontal median filtering with matched subtraction.

8. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 1, 6, or 7, characterized in that, Step S8 is implemented in the following way: Step S81: Based on the source frequency information of the actual earthquake data and the mathematical relationship model established in step S5, calculate the parameters of the function equation, and then obtain the functional relationship equation between the earthquake attributes and the bubble volume fraction at the source frequency of the actual earthquake data. Step S82: Based on the actual seismic attribute profile described in step S7 and the functional relationship equation described in step S81, the volume fraction profile of the seafloor bubble plume is estimated by calculation and inversion.

9. The method for estimating seafloor bubble plume flux based on seismic oceanography according to claim 8, characterized in that, The specific operations for estimating the flow rate of seabed bubble plumes in step S10 include: Step S101: Design a rectangular window of appropriate size, and based on the seismic profile containing the seafloor bubble plume reflection described in step S6, obtain the physical meaning information contained in the rectangular window, including horizontal distance and round-trip travel time. Step S102: Based on the sound velocity-bubble volume fraction function relationship between the sound velocity model and the bubble volume fraction model of the seabed bubble plume described in Step S1, and the bubble volume fraction profile of the seabed bubble plume described in Step S8, calculate the sound velocity of the rectangular window region described in Step S101, and then convert the two-way travel time of the rectangular window described in Step S101 into depth. Step S103: Calculate the bubble volume based on the bubble volume fraction formula, wherein the bubble volume fraction formula is as follows: ， in, This represents the volume fraction of air bubbles. This represents the volume of the bubble. The volume of seawater; Step S104: Based on the rectangular window described in step S101 and the bubble volume described in step S103, combined with the flow field of the seabed bubble plume described in step S9, the bubble volume flux in this region is calculated: ， Where d is the horizontal distance of the seafloor bubble plume in the rectangular window, h is the depth of the seafloor bubble plume in the rectangular window, and v is the velocity of the seafloor bubble plume in the rectangular window. Step S105: Perform statistical analysis on the bubble volume flux described in step S104 to finally estimate the flow flux of seabed bubble plumes.

10. The method for estimating seafloor bubble plume flow based on seismic oceanography according to claim 9, characterized in that, Step S103, calculating the bubble volume using the bubble volume fraction formula, includes the following specific steps: Step S1031: The two-dimensional profile of the seabed bubble plume is the projection of its three-dimensional fluid structure onto a plane; Step S1032: Based on the rectangular window described in step S101, and combined with the seabed bubble plume bubble volume fraction profile and seawater volume formula described in step S8, the bubble volume is calculated.

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