A method for real-time monitoring of leakage in a carbon dioxide storage demonstration project

Abstract

The application discloses a kind of carbon dioxide storage demonstration project leakage real-time monitoring method, it is related to leakage monitoring technical field, comprising: generating the normalized echo intensity and normalized concentration of seawater monitoring area at different depths;Adjacent depth sequence is defined based on normalized echo, the transmission direction polarity of adjacent depth sequence pair is valued based on the time delay of adjacent depth sequence pair;The vertical trend polarity of all spectral center frequency in bubble group is determined, and the vertical trend polarity of concentration distribution in seawater monitoring area is determined according to normalized concentration;Based on transmission direction polarity, the vertical trend polarity of all spectral center frequency and the vertical trend polarity of concentration distribution, the source direction criterion of bubble group is determined.The application improves the accuracy and reliability of leakage identification.

Description

Technical Field

[0001] This invention relates to the field of leakage monitoring technology, and in particular to a real-time leakage monitoring method for a carbon dioxide sequestration demonstration project. Background Technology

[0002] Nearshore carbon dioxide geological sequestration demonstration projects typically deploy a multi-channel real-time monitoring system above the injection section. This includes an underwater acoustic sensor array to acquire bubble scattering echoes, a marine chemical sensor array to acquire the partial pressure of carbon dioxide in seawater and its distribution with depth, and ocean current and sea state observation devices around the project. Under actual sea conditions, minute leakage signals may appear in the injection strata, while strong nearshore winds and waves can create whitecaps on the sea surface, drawing air into the water and forming a cluster of rising bubbles in a short time, producing an acoustic response similar to leakage echoes and causing instantaneous disturbances in surface carbon dioxide measurements. These two sources superimpose in time and space, easily interfering with the monitoring system's rapid identification and location of leaks. In some nearshore areas, the de-embedding of bubbles from waves occurs intermittently, posing challenges to the safety assessment and deployment decisions of the project.

[0003] Existing technologies mostly rely on a single acoustic or chemical quantity for alarms, often triggered by fixed thresholds or empirical rules, which are difficult to withstand short-term fluctuations caused by strong winds and waves. Some solutions only perform intensity comparisons or simple trend observations, lacking systematic interpretation using time delays and spectral core frequencies with depth, making it difficult to provide directional conclusions simultaneously from both propagation and chemical dimensions. At the same time, the sampling frequency is usually fixed, and the resolution cannot be dynamically improved based on criteria to carry out key tracking, resulting in the loss of details during critical periods or mistaking surface disturbances for leakage, making it difficult to meet the real-time, stable, and traceable monitoring requirements of demonstration projects.

[0004] To ensure the long-term stable operation of the demonstration project, a real-time method that can work continuously under complex sea conditions is needed. This method should be able to determine the main propagation direction of the bubble population in the water column, corroborate the changes in chemical distribution, and directly use the determination results for real-time adjustment of the sampling strategy. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies that often rely on fixed thresholds or empirical rules for triggering, making it difficult to withstand short-term fluctuations caused by strong winds and waves. Therefore, this invention proposes a real-time leakage monitoring method for a carbon dioxide sequestration demonstration project.

[0006] To address the problems existing in the prior art, the present invention adopts the following technical solution:

[0007] A real-time leakage monitoring method for a carbon dioxide sequestration demonstration project includes:

[0008] S1, Generate normalized echo intensity and normalized echo intensity at different depths in the seawater monitoring area. concentration;

[0009] S2. Define adjacent depth sequences based on normalized echoes, and assign values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay of adjacent depth sequence pairs.

[0010] S3. Determine the vertical polarity of all spectral center frequencies in the bubble population, based on normalization. Concentration determination in seawater monitoring areas Vertical polarity of concentration distribution;

[0011] S4. Based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is used as a criterion for determining the origin direction of the bubble community.

[0012] S5. Adjust the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the origin direction criterion of the bubble population;

[0013] S6. Generate an updated source direction criterion based on the current sampling frequency, and determine the leakage status of the seawater monitoring area based on the updated source direction criterion.

[0014] Preferably, the normalized echo intensity and normalized [data] of the seawater monitoring area at different depths are generated. Concentration, including:

[0015] Acquire the acoustic spectrum of an underwater acoustic sensor array at different depths;

[0016] Acquiring data from marine chemical sensor arrays at different depths concentration;

[0017] The vertical integral echo intensity is obtained by performing frequency domain integration on the acoustic spectrum.

[0018] The vertical integral echo intensity is normalized to obtain the normalized echo intensity;

[0019] right The concentration is normalized to obtain the normalized value. concentration.

[0020] Preferably, the adjacent depth sequence is defined based on the normalized echo, including:

[0021] At the same depth, all normalized echo intensities are processed into time series to obtain the echo intensity time series;

[0022] Two echo intensity time series at adjacent depths are defined as adjacent depth series.

[0023] Preferably, assigning values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay between adjacent depth sequence pairs includes:

[0024] Cross-correlation is performed on adjacent depth sequence pairs to obtain the cross-correlation function;

[0025] Peak search is performed on the cross-correlation function to obtain the maximum correlation value of the cross-correlation function;

[0026] The time delay corresponding to the maximum correlation value is used as the time delay of adjacent depth sequence pairs;

[0027] If the sign of the time delay is greater than 0, the signal propagation direction of the adjacent depth sequence pair is determined to be uplink propagation, and the polarity of the propagation direction of the adjacent depth sequence pair is assigned a positive 1; otherwise, the signal propagation direction is determined to be downlink propagation, and the polarity of the propagation direction is assigned a negative 1.

[0028] Preferably, determining the vertical trend polarity of all spectral center frequencies in the bubble population includes:

[0029] The spectral center frequencies of the bubble population at different depths were obtained by weighted averaging of the acoustic spectrum.

[0030] Calculate the frequency difference between two spectral center frequencies at adjacent depths;

[0031] The frequency difference sign of the statistical frequency difference;

[0032] The median frequency symbol is obtained by summing the medians of all frequency difference symbols.

[0033] The vertical trend polarity of all spectral center frequencies is determined based on the sign of the median frequency.

[0034] Preferably, based on normalization Concentration determination in seawater monitoring areas The vertical polarity of the concentration distribution includes:

[0035] At the same depth, for all normalizations The concentrations were processed into a time series to obtain the concentration time series.

[0036] Perform a difference operation on two concentration time series at adjacent depths to obtain a concentration difference sequence;

[0037] The sign of the concentration difference sequence is determined to obtain the concentration difference sign.

[0038] The median concentration sign is obtained by summing all the concentration difference signs and summing the medians.

[0039] Determine the seawater monitoring area based on the sign of the median concentration. Vertical polarity of concentration distribution.

[0040] Preferably, based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is a criterion for determining the origin direction of the bubble community, including:

[0041] The consistency of the propagation direction polarity and the vertical trend polarity of all spectral center frequencies is determined to obtain the acoustic polarity result;

[0042] Results on acoustic polarity and The vertical trend polarity of the concentration distribution is jointly determined to obtain a combined polarity value;

[0043] The sign of the combined polarity value is determined to obtain the origin direction criterion for the bubble population.

[0044] Preferably, adjusting the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the origin direction criterion of the bubble population includes:

[0045] If the value of the origin direction criterion is -1, then the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is set to twice the reference sampling frequency; otherwise, the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is kept at the reference sampling frequency.

[0046] Preferably, generating an updated source direction criterion based on the current sampling frequency includes:

[0047] Based on the current sampling frequency, generate the updated normalized echo intensity and the updated normalized... concentration;

[0048] Based on the updated normalized echo intensity and the updated normalized The concentration is generated based on the updated source direction criterion.

[0049] Preferably, the leakage status of the seawater monitoring area is determined based on the updated source direction criterion, including:

[0050] If the updated origin direction criterion value is -1, then it is determined that the injected material is in the formation. If a seabed leak is detected in the seawater monitoring area, the source of the seabed leak will be monitored. Otherwise, if there is surface disturbance caused by bubbles being dislodged from white waves in the seawater monitoring area, the disturbance near the sea surface will be monitored.

[0051] Compared with the prior art, the beneficial effects of the present invention are:

[0052] 1. In this invention, the acoustic response and chemical disturbance signals of seepage bubbles and white wave-embedded bubbles in strong nearshore sea states are superimposed in time and space, making it difficult for monitoring systems to quickly identify and locate leaks. This problem is effectively solved by constructing an acoustic-chemical dual-dimensional polarity fusion judgment system, based on normalization. Concentration time series were constructed, and the results were obtained by difference operation and median summation. The vertical polarity of the concentration distribution forms a chemical dimension criterion. Finally, the source direction criterion is generated by the joint determination of acoustic polarity and chemical polarity, so that the propagation characteristics and material distribution characteristics of the two types of bubbles can be clearly distinguished, eliminating signal superposition interference and improving the accuracy and reliability of leakage identification.

[0053] 2. In this invention, a technical approach of multi-polarity collaborative verification and symbolic criteria is adopted to correlate the vertical trend polarity of the propagation direction polarity spectrum center frequency with... The vertical trend polarity of the concentration distribution is incorporated into a unified judgment framework. First, the consistency between the polarity of the propagation direction and the vertical trend polarity of the spectral center frequency is judged to obtain the acoustic polarity result. Then, the acoustic polarity result is compared with... The vertical trend polarity of the concentration distribution is algebraically summed to obtain a combined polarity value. Finally, the sign of the combined polarity value is determined to output a discretized source direction criterion. The entire process can simultaneously characterize the source direction of the bubble group without the need for a preset empirical threshold, achieving cross-verification of acoustic and chemical dimensions. This effectively avoids misjudgment caused by short-term fluctuations in wind and waves affecting a single parameter, and meets the requirements of the demonstration project for the directionality and stability of monitoring results.

[0054] 3. In this invention, to address the problem that existing technologies typically have fixed sampling frequencies, which cannot dynamically improve resolution based on criteria for focused tracking, leading to the loss of details or misinterpreting surface disturbances as leaks during critical periods, a criterion-driven adaptive sampling and closed-loop monitoring mechanism is designed. This mechanism adjusts the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array in real time based on the source direction criterion of the bubble population. When the value of the source direction criterion is negative one, the current sampling frequency is set to twice the reference sampling frequency to enhance the temporal resolution of seabed leak source monitoring. When the value of the source direction criterion is not negative one, the current sampling frequency is maintained as the reference sampling frequency to avoid resource waste. Attached Figure Description

[0055] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0056] Figure 1This is a flowchart illustrating a real-time leakage monitoring method for a carbon dioxide sequestration demonstration project, as provided in an embodiment of the present invention. Detailed Implementation

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0058] Example: This example provides a real-time leakage monitoring method for a carbon dioxide sequestration demonstration project. See [link to relevant documentation]. Figure 1 Specifically, including:

[0059] S1, Generate normalized echo intensity and normalized echo intensity at different depths in the seawater monitoring area. concentration;

[0060] In embodiments of the present invention, normalized echo intensity and normalized echo data are generated at different depths within a seawater monitoring area. Concentration, including:

[0061] Acquire the acoustic spectrum of an underwater acoustic sensor array at different depths;

[0062] Acquiring data from marine chemical sensor arrays at different depths concentration;

[0063] Specifically, underwater acoustic sensor arrays and marine chemical sensor arrays are deployed vertically along the seawater monitoring area to collect acoustic and chemical signals from the target sea area, respectively. The underwater acoustic sensor arrays receive echo signals scattered by bubble swarms at different depths and perform Fast Fourier Transform (FFT) processing on the received time-domain signals to obtain the acoustic spectrum at that depth. Simultaneously, the marine chemical sensor arrays synchronously collect the carbon dioxide partial pressure values ​​of seawater samples at the depth corresponding to the acoustic acquisition points and convert the measured carbon dioxide partial pressure values ​​into concentration data to obtain the concentration at that depth. concentration.

[0064] Specifically, Concentration refers to the partial pressure concentration of carbon dioxide in seawater, that is, the partial pressure value produced by carbon dioxide dissolved in seawater. It reflects the amount of carbon dioxide dissolved in seawater and its relative change. During the monitoring process, Dissolved carbon dioxide concentration is often used as an important chemical parameter to characterize whether carbon dioxide has leaked. When carbon dioxide injected into the formation leaks, the dissolved carbon dioxide content in the surrounding seawater increases, leading to... The concentration rose abnormally, so this parameter plays a key role in the safety assessment of storage and real-time monitoring of leaks.

[0065] The vertically integrated echo intensity is obtained by performing frequency domain integration on the acoustic spectrum.

[0066] Specifically, the acoustic spectrum collected by the underwater acoustic sensor array at different depths is weighted and integrated according to the frequency dimension. By accumulating the energy distribution in the entire frequency domain point by point, the total energy of all frequency components at that depth is obtained in the vertical direction. This total reflects the overall intensity of the sound wave scattering formed by the bubble group at that depth, and thus forms the vertical integrated echo intensity, which is used to characterize the overall acoustic response amplitude of the carbon dioxide bubble group in the water.

[0067] The vertically integrated echo intensity is normalized to obtain the normalized echo intensity;

[0068] right The concentration is normalized to obtain the normalized value. concentration.

[0069] Specifically, the vertical integrated echo intensity at each depth at the same sampling time and the echo intensity at each depth are... Concentrations were used to form two depth-ordered profile sequences. First, each sequence was time-aligned and unit-consistentized, and then a moving median filter was used to remove instantaneous spikes and significant outliers. Next, the cross-depth median at the same time was used as the profile baseline for that moment. The normalized echo intensity was obtained by ratioing the vertical integral echo intensity at each depth point on the profile to this baseline. The same method was then applied to... Concentration profiles were normalized by baseline ratioing. Concentration; after ratioization, a slight smoothing by depth is performed on the normalized result to suppress minor fluctuations between samples, and the timestamp and depth identifier of each depth point are retained for subsequent adjacent depth difference and cross-correlation calculations; finally, two time-synchronized, depth-corresponding, dimensionless profile data are output, namely the normalized echo intensity profile and the normalized... Concentration profile.

[0070] Specifically, the acoustic spectrum represents the frequency distribution information formed by the scattering and propagation of a group of bubbles in a specific water environment. This frequency distribution can reflect the scale variation and spatial distribution characteristics of the bubbles. Concentration represents the partial pressure of dissolved carbon dioxide in seawater, a physical quantity that characterizes the solubility and concentration gradient of carbon dioxide in seawater. The vertically integrated echo intensity, obtained by frequency domain integration and subtraction of the acoustic spectrum, represents the cumulative result of scattered acoustic energy along the water depth direction. This intensity quantifies the contribution of scattering by bubble groups at different depths to the overall acoustic energy. The normalized echo intensity, obtained after normalization of the vertically integrated echo intensity, represents the relative acoustic energy distribution at different depths after eliminating absolute differences in magnitude, making the results comparable across different depths. Normalized concentration obtained after normalization Concentration represents the relative concentration distribution at different depths after eliminating baseline concentration differences, thus allowing direct correlation with acoustic results and enabling monitoring of carbon dioxide leakage processes.

[0071] Overall, the generation of normalized echo intensity and normalized... Concentration is used to eliminate absolute differences in magnitude and environmental background fluctuations, enabling direct comparison and fusion analysis of acoustic and chemical information at different depths under the same dimensions and relative scale. Normalization suppresses uncertainties caused by transducer sensitivity differences, background noise fluctuations, and natural changes in the aquatic environment, ensuring the obtained echo intensity and... Concentration only reflects the real anomalies related to the activity of bubble groups, thus providing a reliable input basis for subsequent propagation direction determination, spectrum core frequency trend analysis, and differentiation between leakage and surface disturbance, and ensuring that the monitoring results are consistent and comparable in both time and depth dimensions.

[0072] S2. Define adjacent depth sequences based on normalized echoes, and assign values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay of adjacent depth sequence pairs.

[0073] In an embodiment of the present invention, defining adjacent depth sequences based on normalized echoes includes:

[0074] At the same depth, all normalized echo intensities are processed into time series to obtain the echo intensity time series;

[0075] Two echo intensity time series at adjacent depths are defined as adjacent depth series.

[0076] Specifically, normalized echo intensity refers to the dimensionless acoustic energy parameter obtained after depth rationing and baseline correction. This parameter only reflects the true changes in sound wave scattering by the bubble population. Echo intensity time series refers to the dynamic sequence formed by arranging the echo intensities collected continuously over time and normalized at the same depth. This sequence can characterize the energy fluctuation process of the bubble population at that depth over time. Adjacent depth sequence refers to the combination of echo intensity time series formed at two adjacent depth positions. This combination is used to compare the propagation sequence and change characteristics of the same disturbance at different depths, thereby revealing the vertical transmission law and propagation direction characteristics of the bubble population.

[0077] Specifically, at the same depth, the continuously acquired normalized echo intensities are arranged in chronological order to form an echo intensity time series that reflects the change of acoustic energy at that depth over time. Based on this, echo intensity time series at two adjacent depths are paired, and the pairing result is defined as the adjacent depth series for subsequent differential analysis and propagation direction calculation. This method, which first obtains the time-continuous echo intensity at a single depth and then establishes the correspondence between adjacent depths in the depth dimension, ensures the logical connection between the time series and the spatial series, providing reliable input data for accurately extracting the vertical propagation delay and directional polarity of the bubble population.

[0078] In an embodiment of the present invention, assigning a value to the propagation direction polarity of adjacent depth sequence pairs based on the time delay of adjacent depth sequence pairs includes:

[0079] Cross-correlation is performed on adjacent depth sequence pairs to obtain the cross-correlation function;

[0080] Specifically, two echo intensity time series at adjacent depths are aligned along a unified sampling time axis. A time displacement is gradually applied to one of the time series within a certain range. Each displacement is multiplied point-by-point with the other time series and summed over the entire time period. This sum is then divided by the square root of the sum of squares of their respective energy values ​​to achieve standardization. The normalization results corresponding to different displacement values ​​are recorded sequentially, ultimately forming a function curve with time displacement as the independent variable and similarity degree as the dependent variable. This function curve is the cross-correlation function of adjacent depth sequence pairs, used to characterize the propagation correlation of disturbance signals between the two depths.

[0081] Peak search is performed on the cross-correlation function to obtain the maximum correlation value of the cross-correlation function;

[0082] The time delay corresponding to the maximum correlation value is used as the time delay of adjacent depth sequence pairs;

[0083] Specifically, after obtaining the cross-correlation function of adjacent depth sequence pairs, the function curve is first scanned and numerically compared point by point within a preset time delay range to find the peak point with the highest similarity in the curve, thereby obtaining the maximum correlation value of the cross-correlation function. The time displacement corresponding to the maximum correlation value is extracted as the time delay that can characterize the difference in the propagation of the disturbance signal between the two depths. By performing peak search first and then assigning physical meaning to the time displacement corresponding to the peak, it can be ensured that the delay calculation result comes directly from the strongest signal correlation, thus providing a reliable basis for the subsequent determination of the propagation direction.

[0084] Specifically, the cross-correlation function is the result of calculating the similarity between two time series by sliding time displacement between adjacent depth sequences. This function reflects the arrival order and similarity of the same disturbance signal at different depths. The maximum correlation value of the cross-correlation function is the maximum value that appears on the cross-correlation function curve. The larger this value is, the stronger the correspondence between the two time series at adjacent depths under that time delay, representing the highest degree of matching between them. The time delay is the time displacement corresponding to the maximum peak value of the cross-correlation function. This time displacement represents the propagation time difference experienced by the acoustic disturbance or bubble group signal from one depth to an adjacent depth.

[0085] If the sign of the time delay is greater than 0, the signal propagation direction of the adjacent depth sequence pair is determined to be uplink propagation, and the polarity of the propagation direction of the adjacent depth sequence pair is assigned a positive 1; otherwise, the signal propagation direction is determined to be downlink propagation, and the polarity of the propagation direction is assigned a negative 1.

[0086] Specifically, when the sign of the time delay is greater than zero, it indicates that in the calculation of the cross-correlation function, the deep sequence must be shifted backward to achieve maximum correlation with the shallow sequence. This phenomenon suggests that in actual observations, the shallow signal appears earlier than the deep signal; that is, the disturbance source or bubble group is detected first in the shallow layer and then appears in the deep layer. Therefore, it can be inferred that the disturbance or bubble group propagates from the bottom up to the shallow layer, exhibiting an upward propagation trend, and thus the polarity of the propagation direction is assigned a positive one. When the sign of the time delay is less than zero, it indicates that in the calculation of the cross-correlation function, the deep sequence needs to be shifted forward to achieve maximum correlation with the shallow sequence. One result indicates that deep signals appeared earlier than shallow signals during the observation process. That is, the disturbance source or bubble group was first detected in the deep layer and then propagated to the shallow layer. This suggests that the disturbance or bubble group exhibits a downward propagation path, i.e., a downward propagation trend. Therefore, the polarity of the propagation direction is assigned a value of negative one to clearly distinguish the motion direction opposite to the upward propagation in data processing. Through this direction determination method based on the time delay sign, the temporal sequence relationship between sequences can be transformed into clear propagation direction information, thereby ensuring that the polarity of the propagation direction has a clear physical meaning and providing a basis for subsequent comprehensive comparison with the spectral center frequency trend and chemical concentration trend.

[0087] In general, assigning values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay between them is because, in nearshore carbon dioxide sequestration demonstration projects, the movement of bubble swarms in the water can exhibit upward, downward, or oblique propagation. This direction of movement determines the order in which sensors at different depths receive disturbance signals, resulting in a time delay between the echo intensity time series of adjacent depths. By calculating the sign of this time delay, it can be determined whether the disturbance appears first in the shallow or deep layers, thus directly mapping it to an upward or downward propagation trend. Assigning this propagation direction polarity to adjacent depth sequence pairs makes it a physical criterion for describing the movement direction of bubble swarms. This not only avoids confusion between disturbances caused by surface white waves de-embedding bubbles and actual carbon dioxide leakage signals but also ensures the consistency and physical interpretability of the polarity direction in subsequent judgment processes.

[0088] It should be noted that disturbances caused by surface white wave detachment of bubbles refer to the phenomenon in nearshore waters where, when waves break, a large amount of air is drawn into the surface layer of the seawater, forming irregularly distributed groups of bubbles. Driven by surface fluctuations, these bubbles detach and enter the water body in a short period of time, exhibiting rapid upward movement or turbulent motion. This results in echo enhancement and acoustic scattering effects in monitoring sensors that are similar to those of real carbon dioxide leaks. At the same time, there are instantaneous abnormal fluctuations in the concentration of carbon dioxide in the seawater. Although this type of disturbance has the characteristics of bubble signals, its location is concentrated on the surface and it is highly intermittent and sporadic. It does not have the physical property of continuous release from deep layers, so it needs to be distinguished from real leak events.

[0089] S3. Determine the vertical polarity of all spectral center frequencies in the bubble population, based on normalization. Concentration determination in seawater monitoring areas Vertical polarity of concentration distribution;

[0090] In embodiments of the present invention, determining the vertical trend polarity of all spectral center frequencies in the bubble population includes:

[0091] The spectral center frequencies of the bubble population at different depths were obtained by weighted averaging of the acoustic spectrum.

[0092] Specifically, firstly, noise is subtracted and amplitude is calibrated in the acoustic spectrum to ensure that the energy values ​​corresponding to each frequency component accurately reflect the scattering intensity of the bubble population. Then, within the effective frequency band, each frequency point is multiplied by its corresponding energy value and accumulated over the entire frequency domain. Simultaneously, the energy value itself is accumulated as a normalized denominator. Finally, the accumulated value of the frequency-energy product is divided by the accumulated energy value to obtain the spectral core frequency of the bubble population at that depth. By repeating the above operation at all depths and recording the depth and time markers, spectral core frequency profiles of the bubble population at different depths can be formed for further vertical trend polarity determination.

[0093] Specifically, the spectral center frequency refers to the average frequency position in the acoustic spectrum calculated by weighting the energy distribution. This frequency value reflects the main concentrated area of ​​energy scattered by the bubble swarm. Its physical significance lies in its ability to characterize the equivalent scale and acoustic response characteristics of the bubble swarm. When the bubble radius changes, the energy distribution of acoustic scattering also shifts, thus causing a change in the spectral center frequency.

[0094] Calculate the frequency difference between two spectral center frequencies at adjacent depths;

[0095] The frequency difference sign of the statistical frequency difference;

[0096] Specifically, the frequency difference refers to the numerical difference between the spectral core frequencies of two adjacent depths. This difference reflects the shift in the acoustic resonance frequency of the bubble group as it changes with depth, thus revealing the contraction or expansion trend of the bubbles during vertical movement. The sign of the frequency difference refers to the result after symbolic processing of the frequency difference. When the sign is positive, it indicates that the spectral core frequency of the deeper layer is higher than that of the shallower layer, indicating that the bubble radius increases during the ascent. When the sign is negative, it indicates that the spectral core frequency of the deeper layer is lower than that of the shallower layer, indicating that the bubble radius decreases during the descent. This can provide a physical basis for determining the vertical propagation trend of the bubble group.

[0097] The median frequency symbol is obtained by summing the medians of all frequency difference symbols.

[0098] The vertical trend polarity of all spectral center frequencies is determined based on the sign of the median frequency.

[0099] Specifically, after obtaining the signs of the frequency differences between all adjacent depth spectral centers, these signs are used as a discrete finite set for median calculation. By taking the median, the interference of individual outliers or local disturbances on the overall trend judgment can be effectively avoided, thus obtaining a frequency median sign that can represent the overall direction of frequency change in the depth range. The frequency median sign is used as a criterion to assign to the overall spectral center frequency profile to determine the uniform trend polarity of all spectral center frequencies in the vertical direction. If the frequency median sign is positive, it indicates an overall upward trend; if the frequency median sign is negative, it indicates an overall downward trend. This enables the overall determination of the vertical evolution direction of the bubble population in different depth ranges.

[0100] Specifically, determining the vertical trend polarity of all spectral core frequencies based on the median sign is to extract the statistical results that best represent the overall direction from multi-depth frequency variations, thereby avoiding misjudgments caused by local noise or individual outliers. By summarizing the median signs of frequency differences between adjacent depths, a robust overall sign can be obtained. This sign serves as a unified trend indicator and is assigned to the entire spectral core frequency profile, thus ensuring the stability, consistency, and physical interpretability of the determination of the overall vertical propagation trend of the bubble population. This provides a solid basis for subsequent comprehensive judgment of propagation direction polarity and chemical concentration trends.

[0101] In embodiments of the present invention, according to normalization Concentration determination in seawater monitoring areas The vertical polarity of the concentration distribution includes:

[0102] At the same depth, for all normalizations The concentrations were processed into a time series to obtain the concentration time series.

[0103] Perform a difference operation on two concentration time series at adjacent depths to obtain a concentration difference sequence;

[0104] Specifically, the normalized carbon dioxide concentration time series collected at two adjacent depth locations are used as input data. First, the two time series are aligned on the time axis. Then, at each time point, the numerical difference between the deep and shallow concentrations is calculated. The differences at all time points are arranged sequentially to form a concentration difference sequence that reflects the relative change in carbon dioxide concentration between adjacent depths. This difference sequence not only preserves the dynamic characteristics of concentration over time, but also reveals the directionality of vertical transport or diffusion.

[0105] The sign of the concentration difference sequence is determined to obtain the concentration difference sign.

[0106] Specifically, the obtained concentration difference sequence is used as input data. The difference at each time point in the concentration difference sequence is searched one by one. When the difference is greater than zero, it indicates that the concentration in the deeper layer is higher than that in the shallower layer, and the sign of that time point is determined to be positive one. When the difference is less than zero, it indicates that the concentration in the shallower layer is higher than that in the deeper layer, and the sign of that time point is determined to be negative one. When the difference is zero, it indicates that the concentrations in the deeper and shallower layers are equal, and the sign of that time point is determined to be zero. Through this symbolization process, the continuous numerical difference is transformed into a discrete symbol sequence, resulting in a concentration difference symbol that can intuitively represent the direction of concentration change.

[0107] Specifically, the concentration time series refers to the arrangement of normalized carbon dioxide partial pressure concentration data acquired continuously over time at the same depth. This series reflects the dynamic change pattern of carbon dioxide content in seawater at that depth. The concentration difference series refers to the set of differences obtained by subtracting the concentration time series of two adjacent depths point by point, revealing the relative change in carbon dioxide distribution between adjacent depths. The concentration difference sign refers to the result obtained by judging the sign of the concentration difference series point by point. When the sign is positive, it indicates that the concentration in the deeper layer is higher than that in the shallower layer, reflecting the upward transport trend of carbon dioxide. When the sign is negative, it indicates that the concentration in the shallower layer is higher than that in the deeper layer, reflecting the downward diffusion or disturbance trend of carbon dioxide. This parameter provides a basic criterion for determining chemical vertical polarity.

[0108] The median concentration sign is obtained by summing all the concentration difference signs and summing the medians.

[0109] Determine the seawater monitoring area based on the sign of the median concentration. Vertical polarity of concentration distribution.

[0110] Specifically, all concentration difference symbols are aggregated into a set of discrete symbol data in depth order. A median operation is then performed on this set of discrete symbols to obtain a single median concentration symbol, which is used as the representative symbol for the entire profile at that sampling time. This representative symbol is then used as a criterion to determine the seawater monitoring area. The vertical trend polarity of concentration distribution is determined by the following: when the sign is positive, it indicates that the concentration in deeper layers is generally higher than that in shallower layers, and the vertical trend polarity is positive one, representing the direction of concentration field enrichment in deeper layers; when the sign is negative, it indicates that the concentration in shallower layers is generally higher than that in deeper layers, and the vertical trend polarity is negative one, representing the direction of concentration field enrichment in the surface layer.

[0111] Specifically, The vertical polarity of concentration distribution refers to the overall directional criterion obtained by comparing the partial pressure concentration of carbon dioxide at different depths within a seawater monitoring area. This criterion is used to characterize the main trend of concentration variation in the vertical space. When the concentration is generally higher than that in the shallow layer, it indicates that carbon dioxide is diffusing downwards or accumulating in deeper layers in the water body; in this case, the vertical trend polarity is positive one. When the concentration is generally higher than that of deeper layers, it indicates that carbon dioxide is being transported upwards or enriched at the surface in the water body. In this case, the polarity of the vertical trend is negative one.

[0112] Overall, the vertical trend polarity of all spectral center frequencies in the bubble population is determined and combined with normalization. Concentration determination in seawater monitoring areas The vertical trend polarity of the concentration distribution is used to cross-validate carbon dioxide leakage using both acoustic and chemical information. The vertical trend polarity of the spectral center frequency reflects the direction and scale changes of the bubble population in the water. The vertical polarity of the concentration distribution can reflect the dissolution and diffusion process of carbon dioxide in water. By simultaneously calculating and comparing the polarity trends of the two types of physical quantities, misjudgment caused by surface disturbances or environmental noise interference from a single signal can be effectively avoided, thereby improving the reliability of the identification of real leakage events and the physical interpretation.

[0113] S4. Based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is used as a criterion for determining the origin direction of the bubble community.

[0114] In embodiments of the present invention, based on the propagation direction polarity, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is a criterion for determining the origin direction of the bubble community, including:

[0115] The consistency of the propagation direction polarity and the vertical trend polarity of all spectral center frequencies is determined to obtain the acoustic polarity result;

[0116] Specifically, the propagation direction polarity and the vertical trend polarity of all spectral center frequencies are differentially calculated, and then the sign of the difference result is determined. When the difference is zero, it means that the two are completely consistent in direction, and the resulting acoustic polarity is positive one. When the difference is not zero, it means that the two are deviated in direction, and the resulting acoustic polarity is negative one. Through this consistency determination method based on difference calculation, the propagation direction polarity and spectral trend polarity can be unified under the same criterion.

[0117] Results on acoustic polarity and The vertical trend polarity of the concentration distribution is jointly determined to obtain a combined polarity value;

[0118] Specifically, acoustic polarity results and The vertical trend polarity of the concentration distribution is characterized by specific values ​​(such as +1 or -1) representing the vertical trend direction of the corresponding dimension; subsequently, the values ​​corresponding to the acoustic polarity results are compared with... The values ​​corresponding to the vertical trend polarity of the concentration distribution are directly summed algebraically. This summation process integrates monitoring information from both acoustic and chemical dimensions, ultimately yielding a comprehensive result that reflects the vertical propagation of the bubble population. The combined polarity value of the correlation characteristics of vertical concentration distribution.

[0119] The sign of the combined polarity value is determined to obtain the origin direction criterion for the bubble population.

[0120] Specifically, the sign of the joint polarity composite value is determined at each moment. A joint polarity composite value greater than 0 is defined as a positive sign, and a joint polarity composite value less than 0 is defined as a negative sign. This sign is used as the criterion for the origin direction of the bubble group in the final output, thereby determining the overall vertical propagation trend of the bubble group under a unified numerical framework.

[0121] Specifically, the acoustic polarity result refers to the overall acoustic directionality criterion determined by the consistency relationship between the polarity of the propagation direction and the vertical trend polarity of the spectral center frequency. This result reflects the main motion direction of the bubble group in the water body; the combined polarity value refers to the result of combining the acoustic polarity result with... The unified criterion obtained by comprehensively comparing the vertical trend polarity of the concentration distribution, which integrates the directional trends of acoustic and chemical signals, can more accurately reflect the true state of carbon dioxide leakage or surface disturbance under the cross-verification of multi-source information; the origin direction criterion refers to the final directional result obtained after determining the sign of the joint polarity comprehensive value, which is to reveal the origin location and propagation path of the bubble group, and is a key indicator for judging whether the leakage source comes from the seabed strata or surface disturbance.

[0122] Overall, based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is used to determine the origin direction criterion of the bubble group because a single physical quantity is often easily affected by local disturbances or accidental anomalies, resulting in deviations. The three different dimensions of polarity information reflect the signal propagation dynamics, acoustic resonance behavior, and the changing trend of chemical concentration distribution, respectively. Comprehensively judging them under a unified framework can minimize the interference of accidental noise, highlight the true propagation direction of the bubble group as a whole, and thus ensure that the origin direction criterion has stability, reliability, and verifiability.

[0123] S5. Adjust the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the origin direction criterion of the bubble population;

[0124] In embodiments of the present invention, adjusting the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the origin direction criterion of the bubble community includes:

[0125] If the value of the origin direction criterion is -1, then the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is set to twice the reference sampling frequency; otherwise, the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is kept at the reference sampling frequency.

[0126] Specifically, when the source direction criterion value is -1, it indicates a suspected leak on the seabed. In this case, to collect monitoring data from the underwater acoustic sensor array and the marine chemical sensor array more densely and improve the temporal resolution and data precision of the seabed leak source monitoring, the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is adjusted to twice the reference sampling frequency. When the source direction criterion value is not -1, it means that the monitoring scenario is mainly disturbances near the sea surface, and there is no need for excessively high sampling density. Therefore, it is sufficient to keep the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array as the reference sampling frequency. By adaptively adjusting the sampling frequency according to the source direction criterion, the effectiveness of leak source monitoring can be ensured while avoiding unnecessary waste of resources, achieving a balance between monitoring efficiency and resource utilization.

[0127] S6. Generate an updated source direction criterion based on the current sampling frequency, and determine the leakage status of the seawater monitoring area based on the updated source direction criterion.

[0128] In an embodiment of the present invention, generating an updated origin direction criterion based on the current sampling frequency includes:

[0129] Based on the current sampling frequency, generate the updated normalized echo intensity and the updated normalized... concentration;

[0130] Based on the updated normalized echo intensity and the updated normalized The concentration is generated based on the updated source direction criterion.

[0131] Specifically, firstly, according to the adjusted and determined current sampling frequency, the underwater acoustic sensor array is manipulated to collect echo signals from various depths of seawater, while simultaneously the marine chemical sensor array is manipulated to synchronously collect signals from the corresponding depths. Concentration data; then, preprocessing operations such as denoising and amplitude normalization are performed on the acquired echo signals to obtain the updated normalized echo intensity. Concentration data were standardized to eliminate environmental background interference, resulting in updated normalized data. Concentration; then, based on the updated normalized echo intensity, the polarity of its propagation direction and the vertical trend polarity of the spectral center frequency are analyzed, and then combined with the updated normalized... The vertical polarity of the concentration is calculated through algebraic operation rules to generate an updated origin direction criterion that reflects the origin characteristics of the bubble community in the seawater medium at the current moment.

[0132] In an embodiment of the present invention, determining the leakage status of a seawater monitoring area based on an updated source direction criterion includes:

[0133] If the updated origin direction criterion value is -1, then it is determined that the injected material is in the formation. If a seabed leak is detected in the seawater monitoring area, the source of the seabed leak will be monitored. Otherwise, if there is surface disturbance caused by bubbles being dislodged from white waves in the seawater monitoring area, the disturbance near the sea surface will be monitored.

[0134] Specifically, when the updated source direction criterion value is negative one, the system will determine that there is a submarine leak of carbon dioxide injected into the formation in the seawater monitoring area, and immediately focus the monitoring task on the fine-grained tracking of the submarine leak source to ensure that the leak risk can be identified and quantified in the early stage. When the updated source direction criterion is not negative one, the system will determine that there is no significant submarine leak in the seawater monitoring area. In this case, it is considered that the observed disturbance originates from the disturbance caused by the de-embedding of bubbles in the surface white waves. Therefore, the monitoring task will be focused on the disturbance monitoring near the sea surface to avoid misjudgment and ensure the scientific nature of the data interpretation. This logic realizes the effective distinction between deep leakage and shallow disturbance through the source direction criterion, thereby ensuring that the system can conduct targeted monitoring and early warning of potential risks in the carbon dioxide sequestration process.

[0135] Specifically, the updated origin direction criterion is a fusion of the bubble vertical propagation characteristics reflected by the updated normalized echo intensity and the updated normalized... The combined result of the chemical distribution characteristics reflected by the concentration has a clear correspondence between its numerical sign and the origin direction of the bubble population: when the value is -1, it indicates that both acoustic and chemical signals jointly indicate that the bubble population diffuses from the seabed into the water body, which is consistent with the direction of injection into the strata. The material migration characteristics during a subsea leak are consistent, thus confirming the existence of a subsea leak. When the value is not -1, the acoustic and chemical signals together indicate that the bubble group diffuses downward from the sea surface, which is consistent with the physical process of bubbles being de-embedded in white waves and settling in the water. Therefore, it is determined to be a surface disturbance. Through this multi-parameter fusion judgment logic, leaks and natural disturbances can be effectively distinguished, improving the reliability of monitoring results.

[0136] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for real-time monitoring of leaks in a carbon dioxide sequestration demonstration project, characterized in that, Includes the following steps: S1, Generate normalized echo intensity and normalized echo intensity at different depths in the seawater monitoring area. concentration; S2. Define adjacent depth sequences based on normalized echoes, and assign values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay of adjacent depth sequence pairs. S3. Determine the vertical polarity of all spectral center frequencies in the bubble population, based on normalization. Concentration determination in seawater monitoring areas Vertical polarity of concentration distribution; S4. Based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is used as a criterion for determining the origin direction of the bubble community. S5. Adjust the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the origin direction criterion of the bubble population; S6. Generate an updated source direction criterion based on the current sampling frequency, and determine the leakage status of the seawater monitoring area based on the updated source direction criterion.

2. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, Normalized echo intensity and normalized echo data at different depths in the seawater monitoring area were generated. Concentration, including: Acquire the acoustic spectrum of an underwater acoustic sensor array at different depths; Acquiring data from marine chemical sensor arrays at different depths concentration; The vertical integral echo intensity is obtained by performing frequency domain integration on the acoustic spectrum. The vertical integral echo intensity is normalized to obtain the normalized echo intensity; right The concentration is normalized to obtain the normalized value. concentration.

3. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, Based on the definition of normalized echoes, adjacent depth sequences are included, including: At the same depth, all normalized echo intensities are processed into time series to obtain the echo intensity time series; Two echo intensity time series at adjacent depths are defined as adjacent depth series.

4. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, Assigning values ​​to the propagation direction polarity of adjacent depth sequence pairs based on the time delay between them, including: Cross-correlation is performed on adjacent depth sequence pairs to obtain the cross-correlation function; Peak search is performed on the cross-correlation function to obtain the maximum correlation value of the cross-correlation function; The time delay corresponding to the maximum correlation value is used as the time delay of adjacent depth sequence pairs; If the sign of the time delay is greater than 0, the signal propagation direction of the adjacent depth sequence pair is determined to be uplink propagation, and the polarity of the propagation direction of the adjacent depth sequence pair is assigned a positive 1; otherwise, the signal propagation direction is determined to be downlink propagation, and the polarity of the propagation direction is assigned a negative 1.

5. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 2, characterized in that, Determine the vertical polarity of all spectral center frequencies in the bubble population, including: The spectral center frequencies of the bubble population at different depths were obtained by weighted averaging of the acoustic spectrum. Calculate the frequency difference between two spectral center frequencies at adjacent depths; The frequency difference sign of the statistical frequency difference; The median frequency symbol is obtained by summing the medians of all frequency difference symbols. The vertical trend polarity of all spectral center frequencies is determined based on the sign of the median frequency.

6. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, According to normalization Concentration determination in seawater monitoring areas The vertical polarity of the concentration distribution includes: At the same depth, for all normalizations The concentrations were processed into a time series to obtain the concentration time series. Perform a difference operation on two concentration time series at adjacent depths to obtain a concentration difference sequence; The sign of the concentration difference sequence is determined to obtain the concentration difference sign. The median concentration sign is obtained by summing all the concentration difference signs and summing the medians. Determine the seawater monitoring area based on the sign of the median concentration. Vertical polarity of concentration distribution.

7. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, Based on the polarity of the propagation direction, the vertical trend polarity of all spectral center frequencies, and The vertical polarity of the concentration distribution is a criterion for determining the origin direction of the bubble community, including: The consistency of the propagation direction polarity and the vertical trend polarity of all spectral center frequencies is determined to obtain the acoustic polarity result; Results on acoustic polarity and The vertical trend polarity of the concentration distribution is jointly determined to obtain a combined polarity value; The sign of the combined polarity value is determined to obtain the origin direction criterion for the bubble population.

8. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, Adjusting the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array based on the bubble community origin direction criterion includes: If the value of the origin direction criterion is -1, then the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is set to twice the reference sampling frequency; otherwise, the current sampling frequency of the underwater acoustic sensor array and the marine chemical sensor array is kept at the reference sampling frequency.

9. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, The updated source direction criterion is generated based on the current sampling frequency, including: Based on the current sampling frequency, generate the updated normalized echo intensity and the updated normalized... concentration; Based on the updated normalized echo intensity and the updated normalized The concentration is generated based on the updated source direction criterion.

10. The real-time leakage monitoring method for a carbon dioxide sequestration demonstration project according to claim 1, characterized in that, The leakage status of the seawater monitoring area is determined based on the updated source direction criterion, including: If the updated origin direction criterion value is -1, then it is determined that the injected material is in the formation. If a seabed leak is detected in the seawater monitoring area, the source of the seabed leak will be monitored. Otherwise, if there is surface disturbance caused by bubbles being dislodged from white waves in the seawater monitoring area, the disturbance near the sea surface will be monitored.

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