Geological safety operation monitoring system for gas storage

Abstract

The application discloses a kind of gas storage geological safe operation monitoring systems, belong to gas storage safety monitoring field, this method includes fault sealing monitoring subsystem, for real-time monitoring fault zone data;Cap sealing monitoring subsystem, for real-time monitoring cap data.Geo-data processing center, for calculating fault sealing index according to fault zone data, using fault sealing index model;According to cap data, calculate cap sealing index using cap sealing index model;And according to fault sealing index and cap sealing index, using preset safety level evaluation threshold, determine gas storage operation safety level.The application solves the problem that the existing monitoring technology has single monitoring angle, does not have multidimensional sealing analysis and evaluation.

Description

Technical Field

[0001] This invention belongs to the field of gas storage safety monitoring, and particularly relates to a gas storage geological safety operation monitoring system. Background Technology

[0002] A gas storage system consists of two parts: surface engineering and underground gas storage. During the operation of the gas storage system, the dynamic changes in the formation pressure system affect the sealing of faults and caprocks.

[0003] During the long-term operation of the gas storage facility, the alternating stress between the surface engineering and the underground gas storage during the long-term cyclic injection and production process may lead to local shear failure of the fault and caprock, resulting in leakage risks. At the same time, since some well platforms are located on the edge of the slope, on-site observations have shown that some platforms have developed cracks, and there is a possibility of instability and sliding.

[0004] During the periodic injection and extraction of gas at high flow rates in gas storage facilities, the stability and permeability of underground rock masses and faults directly affect the storage capacity, injection and extraction efficiency, and safe operation of the gas storage facility. High-flow-rate alternating injection and extraction may lead to mechanical instability in fault zones, inducing gas leakage. The mechanical mechanisms mainly include two types: first, tensile failure caused by a sharp increase in pore pressure within the rock mass; and second, shear slippage of pre-existing faults. The fault gouge structure and diagenetic cementation filling the fault zone are disrupted, significantly reducing displacement pressure and increasing porosity and permeability, leading to gas leakage along the fault zone.

[0005] During the site selection optimization process for gas reservoirs, although some small faults or fractures may exist, these pre-existing faults typically exhibit good mechanical stability and sealing performance before natural gas injection. However, during the operation of the gas reservoir, the periodic large-volume gas injection and production cause frequent changes in the pore pressure and effective stress of the formation on both sides of the fault zone in the far and near fields. During the gas injection process, gas-water seepage leads to complex hydration reactions between the original formation water and the pseudo-fault, altering the physical properties (porosity and permeability) of the fault zone. When the shear stress on the fault plane exceeds the shear strength, the fault will undergo shear slip failure. The mechanical instability and gas leakage changes of existing faults are controlled by both engineering factors (fluid injection rate and volume, location of injection wells relative to the fault, etc.) and geological conditions and geomechanical characteristics (including the physical and mechanical properties of reservoir rocks, fault distribution and geometry, physical properties of the fault zone, and the stress state of the area where the fault is located, etc.). Therefore, clarifying the influence mechanism of geological and engineering factors on the mechanical and seepage characteristics of fault zones is the key to formulating optimized injection and production schemes for gas storage facilities and ensuring safe and efficient injection and production.

[0006] Physical property sealing is the fundamental mechanism for sealing oil and gas in caprocks. It mainly relies on various properties of the rock itself, such as the dense structure, poor pore connectivity, and large scale of the caprock, to achieve gas sealing. Hydrocarbon concentration sealing and overpressure sealing are two other sealing mechanisms of rocks, both of which require physical property sealing to function effectively.

[0007] Therefore, the most fundamental issue in evaluating the sealing capacity of a caprock is assessing its sealing performance. Currently, evaluations of rock sealing performance primarily focus on breakthrough pressure tests. However, breakthrough pressure is influenced by various factors, including the rock's porosity and permeability characteristics, median radius, specific surface area, and caprock lithology. Therefore, the evaluation of caprock breakthrough pressure in gas storage facilities should not be limited to caprock sealing performance; a comprehensive analysis of other factors affecting breakthrough pressure is also necessary to establish a systematic mechanism and evaluation method for gas storage caprock sealing performance.

[0008] Therefore, it is necessary to conduct comprehensive, multi-dimensional, and multi-parameter monitoring of gas storage facilities to ensure their stability and integrity. Summary of the Invention

[0009] To address the aforementioned shortcomings in existing technologies, this invention provides a geological safety operation monitoring system for gas storage facilities, which solves the problem that existing monitoring technologies have a single monitoring perspective and lack multi-dimensional analysis and evaluation of closure.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a geological safety operation monitoring system for gas storage facilities, comprising: The fault closure monitoring subsystem is used to monitor fault zone data in real time; the fault zone data includes fault zone pressure. Water level Fault zone fluid composition concentration Spatiotemporal distribution of microseismic events and microseismic energy ;in, The x-axis represents the microseismic events. The vertical axis represents the microseismic event. This refers to the depth of microseismic events. For time; A caprock sealing monitoring subsystem is used to monitor caprock data in real time; the caprock data includes bottom hole pressure. Pressure difference between the upper and lower interfaces of the cap layer Surface subsidence rate and surface gas concentration ; The data processing center is used to calculate the fault sealing index using a fault sealing index model based on fault zone data; to calculate the caprock sealing index using a caprock sealing index model based on caprock data; and to determine the operational safety level of the gas storage facility based on the fault sealing index and caprock sealing index, using a preset safety level assessment threshold. The fault sealing index model is specifically a weighted sum of the following: microseismic activity; the ratio of the fault zone fluid composition concentration to the background gas concentration reference value; the ratio of the fault zone pressure change to the allowable pressure fluctuation range; and the ratio of the fault zone water level change to the allowable water level fluctuation range. The caprock sealing index model is specifically a weighted sum of the following: the ratio of the difference between the caprock bottom pressure and the lower pressure limit divided by the caprock pressure range; the ratio of the surface subsidence rate to the upper subsidence rate limit; the ratio of the surface gas concentration to the gas concentration threshold; and the ratio of the pressure difference between the upper and lower interfaces of the caprock to the pressure difference threshold. The expression for the microseismic activity is:

[0011] in, For time windows; This represents the total number of microearthquakes within the time window. For the first The energy of a micro-earthquake; Spatial weights are determined based on the distance from microseismic events to the center of the gas storage facility; Reference energy per unit time.

[0012] Furthermore, the fault sealing monitoring subsystem includes: Fault monitoring wells are deployed in boundary fault zones and collect fault zone pressure, water level, and fluid composition concentration through multi-parameter sensors. The microseismic monitoring network is used to obtain the spatiotemporal distribution and energy of microseismic events based on downhole geophones and surface geophones in old wells.

[0013] Furthermore, the caprock sealing monitoring subsystem includes: Caprock monitoring wells are used to collect bottom hole pressure and pressure difference between the upper and lower interfaces of the caprock. Surface subsidence meter array, used to collect the surface subsidence rate of the surface above the cover layer; Well site gas monitors are used to monitor the concentration of surface gas at well sites.

[0014] Furthermore, the expression for the fault closure index model is as follows:

[0015] in, for The fault closure index at any given time; For time; Weights for the microseismic term; for Microseismic activity at any given time; The weight of the gas concentration term; for The concentration of fluid composition in the fault zone at any given time; This is a reference value for background gas concentration; Weights for stress terms; for The pressure of the fault zone at any given moment; This represents the initial pressure of the fault zone; This refers to the allowable fluctuation range of pressure in the fault zone. Weights for the water level term; for The water level in the fault zone at that moment; This represents the initial water level of the fault zone. This refers to the allowable fluctuation range of the water level. The critical threshold for microseismic activity under strong closure conditions; This is a fault zone pressure change rate indicator function. It is 1 when the fault zone pressure change rate exceeds the threshold, and -1 otherwise. This is a function indicating the rate of change of water level in the fault zone. It is 1 when the rate of change of water level in the fault zone exceeds the threshold, and -1 otherwise.

[0016] Furthermore, the expression for the cap layer closure index model is:

[0017] in, for The capping closure index at any given time; Weights for the caprock pressure term; for The pressure at the bottom of the well at any given moment; This represents the bearing capacity of the cap layer. The weight of the settlement term; for The rate of surface subsidence at any given time; This represents the upper limit of the settling rate. The weight of the gas concentration term; for Surface gas concentration at a given time; The permissible gas concentration threshold at the Earth's surface; Weights for the pressure difference term; for The difference between the pressure at the upper interface and the pressure at the lower interface of the cap layer at any given time; The threshold value for the pressure difference between the upper and lower interfaces of the caprock; Minimum allowable bottom hole pressure to prevent caprock cracking; This is an indicator function for the rate of change of caprock pressure. It is 1 when the rate of change of caprock pressure is greater than the threshold, and -1 otherwise.

[0018] The beneficial effects of this invention are as follows: Fault monitoring simultaneously incorporates dynamic microseismic signals (real-time fault activity) and static fluid, pressure, and water level signals (long-term leakage trends), capturing both short-term sudden fault slip risks and identifying long-term slow leakage hazards, thus achieving dual risk assessment. Using the stable fault state at the initial stage of gas storage operation as a benchmark, rather than the natural original state, it can eliminate normal fluctuation interference from injection and production operations, accurately identify fault anomalies induced by injection and production disturbances, and adapt to the long-term periodic operation scenario of gas storage facilities. Microseismic activity is precisely screened by constructing distance attenuation weights (the closer the microseismic event is to the center of the gas storage facility, the higher the weight; the farther away, the lower the weight) to identify fault activity signals around the storage area that directly threaten the safety of the gas storage facility; it weakens irrelevant microseismic interference far from the gas storage facility, significantly improving the targeting and accuracy of fault activity assessment; and it achieves differentiated assessment by amplifying risks nearby and weakening irrelevant signals. The caprock settlement is directly expressed as a rate, eliminating the need to calculate cumulative displacement and reflecting the current intensity of caprock deformation in real time. The real-time pressure difference between the upper and lower layers of the caprock accurately characterizes the direct driving force for gas to breach the caprock, without the need for initial values, thus avoiding interference from the initial state. This invention achieves real-time, quantitative, and accurate assessment of fault and caprock sealing in gas storage facilities through dimensionless fusion of multi-source heterogeneous monitoring indicators, differentiated normalization design, and adaptive weight calibration. The model strictly adheres to the geological failure mechanism and operational patterns of gas storage facilities, enabling it to identify both short-term sudden risks and provide early warnings of long-term leakage hazards. It solves the technical problems of traditional sealing assessments being qualitative, one-sided, and lagging, providing a reliable quantitative decision-making basis for the geological safety operation of gas storage facilities. Attached Figure Description

[0019] Figure 1 This is a system structure diagram of the present invention. Detailed Implementation

[0020] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0021] like Figure 1 As shown, in one embodiment of the present invention, a geological safety operation monitoring system for a gas storage facility includes: The fault closure monitoring subsystem is used to monitor fault zone data in real time. A caprock sealing monitoring subsystem is used to monitor caprock data in real time. The data processing center is used to calculate the fault sealing index using a fault sealing index model based on fault zone data; to calculate the caprock sealing index using a caprock sealing index model based on caprock data; and to determine the operational safety level of the gas storage facility based on the fault sealing index and caprock sealing index, using preset safety level assessment thresholds. Specifically, the fault sealing index model is a weighted sum of the following: the ratio of microseismic activity, the ratio of the fault zone fluid composition concentration to the background gas concentration reference value, the ratio of the fault zone pressure change to the allowable pressure fluctuation range of the fault zone, and the ratio of the fault zone water level change to the allowable water level fluctuation range. Specifically, the caprock sealing index model is a weighted sum of the following: the ratio of the caprock bottom pressure to the caprock bearing capacity limit, the ratio of the surface subsidence rate to the upper limit of the subsidence rate, the ratio of the surface gas concentration to the gas concentration threshold, and the ratio of the pressure difference between the upper and lower interfaces of the caprock to the upper limit of the pressure difference.

[0022] Specifically, the threshold values ​​for fault sealing index and caprock sealing index are set for different gas storage facility operation safety levels, i.e., preset safety level assessment threshold values. The fault sealing index and caprock sealing index are calculated in real time, and the gas storage facility operation safety level is determined accordingly.

[0023] In this embodiment, the direct monitoring object of the gas storage facility's safety monitoring is whether or not there is a leak. The monitoring design concept is as follows: for surface engineering, the focus is on monitoring deformation and gas leakage; for underground engineering, the focus is on full coverage of the geological body with localized key monitoring; a combination of point, surface, and volume monitoring is used, and monitoring and subsequent analysis are carried out simultaneously.

[0024] ① Use surface settlement meters, water level monitors, pressure monitors, and gas monitors to conduct full-coverage monitoring of the relevant engineering works of the surface injection and production well platform; ② Use microseismic detectors to monitor the geological bodies in the reservoir area; ③ Deploy monitoring wells near the fault to focus on monitoring the fault, caprock, and other areas, monitoring parameters such as fault zone pressure, water level, and fluid composition concentration; the fluid composition concentration in the fault zone can be measured using downhole probes. ④ Combine monitoring well data with microseismic data to form a monitoring network that integrates well points, faults, caprocks, and traps; ⑤ The monitoring data is wirelessly collected and transmitted to the monitoring center for background analysis and evaluation, forming a dynamic online monitoring, analysis and early warning platform.

[0025] In a gas storage facility, the caprock is a low-permeability rock layer used to seal off oil and gas, while a fault is a crack in the geological structure; that is to say, the caprock is a protective layer of the gas storage facility to prevent leakage, while a fault is a destructive fissure that can lead to leakage. Therefore, this embodiment constructs caprock sealing indices and fault sealing indices based on leakage conditions in the caprock and fault, respectively. These sealing indices reflect leakage levels. Since different operating conditions will result in different requirements for the sealing of the caprock and fault, the threshold data for different gas storage facility operating safety levels are determined based on adaptability to on-site operating conditions.

[0026] In this embodiment, taking A Gorge and B Gorge as examples, the monitoring system consists of surface, trap, reservoir temperature, pressure, deformation, gas, water level, and microseismic monitoring. Surface monitoring monitors subsidence, deformation, and gas; trap monitoring monitors pressure, temperature, and water level in faults and caprocks; microseismic monitoring primarily monitors microseismic events, simultaneously monitoring microseismic events, temperature, pressure, and water level in the same well.

[0027] The fault sealing monitoring subsystem includes: Fault monitoring wells are deployed in boundary fault zones and collect fault zone pressure, water level, and fluid composition concentration through multi-parameter sensors. The microseismic monitoring network is used to obtain the spatiotemporal distribution and energy of microseismic events based on downhole geophones and surface geophones in old wells.

[0028] In this embodiment, based on the preliminary feasibility study reports for Gorge A and Gorge B, the stability and sealing of the faults within the gas storage facility were evaluated, and the thickness and continuity of the reservoir were analyzed. Overall, the fault displacement is 50-100m, the strata on both sides are joined, the original gas reservoir state was abnormally high pressure, and the reconstructed gas storage facility did not exceed the original formation pressure. The risk of lateral and vertical leakage near the fault is low. During later operation, it is recommended to deploy monitoring wells near the boundary faults to monitor formation temperature, pressure, and water level; and simultaneously conduct microseismic monitoring.

[0029] In this embodiment, microseismic monitoring features wide coverage, fast measurement speed, strong noise filtering capability, accurate positioning, and convenient field application. By monitoring fault sealing and liquid migration in real time, it provides safety early warning for the normal operation of the gas storage facility and subsequent pressurization. Based on considerations of the geographical conditions and relative location of the two gorge gas storage facilities, monitoring accuracy, and economic costs, a total of 8 seismic monitoring points were designed and arranged in the outer areas of the B Gorge and A Gorge gas storage facilities, with a spacing of 10 kilometers between the monitoring points.

[0030] The fault zone data includes fault zone pressure. Water level Fault zone fluid composition concentration Spatiotemporal distribution of microseismic events and microseismic energy ;in, The x-axis represents the microseismic events. The vertical axis represents the microseismic event. This refers to the depth of microseismic events. For time.

[0031] In this embodiment, the fluid composition concentration in the fault zone... The concentration of natural gas refers to the concentration of natural gas; while the concentration of background gas also refers to the concentration of background natural gas.

[0032] The caprock sealing monitoring subsystem includes: Caprock monitoring wells are used to collect bottom hole pressure and pressure difference between the upper and lower interfaces of the caprock. Surface subsidence meter array, used to collect the surface subsidence rate of the surface above the cover layer; Well site gas monitors are used to monitor the concentration of surface gas at well sites.

[0033] In this embodiment, based on caprock studies, the caprock of the B Gorge is a stable marlstone with a thickness exceeding 60m, and occasional micro-fractures are observed. For the A Gorge gas reservoir, the grayish-white gypsum at the bottom of the Jialingjiang Formation 3 is a good regional caprock, approximately 60-70m thick, distributed throughout the area, with few internal micro-fractures. To monitor the risk of caprock breakthrough due to alternating stress during injection and production, it is necessary to monitor the stability and sealing of the caprock caused by stress concentration. Monitoring wells are recommended to be located near faults along the structural axis, with the completed formation being the Jialingjiang Formation. Parameters such as temperature and bottomhole pressure will be continuously monitored within the well.

[0034] In this embodiment, surface deformation monitoring is conducted as follows: Some injection and production wells in Gorge A and Gorge B are built on platforms formed by excavation and backfilling of the mountain. Due to abundant rainfall in the area, these platforms have experienced subsidence and deformation over time, with varying degrees of deformation at different locations, resulting in cracks parallel to the surface and a potential for landslides. Therefore, monitoring points need to be deployed on different platforms to monitor displacement and water level. Near Well No. 2 on Platform No. 2 in Gorge B, cracks parallel to the edge of the slope were found due to its depositional formation. This area requires close monitoring, and surface subsidence and deformation monitoring points should be established to monitor surface deformation and subsidence using methods such as InSAR.

[0035] Gas monitoring near injection and production wells: During the cyclic injection and production process, pressure changes in injection and production wells cause deformation of the wellbore structure and cementing. Over long periods, this may lead to micro-cracks and gas leakage. Therefore, gas monitoring instruments need to be deployed on the well site platform to monitor gas concentration changes at different locations on the platform at different times. Currently, the A Gorge gas storage facility has a gas gathering and injection station, allowing for the deployment of gas monitoring points at various locations in the area to monitor gas concentration and composition. The gas concentrations monitored in this invention refer to natural gas concentrations.

[0036] In this embodiment, the principle for monitoring the internal temperature and pressure of the gas storage trap is to achieve full coverage. Existing wells are fully utilized; some existing wells and pilot wells are converted into internal monitoring wells after modification to monitor the internal temperature and pressure of the gas reservoir. Distributed fiber optic temperature and pressure gauges are deployed to continuously record the temperature inside the wellbore and the bottom hole pressure. For the B Gorge gas storage, temperature and pressure monitoring points can be deployed in the areas of Tongchu 2, Tongchu 8, and Tong 12 wells to achieve full coverage of the gas storage area; for the A Gorge gas storage, temperature and pressure monitoring points can be deployed in the areas of Cao 31, Cao 9, and Cao 8 wells to achieve full coverage of the gas storage area.

[0037] The caprock data includes bottom hole pressure. Pressure difference between the upper and lower interfaces of the cap layer Surface subsidence rate and surface gas concentration .

[0038] The expression for the fault closure index model is as follows:

[0039] in, for The fault closure index at any given time; For time; Weights for the microseismic term; for Microseismic activity at any given time; The weight of the gas concentration term; for The concentration of fluid composition in the fault zone at any given time; This is a reference value for background gas concentration; Weights for stress terms; for The pressure of the fault zone at any given moment; This represents the initial pressure of the fault zone; This refers to the allowable fluctuation range of pressure in the fault zone. Weights for the water level term; for The water level in the fault zone at that moment; This represents the initial water level of the fault zone. This refers to the allowable fluctuation range of the water level. The critical threshold for microseismic activity under strong closure conditions; This is a fault zone pressure change rate indicator function. It is 1 when the fault zone pressure change rate exceeds the threshold, and -1 otherwise. This is a function indicating the rate of change of water level in the fault zone. It is 1 when the rate of change of water level in the fault zone exceeds the threshold, and -1 otherwise.

[0040] In this embodiment, and These are used to characterize the range within which pressure can fluctuate and the range within which water level can float, respectively. Both are determined based on on-site operating conditions. In this embodiment, the weights... , , and The fitting was determined based on field operation data. Since most of the data during field operation was leak-free, the closure quantification data (corresponding to the closure index) of each sample was evaluated by experts during the fitting process.

[0041] In this embodiment, the change in gas concentration is unidirectional; as long as leakage occurs, the concentration will only increase and will not decrease below the background value. In contrast, changes in pressure and water level are bidirectional; they may increase or decrease, and deviations from the initial values ​​are considered abnormal.

[0042] Microseismic term explanation: In a strongly closed state, microseismic events occur frequently, but their energy is relatively small and their magnitude is relatively low; when the closure is reduced, microseismic events occur frequently and their energy is higher, and they will be distributed in linear strips along the fault plane.

[0043] Gas Term Explanation: Background gas concentration reference value, which is the natural gas background concentration in the fluid when there is no gas reservoir disturbance and no gas leakage in the fault zone. When the fault sealing deteriorates, gas from the reservoir migrates along the fault, and the natural gas concentration in the fluid... Will from Rapidly rising. Therefore, the key to determining whether there is a leak is the "ratio of the current concentration to the natural background value," not the difference from the initial operating value. The gas concentration parameter, directly calculated as the ratio of the current value to the background value, clearly reflects the degree of leakage; subtracting the initial value would actually weaken the "anomaly relative to the natural background." Gas monitoring points are deployed along the direction of gas extraction from the storage facility; when improved sealing leads to gas enrichment, the gas will be confined within the fault and will not diffuse outwards.

[0044] Explanation of pressure and water level terms: During normal operation of the gas storage facility, the pressure and water level in the fault zone will remain at a relatively stable level, which is the initial pressure of the fault zone in the formula. and the initial water level of the fault zone When a fault becomes active (such as during fracture propagation or fluid flow), pressure and water level will deviate from their initial stable values. This deviation can be bidirectional (either increasing or decreasing). Therefore, by calculating the deviation using the difference and then dividing it by a reference value, we can obtain the "relative degree of deviation." The greater the deviation, the higher the risk of abnormal fault activity. and Used to determine whether changes in pressure and water level are risk-type or blockage-type anomalies. Risk-type changes are faster, while blockage-type changes are slower and gradually stabilize. Risk-type changes are caused by a decrease in the sealing capacity, leading to changes in pressure and water level, while blockage-type changes are caused by an increase in the sealing capacity, leading to changes in pressure and water level.

[0045] The initial value is the stability benchmark of the fault under current operating conditions, not the natural background value. During the gas storage injection and production process, the pressure and water level in the fault zone will fluctuate slightly with changes in reservoir pressure. As long as they do not deviate too much from the initial stable value, it is considered normal operation. Only when the deviation exceeds the reference range does it indicate that the fault has undergone abnormal changes (such as opening, sliding, or crossflow), and its sealing performance has decreased.

[0046] The expression for the microseismic activity is:

[0047] in, For time windows; This represents the total number of microearthquakes within the time window. For the first The energy of a micro-earthquake; Spatial weights are determined based on the distance from microseismic events to the center of the gas storage facility; Reference energy per unit time.

[0048] Denominator retention time window T This method converts the cumulative weighted energy within a statistical period into an energy rate per unit time. Unlike traditional static indicators that only count the total cumulative energy, it can reflect the current and instantaneous intensity of fault activity in real time, and can capture short-term sudden fault slippage induced by injection and production disturbances. It can achieve horizontal comparison of activity levels at different durations and different operating stages, regardless of the length of the statistical period. It is adapted to the periodic injection and production operation patterns of gas storage facilities, and accurately identifies the dynamic response of faults during gas injection pressurization and gas production depressurization.

[0049] In this embodiment, the level of seismic activity is actually measured over a period of time. Therefore, at each monitoring moment, seismic data from a fixed window size period from the past to the present is taken. This is a time period set within the system. The value is the reference energy per unit time under the preset safe operating conditions of the gas storage facility. Distance weights can be set custom-defined, or they can be calculated based on a distance decay function. The expression for the distance decay function is: ,in, For the first Distance from a micro-seismic event to the center of the gas storage facility The radius of influence for safety is determined by the geological conditions of the gas storage facility.

[0050] In this embodiment, the energy and spatial location of microseismic events are weighted and integrated to accurately quantify the intensity of fault dynamic activity, thus avoiding the one-sidedness of judging solely by event frequency.

[0051] The expression for the cap layer closure index model is as follows:

[0052] in, for The capping closure index at any given time; Weights for the caprock pressure term; for The pressure at the bottom of the well at any given moment; This represents the bearing capacity of the cap layer. The weight of the settlement term; for The rate of surface subsidence at any given time; This represents the upper limit of the settling rate. The weight of the gas concentration term; for Surface gas concentration at a given time; The permissible gas concentration threshold at the Earth's surface; Weights for the pressure difference term; for The difference between the pressure at the upper interface and the pressure at the lower interface of the cap layer at any given time is positive or negative. The positive and negative effects on the cap layer's sealing properties are distinguished by the positive or negative values ​​of the fitting weights during the fitting process. The threshold value for the pressure difference between the upper and lower interfaces of the caprock; Minimum allowable bottom hole pressure to prevent caprock cracking; This is an indicator function for the rate of change of caprock pressure. It is 1 when the rate of change of caprock pressure is greater than the threshold, and -1 otherwise.

[0053] The pressure change rate indicator function of the caprock is used to determine whether the current operating condition is a stable high-pressure favorable condition or a risky condition. Under risky conditions, the pressure change rate is very fast, while under stable conditions, the sealing is better and the pressure change rate is slow and stable.

[0054] In this embodiment, weight , , and The fitting was determined based on field operation data. Since most of the data during field operation was leak-free, the closure quantification data (corresponding to the closure index) of each sample was evaluated by experts during the fitting process.

[0055] In this embodiment, the caprock's design pressure limit (safe upper limit) is the maximum pressure that the caprock's physical structure can withstand, determined by the geological structure and rock strength, and remains constant. As long as the current pressure approaches or exceeds this limit, the sealing performance deteriorates. Throughout the gas storage injection and extraction process, the caprock pressure rises unidirectionally. The maximum allowable settlement rate threshold (safe upper limit) of the caprock will cause cracking and compaction failure if exceeded. The settlement rate is a dynamic variable, directly reflecting the current degree of deformation in the caprock; the rate itself is a relative change. Once the caprock leaks, the surface natural gas concentration will only increase and will not return to its initial value. The maximum allowable pressure difference (breakthrough threshold) of the caprock will cause gas channeling if exceeded.

[0056] In this embodiment, the fault closure index model and the caprock closure index model are fitted using only a portion of the collected data. In practical applications, fitting terms can be added according to the monitoring modules deployed.

Claims

1. A geological safety operation monitoring system for a gas storage facility, characterized in that, include: The fault closure monitoring subsystem is used to monitor fault zone data in real time; the fault zone data includes fault zone pressure. Water level Fault zone fluid composition concentration Spatiotemporal distribution of microseismic events and microseismic energy ;in, The x-axis represents the microseismic events. The vertical axis represents the microseismic event. This refers to the depth of microseismic events. For time; A caprock sealing monitoring subsystem is used to monitor caprock data in real time; the caprock data includes bottom hole pressure. Pressure difference between the upper and lower interfaces of the cap layer Surface subsidence rate and surface gas concentration ; The data processing center is used to calculate the fault sealing index using a fault sealing index model based on fault zone data; to calculate the caprock sealing index using a caprock sealing index model based on caprock data; and to determine the operational safety level of the gas storage facility based on the fault sealing index and caprock sealing index, using a preset safety level assessment threshold. The fault sealing index model is specifically a weighted sum of the following: microseismic activity, the ratio of fault zone fluid composition concentration to background gas concentration reference value, the ratio of fault zone pressure change to allowable fault zone pressure fluctuation range, and the ratio of fault zone water level change to allowable water level fluctuation range. The expression for the fault sealing index model is: in, for The fault closure index at any given time; For time; Weights for the microseismic term; for Microseismic activity at any given time; The weight of the gas concentration term; for The concentration of fluid composition in the fault zone at any given time; This is a reference value for background gas concentration; Weights for stress terms; for The pressure of the fault zone at any given moment; This represents the initial pressure of the fault zone; This refers to the allowable fluctuation range of pressure in the fault zone. Weights for the water level term; for The water level in the fault zone at that moment; This represents the initial water level of the fault zone. This refers to the allowable fluctuation range of the water level. The critical threshold for microseismic activity under strong closure conditions; This is a fault zone pressure change rate indicator function. It is 1 when the fault zone pressure change rate exceeds the threshold, and -1 otherwise. This is a function indicating the rate of change of water level in the fault zone. It is 1 when the rate of change of water level in the fault zone exceeds the threshold, and -1 otherwise. The caprock sealing index model is specifically a weighted sum of the ratio of the difference between the caprock bottom pressure and the lower pressure limit to the caprock pressure-bearing range, the ratio of the surface subsidence rate to the upper subsidence rate, the ratio of the surface gas concentration to the gas concentration threshold, and the ratio of the pressure difference between the upper and lower interfaces of the caprock to the pressure difference threshold; the expression for the microseismic activity is: in, For time windows; This represents the total number of microearthquakes within the time window. For the first The energy of a micro-earthquake; Spatial weights are determined based on the distance from microseismic events to the center of the gas storage facility; Reference energy per unit time.

2. The gas storage geological safety operation monitoring system according to claim 1, characterized in that, The fault sealing monitoring subsystem includes: Fault monitoring wells are deployed in boundary fault zones and collect fault zone pressure, water level, and fluid composition concentration through multi-parameter sensors. The microseismic monitoring network is used to obtain the spatiotemporal distribution and energy of microseismic events based on downhole geophones and surface geophones in old wells.

3. The gas storage geological safety operation monitoring system according to claim 1, characterized in that, The caprock sealing monitoring subsystem includes: Caprock monitoring wells are used to collect bottom hole pressure and pressure difference between the upper and lower interfaces of the caprock. Surface subsidence meter array, used to collect the surface subsidence rate of the surface above the cover layer; Well site gas monitors are used to monitor the concentration of surface gas at well sites.

4. The gas storage geological safety operation monitoring system according to claim 1, characterized in that, The expression for the cap layer closure index model is as follows: in, for The capping closure index at any given time; Weights for the caprock pressure term; for The pressure at the bottom of the well at any given moment; This represents the bearing capacity of the cap layer. The weight of the settlement term; for The rate of surface subsidence at any given time; This represents the upper limit of the settling rate. The weight of the gas concentration term; for Surface gas concentration at a given time; The permissible gas concentration threshold at the Earth's surface; Weights for the pressure difference term; for The difference between the pressure at the upper interface and the pressure at the lower interface of the cap layer at any given time; The threshold value for the pressure difference between the upper and lower interfaces of the caprock; Minimum allowable bottom hole pressure to prevent caprock cracking; This is an indicator function for the rate of change of caprock pressure. It is 1 when the rate of change of caprock pressure is greater than the threshold, and -1 otherwise.

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