Method and system for preventing and controlling seawater intrusion of underground water-sealed oil depot based on microseismic feedback

Abstract

The application provides a seawater intrusion prevention and control method and system based on microseismic feedback for underground water-sealed oil storage, and belongs to the field of underground space engineering and rock damage mechanics. The method comprises the following steps: arranging microseismic sensors at weak areas of a main cavern, a water curtain tunnel and surrounding rock of the underground water-sealed oil storage; obtaining parameters of microseismic occurrence; establishing a mapping relationship between microseismic monitoring data and a crack opening degree of the surrounding rock, and dynamically mapping cumulative damage of the surrounding rock crack to real-time changes of an equivalent permeability of the crack surrounding rock; combining a plugging mechanism of the underground water-sealed oil storage, and using the corrected equivalent permeability of the crack surrounding rock to calculate a water curtain pressure for maintaining water sealing effectiveness of the underground water-sealed oil storage; and using a PID closed-loop control algorithm to drive the water curtain system, so as to realize dynamic adjustment and optimization of the water curtain pressure. The application overcomes the problem that the underground water-sealed oil storage cannot adapt to dynamic damage of the surrounding rock under microseismic events, thereby reducing the risk of seawater intrusion. Under the premise of ensuring absolute water sealing safety of oil products, the operation energy consumption of the water curtain system is effectively reduced.

Description

Technical Field

[0001] This invention relates to the fields of underground space engineering and rock damage mechanics, and particularly to a method and system for preventing seawater intrusion in underground water-sealed oil depots based on microseismic feedback. Background Technology

[0002] Underground water-sealed caverns are widely used in commercial and strategic storage due to their advantages such as low land occupation, high safety and stability, and good fire resistance. The working principle of an underground water-sealed oil depot is to utilize the seepage of groundwater or an artificial water curtain, based on the principle that water and oil are immiscible, to seal oil within the cavern, thereby achieving the purpose of oil storage.

[0003] However, the existing operation and control technologies of water curtain systems have shown many limitations in practical engineering applications, mainly in the following aspects: First, existing technologies largely assume that the surrounding rock is stable and unchanging, and employ constant pressure water injection (involving precise pressure positioning at design values). However, the surrounding rock of underground water-sealed oil depots is in a dynamic process of change during construction and operation. Especially during operation, the repeated injection and extraction of oil will exert alternating loads on the surrounding rock. This periodic disturbance will lead to cumulative damage from micro-fractures within the surrounding rock. Existing technical methods typically only take reactive measures after macroscopic phenomena such as fracture penetration, large-scale groundwater influx into the cavern, and abnormal drops in monitoring well water levels have occurred.

[0004] Second, the cumulative damage to surrounding rock fractures caused by microseismic activity significantly alters the equivalent permeability of the fractured surrounding rock. According to the Cubic Law, the hydraulic conductivity of a fracture is cubically related to its aperture. Microseismic-induced micron-sized fractures can lead to an order-of-magnitude increase in local hydraulic conductivity. With the water curtain pressure remaining constant, as the surrounding rock damage causes the fracture aperture to increase, the original water curtain pressure may no longer be able to maintain the balance of water and oil pressures inside and outside the protected tunnel.

[0005] Third, commonly used monitoring equipment in underground water-sealed oil depot projects, such as piezometers and level gauges, can only monitor pressure values ​​in the seepage field and cannot capture the dynamic process of fracture propagation. Furthermore, these hydrogeological monitoring sensors are typically arranged in a point-like manner, making it difficult to achieve comprehensive coverage of the entire underground fracture network. While microseismic monitoring technology has been maturely applied in mine hazard monitoring and surrounding rock deformation mechanism research, accurately locating micro-fractures within the surrounding rock and quantifying their released energy, a closed-loop technical path integrating microseismic monitoring and water curtain control has not yet been formed.

[0006] Fourth: Underground water-sealed oil depots built in island environments still face the potential risk of seawater intrusion. Improper control of the water curtain pressure could lead to seawater backflow, affecting oil quality. Achieving a dynamic balance between suppressing seawater intrusion and regulating water flow has become a pressing technical challenge for the industry.

[0007] In conclusion, this invention has significant engineering value and scientific significance in enhancing national strategic petroleum reserves. Summary of the Invention

[0008] To address the risk of water seal failure caused by cumulative microseismic damage in existing underground water-sealed oil depot water curtain systems, this invention proposes a method and system for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback. This method achieves intelligent and refined management of water curtain pressure, aiming to solve the problem of the constant water injection pressure mode used in traditional underground water-sealed oil depot water curtain systems. This invention addresses the cumulative damage to surrounding rock fissures caused by repeated oil injection and discharge during the operation of underground water-sealed oil depots. By combining real-time monitoring of microseismic energy, the water curtain system is dynamically adjusted, thereby enhancing the overall safety of the oil depot. To achieve the above objectives, the technical solution of this invention is as follows: This invention provides a method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback, comprising the following steps: Step 1: After determining the site selection and layout of the underground water-sealed oil depot, a microseismic monitoring system is deployed simultaneously during the construction of the underground water-sealed oil depot. The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. The multiple sets of microseismic sensors are installed in the main cavern, water curtain tunnel and weak rock areas of the underground water-sealed oil depot, and are connected to the ground terminal central control console through a fiber optic network. Step 2: The ground terminal central control console collects signals emitted by the microseismic sensors in real time. After processing by the microseismic monitoring system, the parameters of the microseismic event are obtained, including three-dimensional spatial coordinates and microseismic radiation energy. Step 3: Based on Gibowicz's microseismic energy theory and the relationship between the radiation energy of microseismic events and the evolution of surrounding rock damage, the degree of surrounding rock fracture damage is inverted through microseismic monitoring data, and a quantitative mapping relationship between microseismic radiation energy and fracture aperture is established. Step 4: Using the corrected surrounding rock fracture aperture data, calculate the equivalent permeability of the fractured surrounding rock, and combine it with the sealing mechanism of the underground water-sealed oil depot to calculate the critical water seal pressure to ensure water seal safety. Step 5: Based on the calculated critical water seal pressure, the critical water seal pressure is used as the target setpoint. The PID controller executes the PID closed-loop control algorithm to drive the water curtain system to regulate the pressure, so as to ensure the safety of oil products in the underground water-sealed oil depot.

[0009] Furthermore, in step one, the micro-vibration sensor adopts a tetrahedral structure or a spatial spiral layout.

[0010] Furthermore, in step one, the microseismic monitoring system, based on acoustics and seismology, analyzes the impact on production activities by observing microseismic events. When underground rocks are damaged or moved due to human or natural factors, a weak seismic wave will be generated and propagate outward. By deploying multiple sets of monitoring sensors in the main tunnel, water curtain tunnel, and weak areas of the surrounding rock, microseismic data can be collected in real time. After data processing, the coordinates of the damage can be determined based on the principle of vibration positioning.

[0011] Furthermore, in step three, based on Gibowicz's theory of microseismic energy release mechanism, the microseismic released energy and seismic moment can be obtained. The relationship is approximated as:

[0012] According to the definition of seismic moment: The relationship between the energy released by microseismic events and the fissure aperture of the surrounding rock is derived as follows:

[0013] In the formula, The value represents the change in crack aperture caused by microseismic events, expressed in meters (m). Let be the radius of the seismic source, in meters (m). J represents the energy released by microseismic events, a value obtained from microseismic sensors. The stress drop, in Pa, is obtained from source spectrum analysis; G is the seismic moment, N×m; G is the shear modulus of the surrounding rock, Pa; A is the effective rupture surface area corresponding to the microseismic event, m². 2 .

[0014] Furthermore, in step four, the equivalent permeability of the fractured surrounding rock... The calculation is performed using a formula based on Cubic Law, as follows:

[0015] In the formula, The equivalent permeability of the fractured surrounding rock after microseismic cumulative damage is given by m. 2 ; Fracture surface density, used to characterize the degree of fracture surface development per unit volume of surrounding rock, in meters (m). -1 ; Let m be the initial fracture aperture. The change in crack aperture caused by micro-seismic events, in meters (m).

[0016] Furthermore, the critical water seal pressure P is the water injection pressure required to maintain the safety of the water seal in the underground water-sealed oil depot. It is calculated based on the sealing mechanism of the underground water-sealed oil depot, and the calculation formula is as follows:

[0017] In the formula, The critical water seal pressure is given in Pa. The design pressure for oil storage in the oil depot is given in Pa. The hydrostatic pressure term represents the potential energy between the water curtain orifice and the oil reservoir. The density of water is kg / m³. 3 ; The acceleration due to gravity is m / s². 2 ; The height difference, in meters, is the height difference between the water head at the water curtain orifice and the cavern. The minimum safe water injection flow rate that must be maintained for a single-hole design, in m 3 / s; ρ is the dynamic viscosity of water, Pa·s; The length of the water curtain hole in the calculated section is in meters (m). The equivalent permeability of the fractured surrounding rock after cumulative microseismic damage is given by m. 2 ; To determine the radius of influence, half the spacing of the water intake holes or the distance to the cavern, in meters; Where R is the borehole radius of the water curtain hole, in meters; ln(R / r) w () is dimensionless.

[0018] Furthermore, in step five, the PID controller controls the error value. Target set value Compared with actual measured value The difference between them, control quantity The PID controller outputs commands to drive the water curtain system for pressure regulation. With error The relationship formula is as follows:

[0019] In the formula: In practical engineering, the command to drive the water curtain system to regulate pressure is represented by the frequency of the water supply pump's inverter, in Hz. To control the error value, Pa, the corresponding formula is: ; The target set value, in actual engineering, refers to the calculated critical water seal pressure, in Pa; The actual measured value is the actual water seal pressure read back by the sensor, in Pa. The proportionality constant is expressed in Hz / Pa. The integral coefficient is Hz / (Pa·s); is the differential coefficient, Hz·s / Pa.

[0020] This invention also provides a seawater intrusion prevention and control system for underground water-sealed oil depots based on microseismic feedback, used to implement the above-mentioned seawater intrusion prevention and control method for underground water-sealed oil depots based on microseismic feedback, comprising: Parameter acquisition module: Configured to deploy a microseismic monitoring system in the underground water-sealed oil depot. Through the microseismic monitoring system, the three-dimensional spatial coordinates of the seismic source and the microseismic radiation energy parameters at the time of microseismic occurrence are acquired, which are used to sense and acquire damage information of surrounding rock fissures in real time. The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. The multiple sets of microseismic sensors are installed in the main cavern, water curtain tunnel and weak area of ​​surrounding rock of the underground water-sealed oil depot, and are connected to the ground terminal central control console through a fiber optic network. Damage transformation module: It is configured to perform formula fitting on the surrounding rock fissures and microseismic radiation energy caused by microseismic events based on Gibowicz theory and microseismic monitoring data.

[0021] Pressure determination module: It is configured to use the corrected surrounding rock fracture aperture data, use the Cubic Law-based formula to calculate the equivalent permeability of the surrounding rock fracture, combine the underground water-sealed oil depot sealing mechanism, calculate the critical water seal pressure required to ensure the safety of the water seal under the current state, and determine what adjustments should be made to the water curtain. The PID control module is configured to use the critical water seal pressure calculated by the pressure determination module as the target setpoint, receive the actual water seal pressure of the water curtain system, calculate the pressure deviation between the critical water seal pressure and the actual water seal pressure, and generate a pressure adjustment command based on the pressure deviation using a PID closed-loop control algorithm. This command drives the water curtain system to adjust the water injection pressure so that the actual water seal pressure approaches the critical water seal pressure, thereby ensuring the safety of oil products in the underground water-sealed oil depot.

[0022] Compared to existing technologies, the seawater intrusion prevention and control method and system for underground water-sealed oil depots based on microseismic feedback described in this invention has the following advantages: This invention changes the traditional mode of using constant water injection pressure in the water curtain system of underground water-sealed oil depots. Addressing the problem of cumulative damage to surrounding rock fissures caused by repeated oil injection and discharge during the operation of underground water-sealed oil depots, it dynamically adjusts the water curtain system by real-time monitoring of microseismic energy, thereby improving the safety of the oil depot throughout its entire operation cycle. Based on Cubic Law, this invention innovatively combines microseismic monitoring technology with the water curtain system. By quantifying microseismic radiation energy, it accurately assesses the degree of cumulative damage to the surrounding rock and achieves three-dimensional spatial coordinate positioning of surrounding rock fissures. Simultaneously, it establishes a dynamic control mechanism based on the real-time status of cumulative damage to surrounding rock fissures, effectively solving the problem of the difficulty in simultaneously addressing seawater intrusion and water curtain control, achieving significant safety and economic benefits.

[0023] (1) The present invention deploys microseismic sensors in the main cavern, water curtain tunnel and weak area of ​​surrounding rock of underground water-sealed oil depot, and collects the signals emitted by the microseismic sensors in real time through the microseismic monitoring system, which can obtain the three-dimensional spatial coordinates of the microseismic occurrence and the microseismic radiation energy, thereby providing real-time monitoring data for the prevention and control of seawater intrusion in underground water-sealed oil depot. (2) Based on Gibowicz theory and microseismic monitoring data, this invention establishes a mapping relationship between microseismic radiation energy and surrounding rock fissure aperture, transforms microseismic activity into the cumulative damage increment of surrounding rock fissures, and obtains corrected surrounding rock fissure aperture data, so that the surrounding rock fissure aperture can be quantitatively calculated based on microseismic radiation energy. (3) This invention uses the corrected surrounding rock fissure aperture data to estimate the equivalent permeability of the surrounding rock fissures, and combines it with the sealing mechanism of the underground water-sealed oil depot to calculate the critical water seal pressure, so that the determination of the critical water seal pressure can correspond to the surrounding rock fissure aperture and the permeability of the surrounding rock fissures, thereby improving the accuracy of the critical water seal pressure calculation. (4) Based on the calculated critical water seal pressure, the present invention uses a PID closed-loop control algorithm to drive the water curtain system to regulate the pressure, which can avoid the problem of mismatch between the operating pressure of the water curtain system and the actual demand caused by the long-term use of constant water injection pressure in underground water-sealed oil depots. (5) This invention achieves the linkage of monitoring, calculation and regulation in the process of preventing seawater intrusion in underground water-sealed oil depots by coordinating the microseismic monitoring system, critical water seal pressure calculation and water curtain system pressure regulation. While ensuring the safety of oil products in underground water-sealed oil depots, it is also conducive to reducing the energy consumption of the water curtain system. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart illustrating the implementation steps of a method for preventing seawater intrusion into an underground water-sealed oil depot based on microseismic feedback, as described in this invention. Figure 2 This diagram illustrates the spatial relationship between the microseismic sensor and the water curtain system. Figure 3 This is a block diagram of PID closed-loop control logic. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] This invention provides a method for preventing seawater intrusion in underground water-sealed oil depots based on microseismic feedback. The technical innovation lies in using the microseismic radiation energy collected by a microseismic monitoring system to correct the fissure aperture of the surrounding rock. The corrected fissure aperture data is then used to calculate the equivalent permeability of the fractured surrounding rock. Combined with the sealing mechanism of the underground water-sealed oil depot, the critical water seal pressure is calculated. Finally, a PID controller executes a PID closed-loop control algorithm to drive the water curtain system for pressure regulation. Through this setup, this invention can adjust the operating pressure of the water curtain system in real time according to the changes in surrounding rock fissure damage reflected by microseismic activity, avoiding the problem of existing water curtain systems using constant injection pressure for extended periods, which is mismatched with actual water seal requirements. This improves the safety and economy of preventing seawater intrusion in underground water-sealed oil depots. Figure 1 As shown, the method of this invention includes steps such as deploying a microseismic monitoring system, acquiring microseismic parameters, correcting the fissure aperture of the surrounding rock, calculating the equivalent permeability of the fissure surrounding rock, calculating the critical water seal pressure, and regulating the pressure of the water curtain system. These steps form a feedback loop from the microseismic monitoring results to the water curtain pressure control. Specifically, the method includes the following steps: Step one involves conducting geological surveys at the underground water-sealed oil depot to determine its site selection and layout. During the construction of the underground water-sealed oil depot, a microseismic monitoring system is deployed simultaneously. This system is installed in the water curtain tunnels, main chambers, and areas with weak surrounding rock, and connected to a central control console on the ground via conductors. For example... Figure 2 As shown, multiple sets of microseismic sensors are deployed in the main cavern, water curtain tunnel, and weak rock areas of the underground water-sealed oil depot, and correspond spatially with the water curtain system. This allows the microseismic monitoring data to reflect the development of rock fissures in different areas, providing spatial positioning basis for subsequent water curtain pressure regulation.

[0028] The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. These sensors are installed in the main cavern, water curtain tunnel, and weak rock areas of the underground water-sealed oil depot, and are connected to the central control console on the ground via a fiber optic network. The microseismic sensors adopt a tetrahedral structure or a spatial spiral layout to ensure the three-dimensional positioning accuracy of the seismic source in the target area, and establish a monitoring network for real-time monitoring of underground rock fissures.

[0029] Step two: The central control console of the ground terminal acquires signals from the microseismic sensors in real time. These signals are waveform data, which, after processing by the microseismic monitoring system, yield parameters related to the microseismic event, including three-dimensional spatial coordinates and microseismic radiated energy. Specifically, after demodulation and high-sampling-rate analog-to-digital (A / D) conversion, the signals are immediately triggered by algorithms such as STA / LTA to automatically and accurately identify the first arrival times of P-waves and S-waves. Simultaneously, based on Fourier transform analysis of the signal spectrum, the source radius, stress variation, seismic moment, three-dimensional spatial coordinates, and radiated energy are calculated. ; Step 3: Based on Gibowicz's microseismic energy theory and the relationship between the radiation energy of microseismic events and the evolution of surrounding rock damage, the degree of surrounding rock fracture damage is inverted using microseismic monitoring data to establish a quantitative mapping relationship between microseismic radiation energy and fracture aperture. Step four: Using the corrected surrounding rock fissure aperture data, the equivalent permeability of the fissure surrounding rock is calculated, thereby transforming the changes in microscopic fissures into changes in the macroscopic water conductivity of the medium. Furthermore, combined with the sealing mechanism of the underground water-sealed oil depot, the critical water seal pressure to ensure water seal safety is calculated. This invention innovatively introduces the mutual influence between surrounding rock fissure aperture and water seal pressure.

[0030] Step five: Based on the calculated critical water seal pressure, this critical water seal pressure is used as the target setpoint. A PID closed-loop control algorithm is executed through a PID controller to drive the water curtain system for pressure regulation, ensuring the safety of the oil in the underground water-sealed oil depot. For example... Figure 3 As shown, the PID closed-loop control process uses the critical water seal pressure as the target setpoint and the actual water seal pressure as the feedback quantity. By calculating the pressure deviation between the two, a pressure regulation command is generated, thereby driving the water curtain system to regulate the pressure.

[0031] In step one, the microseismic monitoring system, based on acoustics and seismology, analyzes the impact on production activities by observing microseismic events. When underground rocks are damaged or moved due to human or natural factors, a weak seismic wave will be generated and propagate outward. By deploying multiple sets of monitoring sensors in the main tunnel, water curtain tunnel, and weak areas of the surrounding rock, microseismic data can be collected in real time. After data processing, the coordinates of the damage can be determined based on the principle of vibration positioning.

[0032] The microseismic monitoring sensor uses a high-sensitivity piezoelectric accelerometer array. This sensor has advantages such as high sensitivity, wide bandwidth, anti-electromagnetic interference, and easy reuse, which is beneficial for high-fidelity acquisition of seismic signals.

[0033] In step three, based on Gibowicz's theory of microseismic energy release mechanism, the microseismic released energy and seismic moment can be obtained. The relationship is approximated as:

[0034] According to the definition of seismic moment: The relationship between the energy released by microseismic events and the fissure aperture of the surrounding rock is derived as follows:

[0035] In the formula, The value represents the change in crack aperture caused by microseismic events, expressed in meters (m). Let be the radius of the seismic source, in meters (m). J represents the energy released by microseismic events, a value obtained from microseismic sensors. The stress drop, in Pa, is obtained from source spectrum analysis; G is the seismic moment, N×m; G is the shear modulus of the surrounding rock, Pa; A is the effective rupture surface area corresponding to the microseismic event, m². 2 .

[0036] In step four, the obtained surrounding rock fracture aperture data is utilized. Equivalent permeability of fractured surrounding rock The calculation is performed using a formula based on Cubic Law, as follows:

[0037] In the formula, The equivalent permeability of the fractured surrounding rock after microseismic cumulative damage is given by m. 2 ; Fracture surface density, used to characterize the degree of fracture surface development per unit volume of surrounding rock, in meters (m). -1 ; Let m be the initial fracture aperture. The change in crack aperture caused by micro-seismic events, in meters (m).

[0038] Furthermore, the equivalent permeability k of the fractured surrounding rock is used to characterize the change in the water conductivity of the fractures. As the fracture opening increases, the equivalent permeability of the fractured surrounding rock changes accordingly, thus affecting the hydraulic conditions required for the water curtain system to maintain water seal safety. Therefore, after obtaining the equivalent permeability k of the fractured surrounding rock, it is used as an input parameter in the formula for calculating the critical water seal pressure. Combined with the sealing mechanism of the underground water-sealed oil depot, the critical water seal pressure P required to maintain water seal safety under the current condition is calculated.

[0039] The critical water seal pressure P is the water injection pressure required to maintain the safety of the water seal in an underground water-sealed oil depot. It is calculated based on the sealing mechanism of the underground water-sealed oil depot, and the calculation formula is as follows:

[0040] In the formula, The critical water seal pressure is given in Pa. The design pressure for oil storage in the oil depot is given in Pa. The hydrostatic pressure term represents the potential energy between the water curtain orifice and the oil reservoir. The density of water is kg / m³. 3 ; The acceleration due to gravity is m / s². 2 ; The height difference, in meters, is the height difference between the water head at the water curtain orifice and the cavern. The minimum safe water injection flow rate that must be maintained for a single-hole design, in m 3 / s; ρ is the dynamic viscosity of water, Pa·s; The length of the water curtain hole in the calculated section is in meters (m). The equivalent permeability of the fractured surrounding rock after cumulative microseismic damage is given by m. 2 ; To determine the radius of influence, half the spacing of the water intake holes or the distance to the cavern, in meters; Where R is the borehole radius of the water curtain hole, in meters; ln(R / r) w () is dimensionless.

[0041] In step five, the PID controller controls the error value. Target set value Compared with actual measured value The difference between them, control quantity The PID controller outputs commands to drive the water curtain system for pressure regulation. With error The relationship formula is as follows:

[0042] In the formula: In practical engineering, the command to drive the water curtain system to regulate pressure is represented by the frequency of the water supply pump's inverter, in Hz. To control the error value, Pa, the corresponding formula is: ; The target set value, in actual engineering, refers to the calculated critical water seal pressure, in Pa; The actual measured value is the actual water seal pressure read back by the sensor, in Pa. The proportionality constant is expressed in Hz / Pa. The integral coefficient is Hz / (Pa·s); is the differential coefficient, Hz·s / Pa.

[0043] This invention also provides a seawater intrusion prevention and control system for underground water-sealed oil depots based on microseismic feedback, used to implement the above-mentioned seawater intrusion prevention and control method for underground water-sealed oil depots based on microseismic feedback, comprising: Parameter acquisition module: Configured to deploy a microseismic monitoring system in the underground water-sealed oil depot. Through the microseismic monitoring system, parameters such as the three-dimensional spatial coordinates of the seismic source and the microseismic radiation energy at the time of microseismic occurrence are acquired. This is used to sense and acquire damage information of surrounding rock fissures in real time. The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. The multiple sets of microseismic sensors are installed in the main cavern, water curtain tunnel and weak area of ​​surrounding rock of the underground water-sealed oil depot, and are connected to the ground terminal central control console through a fiber optic network. Damage transformation module: It is configured to perform formula fitting on the surrounding rock fissures and microseismic radiation energy caused by microseismic events based on Gibowicz theory and microseismic monitoring data.

[0044] Pressure determination module: It is configured to use the corrected surrounding rock fracture aperture data, use the Cubic Law-based formula to calculate the equivalent permeability of the surrounding rock fracture, combine the underground water-sealed oil depot sealing mechanism, calculate the critical water seal pressure required to ensure the safety of the water seal under the current state, and determine what adjustments should be made to the water curtain. The PID control module is configured to use the critical water seal pressure calculated by the pressure determination module as the target setpoint, receive the actual water seal pressure of the water curtain system, calculate the pressure deviation between the critical water seal pressure and the actual water seal pressure, and generate a pressure adjustment command based on the pressure deviation using a PID closed-loop control algorithm. This command drives the water curtain system to adjust the water injection pressure so that the actual water seal pressure approaches the critical water seal pressure, thereby ensuring the safety of oil products in the underground water-sealed oil depot.

[0045] The following uses the Huangdao underground water-sealed cavern as an example to illustrate the method of the present invention in detail. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0046] like Figure 1 As shown, this invention provides a method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback, specifically including the following steps: (1) In the early stage of the construction of the underground water-sealed oil depot, after the specific location of the cavern and the distribution of faults are determined through geological exploration, a single-component microseismic sensor is arranged every 30-50 meters in the main cavern, water curtain tunnel and weak surrounding rock area. The range of microseismic sensors is selected from 10Hz to 2000Hz. All microseismic sensors are connected to the ground central control console through optical fiber. During initialization, wave velocity correction is first performed by manual knocking or small-dose fixed-point blasting to establish an accurate three-dimensional P-wave and S-wave velocity field model.

[0047] (2) The ground central control console receives the monitoring data transmitted by the microseismic sensor through the microseismic monitoring system. When the surrounding rock vibrates due to construction or operation disturbance, the elastic wave released by the surrounding rock is received by the microseismic sensor and transmitted to the ground central control console. The data acquisition module of the microseismic monitoring system automatically starts acquisition according to the preset trigger threshold, records the microseismic waveform data, and obtains the source coordinates (x, y, z), seismic moment M0 and microseismic radiation energy E through source location and source parameter inversion.

[0048] (3) Based on the Gibowicz theory, which studies the damage to surrounding rock fissures and the energy release mechanism caused by microseismic events, the energy released by microseismic events can be obtained. With seismic moment The relationship is approximated as:

[0049] According to the definition of seismic moment: The derived verification formula is:

[0050] Verification was performed based on the data derived from the paper on focal parameters and scaling relationships of the Hungarian earthquake (central Pannonia Basin): focal radius. A typical value of 125m is taken. Stress drop. The average value of the paper is taken as 2.6 bar = 0.26 MPa (2.6 × 10⁻⁶). 5 Pa). Radiant energy According to the earthquake magnitude in the paper The energy calculated using the engineering formula for microseismic energy determination is approximately 2.0 × 10⁻⁶. 5 J. Surrounding rock shear modulus Take 30 GPa from the paper. Substitute the data into the derived formula:

[0051] Calculation results: , That is, the calculated increase in crack opening is approximately 31.3. .

[0052] (4) Using the corrected surrounding rock fracture aperture data, a formula based on Cubic Law is adopted: To estimate the equivalent permeability of surrounding rock fractures, and to simplify the calculation, the principal permeability components and initial fracture aperture of a single set of fractures are calculated. Take 50 m; crack density Take 2.0m -1 ; Crack aperture increment Use the 31.3 calculated in step (3) m; connectivity coefficient Set to ideal state 1.0.

[0053]

[0054] After inputting the above data,

[0055] Calculation results: Comparison with initial penetration rate (i.e., use) ): The results showed that the fracture aperture increased from 50... The increase in μm to 50 + 31.3 = 81.3 μm causes the permeability to decrease from... Increase to This represents an increase of approximately 4.3 times. This aligns with the characteristic of the Cubic Law in the formula that it is sensitive to minute changes in aperture.

[0056] (5) Based on the sealing mechanism of the underground water-sealed oil depot, the critical water seal pressure to ensure water seal safety is calculated. According to the actual operating water curtain pressure of the Huangdao underground water-sealed cavern, based on the formula:

[0057] Among them, the hole radius Radius of influence Calculate the segment length Dynamic viscosity of water Assuming the water curtain is 20m higher than the cavern, then its hydrostatic pressure... ( ).

[0058]

[0059] The calculation result is,

[0060] 0.1 + 0.2 + 0.018 ≈ 0.318 MPa The calculated orifice pressure required to maintain the water seal is approximately 0.32 MPa. A review of the paper (Wang et al., 2016) indicates that the actual operating water curtain pressure in the Huangdao underground water-sealed cavern is controlled within the engineering control range of 0.3 MPa to 0.5 MPa. The water curtain pressure of 0.32 MPa calculated in this embodiment falls within the aforementioned engineering control range, demonstrating the rationality of the critical water seal pressure determined using the method of this application, and its ability to meet the water seal safety control requirements of the underground water-sealed oil depot.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback, characterized in that, Includes the following steps: Step 1: After determining the site selection and layout of the underground water-sealed oil depot, a microseismic monitoring system is deployed simultaneously during the construction of the underground water-sealed oil depot. The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. The multiple sets of microseismic sensors are installed in the main cavern, water curtain tunnel and weak rock areas of the underground water-sealed oil depot, and are connected to the ground terminal central control console through a fiber optic network. Step 2: The ground terminal central control console collects signals emitted by the microseismic sensors in real time. After processing by the microseismic monitoring system, the parameters of the microseismic event are obtained, including three-dimensional spatial coordinates and microseismic radiation energy. Step 3: Based on Gibowicz's microseismic energy theory and the relationship between the radiation energy of microseismic events and the evolution of surrounding rock damage, the degree of surrounding rock fracture damage is inverted through microseismic monitoring data, and a quantitative mapping relationship between microseismic radiation energy and fracture aperture is established. Step 4: Using the corrected surrounding rock fracture aperture data, calculate the equivalent permeability of the fractured surrounding rock, and combine it with the sealing mechanism of the underground water-sealed oil depot to calculate the critical water seal pressure to ensure water seal safety. Step 5: Based on the calculated critical water seal pressure, the critical water seal pressure is used as the target setpoint. The PID controller executes the PID closed-loop control algorithm to drive the water curtain system to regulate the pressure, so as to ensure the safety of oil products in the underground water-sealed oil depot.

2. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback as described in claim 1, characterized in that: In step one, the micro-vibration sensor adopts a tetrahedral structure or a spatial spiral layout.

3. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback as described in claim 1, characterized in that: In step one, the microseismic monitoring system, based on acoustics and seismology, analyzes the impact on production activities by observing microseismic events. When underground rocks are damaged or moved due to human or natural factors, a weak seismic wave will be generated and propagate outward. By deploying multiple sets of monitoring sensors in the main tunnel, water curtain tunnel, and weak areas of the surrounding rock, microseismic data can be collected in real time. After data processing, the coordinates of the damage can be determined based on the principle of vibration positioning.

4. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback as described in claim 1, characterized in that: In step three, based on Gibowicz's theory of microseismic energy release mechanism, the microseismic released energy and seismic moment can be obtained. The relationship is approximated as: According to the definition of seismic moment: The relationship between the energy released by microseismic events and the fissure aperture of the surrounding rock is derived as follows: In the formula, The value represents the change in crack aperture caused by microseismic events, expressed in meters (m). Let be the radius of the seismic source, in meters (m). J represents the energy released by microseismic events, a value obtained from microseismic sensors. The stress drop, in Pa, is obtained from source spectrum analysis; G is the seismic moment, N×m; G is the shear modulus of the surrounding rock, Pa; A is the effective rupture surface area corresponding to the microseismic event, m². 2 .

5. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback according to claim 1, characterized in that: In step four, the equivalent permeability of the fractured surrounding rock... The calculation is performed using a formula based on Cubic Law, as follows: In the formula, The equivalent permeability of the fractured surrounding rock after microseismic cumulative damage is given by m. 2 ; Fracture surface density, used to characterize the degree of fracture surface development per unit volume of surrounding rock, in meters. -1 ; Let m be the initial fracture aperture. The value in meters represents the change in crack aperture caused by micro-seismic events.

6. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback according to claim 5, characterized in that: In step four, the critical water seal pressure P is the water injection pressure required to maintain the safety of the water seal in the underground water-sealed oil depot. It is calculated based on the sealing mechanism of the underground water-sealed oil depot, and the calculation formula is as follows: In the formula, The critical water seal pressure is given in Pa. The design pressure for oil storage in the oil depot is given in Pa. The hydrostatic pressure term represents the potential energy between the water curtain orifice and the oil reservoir. The density of water is kg / m³. 3 ; The acceleration due to gravity is m / s². 2 ; The height difference, in meters, is the height difference between the water head at the water curtain orifice and the cavern. The minimum safe water injection flow rate that must be maintained for a single-hole design, in m 3 / s; ρ is the dynamic viscosity of water, Pa·s; The length of the water curtain hole in the calculated section is in meters (m). The equivalent permeability of the fractured surrounding rock after cumulative microseismic damage is given by m. 2 ; To determine the radius of influence, half the spacing of the water intake holes or the distance to the cavern, in meters; Where R is the borehole radius of the water curtain hole, in meters; ln(R / r) w () is dimensionless.

7. The method for preventing seawater intrusion into underground water-sealed oil depots based on microseismic feedback according to claim 1, characterized in that: In step five, the PID controller controls the error value. Target set value Compared with actual measured value The difference between them, control quantity The PID controller outputs commands to drive the water curtain system for pressure regulation. With error The relationship formula is as follows: In the formula: In practical engineering, the command to drive the water curtain system to regulate pressure is represented by the frequency of the water supply pump's inverter, in Hz. To control the error value, Pa, the corresponding formula is: ; The target set value, in actual engineering, refers to the calculated critical water seal pressure, in Pa; The actual measured value is the actual water seal pressure read back by the sensor, in Pa. The proportionality constant is expressed in Hz / Pa. The integral coefficient is Hz / (Pa·s); is the differential coefficient, Hz·s / Pa.

8. A seawater intrusion prevention and control system for underground water-sealed oil depots based on microseismic feedback, used to implement the seawater intrusion prevention and control method for underground water-sealed oil depots based on microseismic feedback as described in any one of claims 1-7, characterized in that: include: Parameter acquisition module: Configured to deploy a microseismic monitoring system in the underground water-sealed oil depot. Through the microseismic monitoring system, the three-dimensional spatial coordinates of the seismic source and the microseismic radiation energy parameters at the time of microseismic occurrence are acquired, which are used to sense and acquire damage information of surrounding rock fissures in real time. The microseismic monitoring system includes a central control console and multiple sets of microseismic sensors. The multiple sets of microseismic sensors are installed in the main cavern, water curtain tunnel and weak area of ​​surrounding rock of the underground water-sealed oil depot, and are connected to the ground terminal central control console through a fiber optic network. Damage transformation module: configured to perform formula fitting on the surrounding rock fissures and microseismic radiation energy caused by microseismic events based on Gibowicz theory and microseismic monitoring data; Pressure determination module: It is configured to use the corrected surrounding rock fracture aperture data, use the Cubic Law-based formula to calculate the equivalent permeability of the surrounding rock fracture, combine the underground water-sealed oil depot sealing mechanism, calculate the critical water seal pressure required to ensure the safety of the water seal under the current state, and determine what adjustments should be made to the water curtain. The PID control module is configured to use the critical water seal pressure calculated by the pressure determination module as the target setpoint, receive the actual water seal pressure of the water curtain system, calculate the pressure deviation between the critical water seal pressure and the actual water seal pressure, and generate a pressure adjustment command based on the pressure deviation using a PID closed-loop control algorithm. This command drives the water curtain system to adjust the water injection pressure so that the actual water seal pressure approaches the critical water seal pressure, thereby ensuring the safety of oil products in the underground water-sealed oil depot.

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