Method for monitoring flow direction, speed and mass flow of underground water flow

Abstract

The invention discloses an underground water flow direction, speed and mass flow monitoring method. Underground water flow direction logging or hydrological logging is a technical means for obtaining underground water flow information through a drill hole or a monitoring well. An array sensor is located in a well logging; the array sensor comprises a cylindrical shell, a heating body, a temperature sensor and an orientation sensor; the size of the cylindrical shell is the same as that of the inner wall of the logging well; the heating body is arranged at the central position of the cylindrical shell; the bottom surface of the cylindrical shell is uniformly divided into N fan-shaped sub-areas along the circumference by taking the heating body as the center, and each sub-area is provided with a temperature sensor; an orientation sensor is arranged on each temperature sensor and is used for monitoring the azimuth angle of the temperature sensor; data collected by the array sensor is transmitted to the controller, and the flow speed, the water flow direction and the total mass flow rate of water flow are obtained through calculation. According to the invention, the measurement difficulty of a heterogeneous aquifer and a thin aquifer is overcome, and wider and more accurate monitoring of the aquifer environment is realized.

Description

Technical Field

[0002] This invention belongs to the field of groundwater monitoring technology, specifically relating to a method for monitoring the direction, velocity, and mass flow rate of groundwater. Background Technology

[0003] Groundwater flow direction logging (or hydrological logging) is a technical means of obtaining groundwater flow information through boreholes or monitoring wells. It is an important foundational work in hydrogeological surveys, water resource management, pollution control, and engineering construction (such as foundation pit drainage and tunnel excavation). Accurately determining the direction of groundwater flow helps to understand the dynamic characteristics of groundwater systems and provides a scientific basis for resource development, environmental protection, and disaster prevention.

[0004] Traditional hydrogeological methods include wellbore water level measurement, tracer logging, ultrasonic logging, and downhole television (MDT) technology. Water level measurement measures the water level elevation at multiple points, creating contour maps and forming a triangular monitoring network. Its disadvantages include poor applicability to heterogeneous aquifers, difficulty in measuring thin aquifers, significant hysteresis effects, difficulties in data interpretation, and the need for numerous measurement points. Tracer logging involves injecting specific tracers, such as sodium fluorescein or isotopes, into the borehole and monitoring their migration path to determine flow direction. Its disadvantages include potential water pollution and interference from adsorption, degradation, or diffusion. Downhole television (MDT) uses downhole imaging to observe the movement of floating objects in the water to determine flow direction. Its disadvantages include high water clarity requirements and inability to operate in turbid water. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention proposes a method for monitoring the direction, velocity, and mass flow rate of groundwater. This method overcomes the measurement challenges of heterogeneous aquifers and thin aquifers, significantly reduces the hysteresis effect in the measurement process, and enables more extensive and accurate monitoring of the aquifer environment.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for monitoring the direction, velocity, and mass flow rate of groundwater flow, comprising the following steps: Step 1: Fabricate the array sensor; Step 2: Place the array sensor into the well log; Step 3: Transmit the data collected by the array sensor to the controller; Step 4: Calculate the flow velocity, flow direction, and total mass flow rate of the water.

[0007] Furthermore, the array sensor includes a cylindrical shell, a heating element, a temperature sensor, and an azimuth sensor; the cylindrical shell has the same dimensions as the inner wall of the well; the heating element is located at the center of the cylindrical shell; with the heating element as the center, the bottom surface of the cylindrical shell is divided into N sector-shaped sub-regions along the circumference, and a temperature sensor is installed in each sector-shaped sub-region; an azimuth sensor is set on each temperature sensor to monitor the azimuth angle of the temperature sensor; the number N is specifically set according to the measurement accuracy requirements.

[0008] Furthermore, each temperature sensor is positioned at the center of the circumference of its respective sector sub-region.

[0009] Furthermore, the areas of the N sector sub-regions are all equal.

[0010] Furthermore, the temperature sensor is a platinum resistance temperature sensor.

[0011] Furthermore, the method for determining the direction of water flow is as follows: Collect the temperature values ​​of all temperature sensors, determine the azimuth angle S corresponding to the temperature sensor with the highest temperature value, and then determine the water flow direction as the azimuth angle S, that is, the direction from the center of the array of sensors to the temperature sensor with the highest temperature value.

[0012] Furthermore, the specific calculation method for the flow velocity of the water is as follows: The basic velocity equation is v=[(Q / (AΔT))-1]² / B² Where: v: fluid velocity (m / s); Q: heating power of the heating element (W); A is the scale coefficient of the temperature sensor, and B is the scale coefficient of the orientation sensor. The scale is set to the standard temperature value. ΔT: Temperature difference (K), the difference between the temperature of the heating element and the highest temperature of the temperature sensor.

[0013] Furthermore, the total mass flow rate Qm is calculated as follows: Qm=π*(D / 2)^2*ρ*v Where D is the logging diameter, ρ is the water fluid density, and v is the average water fluid velocity.

[0014] The beneficial effects of this invention are: 1) This invention can not only accurately measure the change in the flow direction of fluid, but also effectively measure the velocity information of fluid, overcoming the measurement difficulties of heterogeneous aquifers and thin aquifers, significantly reducing the hysteresis effect in the measurement process, and simplifying the data analysis steps; 2) This invention significantly reduces the requirements for water quality and the potential risk of water pollution, expands the application range of the method under various water quality conditions, and enables more extensive and accurate monitoring of aquifer environments. Attached Figure Description

[0015] Figure 1 This is a flowchart of the data processing of the present invention; Figure 2 This is a schematic diagram of the array sensor structure of the present invention; Figure 3 This is a top view of the sensor of the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to specific embodiments.

[0017] This invention can not only accurately determine the change in fluid flow direction, but also effectively measure the fluid velocity information, overcoming the measurement difficulties of heterogeneous aquifers and thin aquifers, significantly reducing the hysteresis effect in the measurement process, and simplifying the data analysis steps; it greatly reduces the requirements for water quality and the potential risk of water pollution, expands the application range of this method under various water quality conditions, and realizes more extensive and accurate monitoring of the aquifer environment.

[0018] This invention provides a method for monitoring the direction and velocity of groundwater flow, comprising the following steps: Step 1: Fabricate the array sensor; like Figure 2 , 3 As shown, the array sensor includes a cylindrical shell, a heating element, a temperature sensor, and an orientation sensor. The cylindrical shell has the same dimensions as the inner wall of the well. The heating element is located at the center of the cylindrical shell. The bottom surface of the cylindrical shell is divided into N equal-sized sector sub-regions around the heating element. Each sector sub-region is equipped with a temperature sensor, located at the center of its respective sector. An orientation sensor is installed on each temperature sensor to monitor its azimuth angle. The number N is determined based on the required measurement accuracy; higher accuracy results in a larger value for N, more sub-regions, and more accurate determination of water flow direction.

[0019] 1) Sensor layout In this embodiment, 90 temperature sensors are arranged in a circular array. Each sensor is an independent channel that can collect temperature data independently. Each temperature sensor is associated with an angle through an azimuth sensor. S1 corresponds to an azimuth angle of 0 degrees. The 90 sensors are evenly distributed within the circumference, with each sensor corresponding to an angle of 4 degrees and numbered S1-S90. A heating element is located in the center of the circle, and the heating element uses constant power heating.

[0020] 2) Working principle Each temperature sensor corresponds to an angle. The azimuth angle of one temperature sensor is used as the starting position, and the remaining temperature sensors are arranged sequentially along the circumference. Each temperature sensor has independent time, azimuth, and temperature information, allowing for convenient calculation of fluid velocity and area. The acquisition software performs consistent calibration on the collected sensor data, ensuring that the measurement error of each sensor is less than 0.01 degrees Celsius under constant temperature conditions. It also filters, calculates, and displays the collected temperature difference data. After the instrument is powered on, the heating element begins constant-power heating, and the downhole instrument is placed stationary at the water layer.

[0021] Conventional temperature sensors can only measure the temperature at one point. Array sensors, on the other hand, distribute multiple temperature sensors on a substrate. These multiple temperature sensors are arranged together to form an array, enabling the detection of the temperature distribution at various points throughout the space. This allows for a direct detection of the temperature at each monitoring point, reflecting temperature changes caused by the flow rate and direction of the medium, and enabling monitoring, analysis, or prediction of fluid flow rate and direction.

[0022] 3) Temperature sensor In this embodiment, a platinum resistance temperature sensor is used. Platinum resistance thermometers are made based on the principle that resistance changes with temperature. Platinum, as a metal, exhibits a good linear relationship between resistance and temperature within a certain temperature range, resulting in high accuracy. Therefore, it is widely used as a temperature sensing element for measuring temperatures from approximately 0 to 100°C. Furthermore, platinum itself is chemically inert in air and is not easily oxidized or contaminated, thus achieving stable resistance-temperature characteristics, good repeatability, and sensitivity to temperature changes. For example, a platinum PT100 resistance thermometer shows a resistance change of approximately 0.39 ohms for every 1°C temperature change, facilitating measurement.

[0023] 4) Azimuth sensor Azimuth sensors are sensors that use geomagnetism for detection. Azimuth sensor logging determines the location and orientation of the wellbore underground by measuring the well inclination angle and the well inclination azimuth angle.

[0024] The principle of azimuth sensor logging is to use a quartz accelerometer and a fluxgate magnetometer to measure the well inclination angle and azimuth angle. The quartz accelerometer consists of two parts: a meter assembly and a servo circuit assembly. When acceleration is applied to the detection mass, it will deviate from its equilibrium position due to inertia. The differential change in the air gap between the two plates of the capacitive sensor and the excitation ring causes a differential change in the two capacitors. The differential capacitance detector in the servo circuit detects this change and outputs information proportional to this displacement in the form of an electrical signal. After amplification and processing by the servo circuit, a DC current is generated and fed back to the torque coil. The interaction between the DC current and the permanent magnet produces a counterforce, causing the pendulum mass to return to its equilibrium position. The current applied to the torque is proportional to the inertial force input to the accelerometer pendulum mass, reflecting the magnitude and direction of the external acceleration force. The fluxgate magnetometer consists of two parts: a probe and an amplifier circuit. A pair of coils connected in series and reversed are wound around a ring-shaped magnetic conductor in the probe. Their physical and mechanical parameters are made symmetrical, and a driving circuit provides the excitation current. In the absence of an external magnetic field, the induced electromotive force at its center tap is zero. When an external magnetic field acts on the coil, due to the nonlinearity of the iron core magnetization curve, a pulsating magnetic field with twice the excitation frequency, proportional to the external magnetic field, acts on the coil, causing it to generate an induced electromotive force. This signal is amplified by frequency selection, demodulated by phase frequency, and integrated to form a feedback current that is sent to the output terminal of the coil. This superimposes a negative feedback current between the two coils and generates a reverse magnetic field in the iron core.

[0025] 5) Sensor and device selection requirements and process requirements All instruments and sensors utilize imported aerospace-grade components, and all resistors are high-temperature, high-precision ceramic resistors. All individual components undergo a high-temperature screening test at 80°C for one hour. All batteries operate continuously for one hour under load at 80°C. Only after all components pass testing can the instrument proceed to the three-stage welding process: low temperature, medium temperature, and high temperature. This welding process ensures that no solder joints will experience incomplete soldering or detachment during temperature changes. After instrument debugging, it undergoes a second 80°C high-temperature test under a re-energized state in an oven. Following the high-temperature test, the instrument undergoes a final vibration test at 5-50Hz.

[0026] Step 2: Place the array sensor into the well; when using it, lower the entire device into the well using a cable; Step 3: Transmit the data collected by the array sensors to the controller; the controller structure and data processing flow adopt existing technologies, such as... Figure 1 As shown; the controller generally includes an analog front-end, a logic processing unit, a data processing unit, a data storage unit, a backup data storage unit, a data interface, downhole data compression encoding, a data bus driver unit, a CPU processor, and a power management unit.

[0027] 1) Simulate front end The analog front-end (AFE) is a circuit located at the input of an electronic system, responsible for preprocessing the input analog signal. Its main functions include signal amplification, filtering, analog-to-digital conversion (ADC), frequency conversion, modulation and demodulation, adjacent-channel processing, level adjustment, and control. Through these functions, the AFE ensures signal quality and accuracy, providing a high-quality signal for subsequent digital signal processing. Furthermore, the AFE features stability, interference immunity, and low power consumption, contributing to improved overall system performance and reliability. It amplifies weak analog signals (such as voltage, current, and temperature) output from sensors or signal sources, ensuring the signal amplitude meets the requirements of subsequent circuit processing. The AFE employs a bandpass filter network, effectively eliminating local noise interference and improving measurement accuracy.

[0028] 2) Logic processing unit The logic processing unit (LPU) is the core component of a computer system responsible for performing logical operations. It is part of the computer processor and is specifically designed to perform logical operations such as Boolean operations like AND, OR, NOT, and XOR. It is closely related to the arithmetic logic unit (ALU), but focuses more on pure logical operations than arithmetic operations. The performance of the LPU directly affects the efficiency of the computer in processing tasks such as conditional judgments and decision-making logic. It allocates the sampling time among various signals and is an indispensable fundamental component of the system.

[0029] 3) Data processing unit A data processing unit (DPU) is a hardware component specifically designed for efficiently handling data-intensive tasks. It primarily optimizes data movement, storage, network transmission, and computation. It typically functions as a coprocessor to the CPU, offloading data management tasks to improve overall system performance.

[0030] 4) Data storage unit and backup data storage unit Data storage units are hardware or software components in a system used for persistent or temporary data storage, responsible for data writing, reading, management, and protection. They are a core part of the system architecture, directly impacting system performance, reliability, and scalability. Backup data storage units are dedicated storage systems for storing data copies, aiming to provide data recovery capabilities in case of original data loss, corruption, or external anomalies. They are a core component of the data protection strategy.

[0031] 5) Data Interface This interface uses Ethernet, the most mainstream local area network (LAN) technology standard. Its data interface is the physical and logical interface for wired communication between network devices. It is an important channel for data exchange with the host computer.

[0032] 6) Downhole data compression coding Data compression coding is a technique that reduces data storage space or transmission bandwidth through specific algorithms. It employs Zstandard lossless compression, which can perfectly recover the original data after compression without causing any information loss. It primarily utilizes redundant information in the data for compression.

[0033] 7) Data bus driver unit This system is an imaging logging system with a large data volume. We employ OFDMA orthogonal coding technology. After power-on, the system automatically establishes an adaptive connection. Using cross-frequency division multiplexing (CFD) technology, it features bidirectional transmission. During data transmission, modulation technology modulates the user data, converting the encoded signal carrying the information into an orthogonal signal via a DAC. After processing by the analog front-end (AFE), the signal is coupled to the cable bus via a transformer. During data reception, the OFDM signal on the cable is processed by the analog front-end (AFE) and then acquired by a high-speed ADC. The signal is then demodulated through calculations.

[0034] 8) CPU processor The Central Processing Unit (CPU) is the core of a computer's computation and control, responsible for interpreting computer instructions and processing data. It mainly consists of arithmetic logic units, register units, control units, cache memory, and buses. As the main control core of this instrument, we have very high requirements for it. In this product, we use a dual-core architecture of ARM and FPGA. This series of microcontrollers is widely used in industrial, automotive, and aerospace fields, and its reliability and stability are excellent. For communication with the host computer, we use USB communication, and the interface has protective functions to prevent damage to the downhole instrument from peripheral devices.

[0035] 9) Power Management Unit The power management unit (PMU) is a critical subsystem in electronic systems responsible for power conversion, distribution, and optimization, directly impacting device energy efficiency, battery life, and stability. This system employs low-dropout, low-power power chips with current loss in the μA range and features overcharge, overcurrent, and overvoltage protection, effectively ensuring battery durability and discharge efficiency.

[0036] Step 4: Calculate the flow velocity, flow direction, and total mass flow rate of the water.

[0037] 1) Basic Principles A flow meter measures fluid mass flow rate by utilizing the temperature field change generated when a fluid flows through a pipe heated by an external heat source, or by utilizing the relationship between the energy required for the fluid temperature to rise to a certain value when heated and the fluid mass. A heating sensor and two temperature sensors are placed in the measuring medium. When one heating sensor is heated above ambient temperature, the other sensor senses the medium temperature. As the medium flow rate increases, the medium carries away more heat, and the temperature difference between the temperature sensors changes with the medium flow rate. Based on the proportional relationship between the temperature difference and the medium flow rate, and using the thermal diffusion law Q = (A + B\sqrt{v}) \Delta T, where Q is the heating power (W), v is the fluid velocity (m / s), and A and B are probe characteristic constants, the fluid velocity can be calculated. Thermal conductivity meters offer advantages such as low pressure loss, wide flow range, high accuracy, high repeatability, high reliability, and no moving parts.

[0038] 2) The specific calculation method for water flow velocity is as follows: The basic velocity equation is v=[(Q / (AΔT))-1]² / B² Where: v: fluid velocity (m / s); Q: heating power of the heating element (W); A is the scale coefficient of the temperature sensor, and B is the scale coefficient of the orientation sensor. The scale is set to the standard temperature value. ΔT: Temperature difference (K), the difference between the temperature of the heating element and the highest temperature of the temperature sensor.

[0039] 3) The method for determining the direction of water flow is as follows: The temperature values ​​of all temperature sensors are collected, and the azimuth angle S corresponding to the temperature sensor with the highest temperature value is determined. The direction of water flow is then determined as azimuth angle S, i.e., the direction from the center of the array of sensors to the temperature sensor with the highest temperature value. In this embodiment, 90 regions are divided, with an angle difference of 4° between adjacent regions. The azimuth angle of the temperature sensor at point C is calibrated as 0°, the azimuth angle of the temperature sensor adjacent to S1 in the counterclockwise direction is 4°, and the azimuth angles of other temperature sensors are deduced accordingly. Figure 3 As shown, the water flow direction is from B to C, and the azimuth angle of the temperature sensor at point C is 0°, which corresponds to the water flow direction of 0°.

[0040] 4) The total mass flow rate is calculated as follows: The total mass flow rate is calculated by measuring the local flow velocity at each sensor and then using area weighting to calculate the total flow rate, including the following steps: Step 1: Determine the area weight represented by each temperature sensor; Step 2: Measure the local flow rate of each temperature sensor and calculate the local mass flow rate; Step 3: Multiply each local mass flow rate by its corresponding area weight, and then sum them to obtain the total mass flow rate. The calculation method is as follows: Total mass flow rate = Σ (local mass flow rate × area weight of the corresponding region).

[0041] Method for determining area weight: Calibration method, which calculates the area weight coefficient of each sensor by using known flow rate and sensor readings.

[0042] The formula for calculating total mass flow rate is: Qm=Σ[ρ_i*v_i*A_i], where: ρ_i is the density of the water at point i (if the temperature and pressure are uniform, the density is the same everywhere); v_i is the local velocity at point i; and A_i is the area weight corresponding to the sensor at point i.

[0043] Since each sensor measures the mass flow rate (directly measuring the mass flow rate based on the principle of thermal diffusion), in reality, q_i = f(heating power, temperature difference) directly yields the mass flow rate (kg / (m²·s)) or standard volumetric flow rate. Therefore, the mass flow rate contribution of each sensor is: m_i = q_i * A_i. The total mass flow rate Q_m = Σ (q_i * A_i).

[0044] To determine the area weight A_i for each sensor, for a circular pipe, if the equal toroidal method (Log-Tchebycheff rule) is used: divide the pipe cross-section into several concentric rings of equal area, and select a specific position on each ring (usually at radius r_j, satisfying the Log-Tchebycheff rule, so that the measurement point is optimally representative of the flow integral). Each point represents the area of ​​a ring, i.e., A_i = π*(r_{i}^2 - r_{i-1}^2) / n_i, where n_i is the number of points on the ring (if there is one point per ring, then n_i=1, and A_i is the area of ​​the ring). Under the condition of equal area distribution, the area weight A_i for each sensor is A_total / n.

[0045] Therefore, the total mass flow rate is: Q_m = (A_total / n) * Σ (ρ_i * v_i) [If the density is uniform, then ρ_i = ρ]. However, since the thermal conductivity flow meter directly measures the mass flow rate (through the principle of heat conduction), each sensor actually outputs the mass flow rate (mass flow rate per unit area, kg / (m²·s)), that is: q_i = ρ_i * v_i (mass flow rate).

[0046] For the array thermal conductivity flowmeter of this invention, using an equal-area distribution of points, the total mass flow rate is equal to the average of the local mass flow rates measured by all sensors multiplied by the total cross-sectional area of ​​the pipe. The calculation formula is: Qm = A_total * (1 / n) * Σq_i = A_total * q_avg. The total cross-sectional area of ​​the pipe, A_total, is π * (D / 2)^2, where D is the logging diameter. q_avg = ρ * v, where ρ is the water density and v is the average water velocity. The average water velocity v can be obtained through simulation using the fluid simulation software ANSYS Fluent, by inputting the logging diameter D and the water pressure.

[0047] The content of this invention is not limited to the embodiments listed. Any equivalent modifications made by those skilled in the art to the technical solutions of this invention by reading this specification are covered by the claims of this invention.

Claims

1. A method for monitoring the direction, velocity, and mass flow rate of groundwater, characterized in that: Includes the following steps: Step 1: Fabricate the array sensor; Step 2: Place the array sensor into the well log; Step 3: Transmit the data collected by the array sensor to the controller; Step 4: Calculate the flow velocity, flow direction, and total mass flow rate of the water.

2. The method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 1, characterized in that: The array sensor includes a cylindrical shell, a heating element, a temperature sensor, and an orientation sensor; the cylindrical shell has the same dimensions as the inner wall of the well logging system. The heating element is located at the center of the cylindrical shell; with the heating element as the center, the bottom surface of the cylindrical shell is divided into N sector-shaped sub-regions along the circumference, and a temperature sensor is installed in each sector-shaped sub-region; an orientation sensor is set on each temperature sensor to monitor the orientation angle of the temperature sensor. The number of N values ​​is set according to the specific measurement accuracy requirements.

3. The method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 2, characterized in that: Each temperature sensor is positioned at the center of its respective sector sub-region.

4. The method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 3, characterized in that: The areas of the N sector sub-regions are all equal.

5. The method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 4, characterized in that: The temperature sensor used is a platinum resistance temperature sensor.

6. The method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 4, characterized in that: The method for determining the direction of water flow is as follows: Collect the temperature values ​​of all temperature sensors, determine the azimuth angle S corresponding to the temperature sensor with the highest temperature value, and then determine the water flow direction as the azimuth angle S, that is, the direction from the center of the array of sensors to the temperature sensor with the highest temperature value.

7. A method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 4, characterized in that: The specific calculation method for the flow velocity of the water is as follows: The basic velocity equation is v=[(Q / (AΔT))-1]² / B² Where: v: fluid velocity (m / s); Q: heating power of the heating element (W); A is the calibration coefficient of the temperature sensor, and B is the calibration coefficient of the orientation sensor. ΔT: Temperature difference (K), the difference between the temperature of the heating element and the highest temperature of the temperature sensor.

8. A method for monitoring the direction, velocity, and mass flow rate of groundwater according to claim 4, characterized in that: The total mass flow rate Qm is calculated as follows: Qm=π*(D / 2)^2*ρ*v Where D is the logging diameter, ρ is the water fluid density, and v is the average water fluid velocity.

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