A physical simulation experiment device and method for tubing leakage DAS monitoring

Abstract

The application provides a tubing leakage DAS monitoring physical simulation experiment device and experiment method, and belongs to the technical field of oil and gas well safety monitoring.The application constructs a physical simulation experiment device composed of a distributed optical fiber acoustic wave monitoring system, a wellbore leakage simulation system, a liquid supply system and a waste liquid recovery system, sets a leakage point simulation assembly with a replaceable leakage channel at a preset position of the simulated wellbore, simulates tubing leakage working conditions under different leakage point positions, leakage point forms, injection flow rates and fluid types, collects acoustic wave profiles of the whole wellbore section by using the distributed optical fiber acoustic wave monitoring system, and constructs a quantitative relationship model of leakage flow rate and acoustic wave energy.The application can simulate complex leakage working conditions of oil and gas wells, realizes rapid replacement and comparison experiments of various leakage point forms, overcomes the limitation of single leakage point type of traditional experiment devices, and provides experiment support for accurate positioning and quantitative evaluation of tubing leakage points based on optical fiber acoustic wave monitoring.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well safety monitoring technology, and in particular to a physical simulation experimental device and method for DAS monitoring of tubing leakage. Background Technology

[0002] As oil and gas exploration and development continue to advance into deeper, deeper, and unconventional areas, the risks and challenges to the integrity of oil and gas wellbores are becoming increasingly prominent. During long-term use, downhole tubing such as tubing, casing, and packers are frequently affected by factors such as corrosion, alternating loads, and mechanical damage, leading to frequent leakage problems. This not only causes losses in oil and gas production but may also trigger major safety accidents such as annular pressure, environmental pollution, and even blowouts. Therefore, accurately identifying the location, extent, and morphology of leakage points has become a key technical requirement for ensuring the safe production of oil and gas wells.

[0003] In recent years, distributed fiber optic sensing technology, especially distributed fiber optic acoustic sensing (DAS) technology, has shown broad application prospects in the field of wellbore integrity monitoring due to its advantages such as real-time continuous monitoring of the entire well section, fast response speed, and strong resistance to electromagnetic interference. Based on the phase change of backscattered Rayleigh light, DAS technology can extract real-time acoustic vibration signals distributed along the wellbore, providing a new solution for continuous leakage diagnosis of the entire well section, which is difficult to achieve with traditional monitoring methods. Therefore, establishing a quantitative relationship between the acoustic response characteristics acquired by DAS and the location and degree of leakage is the key technology for achieving accurate leakage diagnosis.

[0004] Currently, existing technologies have conducted leakage simulation experiments based on DAS, and have initially established a quantitative relationship between leakage flow and acoustic energy. However, the existing experimental devices are too simplified in structure, making it difficult to simulate multiple types of leaks, multiphase fluids, and complex working conditions. Furthermore, there is a lack of systematic comparison of different leak morphologies such as irregular cracks and holes.

[0005] Therefore, there is an urgent need for a set of physical experimental devices and methods that can systematically simulate the complex working conditions of oil and gas wells, so as to conduct in-depth research on the acoustic response mechanism of oil and gas well leakage, clarify the law of influence of leakage acoustic waves, and construct a quantitative relationship model between leakage flow and acoustic energy. This will lay the foundation for breaking through the technical bottleneck of realizing accurate location of leakage points and quantitative evaluation of leakage degree in offshore wells based on distributed optical fiber acoustic monitoring. This is also the core problem that this invention aims to solve.

[0006] Extensive field measurement data shows that there is a strong acoustic vibration response at the leak point in the oil pipe during production, while the acoustic response at the pipe section without leakage is very weak. The essence of this phenomenon is that when the fluid flows through the leak point, the sudden change in flow velocity and pressure release will excite characteristic acoustic signals. Therefore, as long as the quantitative correlation between the leakage amount, the leak point morphology and the intensity of the acoustic response is clarified, the leak location can be accurately located and the leakage amount can be dynamically quantitatively assessed based on real-time DAS data.

[0007] Therefore, it is necessary to establish a physical simulation experimental device and method for DAS leak monitoring of oil and gas well tubing, so as to carry out theoretical research on the correlation between the location and amount of leakage and the acoustic response after tubing rupture. Summary of the Invention

[0008] In view of this, to address the technical problem that existing DAS monitoring simulation experimental devices for tubing leakage are unable to systematically simulate tubing leakage processes under different leakage morphologies and operating conditions, and thus cannot provide experimental support for establishing leakage acoustic response mechanisms and leakage identification methods, this invention provides a physical simulation experimental device and method for tubing leakage DAS monitoring. By constructing a physical simulation experimental device consisting of a distributed fiber optic acoustic monitoring system, a wellbore leakage simulation system, a fluid supply system, and a waste fluid recovery system, a leakage simulation component with replaceable leakage channels is set at a preset location in the simulated wellbore to simulate tubing leakage conditions under different leakage locations, morphologies, injection flow rates, and fluid types. The distributed fiber optic acoustic monitoring system collects acoustic profiles of the entire wellbore section, constructing a quantitative relationship model between leakage flow rate and acoustic energy. This invention can systematically simulate complex leakage conditions in oil and gas wells, enabling rapid replacement and comparison experiments of various leakage morphologies, overcoming the limitation of traditional experimental devices with only one leakage type, and providing experimental support for accurate location and quantitative evaluation of tubing leaks based on fiber optic acoustic monitoring.

[0009] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a physical simulation experimental device for DAS monitoring of oil pipe leakage, comprising: A wellbore leakage simulation system includes a simulated wellbore and a leakage point simulation component installed at a preset position in the simulated wellbore. The leakage point simulation component is equipped with a replaceable leakage channel for simulating tubing leakage conditions. The fluid supply system is connected to the wellbore leakage simulation system and is used to inject working fluid into the simulated wellbore. A waste liquid recovery system, connected to the wellbore leakage simulation system, is used to recover experimental waste liquid; The distributed fiber optic acoustic wave acquisition system is used to acquire acoustic vibration signals of the entire simulated wellbore, enabling real-time display and recording of the acoustic profile of the entire simulated wellbore.

[0010] Preferably, the leak simulation component includes a leak base and a replaceable leak module. The leak module is provided with leak channels of different shapes and / or different sizes. Different leak morphologies can be simulated by replacing the leak module.

[0011] Preferably, the shape of the leakage channel includes one or more of the following: circular hole, square hole, triangular hole, trapezoidal slit, or irregular crack.

[0012] Preferably, the simulated wellbore adopts a segmented structure, and different numbers of leakage segments are combined according to experimental requirements to simulate single leakage point, double leakage point or multi-point leakage conditions.

[0013] Preferably, the liquid supply system includes: Storage tank, used to store working fluid; A high-pressure inlet pump, connected to the outlet of the storage tank, is used to pressurize the working fluid and inject it into the simulated wellbore. A flow meter is used to monitor the injected flow rate; A flow control valve is used to regulate the flow rate of the working fluid entering the simulated wellbore. Pressure gauge, used to monitor injection pressure; A one-way valve is used to prevent the working fluid from flowing back into the storage tank.

[0014] Preferably, the distributed fiber optic acoustic wave acquisition system includes: A single-mode armored optical fiber is laid along the outer wall of the simulated well and covers the test well section including the leakage simulation component, for sensing the acoustic vibration signal generated when the working fluid leaks out through the leakage channel. An optical pulse signal demodulator, connected to the single-mode armored optical fiber, is used to demodulate the acoustic vibration signal sensed by the single-mode armored optical fiber. The display terminal, connected to the optical pulse signal demodulator, is used to display and record the acoustic profile of the entire simulated wellbore in real time.

[0015] Preferably, the sampling frequency of the distributed fiber optic acoustic wave acquisition system is not less than 10 kHz, and the spatial resolution is better than 1 m.

[0016] Preferably, the waste liquid recovery system is connected to the outlet of the simulated well and the leakage outlet of the leakage point simulation component, respectively, for collecting the working fluid discharged from the outlet of the simulated well and the working fluid leaked from the leakage channel during the experiment.

[0017] Secondly, the present invention provides an experimental method for the above-mentioned physical simulation experimental device for DAS monitoring of oil pipe leakage, comprising the following steps: Step S1: Install the experimental apparatus and assemble a leakage channel of specified shape and size at a preset position in the simulated wellbore; Step S2: Inject working fluid into the simulated wellbore through the fluid supply system and adjust the injection flow rate; Step S3: Use a distributed fiber optic acoustic acquisition system to acquire the acoustic profile of the entire wellbore section and record the acoustic response signals under different injection flow rates; Step S4: Replace the leakage channels with different shapes and / or different sizes, repeat steps S2 to S3, and collect acoustic response data under different leakage point morphologies. Step S5: Change the working fluid with different water contents, repeat steps S2 to S4, and collect acoustic response data under different fluid types; Step S6: Change the installation position of the leak point simulation component on the simulated wellbore, and repeat steps S2 to S5 to collect acoustic response data at different leak locations; Step S7: Process the collected acoustic response data, construct a quantitative relationship model between leakage flow and acoustic energy, and identify the leakage location, leakage point morphology and leakage amount based on the location and intensity characteristics of the acoustic response.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention constructs a fully functional tubing DAS leak monitoring simulation experimental device, which integrates a distributed fiber optic acoustic wave acquisition system, a wellbore leakage simulation system, a fluid supply system, and a waste fluid recovery system. It can systematically simulate various leakage conditions of fluid after tubing rupture during oil and gas well production, under different leak locations, leak morphologies, injection flow rates, and fluid types with different water content. Using the distributed fiber optic acoustic wave monitoring system in this invention, the acoustic profile of the simulated tubing rupture in the oil and gas well can be monitored in real time and accurately.

[0019] This invention employs a modularly designed leak point simulation component, which allows for the rapid replacement of leak channel modules of different shapes and sizes. It enables systematic comparison of various leak point morphologies, such as circular holes, rectangular slits, triangular holes, elliptical holes, square holes, trapezoidal slits, and irregular cracks, overcoming the limitation of traditional experimental devices with only one type of leak point.

[0020] The experimental method provided by this invention can be used to study the acoustic response mechanism of oil and gas well leakage, clarify the influence law of leakage acoustic waves, and construct a quantitative relationship model between leakage flow and acoustic energy. This lays the foundation for breaking through the technical bottleneck of achieving accurate location of oil pipe leaks and quantitative evaluation of leakage degree based on distributed optical fiber acoustic monitoring. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2The front view of the component simulating the leak; Figure 3 A top view of the component simulating the leak; Figure 4 Schematic diagrams of four shapes for replaceable leakage modules; Figure 5 This is a schematic diagram of the simulated wellbore base pipe (tubing and casing) structure in this invention; Figure 6 This is a front view of the experimental section in this invention; Figure 7 This is a top view of the test section in this invention; Figure 8 This is a schematic diagram of the flange plug structure in this invention; Figure 9 Leakage flow rate - acoustic energy relationship diagram for leaks of different shapes; Figure 10 Leakage flow rate - acoustic energy relationship under different fluid types with different water contents; Figure 11 Leakage flow rate - acoustic energy relationship diagram for leak points of different sizes.

[0022] In the diagram, 1. Distributed fiber optic acoustic wave acquisition system; 101. Optical pulse signal demodulator; 102. Display terminal; 103. Single-mode armored optical fiber; 2. Leakage simulation system; 201. Simulated sleeve; 202. Simulated artificial leak; 203. Simulated oil pipe; 3. Liquid supply system; 301. Liquid storage tank; 302. High-pressure liquid inlet pump; 303. First pressure gauge; 304. First flow meter; 305. First flow control valve; 306. Check valve; 4. Waste liquid recovery system; 401. Recovery tank; 402. Second flow meter; 403. Second flow control valve; 404. Third pressure gauge; 405. Third flow meter; 406. Third flow control valve; 407. Second pressure gauge. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1As shown, the present invention provides a physical simulation experimental device for DAS monitoring of oil pipe leakage, which is used to simulate the oil leakage process caused by perforation, cracking or local damage of oil pipe during production. It uses a distributed fiber optic acoustic wave monitoring system to collect the acoustic vibration signal generated when oil leaks out through the leak point, thereby establishing the correspondence between the location, shape, size and flow rate of the leak point and the acoustic wave response characteristics.

[0025] Specifically, the device includes: The wellbore leakage simulation system 2 includes a simulated wellbore and a leakage point simulation component installed at a preset position in the simulated wellbore. The leakage point simulation component is equipped with a replaceable leakage channel for simulating tubing leakage conditions. The fluid supply system 3 is connected to the wellbore leakage simulation system and is used to inject working fluid into the simulated wellbore. Waste liquid recovery system 4 is connected to the wellbore leakage simulation system and is used to recover experimental waste liquid; The distributed fiber optic acoustic wave acquisition system 1 is used to acquire acoustic vibration signals of the entire simulated well shaft, and realize the real-time display and recording of the acoustic profile of the entire simulated well shaft.

[0026] The above-mentioned physical simulation experimental device for tubing leakage DAS monitoring provided by the present invention consists of four major systems: a wellbore leakage simulation system 2, a fluid supply system 3, a waste fluid recovery system 4, and a distributed fiber optic acoustic wave acquisition system 1. The fluid supply system 3 injects working fluid into the simulated wellbore. When the working fluid flows through the replaceable leakage channel on the leakage point simulation component at a preset position in the simulated wellbore, leakage occurs, generating acoustic vibration signals. The distributed fiber optic acoustic wave acquisition system 1 collects and records the acoustic wave profile of the entire wellbore section in real time. This invention solves the problem that existing experimental devices have simplified structures and cannot systematically simulate the tubing leakage process and collect acoustic wave response data of the entire well section. The experimental device of the present invention constructs a complete physical simulation experimental device, integrating leakage simulation, fluid supply, waste fluid recovery, and acoustic wave acquisition functions. It can monitor and record the acoustic wave profile of the entire well section in real time during the tubing leakage process, providing an experimental platform for establishing a mechanism for studying the acoustic wave response of leakage.

[0027] In one specific embodiment of the present invention, exemplarily, such as Figure 1As shown, the liquid supply system 3 includes a storage tank 301, a high-pressure inlet pump 302, a first pressure gauge 303, a first flow meter 304, a first flow control valve 305, and a check valve 306. The storage tank 301 is used to store the oil required for the experiment. The high-pressure inlet pump 302 is used to pressurize the oil and inject it into the simulated wellbore. The pressure gauge is used to monitor the injection pressure, the flow meter is used to monitor the injection flow rate, the flow control valve is used to regulate the flow rate of the oil entering the simulated wellbore, and the check valve 306 is used to prevent oil backflow. By adjusting the high-pressure inlet pump 302 and the first flow control valve 305, The flow rate of the working fluid injected into the simulated wellbore is precisely controlled and adjusted to study the acoustic response under different leakage flow rates, satisfying experimental conditions that can form different injection flow rates and different leakage intensities. This is used to study the relationship between oil leakage flow rate and DAS acoustic response and to provide a data basis for it. The first pressure gauge 303 monitors the injection pressure to ensure that the experimental conditions are controllable, and the one-way valve 306 prevents backflow from interfering with the accuracy of the experimental data. Pressure monitoring provides a more complete record of operating parameters for the experiment, and the one-way valve 306 ensures the stability and safety of the fluid supply system 3.

[0028] In one specific embodiment of the present invention, the distributed optical fiber acoustic wave acquisition system 1 includes: A single-mode armored optical fiber 103 is laid along the outer wall of the simulated well and covers the test well section including the leakage simulation component, for sensing the acoustic vibration signal generated when the working fluid leaks out through the leakage channel. An optical pulse signal demodulator 101 is connected to the single-mode armored optical fiber 103 and is used to demodulate the acoustic vibration signal sensed by the single-mode armored optical fiber 103. The display terminal 102 is connected to the optical pulse signal demodulator 101 and is used to display and record the acoustic profile of the entire simulated wellbore in real time.

[0029] For example, such as Figure 1As shown, the distributed fiber optic acoustic wave acquisition system 1 includes an optical pulse signal demodulator 101, a display terminal 102 (such as a portable PC display terminal 102), and a single-mode armored optical fiber 103. The single-mode armored optical fiber 103 is laid along the outer wall of the simulated casing 201 and the simulated tubing 203, then folds back and passes through the inside of the wellbore, completely covering the test section containing the simulated artificial leak point component 202, realizing full-domain monitoring of acoustic wave signals inside and outside the wellbore. When the supply system injects oil into the simulated wellbore, the oil flows along the inside of the simulated wellbore and leaks at the simulated artificial leak point 202 (leak point simulation component). When the oil passes through the leak point... Local pressure release and fluid disturbance are generated, thereby forming an acoustic vibration signal. This acoustic vibration signal is sensed by a single-mode armored optical fiber 103, demodulated by an optical pulse signal demodulator 101, and transmitted to a display terminal 102 to realize the real-time display and recording of the acoustic profile of the entire simulated wellbore. This provides a means to continuously and in real-time acquire acoustic vibration signals along the entire wellbore. Based on the phase change principle of backscattered Rayleigh light, DAS technology can realize real-time continuous monitoring of the entire well section, with fast response speed and strong anti-electromagnetic interference capability, providing a technical means for continuous leakage diagnosis of the entire well section, which is difficult to achieve by traditional monitoring methods.

[0030] In one specific embodiment of the present invention, the sampling frequency of the distributed optical fiber acoustic wave acquisition system 1 is not less than 10 kHz and the spatial resolution is better than 1 m, which can realize high-fidelity acquisition of high-frequency acoustic wave signals and meet the needs of refined analysis of acoustic wave characteristics under different leakage conditions.

[0031] In one specific embodiment of the present invention, the waste liquid recovery system 4 is connected to the outlet of the simulated well and the leakage outlet of the leakage point simulation component, respectively, for collecting the working fluid discharged from the outlet of the simulated well and the working fluid leaked from the leakage channel during the experiment; through two independent recovery pipelines, the outlet flow rate and leakage flow rate can be counted separately, and the flow meter data can be combined to provide accurate data support for the construction of a quantitative relationship model.

[0032] For example, such as Figure 1As shown, the waste liquid recovery system 4 includes a recovery tank 401, a second flow meter 402, a second flow control valve 403, a third pressure gauge 404, a third flow meter 405, a third flow control valve 406, and a second pressure gauge 407. The waste liquid recovery system 4 is connected to the main outlet of the simulated wellbore and the leakage outlet at the annulus of the simulated casing 201, respectively, to collect the oil discharged from the outlet of the simulated wellbore and the oil leaking from the annulus of the simulated casing 201 during the experiment. The top of the simulated artificial leak point 202 is completely sealed and does not have the function of leakage discharge; it is only used for disassembling and replacing the simulated artificial leak point tooling. The waste liquid recovery system 4 can centrally recover the experimental oil and combine the flow meter data to statistically analyze the outlet flow rate and leakage flow rate, providing a data basis for subsequently establishing the relationship between leakage flow rate and sound wave energy.

[0033] For example, such as Figure 1 As shown, the leakage simulation system 2 includes a simulated wellbore and leakage simulation components. The main body of the simulated wellbore is composed of a transparent acrylic (plexiglass) base tube and a special steel pipe, which is used to simulate the tubing structure and form the simulated wellbore base tube. The transparent acrylic (plexiglass) base tube facilitates direct observation of fluid flow and leakage processes in the wellbore annulus. The two ends of the steel pipe are respectively machined with internal threads, and a certain length margin is reserved. An installation interface is set in the middle of the simulated wellbore for assembling leakage simulation components of different specifications, so as to realize the adjustment of leakage location, leakage shape and leakage amount.

[0034] like Figure 5 As shown, the simulated wellbore base tubing adopts a double-layer tubing string structure combining tubing and casing. The simulated tubing is the inner tubing string, serving as the main channel for working fluid flow. The simulated casing is the outer tubing string, coaxially fitted around the simulated tubing, forming an annular space between them. After the simulated tubing is combined with the test section, an interface structure for installing the artificial leak simulation component is formed at a preset position. The simulated casing has an operating opening at a corresponding position for operation when replacing the leak tooling. The simulated tubing and casing are assembled using a segmented structure, enabling... The test section, flange plug, and replaceable leak point tooling together form a complete tubing leakage simulation system. Before the experiment, the simulated tubing and simulated casing are assembled to form a simulated wellbore. During the experiment, the working fluid flows along the inside of the simulated tubing and leaks at the preset leak point. The leaked working fluid is collected in the annulus and discharged. The distributed fiber optic acoustic wave acquisition system synchronously acquires the acoustic vibration response inside and outside the tubing. By changing the position of the artificial leak point simulation component at different pipe sections or different installation interfaces, the acoustic response when leakage occurs at different locations in the tubing can be simulated.

[0035] like Figure 6-7As shown, the test section is used to connect the simulated tubing, forming a segmented connection structure. Both ends of the test section are equipped with threaded connections compatible with the simulated tubing, allowing it to be used with the simulated wellbore, leakage simulation components, or other connectors. An installation interface is located in the middle of the test section for installing the leakage simulation component, thereby creating a controllable leakage channel at a predetermined section of the simulated wellbore. By setting different numbers of test sections and combining them at different locations within the simulated wellbore, the length of the simulated wellbore, connection positions, and leakage arrangement can be adjusted according to experimental requirements, thus enabling single-leakage, double-leakage, and multi-leakage monitoring experiments under different tubing string structures.

[0036] like Figure 2-4 As shown, in one specific embodiment of the present invention, the leak simulation component is integrally installed at a predetermined interface on the oil pipe wall; as Figure 2-3 As shown, the leak point simulation component is designed with a concave fitting surface on the side facing the oil pipe, which is adapted to the arc-shaped surface of the outer wall of the oil pipe. During assembly, this concave fitting surface achieves a perfect surface-to-surface contact with the outer wall of the oil pipe. The function of this concave structure is twofold: firstly, to ensure that the leak point fixture is firmly seated in the preset installation position of the oil pipe without tilting; secondly, this perfect fit ensures a smooth transition between the leak point component and the outer wall of the oil pipe after installation, effectively preventing the leak point component from forming a local protrusion on the outer wall of the oil pipe. This prevents the working fluid flowing in the oil pipe from generating turbulence and vibration interference due to impact with the protruding structure, thereby ensuring that the acoustic signal collected by the distributed fiber optic acoustic wave acquisition system 1 truly reflects the leakage characteristic signal generated when the working fluid leaks out through the leakage channel, and avoiding noise interference introduced by abrupt changes in the flow channel from affecting the accuracy of the experimental data; for example Figure 4 As shown, the replaceable leakage module is equipped with leakage channels of different shapes and / or sizes. The module can be replaced by quick plugging and unplugging to change the shape and size of the leakage channel. The leakage module preferably adopts a standardized interface design. The shape of the leakage channel includes one or more of the following: circular hole, square hole, triangular hole, trapezoidal slit, or irregular crack. Its equivalent diameter or equivalent slit width can be serialized according to experimental requirements, covering types such as micro-cracks, small hole leakage, large hole leakage, and crack leakage. In addition, the leakage point simulation component is also equipped with an independent switching valve to control the opening and closing of a single leakage point, realizing selective simulation under multiple leakage point conditions. The present invention adopts a modular design, realizing the rapid replacement of leakage point morphology. Under the premise of keeping other experimental conditions consistent, the influence of different leakage point shapes and sizes on acoustic response can be compared systematically. This overcomes the limitation of the single leakage point type in traditional experimental devices and provides an experimental basis for in-depth research on the quantitative relationship between leakage point morphology and acoustic response.

[0037] like Figure 8As shown, the flange plug is installed at a pre-set operating opening on the casing wall. This flange plug is a blind-plate type, with an arc-shaped contact surface on the side facing the casing that matches the curvature of the casing's outer wall. During assembly, this arc-shaped contact surface fits tightly against the casing's outer wall, completely sealing the operating opening on the casing and preventing leakage of working fluid from the annulus. The sole purpose of this operating opening is as an operating window when replacing the tubing leak tool: when it is necessary to replace a leak module of different shape or size, only the flange plug needs to be removed, and a tool can be inserted through the opening on the casing to quickly disassemble and assemble the replaceable leak tool on the tubing without disassembling the entire simulated wellbore string. After replacement, the flange plug can be reinstalled to restore the seal. This structural design achieves both convenient replacement of the leak tool and reliable sealing at the casing opening during the experiment.

[0038] For example, such as Figure 2-3 As shown, the artificial leak point simulation component is used to form a leakage channel at a preset location in the simulated wellbore. This component is installed in the middle of the simulated casing 201 (such as at a preset interface in the simulated wellbore) to simulate leak points formed by corrosion, erosion, mechanical damage, or crack expansion in the tubing. During experimental installation, the artificial leak point simulation component is connected to the simulated wellbore, and a leak point fixture of a specified shape and size is installed according to experimental requirements so that the oil can leak out from the preset leak point. This component is mainly used in the single leak point simulation stage and the stage of changing different leak point morphologies in the experimental method.

[0039] For example, such as Figure 4 As shown, the leakage module is equipped with leakage channels of different shapes and sizes. These leakage channels can be circular holes, square holes, triangular holes, trapezoidal cracks, or other irregular shapes. Different leak point shapes are used to simulate different types of leakage channels that may occur in actual oil pipes, such as perforation-type leakage, crack-type leakage, localized damage-type leakage, and irregular corrosion-type leakage. During the experiment, while keeping the oil type, leak point location, and injection conditions basically consistent, DAS acoustic response data under corresponding working conditions were collected by changing replaceable leak point fixtures of different shapes or sizes. This allowed for the analysis of the influence of leak point shape and size on acoustic energy, characteristic frequency bands, and leakage amount identification results.

[0040] In this implementation, the leakage channels cover a variety of typical leakage point morphologies, which can more realistically simulate on-site working conditions and improve the representativeness and applicability of experimental results.

[0041] In one specific embodiment of the present invention, the simulated wellbore adopts a segmented structure (e.g., the simulated casing 201 and the simulated tubing 203 are connected by threads, a leakage point simulation component is installed in the middle section of 201, and the number of leakage points is changed by increasing or decreasing the number of pipe segments). Adjacent pipe segments are connected by threads, and different numbers of leakage segments are combined according to experimental requirements to simulate single leakage point, double leakage point, or multi-point leakage conditions. One end of the simulated wellbore is provided with a fluid inlet, which is connected to the fluid supply system 3, and the other end is provided with a fluid outlet, which is connected to the waste liquid recovery system 4, forming a complete circulation loop. The present invention solves the problem that existing devices are difficult to simulate complex conditions of different leakage locations and multi-point leakage. By flexibly adjusting the location and number of leakage points through the segmented structure, the influence of leakage location changes and multi-point leakage on the acoustic response can be systematically studied.

[0042] like Figure 9 As shown, the relationship between leakage flow rate and acoustic energy for leaks of different shapes is illustrated. This figure is the result of processing experimental data and is used to characterize the correspondence between oil leakage flow rate and acoustic energy under different leak shape conditions. During the experiment, multiple oil injection flow rate conditions were set up for different leak shapes. The distributed fiber optic acoustic acquisition system 1 was used to collect the acoustic profile of the entire wellbore section, and the collected data was subjected to noise reduction, spectrum analysis, feature extraction, and acoustic energy calculation. Based on the processing results, leakage flow rate-acoustic energy relationship curves corresponding to different leak shapes were plotted to determine the leak shape and evaluate the leakage amount.

[0043] like Figure 10 As shown, a graph depicting the relationship between leakage flow rate and acoustic energy under different water content conditions is presented. This graph is also the result of processing experimental data and is used to characterize the correspondence between leakage flow rate and acoustic energy under different water content fluid types. During the experiment, while maintaining the leak location, shape, and size as basically consistent, oil samples with different water contents were replaced, and flow rate adjustment and acoustic data acquisition were repeated. By processing the acoustic response data under different water content fluid types, the influence of water content changes on acoustic energy response and leakage identification results can be obtained, thereby improving the accuracy of oil pipe leak location and quantitative evaluation of leakage based on DAS acoustic monitoring.

[0044] like Figure 11As shown, the diagram illustrates the relationship between leakage flow rate and acoustic energy for different leak point sizes. This diagram is the result of processing experimental data and is used to characterize the correspondence between different leak point characteristic sizes and leakage flow rate and acoustic energy under the same leak point shape. During the experiment, while maintaining basically consistent fluid type, leak point location, and injection conditions, leak point modules with different characteristic sizes were installed sequentially for the same geometric shape (such as a circular orifice), and flow rate adjustment experiments were conducted and acoustic response data were collected. Based on the processing results, leakage flow rate-acoustic energy relationship curves corresponding to different leak point sizes were plotted. This family of curves is used to invert the equivalent diameter of the leak point based on the measured acoustic energy, thereby achieving a quantitative evaluation of the leak point size.

[0045] Secondly, the present invention provides an experimental method for the above-mentioned physical simulation experimental device for DAS monitoring of oil pipe leakage, comprising the following steps: Step S1: Install the experimental apparatus and assemble a leakage channel of specified shape and size at a preset position in the simulated wellbore; Step S2: Inject working fluid into the simulated wellbore through the fluid supply system 3 and adjust the injection flow rate; Step S3: Use the distributed fiber optic acoustic acquisition system 1 to acquire the acoustic profile of the entire wellbore section and record the acoustic response signals under different injection flow rates; Step S4: Replace the leakage channels with different shapes and / or different sizes, repeat steps S2 to S3, and collect acoustic response data under different leakage point morphologies. Step S5: Change the working fluid with different water contents, repeat steps S2 to S4, and collect acoustic response data under different fluid types; Step S6: Change the installation position of the leak point simulation component on the simulated wellbore, and repeat steps S2 to S5 to collect acoustic response data at different leak locations; Step S7: Process the collected acoustic response data, construct a quantitative relationship model between leakage flow and acoustic energy, and identify the leakage location, leakage point morphology and leakage amount based on the location and intensity characteristics of the acoustic response.

[0046] The experimental method provided by the present invention will be clearly and thoroughly described below with reference to specific embodiments.

[0047] Example: Based on the above experimental setup, the experimental method in this example includes the following steps: Step S1: Install the above experimental apparatus: When installing the experimental device, connect the oil pipes to the leak point simulation system 2, the liquid supply system 3, and the waste liquid recovery system 4 via threaded connections; select the target leak point location in the leak point simulation system 2, and assemble a replaceable leak module of a specified shape and size at the corresponding installation interface. In addition to the four types of leak points set above, leaks may also occur at the threaded connections of the device, so these are also set as leak points. Place the distributed fiber optic acoustic wave monitoring system on the left side of the oil pipe, connect the upper part of the oil pipe to the waste liquid recovery tank 401 via a liquid delivery line, and connect the lower part of the oil pipe to the storage tank 301 via a liquid delivery line. Step S2: Select the leak point in the leak point simulation system 2 as the leakage hole a, and ensure that the leakage hole a leaks completely and there are no other leak points. Step S3: Open the inlet valve and the high-pressure inlet pump 302, and set the initial flow rate of the high-pressure inlet pump 302 to Q1; Step S4: After the flow meter reading stabilizes, turn on the distributed fiber optic acoustic monitoring system, collect the acoustic profile E1 of the entire wellbore section, and mark the acoustic response profile E at the simulated leak point. 11 ; Step S5: Change the flow rate Q2 of the high-pressure inlet pump 302; Step S6: After the flow meter reading stabilizes, turn on the distributed fiber optic acoustic monitoring system, collect the acoustic profile E2 of the entire wellbore section, and mark the acoustic response profile E at the simulated leak point. 21 ; Step S7: Repeat steps S3-S6, recording the traffic as Q1-Q n At that time, the intensity of the acoustic response signal at the leak point; Step S8: Turn off the high-pressure liquid pump, replace the leakage hole a in the leakage point simulation system 2 with another size specification, repeat steps S3-S7, and obtain the acoustic response signal intensity corresponding to the leakage hole a of another size. Step S9: Turn off the high-pressure inlet pump 302, replace the leakage hole b in the leakage simulation system 2, and repeat steps S3-S7 to obtain the intensity of the acoustic response signal corresponding to the leakage hole b. Step S10: Repeat steps S8 and S9, replace the remaining leakage holes, and obtain the corresponding acoustic response signal intensity at leakage holes of different shapes and sizes. Obtain the acoustic response signal intensity of a working fluid under different leakage shapes and leakage flow rates. At this point, the first set of leakage acoustic data acquisition has been completed. Step S11: Replace with working fluids of different water contents, open the inlet valve and high-pressure inlet pump 302, and set the initial flow rate of the high-pressure pump to Q. 21 Repeat steps S2-S10. At this point, the second set of lost acoustic wave data acquisition has been completed. Step S12: Repeat step S11 to complete the simulation of leakage acoustic data under different flow rates and different moisture contents; Step S13: Change the location of the leak point, install the leak point simulation component to different pipe sections of the simulated well body, repeat steps S2 to S12, collect acoustic response data at different leakage locations, and establish an acoustic response database containing different leak point locations, leak point morphology, leakage flow rate and fluids with different water content. Step S14: Process the acoustic data collected in step S13 and plot it as a function graph of flow rate and acoustic signal strength characteristics. Based on the location and strength characteristics of the acoustic response, the location, shape, and amount of leakage can be directly determined. This realizes the diagnosis of the leakage amount and shape of the simulated leak point based on the acoustic profile and the flow rate of the leakage section. The specific steps are as follows: Step S14-1: Establish the functional relationship between sound wave energy and influencing factors; The relative acoustic energy E described in this invention has a definite functional relationship with the following experimental parameters: ; Where Q is the leakage flow rate in L / min; S is the leakage point geometry type; D is the equivalent diameter of the leakage point in mm; μ is the fluid dynamic viscosity in mPa·s; ρ is the fluid density in kg / m³; f w Moisture content, in percentages (%) Step S14-2: Construct a graph of the quantitative relationship function; Plot the following three types of relationship curves with leakage flow rate Q as the x-axis and sound wave energy E as the y-axis: Q-E relationship curves under different leak point shapes, such as Figure 9 As shown; Q-E relationship curves at different fluid water contents, such as Figure 10 As shown; Q-E relationship curves for different leak point sizes, such as Figure 11 As shown; Step S14-3: Establish a quantitative identification method for missing parameters; 1) Leakage location identification: Determine the depth location of the leakage point based on the axial position of the abnormal peak of the acoustic energy response on the measured acoustic profile; 2) Leak morphology identification: Compare the Q-E data points at the measured leak locations with... Figure 9 The standard curves of different leak shapes are compared. The least squares method is used to calculate the fitting error between the measured point and each standard curve. The leak shape corresponding to the curve with the smallest fitting error is the identified leak shape. 3) Quantitative evaluation of leakage: After determining the leak point morphology and fluid water content, the corresponding Q-E standard curve is selected as the calibration curve, and the measured acoustic energy E is substituted into the fitting equation of the curve. Q = f (E In the process, the leakage flow rate Q under the current operating conditions is obtained through inversion calculation, thereby achieving a quantitative evaluation of the leakage amount; Step S14-4: Verify the recognition results; The leakage amount and leakage point morphology identified in step S14-3 are compared with the leakage parameters actually set in the experiment to verify the accuracy and reliability of the quantitative relationship model. The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A physical simulation experimental device for DAS monitoring of oil pipe leakage, characterized in that, include: A wellbore leakage simulation system includes a simulated wellbore and a leakage point simulation component installed at a preset position in the simulated wellbore. The leakage point simulation component is equipped with a replaceable leakage channel for simulating tubing leakage conditions. The fluid supply system is connected to the wellbore leakage simulation system and is used to inject working fluid into the simulated wellbore. A waste liquid recovery system, connected to the wellbore leakage simulation system, is used to recover experimental waste liquid; The distributed fiber optic acoustic wave acquisition system is used to acquire acoustic vibration signals of the entire simulated wellbore, enabling real-time display and recording of the acoustic profile of the entire simulated wellbore.

2. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 1, characterized in that, The leak simulation component includes a leak base and a replaceable leak module. The leak module is provided with leak channels of different shapes and / or different sizes. Different leak morphologies can be simulated by replacing the leak module.

3. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 2, characterized in that, The shape of the leakage channel includes one or more of the following: circular hole, square hole, triangular hole, trapezoidal slit, or irregular crack.

4. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 1, characterized in that, The simulated wellbore adopts a segmented structure, and different numbers of leakage segments are combined according to experimental requirements to simulate single leakage point, double leakage point or multi-point leakage conditions.

5. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 1, characterized in that, The liquid supply system includes: Storage tank, used to store working fluid; A high-pressure inlet pump, connected to the outlet of the storage tank, is used to pressurize the working fluid and inject it into the simulated wellbore. A flow meter is used to monitor the injected flow rate; A flow control valve is used to regulate the flow rate of the working fluid entering the simulated wellbore.

6. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 5, characterized in that, Also includes: A pressure gauge is used to monitor injection pressure; A one-way valve is used to prevent the working fluid from flowing back into the storage tank.

7. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 1, characterized in that, The distributed fiber optic acoustic wave acquisition system includes: A single-mode armored optical fiber is laid along the outer wall of the simulated well and covers the test well section including the leakage simulation component, for sensing the acoustic vibration signal generated when the working fluid leaks out through the leakage channel. An optical pulse signal demodulator, connected to the single-mode armored optical fiber, is used to demodulate the acoustic vibration signal sensed by the single-mode armored optical fiber. The display terminal, connected to the optical pulse signal demodulator, is used to display and record the acoustic profile of the entire simulated wellbore in real time.

8. The physical simulation experimental device for DAS monitoring of oil pipe leakage according to claim 1, characterized in that, The sampling frequency of the distributed fiber optic acoustic wave acquisition system is not less than 10 kHz, and the spatial resolution is better than 1 m.

9. A physical simulation experimental device for DAS monitoring of oil pipe leakage according to any one of claims 1-8, characterized in that, The waste liquid recovery system is connected to the outlet of the simulated well and the leakage outlet of the leakage point simulation component, respectively, and is used to collect the working fluid discharged from the outlet of the simulated well and the working fluid leaked from the leakage channel during the experiment.

10. The experimental method of the physical simulation experimental device for monitoring oil pipe leakage DAS according to any one of claims 1-9, characterized in that, Includes the following steps: Step S1: Install the experimental apparatus and assemble a leakage channel of specified shape and size at a preset position in the simulated wellbore; Step S2: Inject working fluid into the simulated wellbore through the fluid supply system and adjust the injection flow rate; Step S3: Use a distributed fiber optic acoustic acquisition system to acquire the acoustic profile of the entire wellbore section and record the acoustic response signals under different injection flow rates; Step S4: Replace the leakage channels with different shapes and / or different sizes, repeat steps S2 to S3, and collect acoustic response data under different leakage point morphologies. Step S5: Change the working fluid with different water contents, repeat steps S2 to S4, and collect acoustic response data under different fluid types; Step S6: Change the installation position of the leak point simulation component on the simulated wellbore, and repeat steps S2 to S5 to collect acoustic response data at different leak locations; Step S7: Process the collected acoustic response data, construct a quantitative relationship model between leakage flow and acoustic energy, and identify the leakage location, leakage point morphology and leakage amount based on the location and intensity characteristics of the acoustic response.

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