Fiber bragg grating flow sensor and oil field separated layer water injection rate monitoring system and method

Abstract

The invention relates to the technical field of fiber bragg grating flow sensor monitoring, and discloses a fiber bragg grating flow sensor and an oil field layered water injection rate monitoring system and method.The fiber bragg grating flow sensor comprises a flow sensor, a sensitive diaphragm and a fiber bragg grating sensor, the flow sensor is recessed inwards to form a containing area. The sensitive diaphragm is arranged in the accommodating area, and a first waterproof gasket is arranged between the sensitive diaphragm and the accommodating area; and the fiber bragg grating sensor is arranged on the sensitive diaphragm. Through the integrated design, the overall size is small, and the underground space requirement is easily met; the pressure difference is converted into the wavelength change of the fiber Bragg grating sensor through the deflection of the sensitive diaphragm, and accumulated errors are not easy to introduce.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber grating flow sensor monitoring, and particularly relates to a fiber grating flow sensor, an oilfield layered water injection volume monitoring system and method. BACKGROUND

[0002] Layered water injection is an important engineering means for maintaining reservoir pressure, improving oil displacement efficiency and realizing injection-production ratio control in oilfields. In the water injection system, the water injection volume of different perforated layers or injection ports directly affects the injection efficiency and recovery rate of the oilfield. Therefore, being able to realize in-situ, long-term and per-port quantitative monitoring of each water injection port or each layered port in the well has important significance for water injection optimization, water distributor adjustment, early abnormality identification (such as single-layer plugging, casing leakage or high-permeability layer bypass injection) and decision support. The existing measurement / inversion methods for layered water injection volume or injection location identification mainly include: ground or wellhead total flow metering + downhole well testing / tracer inversion (tracer method, DTS temperature pulse inversion, etc.) and mechanical / electromagnetic flow meters (such as spinner, vortex, volumetric, turbine, etc.) directly installed in the well. The tracer / temperature inversion method can provide layer positioning and qualitative allocation information, but usually requires test conditions, complex data inversion and is difficult to provide high-precision per-port flow in long-term online mode; the mechanical or electric downhole flow meter has problems such as wear, blockage, high difficulty in operation and maintenance and complex installation in high-temperature, high-pressure, multiphase and particle-containing environments, and the cost and reliability are difficult to meet the long-term operation requirements of conventional engineering in multi-point layered measurement.

[0003] For example, a lever-type fiber grating flow sensor for a water injection well and a detection method are disclosed in Chinese Patent Publication No. CN115752607A. In the above technical solution, the impact force of the flow resistance target plate is transmitted by a flexible hinge lever. On the one hand, the flexible hinge is made of elastic material, which is prone to material aging and elastic attenuation in the long-term high-temperature and high-pressure environment in the well, resulting in a decrease in displacement amplification precision. On the other hand, the flow resistance target plate is directly impacted by the flow, which is prone to being impacted and worn by particles and impurities in the downhole fluid, affecting the stress detection accuracy, and the impurities may be stuck in the lever structure, causing the sensor to fail. In addition, the flow measurement in the above technical solution needs to go through several mechanical transmission links, such as fluid impact on the target plate, force transmission by the force transmission rod, lever displacement amplification and stretching of the FBG, and each link may produce errors, affecting the accuracy of flow measurement. SUMMARY

[0004] In order to overcome at least one of the defects of the prior art described above, the present application provides a fiber grating flow sensor and an oilfield layered water injection volume monitoring system and method. Through integrated design, the overall size is small, which is easy to meet the space requirements in the well; the differential pressure is converted into wavelength change of the fiber Bragg grating sensor by the deflection of the sensitive diaphragm, which is not prone to introducing cumulative errors.

[0005] The technical scheme of the present application is implemented as follows: The optical fiber grating flow sensor comprises a flow sensor, a sensitive diaphragm and an optical fiber Bragg grating sensor, wherein the flow sensor is provided with a water inlet and a water outlet in communication, and the flow sensor is internally recessed to form an accommodation area; the sensitive diaphragm is arranged in the accommodation area, and a first waterproof gasket is arranged between the sensitive diaphragm and the accommodation area; and the optical fiber Bragg grating sensor is arranged on the sensitive diaphragm.

[0006] On the basis of the above technical scheme, preferably, the accommodation area is provided with a flange in the outer periphery, the outer edge of the sensitive diaphragm abuts against the flange, and the sensitive diaphragm and the flange are connected through a first fastener.

[0007] On the basis of the above technical scheme, preferably, the flow sensor comprises a flow sensor tool body and a flow sensor tool cover plate, wherein the water inlet and the water outlet are arranged on the flow sensor tool body and located at both ends of the flow sensor tool body; the flow sensor tool cover plate is arranged on the flow sensor tool body, a second waterproof gasket is arranged between the flow sensor tool cover plate and the flow sensor tool body, and the flow sensor tool cover plate is used for closing the sensitive diaphragm and the optical fiber Bragg grating sensor.

[0008] On the basis of the above technical scheme, preferably, the flow sensor tool body and the flow sensor tool cover plate are connected through a second fastener.

[0009] On the basis of the above technical scheme, preferably, the flow sensor tool cover plate is provided with an inlet pressure hole near the water inlet, and the flow sensor tool body is provided with an outlet pressure hole near the water outlet.

[0010] On the basis of the above technical scheme, preferably, the flow sensor tool body is provided with a lead-out hole, and the lead-out hole is provided with a waterproof ring.

[0011] The oilfield layered water injection quantity monitoring system comprises the optical fiber grating flow sensor, and further comprises a water injection layer water distributor and an oil pipe, and the optical fiber grating flow sensor is provided with two, wherein the water outlet of one optical fiber grating flow sensor is in communication with one end of the water injection layer water distributor; the water inlet of the other optical fiber grating flow sensor is in communication with the other end of the water injection layer water distributor; and the water outlet of the other optical fiber grating flow sensor is in communication with one end of the oil pipe.

[0012] On the basis of the above technical scheme, preferably, further comprising a demodulation module and a computer unit, wherein the flow sensor, the fiber Bragg grating sensor and the demodulation module are electrically connected; the computer unit and the demodulation module are electrically connected.

[0013] A method for monitoring the water injection volume of an oilfield layer, using the above-mentioned monitoring system for the water injection volume of an oilfield layer, comprising the following steps: The cross-sectional area of the water flow in the oil pipe ; Wherein, The inner diameter of the oil pipe; The cross-sectional area of the water flow in the fiber grating flow sensor ; Wherein, The inner diameter of the water inlet or outlet; According to Bernoulli's equation, ; Wherein, , ; The water flow pressure in the oil pipe, The water flow pressure in the fiber grating flow sensor, The water flow velocity in the oil pipe, The water flow velocity in the fiber grating flow sensor, The volume flow rate, The fluid density, The gravitational acceleration; The pressure difference between the water flow pressure in the oil pipe And the water flow pressure in the fiber grating flow sensor = - ; ; It is obtained that Wherein β= ; The deflection of the fiber Bragg grating sensor ; Wherein, The elastic modulus of the sensitive diaphragm, The Poisson's ratio of the sensitive diaphragm, h is the thickness of the sensitive diaphragm, the sensitive diaphragm (2) is a square, The side length of the sensitive diaphragm (2), the distance from the center of the sensitive diaphragm (2) to each side is a; The wavelength change of the fiber Bragg grating sensor The relationship between the volume flow rate Is = wherein l is the length of the fiber Bragg grating sensor.

[0014] In summary, the optical fiber grating flow sensor and the oil field layered water injection volume monitoring system and method provided by the present application have the following beneficial effects compared with the prior art: (1) The fiber Bragg grating sensor is integrated on the flow sensor tool, the overall size is small, the downhole space requirement is easily met, and the integrated design of the device is easily realized; (2) The fiber Bragg grating sensor is used, effectively solving the problem that the traditional flowmeter is easily affected by the special downhole conditions, resulting in poor flow monitoring accuracy and slow response; (3) Real-time monitoring of the water injection layer water distributor is realized, and the demodulation modularization and computer unit can realize measurement and adjustment at the same time, without the need for multiple trips of the sensor, reducing the workload and time cost, and also reducing the risk of device falling; (4) The water flow in the oil pipe can be monitored by monitoring the wavelength change of the fiber Bragg grating sensor, which is simple and fast; (5) The first waterproof gasket and the second waterproof gasket and the waterproof ring improve the waterproof performance of the fiber Bragg grating sensor and the flow sensor, effectively resisting downhole fluid corrosion and scaling, avoiding electrical damage and signal drift; (6) The differential pressure measurement logic is used, the pressure difference is obtained through the inlet pressure hole and the outlet pressure hole, the sensitive diaphragm directly drives the fiber Bragg grating sensor to deform, reducing the mechanical transmission error, and the measurement accuracy is better. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 It is a schematic diagram of the three-dimensional structure of embodiment 1 of the present application; Figure 2 It is a schematic diagram of the cross-sectional structure of embodiment 1 of the present application; Figure 3 It is a schematic diagram of the three-dimensional structure of the flow sensor tool main body of embodiment 1 of the present application; Figure 4 It is a schematic diagram of the three-dimensional structure of the flow sensor tool main body and the sensitive diaphragm of embodiment 1 of the present application; Figure 5 It is a schematic diagram of the three-dimensional structure of the flow sensor tool cover plate of embodiment 1 of the present application; Figure 6 is a structural block diagram of embodiment 2 of the present application; Figure 7 is a schematic diagram of a fiber grating flow sensor mounting structure of embodiment 2 of the present application.

[0017] Wherein, the reference signs have the following meanings: 1, flow sensor; 11, water inlet; 12, water outlet; 13, containing area; 131, flange; 14, flow sensor tool main body; 141, inlet pressure tapping hole; 142, outlet pressure tapping hole; 143, lead-out hole; 15, flow sensor tool cover plate; 151, second waterproof gasket; 16, flow-through space; 2, sensitive diaphragm; 3, fiber Bragg grating sensor; 4, first fastener; 5, second fastener; 6, water injection layer water distributor; 7, oil pipe; 8, demodulation module; 9, computer unit; 10, fiber grating flow sensor. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0019] Referring to Figures 1-5 , embodiment 1 of the present application discloses a fiber grating flow sensor 10, which comprises a flow sensor 1, a sensitive diaphragm 2, and a fiber Bragg grating sensor 3.

[0020] Referring to Figure 1 and Figure 2 , in the present embodiment 1, the flow sensor 1 is provided with a water inlet 11 and a water outlet 12, the flow sensor 1 is in a cylindrical structure, the water inlet 11 and the water outlet 12 are located on two opposite end faces of the flow sensor 1, the water inlet 11 and the water outlet 12 are arranged in communication, a flow-through space 16 is formed between the water inlet 11 and the water outlet 12, the flow-through space 16 can allow horizontal steady flow to pass through, reducing obstruction and energy loss, and the cylindrical structure is easy to install, facilitates cooperation with the subsequent oil pipe 7, is easy to maintain, and reduces maintenance cost and difficulty; the cylindrical structure has good symmetry and mechanical stability. When subjected to external force, the cylindrical structure can uniformly disperse stress, reduce local stress concentration, and thus reduce the risk of structural damage.

[0021] Referring to 1, Figure 3 and Figure 5As shown in the embodiment 1, the flow sensor 1 comprises a flow sensor tool body 14 and a flow sensor tool cover plate 15, the flow sensor tool body 14 and the flow sensor tool cover plate 15 form a cylindrical structure, the flow sensor tool cover plate 15 is arranged on the flow sensor tool body 14, and the flow sensor tool cover plate 15 is used to seal the sensitive diaphragm 2 and the fiber Bragg grating sensor 3. Specifically, a recessed area is arranged on the annular surface of the flow sensor tool body 14, and the flow sensor tool cover plate 15 is arranged in the recessed area. The recessed area provides accurate installation positioning for the flow sensor tool cover plate 15. When installing, the flow sensor tool cover plate 15 only needs to be placed in the recessed area, and the position can be quickly determined without complex alignment operation, which greatly simplifies the installation process, improves the installation efficiency, and ensures the normal work of the sensor.

[0022] As shown in the embodiment 1, the flow sensor 1 comprises a flow sensor tool body 14 and a flow sensor tool cover plate 15, the flow sensor tool body 14 and the flow sensor tool cover plate 15 form a cylindrical structure, the flow sensor tool cover plate 15 is arranged on the flow sensor tool body 14, and the flow sensor tool cover plate 15 is used to seal the sensitive diaphragm 2 and the fiber Bragg grating sensor 3. Specifically, a recessed area is arranged on the annular surface of the flow sensor tool body 14, and the flow sensor tool cover plate 15 is arranged in the recessed area. The recessed area provides accurate installation positioning for the flow sensor tool cover plate 15. When installing, the flow sensor tool cover plate 15 only needs to be placed in the recessed area, and the position can be quickly determined without complex alignment operation, which greatly simplifies the installation process, improves the installation efficiency, and ensures the normal work of the sensor. Figure 3 、 Figure 4 and Figure 5 As shown in the embodiment 1, the flow sensor 1 comprises a flow sensor tool body 14 and a flow sensor tool cover plate 15, the flow sensor tool body 14 and the flow sensor tool cover plate 15 form a cylindrical structure, the flow sensor tool cover plate 15 is arranged on the flow sensor tool body 14, and the flow sensor tool cover plate 15 is used to seal the sensitive diaphragm 2 and the fiber Bragg grating sensor 3. Specifically, a recessed area is arranged on the annular surface of the flow sensor tool body 14, and the flow sensor tool cover plate 15 is arranged in the recessed area. The recessed area provides accurate installation positioning for the flow sensor tool cover plate 15. When installing, the flow sensor tool cover plate 15 only needs to be placed in the recessed area, and the position can be quickly determined without complex alignment operation, which greatly simplifies the installation process, improves the installation efficiency, and ensures the normal work of the sensor.

[0023] As shown in the embodiment 1, the flow sensor 1 comprises a flow sensor tool body 14 and a flow sensor tool cover plate 15, the flow sensor tool body 14 and the flow sensor tool cover plate 15 form a cylindrical structure, the flow sensor tool cover plate 15 is arranged on the flow sensor tool body 14, and the flow sensor tool cover plate 15 is used to seal the sensitive diaphragm 2 and the fiber Bragg grating sensor 3. Specifically, a recessed area is arranged on the annular surface of the flow sensor tool body 14, and the flow sensor tool cover plate 15 is arranged in the recessed area. The recessed area provides accurate installation positioning for the flow sensor tool cover plate 15. When installing, the flow sensor tool cover plate 15 only needs to be placed in the recessed area, and the position can be quickly determined without complex alignment operation, which greatly simplifies the installation process, improves the installation efficiency, and ensures the normal work of the sensor. Figure 2As shown in the embodiment 1, the fiber Bragg grating sensor 3 is arranged on the sensitive diaphragm 2, specifically, the fiber Bragg grating sensor 3 is pasted on the center of the sensitive diaphragm 2 by AB glue, and the sensitive diaphragm 2 is a component of the flow sensor 1 directly subjected to the water flow pressure. When the water flow passes through the flow sensor 1, the pressure distribution is generated on the surface of the sensitive diaphragm 2, and the fiber Bragg grating sensor 3 pasted on the center of the sensitive diaphragm 2 can sense the deformation of the sensitive diaphragm 2 caused by the water flow pressure, so that the fiber Bragg grating sensor 3 can accurately measure the pressure change related to the flow, thereby improving the accuracy of the flow measurement.

[0024] Referring to Figure 3 and Figure 4 As shown in the embodiment 1, the containing area 13 is in a square distribution, and the sensitive diaphragm 2 is also in a square distribution, and the sensitive diaphragm 2 is just adapted to the containing area 13. The outer periphery of the containing area 13 is provided with a flange 131, and the outer edge of the sensitive diaphragm 2 abuts against the flange 131. Moreover, the sensitive diaphragm 2 and the flange 131 are connected through the first fastener 4. Specifically, the corresponding positions of the sensitive diaphragm 2 and the flange 131 are provided with shaft holes, and the first fastener 4 is an M1 bolt. The sensitive diaphragm 2 is connected with the flow sensor tool body 14 through the M1 bolt. Specifically, it is also necessary to note that the first waterproof gasket is arranged between the sensitive diaphragm 2 and the flange 131. The flange 131 can make the sensitive diaphragm 2 accurately placed at the predetermined position, avoiding deviation. Moreover, the sensitive diaphragm 2 is firmly fixed on the flow sensor tool body 14 through the cooperation of the M1 bolt and the shaft hole, so as to ensure that the sensitive diaphragm 2 will not be displaced or loosened during the working process, thereby ensuring the stability of the structure of the flow sensor 1. The M1 bolt is a common standard fastener, and the price is relatively low, which can effectively reduce the overall cost.

[0025] Referring to Figure 1 , Figure 3 and Figure 4It is shown in the present embodiment 1, it also needs to be explained that the flow sensor tool cover plate 15 is provided with a second waterproof gasket 151 between the flow sensor tool main body 14, the flow sensor tool main body 14 and the flow sensor tool cover plate 15 are connected through the second fastener 5, specifically, the second fastener 5 is M2 bolt fixed, M2 bolt is a common standard fastener, when installing the flow sensor tool cover plate 15, only need to place the cover plate on the tool main body, then use screwdriver to tighten M2 bolt one by one, can greatly shorten the installation time, improve the installation efficiency, and through the setting of the second waterproof gasket 151, the flow sensor tool main body 14 and the flow sensor tool cover plate 15 can be prevented from being eroded, and the sealing effect is guaranteed. It needs to be explained that the second waterproof gasket 151 is made of silicone rubber, fluorine rubber or polytetrafluoroethylene material, which has good corrosion resistance and can resist the corrosion of various chemicals in oilfield fluid.

[0026] Referring to Figure 1 and Figure 2 It is shown in the present embodiment 1, the flow sensor tool cover plate 15 is provided with an inlet pressure hole 141 near the water inlet 11, and the flow sensor tool main body 14 is provided with an outlet pressure hole 142 near the water outlet 12. By setting the inlet pressure hole 141 and the outlet pressure hole 142, the pressure value of the water when entering and flowing out of the flow sensor 1 can be directly and accurately obtained. Since the water inlet 11 and the water outlet 12 are the key positions of the fluid flowing through the flow sensor 1, the pressure change at these two positions can directly reflect the flow state and flow rate of the fluid. By accurately measuring the pressure at these two positions, the flow rate of the fluid can be more accurately calculated, greatly improving the accuracy of flow measurement.

[0027] Referring to Figure 1 It is shown in the present embodiment 1, the flow sensor 1 tool body is provided with a lead-out hole 143, and a waterproof ring is arranged at the lead-out hole 143. In this way, the jumper wire of the fiber Bragg grating sensor 3 can be led out through the lead-out hole 143. The waterproof ring is wrapped around the jumper wire to limit it in a specific path, avoiding random bending and winding of the jumper wire inside the tool, reducing the risk of jumper wire damage caused by friction with other components or being scratched by sharp objects. Moreover, this design avoids water involvement of the jumper wire and facilitates connection with subsequent demodulation equipment.

[0028] Referring to Figure 6 and Figure 7As shown in Embodiment 2, this invention discloses an oilfield stratified water injection monitoring system, including the aforementioned fiber optic flow sensor 10, a water injection layer distributor 6, and an oil pipe 7. Specifically, two fiber optic flow sensors 10 are provided. The outlet 12 of one fiber optic flow sensor 10 is connected to one end of the water injection layer distributor 6, specifically, the outer wall of the flow sensor 10 is designed to fit against the inner wall of the water injection layer distributor 6. The inlet 11 of the other fiber optic flow sensor 10 is connected to the other end of the water injection layer distributor 6, specifically, the outer wall of the other fiber optic flow sensor 10 is designed to fit against the inner wall of the water injection layer distributor 6. The outlet 12 of the other fiber optic flow sensor 10 is connected to one end of the oil pipe 7. The two fiber optic flow sensors 10 are respectively installed above and below the water injection layer distributor 6. The fluid enters from the ground and flows vertically downwards through a fiber optic flow sensor 10, a water injection layer distributor 6, another fiber optic flow sensor 10, and an oil pipe 7. The two fiber optic flow sensors 10 are respectively located at both ends of the water injection layer distributor 6, enabling precise measurement of the fluid flow rate entering and exiting the distributor 6. By comparing the measurement data from the two sensors, the actual flow rate through the water injection layer distributor 6 can be more accurately determined, allowing for timely detection of flow rate changes and providing reliable data support for accurate monitoring of stratified water injection in the oilfield. The outer wall of the fiber optic flow sensor 10 is designed to fit snugly against the inner wall of the water injection layer distributor 6, enhancing the connection stability and sealing between the two. This snug structure effectively prevents fluid leakage at the connection point, ensuring that the fluid flows along the predetermined path, while also reducing interference from the external environment on the flow measurement and improving measurement accuracy.

[0029] See Figure 6 As shown, in this embodiment 2, a demodulation module 8 and a computer unit 9 are also included. The flow sensor 1 and the fiber Bragg grating sensor 3 are electrically connected to the demodulation module 8, and the computer unit 9 is also electrically connected to the demodulation module 8. The demodulation module 8 has professional signal demodulation capabilities, which can accurately convert the optical signal sensed by the fiber Bragg grating sensor 3 into a processable electrical signal, while simultaneously receiving the electrical signal from the flow sensor 1. This electrical connection method ensures the high efficiency and stability of data acquisition, reduces signal loss and interference during transmission, and provides high-quality raw data for subsequent data processing. The flow sensor 1 is connected to the demodulation module 8 on the ground via an optical fiber patch cord. The computer unit 9 on the ground acquires and processes the signal to achieve real-time monitoring of the water injection volume of each injection layer.

[0030] Embodiment 3 of the present invention discloses a method for monitoring stratified water injection volume in oilfields, which employs the aforementioned oilfield stratified water injection volume monitoring system and includes the following steps: Cross-sectional area of ​​water flowing inside the oil pipe is:

[0031] wherein, is the inner diameter of the oil pipe, since the oil pipe is cylindrical, the cross-sectional area of the water flow in the oil pipe can be obtained according to the formula of the area of a circle; the cross-sectional area of the water flow in the fiber grating flow sensor :

[0032] wherein, is the inner diameter of the inlet or outlet, since the fiber grating flow sensor is cylindrical, the cross-sectional area of the water flow in the fiber grating flow sensor can be obtained according to the formula of the area of a circle; According to the continuity equation of fluid mechanics , is the liquid flow rate at i, is the volume flow rate, is the cross-sectional area at i, the volume flow rate in the same pipeline is constant, while the liquid flow rate and the cross-sectional area are inversely proportional, so as to obtain the water flow rate in the oil pipe is:

[0033]

[0034] wherein, in practice, the Bernoulli equation should be ; is the height of pipeline i from the ground, since the sensor length is small, the influence of the sensor height difference on the pressure difference can be ignored, and the Bernoulli equation is simplified to

[0035] is the water flow pressure in the oil pipe, is the water flow pressure in the fiber grating flow sensor, is the water flow rate in the oil pipe, is the water flow rate in the fiber grating flow sensor, is the fluid density, is the acceleration of gravity; The pressure difference between the water flow pressure in the oil pipe and the water flow pressure in the fiber grating flow sensor = - ;​ derived

[0036] wherein, β= , β is the ratio of the inner diameter of the water flow when flowing in the fiber grating flow sensor to the cross-sectional area of the water flow when flowing in the oil pipe, ; , greater than ; The above Bernoulli equation is simplified to , , - , , = ; wherein the sensitive diaphragm is square and the side length is 2a, the distance from the center of the sensitive diaphragm 2 to each side is a; the deflection of the fiber Bragg grating sensor ; wherein E is the elastic modulus of the sensitive diaphragm, is the Poisson's ratio of the sensitive diaphragm, h is the thickness of the sensitive diaphragm, the analytic solution coefficient of the central deflection of the square thin plate under the uniform load under the fixed boundary condition of four sides is the fitting result of the boundary condition; The fiber Bragg grating sensor is pasted on the surface of the sensitive diaphragm, and the deflection of the diaphragm will cause the wavelength change of the fiber Bragg grating sensor ,

[0037] l is the length of the fiber Bragg grating sensor, and the above formula and the deflection are brought into and arranged to obtain =

[0038] By monitoring the wavelength change of the fiber Bragg grating sensor in the flow sensor, the flow of the water in the oil pipe can be obtained, the flow sensor is connected to the demodulation equipment on the ground through the fiber jumper, and the computer on the ground acquires and processes the signal, so that the real-time monitoring of the injection volume of each injection layer is realized.

[0039] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fiber Bragg grating flow sensor, characterized in that, It includes a flow sensor (1), a sensitive diaphragm (2), and a fiber Bragg grating sensor (3), wherein, The flow sensor (1) has an inlet (11) and an outlet (12) connected together, and the flow sensor (1) has an indentation forming a receiving area (13); The sensitive membrane (2) is disposed in the receiving area (13), and a first waterproof gasket is disposed between the sensitive membrane (2) and the receiving area (13); The fiber Bragg grating sensor (3) is disposed on the sensitive diaphragm (2).

2. The fiber Bragg grating flow sensor (10) according to claim 1, characterized in that, The accommodating area (13) is provided with a flange (131) on its outer periphery. The outer edge of the sensitive diaphragm (2) abuts against the flange (131), and the sensitive diaphragm (2) and the flange (131) are connected by a first fastener (4).

3. The fiber Bragg grating flow sensor according to claim 1, characterized in that, The flow sensor (1) includes a flow sensor fixture body (14) and a flow sensor fixture cover plate (15), wherein, The inlet (11) and the outlet (12) are opened on the main body (14) of the flow sensor fixture and are located at both ends of the main body (14); The flow sensor fixture cover plate (15) is placed on the flow sensor fixture body (14). A second waterproof gasket (151) is provided between the flow sensor fixture cover plate (15) and the flow sensor fixture body (14). The flow sensor fixture cover plate (15) is used to seal the sensitive diaphragm (2) and the fiber Bragg grating sensor (3).

4. A fiber Bragg grating flow sensor according to claim 3, characterized in that, The flow sensor fixture body (14) and the flow sensor fixture cover plate (15) are connected by a second fastener (5).

5. A fiber Bragg grating flow sensor according to claim 3, characterized in that, The flow sensor fixture cover plate (15) has an inlet pressure tap (141) near the water inlet (11), and the flow sensor fixture body (14) has an outlet pressure tap (142) near the water outlet (12).

6. The fiber Bragg grating flow sensor (10) according to claim 3, characterized in that, The flow sensor fixture body (14) has an outlet hole (143) and a waterproof ring is provided at the outlet hole (143).

7. An oilfield stratified water injection monitoring system, comprising the fiber optic grating flow sensor (10) as described in any one of claims 1-6, characterized in that, It also includes a water distributor (6) and an oil pipe (7), and two fiber optic flow sensors (10) are provided, among which, The outlet (12) of one of the fiber optic flow sensors (10) is connected to one end of the water distribution device (6) of the water injection layer; The inlet (11) of another fiber optic flow sensor (10) is connected to the other end of the water injection layer distributor (6); The outlet (12) of another fiber optic flow sensor (10) is connected to one end of the oil pipe (7).

8. The oilfield stratified water injection monitoring system according to claim 7, characterized in that, It also includes a demodulation module (8) and a computer unit (9), wherein, The flow sensor (1), the fiber Bragg grating sensor (3), and the demodulation module (8) are electrically connected; The computer unit (9) is electrically connected to the demodulation module (8).

9. A method for monitoring stratified water injection volume in oilfields, employing the oilfield stratified water injection volume monitoring system as described in any one of claims 7-8, characterized in that, Includes the following steps: Cross-sectional area of ​​water flowing inside the oil pipe (7) ; in, The inner diameter of the oil pipe (7); Cross-sectional area of ​​water flowing inside the fiber optic grating flow sensor (10) ; in, The inner diameter of the inlet (11) or outlet (12); According to Bernoulli's equation ; in, , ; The water pressure inside the oil pipe (7) The water pressure inside the fiber Bragg grating flow sensor (10) is the pressure of the water flow. The water flow velocity inside the oil pipe (7) The water flow velocity inside the fiber optic grating flow sensor (10) is... Volumetric flow rate, For fluid density, It is the acceleration due to gravity; Water pressure inside the oil pipe (7) Water pressure within the fiber optic grating flow sensor (10) Pressure difference between = - ; The conclusion is , where β= ; Where β is the inner diameter of the water flow within the fiber Bragg grating flow sensor. Cross-sectional area of ​​water flowing inside the oil pipe The ratio; The deflection of the fiber Bragg grating sensor (10) ; in, The elastic modulus of the sensitive diaphragm (2) is Let h be the Poisson's ratio of the sensitive diaphragm (2), and h be the thickness of the sensitive diaphragm (2). The sensitive diaphragm (2) is square. Let a be the side length of the sensitive diaphragm (2), and let a be the distance from the center of the sensitive diaphragm (2) to each side. Wavelength variation of the fiber Bragg grating sensor With volumetric flow rate The relationship between them is = ; where l is the length of the fiber Bragg grating sensor (10).

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