Pressure measurement device and method, downhole pressure monitoring system

Abstract

This invention discloses a pressure measurement device and method, and a downhole pressure monitoring system. The device includes: at least one elastic pipe section with a pressure-bearing cavity inside, filled with a pressure-bearing fluid; and a sensing optical cable, including at least one strain-sensing optical fiber, distributed along the axial direction of the elastic pipe section and in contact with it. When the elastic pipe section is placed in the area to be measured, it deforms under the influence of a pressure difference between its internal and external parts, transmitting the deformation to the sensing optical cable. This invention measures the pressure difference between the internal and external parts of the elastic pipe section by measuring its deformation through the sensing optical cable, thereby determining the pressure in the area to be measured. By filling the pressure-bearing cavity of the elastic pipe section with pressure-bearing fluid, the invention allows the elastic pipe section to withstand greater external pressure, thus improving the pressure measurement range. Furthermore, by controlling the degree of deformation of the elastic pipe section under the influence of the pressure difference, the measurement accuracy can be controlled, improving the measurement precision.

Description

Technical Field

[0001] This invention relates to the fields of hydrogeological monitoring and geophysical exploration technology, and in particular, to a pressure measurement device and method, and a downhole pressure monitoring system. Background Technology

[0002] Pressure is a crucial measurement parameter in the production process of many industries. The phase state of matter, fluid transport, and physicochemical reactions are all reflected in pressure. Pressure not only reflects production capacity-related indicators but is also a vital safety indicator in the production process. Any engineering installation or natural rock and soil mass can only withstand pressure within a certain range; exceeding this allowable pressure range can lead to engineering accidents and cause significant losses. For example, in the oil and gas development industry, pressure changes reflect the production status and properties of oil wells and are an important basis for assessing wellbore integrity; therefore, pressure is a parameter that must be accurately measured in oil and gas development. Similar issues exist in the field of carbon dioxide geological storage.

[0003] In the field of well logging, downhole pressure monitoring methods include capillary pressure measurement, PSI downhole pressure measurement, and PDMS permanent downhole pressure monitoring. These technologies generally suffer from significant problems in one or more aspects such as cost, accuracy, real-time performance, distributed operation, and resolution, failing to meet the increasingly demanding requirements for refined downhole pressure assessment. In recent years, Distributed Fiber Optic Sensing (DFOS) technology has been widely applied and has seen significant development in the oil and gas industry, sustainable energy, and structural health monitoring. The advantages of DFOS systems include light weight, small size, resistance to electromagnetic interference, remote monitoring, high temperature and high pressure (HTHP) resistance, multiplexing, and intelligent sensing. Therefore, it can replace traditional resistive and vibrating wire sensors, especially in harsh environments and inaccessible to technicians.

[0004] Preliminary research progress has been made in downhole pressure measurement based on fiber optic sensing technology. Examples include chain-type single-point fiber optic pressure sensors based on fiber Bragg gratings and pressure measurement cables based on microstructure fiber optic technologies such as side-hole polarization-maintaining. One existing solution characterizes pressure using vertically deployed strain-sensing cables. However, optical fibers can only sense the axial deformation of the fiber core. For vertically deployed cables, the axial deformation caused by external pressure is very limited. Furthermore, this solution involves multiple layers of protective encapsulation, leading to significant strain transmission losses and thus limiting the achievable accuracy. Another existing solution uses fiber Bragg grating sensing technology, which only allows for single-point measurement. Even with multiplexing techniques, the number of sensing points is still very limited, clearly failing to meet the requirements for distributed, large-scale, accurate fluid pressure measurement. Summary of the Invention

[0005] The purpose of this invention is to provide a pressure measurement device and method, and a downhole pressure monitoring system, to solve the technical problem that current pressure measurement devices based on sensing optical cables cannot achieve accurate pressure measurement over a wide range.

[0006] The above-mentioned objectives of the present invention can be achieved by the following technical solutions:

[0007] The present invention provides a pressure measuring device, comprising: at least one elastic tube segment having a pressure-bearing cavity inside, the pressure-bearing cavity being filled with a pressure-bearing fluid; and a sensing optical cable including at least one strain-sensing optical fiber, the sensing optical cable being distributed along the axial direction of the elastic tube segment and in contact with the elastic tube segment; wherein, when the elastic tube segment is placed in the area to be measured, the elastic tube segment can deform under the action of the internal and external pressure difference and transmit the deformation to the sensing optical cable.

[0008] In embodiments of the present invention, the sensing optical cable is spirally wound around the inner wall, outer wall, or interior of the elastic tube segment along its axial direction; wherein, the number of sensing optical cables is one; or the number of sensing optical cables is two, and the two sensing optical cables are arranged crosswise to form a sensing topology. In embodiments of the present invention, the sensing optical cable has an angle with the radial direction of the elastic tube segment, and the angle is less than or equal to the arctangent of the Poisson's ratio of the elastic tube segment.

[0009] In embodiments of the present invention, the sensing optical cable further includes at least one temperature sensing optical fiber.

[0010] In an embodiment of the present invention, the pressure measurement range of the pressure measuring device is smaller than the pressure of the pressure-bearing cavity.

[0011] In embodiments of the present invention, there are multiple elastic tube segments, which are connected in series, and the pressure-bearing cavities of each elastic tube segment are independently arranged.

[0012] In embodiments of the present invention, the pressure measuring device includes an elastic tube and a plurality of packers. The plurality of packers are spaced apart along the axial direction of the elastic tube within the elastic tube. The elastic tube forms a plurality of elastic tube segments connected as one unit, and the inner cavity of the elastic tube is divided by the plurality of packers to form a plurality of independent pressure-bearing cavities. Alternatively, the plurality of elastic tube segments are of a split structure, with both ends of each elastic tube segment sealed by a front packer and a rear packer. Between two adjacent elastic tube segments, the rear packer of the preceding elastic tube segment is connected to the front packer of the following elastic tube segment through a series connection structure.

[0013] In embodiments of the present invention, the packer is provided with a through hole for passing through the sensing optical cable and sealingly connecting it to the sensing optical cable; or the series connection structure is provided with a cable passage for passing through the sensing optical cable; or the sensing optical cable includes multiple sensing optical cable segments that are respectively in contact with multiple elastic tube segments, and adjacent two sensing optical cable segments are electrically connected through the series connection structure.

[0014] The present invention also provides a pressure measurement method, comprising the following steps: preparing a sensing optical cable and at least one elastic tube segment, such that the sensing optical cable is distributed along the axial direction of the elastic tube segment and in contact with the elastic tube segment; filling a pressure-bearing fluid into a pressure-bearing cavity within the elastic tube segment until the pressure within the pressure-bearing cavity reaches a preset pressure; placing the elastic tube segment in the area to be measured, causing the elastic tube segment to deform under the action of its internal and external pressure difference and transmitting the deformation to the sensing optical cable, and measuring the strain of the elastic tube segment through the sensing optical cable; and measuring the pressure of the area to be measured based on the preset pressure and the strain.

[0015] In an embodiment of the present invention, determining the pressure of the area to be tested based on the preset pressure and the strain includes the following steps: determining the axial strain of the elastic tube segment based on the strain and the laying angle of the sensing optical cable; and determining the pressure of the area to be tested based on the preset pressure and the axial strain.

[0016] In embodiments of the present invention, the measurement method further includes adjusting the measurement range and measurement accuracy by adjusting the preset pressure and the material, diameter, and wall thickness of the elastic tube segment.

[0017] The present invention also provides a downhole pressure monitoring system, comprising: at least one of the above-mentioned pressure measuring devices, the pressure measuring devices being installed in the downhole area; and an optical fiber composite demodulator being installed in the surface area and electrically connected to the sensing optical cable of the pressure measuring device.

[0018] In embodiments of the present invention, the pressure measuring device is disposed in the annulus region between the casing and the injection pipe; and / or the pressure measuring device is disposed in the downhole region during drilling and embedded in the cement outside the casing through a cementing process; and / or the pressure measuring device is fitted to the outer wall surface of the casing through a clamping device fitted over the casing; and / or the pressure measuring devices are spaced apart around the casing and connected to the clamping device through a connecting structure.

[0019] The features and advantages of this invention are:

[0020] The pressure measuring device and method of the present invention can measure the internal and external pressure difference of the elastic tube segment by measuring the deformation of the elastic tube segment through a sensing optical cable, that is, the relationship between the pressure of the area to be measured and the pressure of the pressure-bearing cavity. Therefore, the pressure of the area to be measured can be determined based on the measured internal and external pressure difference and the known pressure of the pressure-bearing cavity. The present invention fills the pressure-bearing cavity of the elastic tube segment with pressurized fluid, so that the elastic tube segment can withstand greater external pressure, thereby improving the pressure measurement range. Furthermore, the measurement accuracy can be controlled by controlling the degree of deformation of the elastic tube segment under the action of its internal and external pressure difference.

[0021] The downhole pressure monitoring system of the present invention enables real-time monitoring of downhole pressure by lowering a pressure measuring device into the downhole area and electrically connecting the sensing optical cable of the pressure measuring device to a fiber optic composite demodulator in the surface area, thereby effectively ensuring the long-term stable and reliable operation of oil and gas production wells, injection wells and / or monitoring wells. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a diagram showing the arrangement of the elastic tube segment and the sensing optical cable in one embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the force on the elastic pipe section under pressure difference in this invention.

[0025] Figure 3 This is a schematic cross-sectional view of a sensing optical cable in one embodiment of the present invention.

[0026] Figure 4 This is a three-dimensional cross-sectional schematic diagram of the elastic tube segment and the sensing optical fiber in one embodiment of the present invention.

[0027] Figure 5 This is a schematic cross-sectional view of the elastic tube segment and the sensing optical fiber in one embodiment of the present invention.

[0028] Figure 6 This is a three-dimensional cross-sectional schematic diagram of the elastic tube segment and the sensing optical fiber in another embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of the cross-section of the elastic tube segment and the sensing optical fiber in another embodiment of the present invention.

[0030] Figure 8This is a three-dimensional cross-sectional schematic diagram of the elastic tube segment and the sensing optical fiber in another embodiment of the present invention.

[0031] Figure 9 This is a cross-sectional schematic diagram of the elastic tube segment and the sensing optical fiber in another embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram of multiple elastic pipe segments connected in series in this invention.

[0033] Figure 11 This is a schematic diagram of a series connection structure in one embodiment of the present invention.

[0034] Figure 12 This is a schematic diagram of a series connection structure in another embodiment of the present invention.

[0035] Figure 13 This is a schematic diagram of the series connection structure in another embodiment of the present invention.

[0036] Figure 14 This is a diagram showing the arrangement of the elastic tube segment and the sensing optical cable in another embodiment of the present invention.

[0037] In the picture:

[0038] 10. Flexible pipe section; 101. Wall; 102. Outer wall channel; 103. Inner wall channel;

[0039] 11. Packer;

[0040] 12. Sensing optical cable; 121. Temperature sensing optical fiber; 122. Strain sensing optical fiber; 123. Other sensing optical fibers; 124. Outer sheath; 125. Filler layer;

[0041] 13. Pressure chamber;

[0042] 141. Front packer; 142. Rear packer;

[0043] 15. Series connection structure; 151. Connecting pipe; 152. Internal threaded bolt; 153. External threaded bolt; 154. First jumper connector; 155. Second jumper connector; 156. Connecting pipe section;

[0044] 16. Jumper wire. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Implementation Method 1

[0047] like Figures 1 to 3 As shown, the present invention provides a pressure measuring device, comprising: at least one elastic tube segment 10, wherein a pressure-bearing cavity 13 is provided inside the elastic tube segment 10, and the pressure-bearing cavity 13 is filled with a pressure-bearing fluid; a sensing optical cable 12, including at least one strain-sensing optical fiber 122, the sensing optical cable 12 being distributed along the axial direction of the elastic tube segment 10 and in contact with the elastic tube segment 10; wherein, when the elastic tube segment 10 is placed in the area to be measured, the elastic tube segment 10 can deform under the action of the internal and external pressure difference and transmit the deformation to the sensing optical cable 12.

[0048] The pressure measuring device of the present invention can measure the pressure difference between the inside and outside of the elastic tube segment 10, i.e., the pressure of the area to be measured (defined as the pressure to be measured p), by measuring the deformation of the elastic tube segment 10 through the sensing optical cable 12. e The pressure of the pressure chamber 13 (defined as the preset pressure p) i The relationship between the internal and external pressure differences and the known pressure of the pressure-bearing cavity 13 is used to determine the pressure of the area to be measured. The present invention fills the pressure-bearing cavity 13 of the elastic tube section 10 with pressurized fluid, so that the elastic tube section 10 can withstand greater external pressure, thereby improving the pressure measurement range. Furthermore, the measurement accuracy can be improved by controlling the degree of deformation of the elastic tube section 10 under the action of its internal and external pressure differences.

[0049] Specifically, such as Figure 2 As shown, the pressure in the pressure chamber 13 is a known preset pressure p. i The pressurized fluid includes, but is not limited to, gases, liquids, or gas-liquid mixtures. The pressure in the area to be measured is the unknown test pressure p. e This includes, but is not limited to, the fluid pressure in the area to be measured. Combined with... Figure 1 and Figure 2 As shown, the elastic tube segment 10 is placed in the area to be tested, and the elastic tube segment 10 is subjected to a preset pressure p. i and the pressure to be measured p e The elastic tube segment 10 deforms under the action of pressure difference and is transmitted to the sensing optical cable 12. The strain of the elastic tube segment 10 is measured by the sensing optical cable 12, and then the strain can be determined according to the preset pressure p. i And strain, the pressure to be measured p e The working principle involved in the sensing optical cable 12 measuring the strain of the elastic tube segment 10 is the same as that in the prior art, and will not be described in detail here.

[0050] Preferably, the axial strain of the elastic tube segment 10 is determined based on the strain of the elastic tube segment 10 measured by the sensing optical cable 12 and the arrangement angle of the sensing optical cable 12 relative to the axial direction of the elastic tube segment 10, and then the strain is determined according to the preset pressure p. i And axial strain, determine the pressure to be measured p eSpecifically, the pressure to be measured is determined using the relationship between the pressure to be measured, the preset pressure, and the axial strain.

[0051] The relationship between the pressure to be measured, the preset pressure, and the axial strain is as follows:

[0052]

[0053] Where, p e The pressure to be measured is given by n, where n is the deformation transmission loss compensation coefficient between the elastic tube section 10 and the sensing optical cable 12, r is the radius of the pressure-bearing cavity 13 of the elastic tube section 10, t is the thickness of the wall 101 of the elastic tube section 10, E is the Young's modulus of elasticity of the elastic tube section 10, and p is the pressure to be measured by n. i For the preset pressure, ε A Let ε be the axial strain of the elastic pipe section 10, and υ be Poisson's ratio. A The parameters are the extension measurement parameters obtained by processing the strain measured by the sensing optical cable 12; Poisson's ratio υ and Young's modulus E of the elastic tube 10 are material parameters that can be determined by combining existing technology; the radius r of the pressure-bearing cavity 13 of the elastic tube 10 and the thickness t of the wall 101 of the elastic tube 10 are geometric parameters of the elastic tube 10 that can be determined; the preset pressure p i The deformation transmission loss compensation coefficient n is an engineering parameter that can be measured using existing technology. Therefore, by substituting the above parameter into the above formula, the unknown pressure p can be measured. e .

[0054] In addition, the circumferential strain of the elastic tube segment 10 and the preset pressure p can be directly measured based on the sensing optical cable 12. i Determine the pressure to be measured, p e The relationship between the pressure to be measured, the preset pressure, and the circumferential strain is as follows:

[0055]

[0056] Where, p e The pressure to be measured is given by n, where n is the deformation transmission loss compensation coefficient between the elastic tube section 10 and the sensing optical cable 12, r is the radius of the pressure-bearing cavity 13 of the elastic tube section 10, t is the thickness of the wall 101 of the elastic tube section 10, E is the Young's modulus of elasticity of the elastic tube section 10, and p is the pressure to be measured by n. i For the preset pressure, ε c υ represents the circumferential strain of the elastic tube segment 10, and υ represents Poisson's ratio.

[0057] like Figure 1As shown, in an embodiment of the present invention, the sensing optical cable 12 is arranged linearly along the axial direction of the elastic tube segment 10 and contacts the elastic tube segment 10. In some preferred embodiments of the present invention, the sensing optical cable 12 is spirally wound along the axial direction of the elastic tube segment 10 and contacts the elastic tube segment 10, so that the deformation of the elastic tube segment 10 at any position in its axial direction and at any position in its circumferential direction can be transmitted to the sensing optical cable 12, thereby significantly improving the spatial resolution and sensing accuracy of the sensing optical cable 12. The number of sensing optical cables 12 can be as follows: Figure 1 The image shown is of only one, but it can also be like... Figure 14 The image shows two sensing optical cables 12, which are spirally wound and cross-arranged to form a sensing topology, thereby enabling the acquisition of axial and circumferential strain at any position of the elastic tube segment 10. The angle of the cross arrangement is not specifically limited.

[0058] like Figure 4 and Figure 5 As shown, in some embodiments, the sensing optical cable 12 is wound around the outer wall surface of the elastic tube segment 10. Specifically, a spiral outer wall channel 102 is formed on the outer wall surface of the elastic tube segment 10, and the sensing optical cable 12 is placed in the outer wall channel 102. Figure 6 and Figure 7 As shown, in other embodiments, the sensing optical cable 12 is wound around the inner wall surface of the elastic tube segment 10. Specifically, a spiral inner wall channel 103 is formed on the inner wall surface of the elastic tube segment 10, and the sensing optical cable 12 is placed in the inner wall channel 103. Figure 8 and Figure 9 As shown, the sensing optical cable 12 is wound inside the wall 101 of the elastic tube segment 10. Specifically, the sensing optical cable 12 is embedded inside the wall 101 of the elastic tube segment 10 during the injection molding process.

[0059] like Figure 1 As shown, in the embodiment of the present invention, there is an angle between the radial direction of the sensing optical cable 12 and the elastic tube segment 10. The angle is less than or equal to the arctangent of the Poisson's ratio of the elastic tube segment, that is, the angle θ is related to the Poisson's ratio v of the elastic tube segment 10: θ ≤ arctanν. The radial direction of the elastic tube segment 10 is the cross-sectional direction of the elastic tube segment 10. By controlling the angle θ between the radial direction of the sensing optical cable 12 and the elastic tube segment 10, the sensing optical cable 12 is kept in a tensile state at all positions when it deforms with the elastic tube segment 10 during the measurement process, thus exhibiting a certain degree of deformation. This ensures the accuracy of the measurement and avoids situations where parts of the sensing optical cable 12 are under compression, resulting in insignificant deformation and making it impossible to accurately measure the strain at the corresponding position of the elastic tube segment 10.

[0060] Combination Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the pressure measurement range of the pressure measuring device is smaller than the preset pressure of the pressure chamber 13. That is, the pressure measurement range can be adjusted by adjusting the magnitude of the preset pressure of the pressure chamber 13, so that the preset pressure of the pressure chamber 13 is greater than the pressure to be measured in the area to be measured. This allows the elastic tube segment 10 to deform into an outward expansion deformation, which is more conducive to controlling the various positions of the sensing optical cable 12 to be in a tensile state.

[0061] Furthermore, since the measurement accuracy of the sensing optical cable 12 is related to its deformation degree, and the measurement range of the sensing optical cable 12 is related to its deformation range, the measurement range and measurement accuracy can be adjusted by adjusting the degree and range of deformation of the sensing optical cable 12 with the elastic tube.

[0062] Specifically, the measurement range and accuracy are adjusted by modifying the preset pressure, the material, diameter, and wall thickness of the elastic tube 10. For example, when the pressure to be measured remains constant and is greater than the preset pressure, the greater the preset pressure, the smaller the outward expansion deformation of the elastic tube 10 and the smaller the tensile deformation of the sensing optical cable 12, and vice versa. When the pressure to be measured is less than the preset pressure of the pressure chamber 13 and the pressure difference between the two remains constant, the larger the diameter of the elastic tube 10, the thicker the wall 101, and / or the greater the Young's modulus of the material, the smaller the outward expansion deformation of the elastic tube 10 and the smaller the tensile deformation of the sensing optical cable 12, and vice versa.

[0063] like Figure 3 As shown, in some embodiments of the present invention, the sensing optical cable 12 further includes at least one temperature sensing optical fiber 121. On the one hand, since the deformation of the elastic tube segment 10 and the strain sensing optical fiber 122 is also temperature-dependent, by setting the temperature sensing optical fiber 121 to measure the temperature, temperature compensation can be achieved, improving the accuracy and precision of pressure measurement. For example, the Young's modulus E of the elastic tube segment 10 and the deformation transmission loss compensation coefficient n can be corrected based on the measured temperature, thereby improving the accuracy of the measurement results. On the other hand, the temperature sensing optical fiber 121 can be used to measure temperature, enabling simultaneous measurement of temperature and pressure. Specifically, the sensing optical cable 12 is a dual-core optical cable.

[0064] In other embodiments of the present invention, the sensing optical cable 12 is a multi-core optical cable. The sensing optical cable 12 also includes at least one other sensing optical fiber 123 for measuring other parameters. Specifically, the sensing optical cable 12 includes a filling layer 125 covering the strain sensing optical fiber 122, the temperature sensing optical fiber 121, and the other sensing optical fibers 123, and an outer sheath 124 covering the filling layer 125.

[0065] like Figure 10As shown, in this embodiment of the invention, there are multiple elastic tube segments 10, which are connected in series, and the pressure-bearing chambers 13 of each elastic tube segment 10 are independently arranged. By connecting multiple elastic tube segments 10 in series and making the pressure-bearing chambers 13 of each elastic tube segment 10 independent, multiple independent pressure measurement units are formed in conjunction with the sensing optical cable 12, thereby forming a distributed pressure measurement device. Furthermore, the deformation of each elastic tube segment 10 does not affect each other, so the measurement results of each pressure measurement unit will not interfere with each other, ensuring the measurement accuracy of each pressure measurement unit. In addition, the number of elastic tube segments 10 can be set according to the measurement distance, thereby meeting the requirements for long-distance measurement.

[0066] Specifically, the distributed pressure measurement device of the present invention is particularly suitable for downhole pressure measurement, such as pressure measurement in carbon dioxide geological storage injection wells or monitoring wells. The pressure measurement device is lowered into the area to be measured downhole. The sensing optical cable 12 can be connected to the fiber optic composite demodulator in the surface area through single-end monitoring or double-end monitoring. One or both ends of the sensing optical cable 12 extend to the wellhead and are electrically connected to the fiber optic composite demodulator in the surface area through jumper 16. The fiber optic composite demodulator processes and analyzes the fiber optic signal of the sensing optical cable 12 to obtain the strain of the elastic pipe section 10. When single-end monitoring is used, a reflection canceller is connected to the far end of the sensing optical cable 12. The number of pressure measurement devices can be one or more, and the sensing optical cables 12 of multiple pressure measurement devices are interconnected by fusion splicing.

[0067] like Figure 10 As shown, in some embodiments of the present invention, the pressure measuring device includes an elastic tube and a plurality of packers 11. The plurality of packers 11 are spaced apart along the axial direction of the elastic tube within the elastic tube. The elastic tube forms a plurality of elastic tube segments 10 connected as one unit, and the inner cavity of the elastic tube is divided by the plurality of packers 11 to form a plurality of independent pressure-bearing cavities 13. Specifically, the packers 11 are provided with through holes for threading and sealingly connecting the sensing optical cable 12.

[0068] like Figures 11 to 13As shown, in other embodiments of the present invention, the multiple elastic tube segments 10 are of a split structure. Both ends of each elastic tube segment 10 are sealed by a front packer 141 and a rear packer 142. Between adjacent elastic tube segments 10, the rear packer 142 of the preceding elastic tube segment 10 is connected to the front packer 141 of the following elastic tube segment 10 via a series connection structure 15. By designing the multiple elastic tube segments 10 as split units and connecting them via a series connection structure 15, it is convenient to adjust each pressure measuring unit separately, ensuring that the deformation of each pressure measuring unit meets the plane strain condition. This also facilitates engineering construction, effectively shortens the construction period, facilitates the continuity of the pressure measuring device, and ensures the safety of the sensing optical cable 12 in long-distance measurement projects.

[0069] In some embodiments, the series connection structure 15 includes multiple connecting pipe segments 156. In one embodiment, the multiple connecting pipe segments 156 are a separate structure, with the front end of the connecting pipe segment 156 connected to the rear end packer 142 of the preceding elastic pipe segment 10, and the rear end of the connecting pipe segment 156 connected to the front end packer 141 of the following elastic pipe segment 10. Each connecting pipe segment 156 is provided with a passage for threading the sensing optical cable 12. In another embodiment, the multiple connecting pipe segments 156 are connected as a single unit, i.e., a one-piece connected pipe 151. The connected pipe 151 passes through each front end packer 141, each rear end packer 142, and each elastic pipe segment 10 along the axial direction of each elastic pipe segment 10, and the connected pipe 151 is sealed to each front end packer 141 and each rear end packer 142. The connected pipe 151 is provided with a passage for threading the sensing optical cable 12.

[0070] In another embodiment, the sensing optical cable 12 includes multiple sensing optical cable segments that are in contact with multiple elastic tube segments 10, and adjacent sensing optical cable segments are electrically connected by a series connection structure 15. Specifically, the series connection structure 15 is generally a connector structure, including an internal threaded bolt 152 and an external threaded bolt 153, one of which is located on the rear end packer 142 of the preceding elastic tube segment 10, and the other is located on the front end packer 141 of the following elastic tube segment 10. In addition, the series connection structure 15 also includes a first jumper connector 154 and a second jumper connector 155, one of which is located on the internal threaded bolt 152, and the other is located on the external threaded bolt 153. Two sensing optical cable segments wound on adjacent elastic tube segments 10 are connected, one of which is welded to the first jumper connector 154 and the other is welded to the second jumper connector 155. After the first jumper connector 154 and the second jumper connector 155 are plugged in, the two sensing optical cable segments are electrically connected.

[0071] In addition, the series connection structure 15 can also be a connection structure using splines, snap hooks, flanges, etc., to realize the connection of multiple pressure measurement units.

[0072] Based on the above description, the pressure measuring device of the present invention has the following beneficial effects:

[0073] First, it meets the requirements of high precision, wide range, long distance measurement, distributed operation, good real-time performance, and controllable cost, and can solve the shortcomings of existing pressure measurement devices, such as short distance measurement, few sensing points, low sensing accuracy, and inability to perform continuous measurement.

[0074] Second, it has the ability to sense temperature and pressure in real time with high precision at any location along the entire measurement line.

[0075] Third, it is applicable to measurements in various complex working conditions and harsh environments, and has the ability to conduct long-term stable monitoring in geological or hydrological environments with high temperature, low temperature, high pressure, high ground stress and highly corrosive acidic fluids.

[0076] Fourth, the modular design allows it to be adapted to various engineering processes for installation and deployment. It can be installed as a permanent monitoring tool during the construction phase or deployed into existing projects for measurement, which also helps to improve the efficiency of monitoring operations.

[0077] Implementation Method 2

[0078] The present invention also provides a pressure measurement method. Since the principle of this method in solving the problem is similar to that of the pressure measurement device described above, the implementation of this method can refer to the implementation of the pressure measurement device described above, and the repeated parts will not be described again.

[0079] Combination Figure 1 As shown, the pressure measurement method of the present invention includes the following steps: preparing a sensing optical cable 12 and at least one elastic tube segment 10, such that the sensing optical cable 12 is distributed along the axial direction of the elastic tube segment 10 and in contact with the elastic tube segment 10; filling the pressure-bearing cavity 13 in the elastic tube segment 10 with a pressure-bearing fluid until the pressure in the pressure-bearing cavity 13 is a preset pressure; placing the elastic tube segment 10 in the area to be measured, causing the elastic tube segment 10 to deform under the action of the pressure difference between its inside and outside and transmitting the deformation to the sensing optical cable 12, and measuring the strain of the elastic tube segment 10 through the sensing optical cable 12; and measuring the pressure of the area to be measured based on the preset pressure and strain.

[0080] In an embodiment of the present invention, determining the pressure of the area to be measured based on the preset pressure and the strain includes the following steps: determining the axial strain of the elastic tube segment based on the strain and the arrangement angle of the sensing optical cable relative to the axial direction of the elastic tube segment; and determining the pressure of the area to be measured based on the preset pressure and the axial strain.

[0081] Specifically, the pressure to be measured is determined by using the relationship between the pressure to be measured, the preset pressure, and the axial strain.

[0082] The relationship between the pressure to be measured, the preset pressure, and the axial strain is as follows:

[0083]

[0084] Where, p e The pressure to be measured is given by n, where n is the deformation transmission loss compensation coefficient between the elastic tube section 10 and the sensing optical cable 12, r is the radius of the pressure-bearing cavity 13 of the elastic tube section 10, t is the thickness of the wall 101 of the elastic tube section 10, E is the Young's modulus of elasticity of the elastic tube section 10, and p is the pressure to be measured by n. i For the preset pressure, ε A υ represents the axial strain of the elastic tube section 10, and υ represents Poisson's ratio.

[0085] In embodiments of the present invention, the measurement method further includes adjusting the measurement range and measurement accuracy by adjusting the preset pressure and the material, diameter, and wall thickness of the elastic tube section 10.

[0086] Implementation Method 3

[0087] Combination Figure 10 As shown, the present invention also provides a downhole pressure monitoring system, comprising: at least one pressure measuring device installed in the downhole area; and a fiber optic composite demodulator installed in the surface area and electrically connected to the sensing optical cable 12 of the pressure measuring device. The pressure measuring device in this embodiment has the same specific structure, working principle, and beneficial effects as the pressure measuring device in Embodiment 1, and will not be described again here.

[0088] In some embodiments of the present invention, the pressure measuring device is disposed in the annular region between the sleeve and the injection pipe, that is, it is disposed in close contact with the inner wall surface of the sleeve or the outer wall surface of the injection pipe and / or spaced apart from the sleeve and the injection pipe.

[0089] In some embodiments of the present invention, the pressure measuring device is deployed in the downhole area during drilling and embedded in the cement outside the casing using a cementing process. The pressure measuring device is in contact with the formation and the fluids between the formations. Since the formation pressure remains constant, the pressure change of the formation fluid can be determined based on the change in the pressure to be measured measured by the pressure measuring device.

[0090] In some embodiments of the present invention, the pressure measuring device is fitted to the outer wall surface of the sleeve through a clamp fitted over the sleeve.

[0091] In some embodiments of the present invention, pressure measuring devices are spaced apart around the casing and connected to the pipe clamp via a connecting structure, with a gap between the pressure measuring devices and the casing.

[0092] The above descriptions are merely a few embodiments of the present invention. Those skilled in the art can make various modifications or variations to the embodiments of the present invention based on the content disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. A pressure measuring device, characterized in that, include: At least one elastic tube segment has a pressure-bearing cavity inside, and the pressure-bearing cavity is filled with a pressure-bearing fluid; A sensing optical cable includes at least one strain-sensing optical fiber, the sensing optical cable being distributed along the axial direction of the elastic tube segment and in contact with the elastic tube segment; When the elastic tube segment is placed in the area to be tested, the elastic tube segment can deform under the action of the internal and external pressure difference and transmit the deformation to the sensing optical cable.

2. The pressure measuring device as described in claim 1, characterized in that, The sensing optical cable is spirally wound around the inner wall, outer wall, or interior of the elastic tube segment along its axial direction. Wherein, the number of the sensing optical cables is one; or The number of sensing optical cables is two, and the two sensing optical cables are arranged in a cross pattern to form a sensing topology.

3. The pressure measuring device as described in claim 2, characterized in that, The sensing optical cable and the radial direction of the elastic tube segment have an angle, the angle of which is less than or equal to the arctangent of the Poisson's ratio of the elastic tube segment.

4. The pressure measuring device as described in claim 1, characterized in that, The sensing optical cable also includes at least one temperature sensing optical fiber.

5. The pressure measuring device as described in claim 1, characterized in that, The pressure measurement range of the pressure measuring device is smaller than the pressure of the pressure chamber.

6. The pressure measuring device according to any one of claims 1-5, characterized in that, The number of elastic tube segments is multiple, and the multiple elastic tube segments are connected in series, and the pressure-bearing cavity of each elastic tube segment is set independently.

7. The pressure measuring device as described in claim 6, characterized in that, The pressure measuring device includes an elastic tube and multiple packers. The multiple packers are spaced apart along the axial direction of the elastic tube inside the elastic tube. The elastic tube forms multiple elastic tube segments connected as one unit, and the inner cavity of the elastic tube is divided by the multiple packers to form multiple independent pressure-bearing cavities. or The multiple elastic tube segments are of a split structure, and the two ends of each elastic tube segment are sealed by a front packer and a rear packer; between two adjacent elastic tube segments, the rear packer of the preceding elastic tube segment is connected to the front packer of the following elastic tube segment through a series connection structure.

8. The pressure measuring device as described in claim 7, characterized in that, The packer is provided with a through hole for passing through the sensing optical cable and sealingly connecting it to the sensing optical cable; or The series connection structure is provided with a through-path for threading the sensing optical cable; or The sensing optical cable includes multiple sensing optical cable segments that are in contact with multiple elastic tube segments respectively, and adjacent sensing optical cable segments are electrically connected through the series connection structure.

9. A pressure measurement method, characterized in that, Includes the following steps: Prepare a sensing optical cable and at least one elastic tube segment, such that the sensing optical cable is distributed along the axial direction of the elastic tube segment and in contact with the elastic tube segment; The pressurized fluid is filled into the pressure chamber within the elastic tube section until the pressure inside the pressure chamber reaches the preset pressure. The elastic tube segment is placed in the area to be tested, and the elastic tube segment is deformed under the action of the internal and external pressure difference and transmitted to the sensing optical cable. The strain of the elastic tube segment is measured through the sensing optical cable. The pressure of the area to be tested is measured based on the preset pressure and the strain.

10. The pressure measurement method as described in claim 9, characterized in that, Determining the pressure of the area to be measured based on the preset pressure and the strain includes the following steps: The axial strain of the elastic tube segment is determined based on the strain and the arrangement angle of the sensing optical cable relative to the axial direction of the elastic tube segment. The pressure in the area to be measured is determined based on the preset pressure and the axial strain.

11. The pressure measurement method as described in claim 9, characterized in that, Also includes: The measurement range and accuracy can be adjusted by adjusting the preset pressure, as well as the material, diameter, and wall thickness of the elastic tube section.

12. A downhole pressure monitoring system, characterized in that, include: At least one pressure measuring device according to any one of claims 1-8, said pressure measuring device being installed in a downhole area; The fiber optic composite demodulator is installed in the ground area and electrically connected to the sensing optical cable of the pressure measuring device.

13. The downhole pressure monitoring system as described in claim 12, characterized in that, The pressure measuring device is positioned in the annular region between the casing and the injection pipe; and / or The pressure measuring device is deployed in the downhole area during drilling and embedded in the cement outside the casing through cementing process. and / or The pressure measuring device is fitted to the outer wall of the sleeve through a clamp fitted over the sleeve; and / or The pressure measuring devices are spaced apart around the casing and connected to the pipe clamp via a connecting structure.

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