Optical fiber high-temperature and high-pressure sensor packaging structure and method for oil-gas well underground exploration

Abstract

The optical fiber high-temperature and high-pressure sensor packaging structure comprises an optical fiber connected with an optical fiber sensing structure, and is characterized in that the optical fiber and the optical fiber sensing structure extend into a metal outer pipe from one end of the metal outer pipe, the optical fiber sensing structure is located in the middle of the metal outer pipe, and the optical fiber is sleeved with a thin steel pipe; one end of the thin steel pipe is located in the metal outer pipe, the other end of the thin steel pipe is located outside the metal outer pipe, an optical high-temperature curing glue section is filled between the thin steel pipe and a port of the metal outer pipe, the end of the thin steel pipe located in the metal outer pipe is located in the optical high-temperature curing glue section, and a certain distance is reserved between the end face of the optical high-temperature curing glue section and the optical fiber sensing structure. A filter is arranged at the other end of the metal outer pipe. The optical high-temperature curing adhesive is combined, and an optical fiber-metal low-temperature glass solder welding method is adopted, so that a better sealing effect is achieved, and the packaging service life of the sensor is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to an optical fiber sensor packaging method for simultaneous measurement of high temperature and high pressure during oil and gas well exploration. Background Art

[0002] The development of oil and gas resources is a strategic industry that affects the country's energy stability and economic security. With the continuous deepening and increasing complexity of oil field development, advanced drilling technology, geophysical technology, logging technology, reservoir description and other new oil field technologies are changing with each passing day. Oil field dynamic monitoring data plays an increasingly important role in guiding the adjustment of oil field development plans, detailed description of oil reservoirs, and the formulation of production increase measures. In recent years, improving reservoir dynamics and implementing optimized oil production have become the research focus of oil and gas development. Among them, the management of reservoir temperature and pressure is the basis for effective management of reservoirs and improving recovery rates.

[0003] The harsh environment in oil and gas wells mainly includes high temperature environment, high pressure environment, strong corrosion environment and electromagnetic interference. Although optical fiber temperature and pressure sensors have been developing rapidly, there are few sensors that can be actually used for oil and gas well monitoring, and the installation of downhole sensors is relatively difficult. This requires that the sensor packaging needs to be combined with the actual downhole application environment to make comprehensive considerations on the shell size, structural installation and other aspects. Therefore, a packaging method is required to enable optical fiber temperature and pressure sensors to achieve long-term monitoring in the high temperature and high pressure environment of oil and gas wells.

[0004] When optical fiber sensors measure temperature and pressure, commonly used temperature and pressure sensing structures include fiber grating structures and fiber Fabry-Perot interference structures. The test range of temperature and pressure of these structures depends on the type of optical fiber and the packaging structure of the sensor. First of all, for the selection of optical fiber types, commonly used optical fiber coatings will choose resin or polymer materials, but these materials will soften or deteriorate at temperatures above 250°C, and their mechanical strength and anti-interference capabilities will be greatly reduced, leading to sensor failure. Therefore, in high temperature environments, resin coatings may not be a good choice, and special coated optical fibers with better mechanical strength and flexibility and the ability to withstand extreme high and low temperature environments are required.

[0005] In addition, as for the packaging method and packaging structure of the sensor, the commonly used packaging method of the optical fiber pressure sensor adopts epoxy resin adhesive sealing. However, since the epoxy resin adhesive is brittle, has poor peeling resistance, cracking resistance, and impact resistance, and poor mechanical shock and thermal shock resistance, it is easy to debond when the surface treatment is not thorough or the glue is left to air for too long after coating. Therefore, the use of epoxy resin adhesive alone in the packaging process is prone to failure in long-term monitoring in the high temperature and high pressure environment underground, resulting in liquid flow through the sensor device inside and outside, and the measured pressure value deviates from the actual pressure value, which has an adverse effect on the real-time monitoring of temperature and pressure. Therefore, the use of epoxy resin adhesive sealing alone will not play an effective sealing and isolation role. It is necessary to adopt a more rigorous and reliable packaging method in a high temperature and high pressure environment to increase the effective packaging life of the sensor. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a fiber optic high temperature and high pressure sensor packaging structure and method for oil and gas downhole exploration with reasonable design and long sensor service life.

[0007] The technical solution adopted to solve the above technical problems is: an optical fiber high-temperature and high-pressure sensor packaging structure for oil and gas downhole exploration, including an optical fiber connected to a fiber optic sensing structure, the optical fiber and the fiber optic sensing structure extend from one end of a metal outer tube into the metal outer tube, the fiber optic sensing structure is located in the middle of the metal outer tube, a thin steel tube is mounted on the optical fiber, one end of the thin steel tube is located inside the metal outer tube, and the other end is located outside the metal outer tube, an optical high-temperature curing glue segment is filled between the thin steel tube and the metal outer tube port, the end of the thin steel tube located inside the metal outer tube is located in the optical high-temperature curing glue segment, and the end face of the optical high-temperature curing glue segment is at a certain distance from the optical fiber sensing structure, and a filter is arranged on the other end of the metal outer tube.

[0008] As a preferred technical solution, one end of the thin steel tube close to the optical fiber sensing structure is fixedly connected to the optical fiber through low-temperature glass solder.

[0009] As a preferred technical solution, the filter is a metal sintered filter.

[0010] As a preferred technical solution, a plastic rubber sleeve is sleeved on one end of the thin steel tube located outside the metal outer tube and on the optical fiber pigtail.

[0011] As a preferred technical solution, the optical fiber is a metal-coated optical fiber.

[0012] The present invention also provides a packaging method for an optical fiber high temperature and high pressure sensor for oil and gas downhole exploration, comprising the following steps:

[0013] Step 1. Take a section of thin steel tube, insert the optical fiber connected with the optical fiber sensing structure into the thin steel tube, leave a certain distance L1 between the end of the thin steel tube close to the optical fiber sensing structure and the optical fiber sensing structure, peel off the optical fiber coating layer on the side of the optical fiber close to the optical fiber sensing structure and the thin steel tube at the connection, and fill it with glass solder, heat the thin steel tube with an electromagnetic induction heater to melt the glass solder, and then weld the optical fiber and the thin steel tube with the cooled glass solder;

[0014] Step 2. Place the optical fiber sensing structure with a thin steel tube made in step 1 inside the metal outer tube, fill a section of optical high-temperature curing glue between the thin steel tube and the end of the metal outer tube, the end of the thin steel tube inside the metal outer tube is located in the optical high-temperature curing glue section, and there is a certain distance L2 between the end face of the optical high-temperature curing glue section and the optical fiber sensing structure, L2<L1;

[0015] Step 3. A filter is installed on the other end of the metal outer tube, and a plastic rubber sleeve is installed on the end of the thin steel tube located outside the metal outer tube and the optical fiber pigtail to complete the packaging.

[0016] As a preferred technical solution, a certain distance L1=3~5cm is left between the end of the thin steel tube close to the optical fiber sensing structure and the optical fiber sensing structure; the end of the thin steel tube inside the metal outer tube is located in the optical high-temperature curing glue segment and the end face of the optical high-temperature curing glue segment and the optical fiber sensing structure have a certain distance L2=1~2cm.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention combines optical high temperature curing adhesive and adopts an optical fiber-metal low temperature glass solder welding method to achieve a better sealing effect and increase the packaging life of the sensor.

[0019] The present invention uses a metal sintered filter and a plastic rubber sleeve, thereby enhancing the sealing performance of the sensor package and protecting the sensor from being damaged by particulate impurities in external crude oil.

[0020] The optical fiber material and stainless steel material used in the present invention have good corrosion resistance and are suitable for the strong corrosion environment in oil and gas wells.

[0021] The all-fiber sensing structure selected by the present invention does not involve electromagnetic components and has the ability to resist electromagnetic interference that may exist in oil and gas wells.

[0022] The present invention improves the performance of the optical fiber sensor in the oil and gas well, so that the sensor can work stably and for a long time in a harsh environment of high temperature and high pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the packaging structure of the optical fiber sensor according to Example 1 of the present invention.

[0024] Figure 2 The sensor packaged in Example 1 was subjected to pressure testing at room temperature and 100 MPa and its pressure sensitivity.

[0025] Figure 3 The sensor packaged in Example 1 is subjected to a variable pressure test at room temperature to 150° C. and its pressure sensitivity.

[0026] Among them: single-mode optical fiber 1, plastic rubber sleeve 2, thin steel tube 3, optical high-temperature curing glue section 4, low-temperature glass solder section 5, metal outer tube 6, optical fiber sensing structure 7, metal sintered filter 8. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the following embodiments.

[0028] Example 1

[0029] exist Figure 1 In this embodiment, the packaging of an optical fiber pressure sensor based on a sensing suspended core structure for oil and gas well exploration is taken as an example. The sensor is composed of a single-mode optical fiber 1, a hollow-core optical fiber, and a thin-diameter optical fiber connected in sequence. The single-mode optical fiber has a metal coating on the outside, and the hollow-core optical fiber and the thin-diameter optical fiber are pure quartz materials without a coating layer. The hollow-core optical fiber and the thin-diameter optical fiber constitute the sensing structure 7 of the sensor.

[0030] The packaging structure of the optical fiber sensor for oil and gas well exploration in this embodiment, the single-mode optical fiber 1 and the optical fiber sensing structure 7 extend from one end of the metal outer tube 6 into the metal outer tube 6, the optical fiber sensing structure 7 is located in the middle of the metal outer tube 6, a thin steel tube 3 is mounted on the single-mode optical fiber 1, one end of the thin steel tube 3 is located in the metal outer tube 6, and the other end is located outside the metal outer tube 6, the end of the thin steel tube 3 located in the metal outer tube 6 is fixed to the single-mode optical fiber 1 through a low-temperature glass solder segment 5, and an optical high-temperature curing glue segment 4 is filled between the thin steel tube 3 and the end of the metal outer tube 6. The end of the thin steel tube 3 in the tube 6 is located in the optical high temperature curing glue section 4 and the end face of the optical high temperature curing glue section 4 is at a certain distance from the optical fiber sensing structure 7. A metal sintering filter 8 is installed on the other end of the metal outer tube 6 to provide the sensor with a stable liquid environment to protect the sensor and prevent particulate impurities that may exist in the external crude oil from entering the sensor tube body to damage the sensing structure 7. The metal sintering filter 8 plays a role in filtering crude oil in a single direction, and at the same time will not isolate the internal and external environment of the sensor, nor will it affect the sensor's measurement of downhole temperature and pressure. The thin steel tube 3 is located at one end of the outer side of the metal outer tube 6 and is covered with a plastic rubber sleeve 2 on the single-mode optical fiber 1 pigtail to protect the optical fiber.

[0031] The metal outer tube 6 and the thin steel tube 3 of the present embodiment are both made of 316L stainless steel, which is resistant to high temperatures and corrosion.

[0032] The packaging method of the optical fiber sensor of this embodiment includes the following steps:

[0033] Step 1. Take a section of thin steel tube 3, and insert the optical fiber connected to the optical fiber sensing structure 7 into the thin steel tube 3. Leave a certain distance L1=4cm between the end of the thin steel tube 3 close to the optical fiber sensing structure 7 and the optical fiber sensing structure 7, which can also be 3cm or 5cm. Peel off the optical fiber coating layer on the side of the optical fiber close to the optical fiber sensing structure 7 where it is connected to the thin steel tube 3, and fill it with glass solder. Heat the thin steel tube 3 through an electromagnetic induction heater to melt the low-temperature glass solder, and then weld the optical fiber to the thin steel tube 3 with the cooled solder.

[0034] Step 2. Place the optical fiber sensing structure 7 with the thin steel tube 3 manufactured in step 1 inside the metal outer tube 6, and fill a section of optical high-temperature curing glue, model 353ND, between the thin steel tube 3 and the end of the metal outer tube 6. The end of the thin steel tube 3 inside the metal outer tube 6 is located in the optical high-temperature curing glue section 4, and the end face of the optical high-temperature curing glue section 4 is at a certain distance L2=1.5cm from the optical fiber sensing structure 7, which can also be 1cm or 2cm.

[0035] Among them, the optical high temperature curing glue is a two-component optical AB glue, which needs to be evenly mixed in a ratio of 10:1 and defoamed before filling;

[0036] Step 3. The thin steel tube 3 is tightly connected to the tubular housing by deforming the copper threaded pressure cap;

[0037] Step 4. A filter is installed on the other end of the metal outer tube 6, and a plastic rubber sleeve 2 is mounted on the end of the thin steel tube 3 located outside the metal outer tube 6 and on the optical fiber pigtail to complete the packaging.

[0038] In order to verify the beneficial effects of the present invention, this embodiment performs a high voltage test on the sensor:

[0039] 1. The high temperature and high pressure simultaneous measurement capability was tested. The test results are as follows:

[0040] 1. Test Instrument

[0041] Pressure calibration device: pressure pump (ConST137A, 0~260MPa, hydraulic, Beijing Const), standard pressure calibrator (ConST211, 0~160MPa, accuracy: 0.02%, hydraulic, Beijing Const).

[0042] Temperature changing device: Electric heating blast drying oven (0~300℃, electric heating wire heating)

[0043] 2. Experimental Design and Results Analysis

[0044] A pressure calibrator with a calibration accuracy of 0.02% and a pressure range of 0MPa to 160MPa was used to carry out preliminary measurement of the oil pressure under laboratory conditions. The optical fiber temperature and pressure sensor was connected to the pressure pump adapter in the temperature chamber through a threaded interface, and the tail end of the sensor optical fiber was connected to the Si255 optical fiber demodulator through a jumper. The temperature and pressure test of the sensor was achieved through the pressure gauge step-up and step-down device and the temperature chamber temperature rise and fall, and the reflection spectrum was observed and recorded.

[0045] HCF-193-100, SMF-250-130, and TCF-80 were used to prepare the all-fiber suspended core stress concentration amplification structure, and the performance was tested under laboratory conditions. Under different temperature conditions, multiple groups of sensors were tested by boost and buck cycle tests, such as Figure 2 As shown, the test results show that the sensor performance is good under the conditions of temperature and pressure of 150℃ and 50MPa (such as Figure 3 As shown), it has good linearity, high sensitivity and good repeatability. It verifies that the structure can withstand the performance indicators of 150°C and 50MPa under the simultaneous action of temperature and pressure, and the sensor performance is stable. The repeatability and consistency of multiple tests are good, which verifies the effectiveness and reliability of the packaging method and can meet the actual application requirements of oil and gas wells.

[0046] 2. Pressure test of the sensor packaged by the present invention and the sensor packaged by common methods at room temperature and high pressure

[0047] Under laboratory conditions, the sensor packaged in the present invention can withstand a high pressure of 100 MPa at room temperature. Figure 2 As shown in the figure, compared with the situation that the top seal fails when the epoxy resin seal is used alone at a pressure test of only 10MPa, the overall pressure resistance performance has been improved by nearly 10 times. In addition, the sensor test performance is stable, and the repeatability and consistency of multiple tests are good, which verifies the long-term effectiveness and reliability of this packaging method.

Claims

1. An optical fiber high temperature and high pressure sensor packaging structure for oil and gas downhole exploration, comprising an optical fiber connected to an optical fiber sensing structure, characterized in that: The optical fiber and the optical fiber sensing structure extend from one end of the metal outer tube into the metal outer tube. The optical fiber sensing structure is located in the middle of the metal outer tube. A thin steel tube is mounted on the optical fiber. One end of the thin steel tube is located inside the metal outer tube and the other end is located outside the metal outer tube. An optical high-temperature curing glue segment is filled between the thin steel tube and the port of the metal outer tube. The end of the thin steel tube located inside the metal outer tube is located in the optical high-temperature curing glue segment and the end face of the optical high-temperature curing glue segment is at a certain distance from the optical fiber sensing structure. A filter is arranged on the other end of the metal outer tube.

2. The optical fiber high temperature and high pressure sensor packaging structure for oil and gas downhole exploration according to claim 1 is characterized in that: One end of the thin steel tube close to the optical fiber sensing structure is fixedly connected to the optical fiber through low-temperature glass solder.

3. The optical fiber high temperature and high pressure sensor packaging structure for oil and gas downhole exploration according to claim 1 or 2, characterized in that: The filter is a metal sintered filter.

4. The optical fiber high temperature and high pressure sensor packaging structure for oil and gas downhole exploration according to claim 3 is characterized in that: The thin steel tube is located at one end outside the metal outer tube and a plastic rubber sleeve is sleeved on the optical fiber pigtail.

5. The optical fiber high temperature and high pressure sensor packaging structure for oil and gas downhole exploration according to claim 4 is characterized in that: The optical fiber is a metal-coated optical fiber.

6. A packaging method for an optical fiber high temperature and high pressure sensor for oil and gas downhole exploration, characterized in that: The following steps are involved: Step 1. Take a section of thin steel tube, insert the optical fiber connected with the optical fiber sensing structure into the thin steel tube, leave a certain distance L1 between the end of the thin steel tube close to the optical fiber sensing structure and the optical fiber sensing structure, peel off the optical fiber coating layer on the side of the optical fiber close to the optical fiber sensing structure and the thin steel tube at the connection, and fill it with glass solder, heat the thin steel tube with an electromagnetic induction heater to melt the glass solder, and then weld the optical fiber and the thin steel tube with the cooled glass solder; Step 2. Place the optical fiber sensing structure with a thin steel tube made in step 1 inside the metal outer tube, fill a section of optical high-temperature curing glue between the thin steel tube and the end of the metal outer tube, the end of the thin steel tube inside the metal outer tube is located in the optical high-temperature curing glue section, and there is a certain distance L2 between the end face of the optical high-temperature curing glue section and the optical fiber sensing structure, L2<L1; Step 3. A filter is installed on the other end of the metal outer tube, and a plastic rubber sleeve is installed on the end of the thin steel tube located outside the metal outer tube and the optical fiber pigtail to complete the packaging.

7. The packaging method of the optical fiber high temperature and high pressure sensor for oil and gas downhole exploration according to claim 6, characterized in that: There is a certain distance L1=3~5cm between the end of the thin steel tube close to the optical fiber sensing structure and the optical fiber sensing structure; the end of the thin steel tube inside the metal outer tube is located in the optical high-temperature curing glue section and there is a certain distance L2=1~2cm between the end face of the optical high-temperature curing glue section and the optical fiber sensing structure.

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