WO2022088512A1 - 密绕光纤型超敏油井传感光缆 - Google Patents

密绕光纤型超敏油井传感光缆 Download PDF

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WO2022088512A1
WO2022088512A1 PCT/CN2021/071275 CN2021071275W WO2022088512A1 WO 2022088512 A1 WO2022088512 A1 WO 2022088512A1 CN 2021071275 W CN2021071275 W CN 2021071275W WO 2022088512 A1 WO2022088512 A1 WO 2022088512A1
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optical fiber
elastic
sensing optical
sensing
oil well
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PCT/CN2021/071275
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English (en)
French (fr)
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饶云江
韩冰
姚家珍
栗鸣
***
蒋新力
曹珊珊
吴明埝
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电子科技大学
中天电力光缆有限公司
江苏中天科技股份有限公司
四川光盛物联科技有限公司
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Publication of WO2022088512A1 publication Critical patent/WO2022088512A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/268—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light using optical fibres

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  • the invention relates to the technical field of sensing optical cables, in particular to a densely wound optical fiber type ultra-sensitive oil well sensing optical cable.
  • optical fiber distributed sensing technology uses the sensing optical cable as the sensing medium, which can detect the information of each point on the optical fiber in the sensing optical cable, and the spatial resolution and cost performance are much higher. Therefore, when optical fiber distributed sensing technology is applied to oil and gas exploration and development in wells, the detection efficiency is significantly improved, the overall cost is greatly reduced, and it has huge social and economic benefits.
  • the sensing fibers in the optical cable used are mostly vertical or wound around the central reinforcing member with a large pitch, and the sensitivity of the sensing optical cable is limited.
  • the existing sensing optical cables since most of the existing sensing optical cables only contain a single optical fiber, it is difficult to realize multi-parameter measurement when a single-wavelength signal light source is used.
  • the existing ordinary sensing optical cables are mostly used in normal temperature environments such as ground monitoring or pipeline security monitoring, and it is difficult to meet the requirements for the sensing optical cables to have good high temperature resistance for oil and gas exploration and development in wells.
  • the present invention provides a densely wound optical fiber type ultra-sensitive oil well sensing optical cable.
  • the method of using the sensing optical fiber intermittently and tightly wound on the elastic sensitization structure can effectively The sensitivity of the sensing optical cable is improved, so that it can meet the requirements of high precision and high efficiency in oil and gas exploration and development in wells.
  • Densely wound optical fiber type ultra-sensitive oil well sensing optical cable including outer sheath, solidified layer, sensing optical fiber, elastic sensitization structure and tensile strength member; the sensing fiber is wound on the elastic sensitized structure and fixed by the solidified layer.
  • the sensing fiber consists of staggered densely wound sections and non-densely wound sections.
  • the densely wound section of the sensing fiber is wound on the elastic sensitizing structure with a pitch of 100 ⁇ m to 1 mm; the non-densely wound section of the sensing fiber is wound on the elastic sensitization structure with a pitch of 1 mm to 1000 mm.
  • the sensing fiber includes a single-mode fiber, and the single-mode fiber passes through two optical signals of different wavelengths, so as to realize the simultaneous separation and measurement of the acoustic wave and the temperature.
  • the sensing fiber includes two single-mode fibers, and the two single-mode fibers are respectively used for the measurement of sound waves and temperature.
  • the outer sheath and the elastic sensitization structure are made of high temperature resistant material; the surface of the sensing optical fiber is coated with a high temperature resistant material coating.
  • the elasticity-sensitizing structure is a solid structure.
  • the elastic sensitization structure is a hollow structure composed of an elastic support layer and an air layer.
  • a metal support layer is provided between the elastic support layer and the air layer.
  • the outer surface of the elastic sensitization structure is coated with a metal sensitization layer.
  • the metal sensitization layer is made of copper.
  • the sensing optical fiber of the present invention is tightly wound on the elastic sensitization structure by using the staggered densely wound section and non-densely wound section structure, which can ensure a longer sensing distance and make the winding part of the optical fiber per unit length.
  • the actual length is longer, and the scattered light signal accumulated by external disturbance changes more strongly.
  • the deformation and temperature change of the elastic sensitizing structure under the influence of the external environment can further improve the deformation and temperature change of the sensing optical fiber, so that the sound pressure sensitivity and temperature sensitivity of the sensing optical cable can be improved by orders of magnitude.
  • the present invention injects detection signal light of different wavelengths into the sensing optical fiber in the sensing optical fiber through the wavelength division multiplexing technology, and separates and demodulates the signal light of different wavelengths at the receiving end, which can realize the simultaneous multi-parameter synchronization of a single sensing optical fiber Measurement.
  • the optical cable of the present invention is applied to the field of optical fiber distributed sensing technology.
  • the outer sheath is made of materials such as high temperature resistant polyether ether ketone, and the sensing optical fiber is coated with high temperature resistant materials such as polyimide. Silicone rubber
  • the elastic sensitization structure is made of high temperature resistant materials with low Young's modulus, so that the optical cable has the characteristics of high temperature resistance, making it more suitable for long-term monitoring in oil and gas wells in the high temperature environment of 200-300 °C.
  • a metal sensitization layer is coated on the inner elastic sensitization structure of the sensing optical cable, while ensuring that the elastic sensitizing structure improves the sound pressure sensitivity of the sensing optical cable, the thermal conductivity of the elastic sensitizing structure is further improved, and the Sensing the temperature change of the optical fiber to improve the temperature sensitivity of the sensing optical cable.
  • FIG. 1 is a schematic cross-sectional view of the present invention
  • FIG. 2 is a schematic diagram of the winding structure of the sensing optical fiber and the elastic sensitization structure of the present invention
  • FIG. 3 is a schematic diagram of the light intensity integral effect along the distance when the sensing optical fiber is not wound when the temperature changes according to the present invention
  • FIG. 4 is a schematic diagram of the light intensity integral effect along the distance when the sensing optical fiber is wound when the temperature changes according to the present invention
  • FIG. 5 is a schematic diagram of a hollow elastic sensitization structure of the present invention.
  • FIG. 6 is a schematic diagram of an elastic sensitization structure containing a metal support layer of the present invention.
  • FIG. 7 is a schematic diagram of an elastic sensitization structure coated with a metal sensitization layer of the present invention.
  • FIGS. 1-2 and Figures 5-7 are schematic structural diagrams of the densely wound optical fiber type ultra-sensitive oil well sensing cable according to some embodiments of the present application. Introduced around the fiber-optic ultra-sensitive oil well sensing cable. It should be noted that FIGS. 1 to 2 and FIGS. 5 to 7 are only examples, and do not limit the specific shape and structure of the densely wound optical fiber type ultra-sensitive oil well sensing cable.
  • the densely wound optical fiber type ultra-sensitive oil well sensing optical cable includes an outer sheath 1, a cured layer 2, a sensing optical fiber 3, an elastic sensitization structure 4 and a tensile strength member 6;
  • the sensing fiber 3 is wound on the elastic sensitizing structure 4 and fixed by the solidified layer 2, and the sensing fiber 3 is composed of densely wound sections and non-densely wound sections distributed in a staggered manner.
  • the sensing optical fiber 3 is tightly wound on the elastic sensitizing structure 4 by means of staggered densely wound sections and non-densely wound section structures, which can ensure a longer sensing distance and make the winding part unit length.
  • the actual length of the optical fiber is longer, and the scattered light signal accumulated by the external disturbance changes more strongly.
  • the deformation and temperature change of the elastic sensitizing structure 4 under the influence of the external environment can further enhance the deformation and temperature change of the sensing optical fiber 3, so that the sound pressure sensitivity and temperature sensitivity of the sensing optical cable can be improved by orders of magnitude.
  • the outer sheath 1 and the tensile strength member 6 are used to protect the sensing optical fiber 3 and the elastic sensitization structure 4 and enhance the overall strength of the optical cable.
  • the tensile strength member 6 is an armored structure formed by winding steel wires.
  • the cured layer 2 is formed by curing glue.
  • the cured layer 2 can also play a certain protective role on the sensing fiber 3 .
  • the densely wound section of the sensing fiber 3 is wound on the elastic sensitization structure with a pitch of 100 ⁇ m ⁇ 1 mm; the non-densely wound section of the sensing fiber 3 is wound on the elastic sensitization structure 4 with a pitch of 1 mm to 1000 mm. superior.
  • the winding method of the sensing optical fiber 3 is shown in FIG. 2 .
  • a section of the sensing optical fiber 3 is wound on the elastic sensitization structure 4 with a certain prestress and a larger pitch of 1 mm to 1000 mm, and a section is close to the elastic sensitization structure 4 with no gap. It is wound laterally or wound on the elastic sensitization structure 4 with a smaller pitch of 100 ⁇ m to 1 mm, and so on.
  • the densely wound section of the sensing optical fiber 3 is tightly wound on the elastomer sensitizing structure 4 to enhance the sound pressure and temperature sensitivity of the sensing optical cable, and the non-densely wound section of the sensing optical fiber 3 is wound on the elastic sensitizing structure 4 with a larger pitch. to prevent the fiber from breaking due to bending.
  • the sensing fiber 3 includes a single-mode fiber, and the single-mode fiber has two optical signals of different wavelengths passing through it, so as to simultaneously realize the separate measurement of the acoustic wave and the temperature.
  • the sensing optical fiber 3 transmits detection signal lights of two different wavelengths at the same time, and a single optical cable can measure multiple parameters at the same time through the wavelength division multiplexing technology, which greatly improves the measurement of the sensing optical fiber 3 efficiency.
  • the temperature information detected by the system can not only monitor the changes of the external environment in real time, but also can be used to perform temperature compensation for the distributed acoustic wave sensing system.
  • the sensing fiber 3 in some embodiments, a structure in which the sensing fiber includes two single-mode fibers can also be used, and the two single-mode fibers are respectively used for the measurement of sound waves and temperature.
  • the sound pressure sensitivity of an optical fiber refers to the ratio of the phase difference of the optical fiber caused by the acoustic signal to the free-field sound pressure at the center of the sound field:
  • phase change of the light beam transmitted in the sensing fiber 3 due to the effect of sound pressure can be divided into two parts, one part is the phase change caused by the sound pressure directly acting on the sensing fiber 3 The other part is that the deformation caused by the sound pressure acting on the elastic sensitizing structure 4 drives the sensing fiber 3 to produce a phase change.
  • L is the effective sensing length of the fiber
  • ⁇ is the propagation constant in the fiber
  • n is the core refractive index of the fiber
  • D is the core diameter
  • V is the normalized frequency
  • V is the normalized waveguide refractive index of the fiber.
  • b has a certain corresponding relationship.
  • ⁇ L 1 is the change in length of the optical fiber directly under the action of external pressure
  • ⁇ L 2 is the change in the length of the optical fiber caused by the deformation of the elastic sensitizing structure 4 under the action of sound pressure.
  • the present invention adopts the structure in which the sensing optical fiber 3 is intermittently and tightly wound on the elastic sensitizing structure 4, which can significantly improve the sound pressure sensitivity of the sensing optical fiber cable.
  • the Stokes photon number N s and the anti-Stokes photon number N a are:
  • K s and Ka are the coefficients related to the cross-section of Stokes light and anti-Stokes light, respectively
  • S is the backscattering factor
  • v s and v a are Stokes and anti-Stokes light , respectively frequency of Stokes light
  • ⁇ 0 , ⁇ s , ⁇ a are the transmission losses of incident light
  • Stokes scattered light and anti-Stokes scattered light respectively
  • z is the distance of the point to be measured
  • R s (T) and R a (T) are the coefficients related to the number of layouts on the low and high energy levels of the fiber molecule, respectively.
  • the external temperature change can be sensed, and the relationship between the number of photons is:
  • the optical fiber distributed temperature sensing technology is to integrate the Raman scattered light intensity in the optical fiber within the system spatial resolution range to calculate and invert the external temperature.
  • the Raman scattered light The intensity is only enhanced at the temperature change point. If the spatial resolution is greater than the thermal radiation range, there will be a measurement error between the calculated results of the system and the actual temperature field; however, as shown in Figure 4, the sensing fiber 3 is wound around the elastic sensitization structure 4
  • the actual length of the sensing fiber 3 per unit length can be increased, that is, when the external temperature field changes, even if the spatial resolution is greater than the thermal radiation range, the Raman scattered light intensity calculated by the DTS system integral in the unit length is still accurate, and the system precision and higher spatial resolution.
  • the spatial resolution of the DTS system is 20m
  • the sensing fiber 3 is tightly wound on an elastic body with an outer diameter of 15mm
  • the actual distance of winding the 20m sensing fiber 3 is 0.106m.
  • the received signal strength of DTS can be increased by 22.76dB at this time.
  • the outer sheath 1 and the elastic sensitization structure 4 are made of high temperature resistant material; the surface of the sensing optical fiber 3 is coated with a high temperature resistant material coating.
  • the outer sheath 1 can be made of a high-temperature-resistant polyetheretherketone material
  • the sensing fiber 3 can be coated with a high-temperature-resistant material such as polyimide, and a low Young's modulus such as silicone rubber can be used.
  • a large amount of high temperature resistant material is used to make the elastic sensitization structure 4, so that the optical cable has high temperature resistance characteristics, making it more suitable for long-term monitoring in oil and gas wells in a high temperature environment of 200-300 °C.
  • the elasticity-sensitizing structure 4 is a solid structure.
  • the elastic sensitization structure 4 of the solid structure has high mechanical strength, but has many consumables, and the overall weight of the optical cable is heavier.
  • the elastic sensitization structure 4 is a hollow structure composed of an elastic support layer 401 and an air layer 402 .
  • the sensitivity of the elastic sensitizing structure 4 of the hollow structure is higher than that of the solid structure, the total weight of the optical cable is lighter, the consumables are less, but the mechanical strength is slightly worse.
  • the Young's modulus of the core of the sensing fiber 3 is 72GPa
  • the Poisson's ratio is 0.17
  • the Young's modulus of the elastic support layer 401 in the elastic sensitizing structure 4 is 500MPa
  • the Poisson's ratio is 0.465
  • the outer diameter is 15mm
  • the inner diameter is 6mm
  • the sound pressure sensitivity of the sensing fiber 3 is -184.45dB re rad/ ⁇ Pa through calculation
  • the sound pressure sensitivity of the sensing fiber 3 after being wound around the elastic sensitizing structure 4 is -155.39dB re rad/ ⁇ Pa.
  • a metal support layer 403 is disposed between the elastic support layer 401 and the air layer 402 .
  • the metal support layer 403 can enhance the mechanical strength of the optical sensing cable, so as to overcome the problem of low mechanical strength of the elastic sensitizing structure 4 of the hollow structure while ensuring the sensitivity.
  • the Young's modulus of the metal support layer 403 is 70.3 GPa
  • the Poisson's ratio is 0.345
  • the outer diameter is 8 mm
  • the inner diameter is 6 mm.
  • the sound pressure sensitivity of the single-mode sensing fiber 301 after winding is -156.79dB re rad/ ⁇ Pa.
  • the outer surface of the elastic sensitizing structure 4 is coated with a metal sensitizing layer 5 .
  • the elastic sensitization structure 4 is coated with a metal sensitization layer 5 to improve the temperature sensitivity of the sensing optical cable.
  • the temperature sensitivity of the Raman scattering-based DTS using the anti-Stokes Raman backscattering demodulation method can be expressed as:
  • h is the Planck coefficient
  • k is the Boltzmann constant
  • ⁇ v is the fiber phonon frequency
  • T 0 is the real-time fiber temperature
  • T is the temperature change in a local area of the fiber.
  • the thermal conductivity of SiO 2 is about 7.6W/mK
  • the thermal conductivity of metal is about 30-300W/mK.
  • the metal sensitizing layer 5 is made of copper. Since copper has good thermal conductivity, the thermal conductivity of the elastic sensitization structure 4 can be improved, so as to improve the temperature sensitivity of the optical sensing cable.
  • the diameter of the elastic sensitizing structure 4 is 0.5 cm ⁇ 2 cm.

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Abstract

一种密绕光纤型超敏油井传感光缆，包括抗拉加强件（6）、外护套（1）、固化层（2）、传感光纤（3）和弹性增敏结构（4）。传感光纤（3）缠绕在弹性增敏结构（4）上并通过固化层（2）固定，传感光纤（3）由交错分布的密绕段和非密绕段构成。传感光纤（3）包括两根单模光纤，两根单模光纤分别用于声波和温度的测量。传感光缆的声压灵敏度及温度灵敏度显著提高，可用于井中高温环境下长时间、高灵敏的勘探与开发监测。

Description

密绕光纤型超敏油井传感光缆 技术领域
本发明涉及传感光缆技术领域，具体是指密绕光纤型超敏油井传感光缆。
背景技术
传统井中油气勘探采用电子检波器进行测试，每次测量中单个电子检波器仅能测量单点信息，串联多个电子检波器的方案成本较高，难以实现单炮覆盖全井范围的探测。然而，光纤分布式传感技术利用传感光缆作为传感媒介，可以对传感光缆内光纤上每一点的信息进行探测，空间分辨率及性价比要高很多。因此，光纤分布式传感技术应用于井中油气勘探开发时，探测效率显著提升，整体成本大幅下降，具有巨大的社会及经济效益。
现有光纤分布式传感***在实际应用中，使用的光缆内传感光纤多为竖直状态或以较大螺距缠绕于中心加强件，传感光缆灵敏度有限。同时，由于现有传感光缆内部大多仅包含单根光纤，在使用单波长信号光源的情况下难以实现多参量测量。此外，现有普通传感光缆多应用于地面监测或管道安防监测等常温环境，难以满足井中油气勘探开发对传感光缆具有良好耐高温性能的要求。
发明内容
基于以上技术问题，本发明提供了一种密绕光纤型超敏油井传感光缆，针对现有传感光缆灵敏度较低的问题，利用传感光纤间断紧密缠绕于弹性增敏结构的方法，有效提升了传感光缆的灵敏度，使其满足井中油气勘探开发高精度、高效率的要求。
为解决以上技术问题，本发明采用的技术方案如下：
密绕光纤型超敏油井传感光缆，包括外护套、固化层、传感光纤、弹性增敏结构和抗拉加强件；传感光纤缠绕在弹性增敏结构上并通过固化层固定，传感光纤由交错分布的密绕段和非密绕段构成。
作为一种优选的方式，传感光纤的密绕段以100μm～1mm的螺距缠绕在弹性增敏结构上；传感光纤的非密绕段以1mm～1000mm的螺距缠绕在弹性增敏结构上。
作为一种优选的方式，传感光纤包括一根单模光纤，单模光纤内通过有两个不同波长的光信号，用于实现同时对声波和温度的分离测量。
作为一种优选的方式，传感光纤包括两根单模光纤，两根单模光纤分别用于声波和温度的测量。
作为一种优选的方式，外护套、所述弹性增敏结构采用耐高温材料制成；传感光纤表面涂覆有耐高温材料涂层。
作为一种优选的方式，弹性增敏结构为实心结构。
作为一种优选的方式，弹性增敏结构为弹性支撑层和空气层构成的空心结构。
作为一种优选的方式，弹性支撑层和空气层之间设有金属支撑层。
作为一种优选的方式，弹性增敏结构外表面镀有金属增敏层。
作为一种优选的方式，金属增敏层由铜构成。
与现有技术相比，本发明的有益效果是：
(1)本发明传感光纤利用交错分布的密绕段和非密绕段结构间断紧密缠绕在弹性增敏结构上，可在保证较长传感距离的同时，使缠绕部分单位长度上的光纤实际长度更长，受到外界扰动累积的散射光信号变化更强。且弹性增敏结构受到外界环境影响产生形变及温度变化可进一步提升传感光纤产生形变及温度变化，使得传感光缆的声压灵敏度及温度灵敏度能够得到数量级的提高。
(2)本发明通过波分复用技术向传感光缆内传感光纤打入不同波长的探测信号光，在接收端对不同波长信号光分离解调，可实现单根传感光缆多参量同时测量。
(3)本发明光缆应用于光纤分布式传感技术领域，通过采用耐高温的聚醚醚酮等材料制作外护套，聚酰亚胺等耐高温材料对传感光纤进行涂覆，硅橡胶等低杨氏模量的耐高温材料制作弹性增敏结构，使光缆具备耐高温特性，使其更适于在200～300℃高温环境的油气井中进行长久监测。
(4)本发明通过传感光缆内弹性增敏结构外镀一层金属增敏层，在保证弹性增敏结构提升传感光缆声压灵敏度的同时，提高弹性增敏结构的导热性能，进一步提升传感光纤温度变化，提高传感光缆的温度灵敏度。
附图说明
本申请将以示例性实施例的方式进一步说明，这些示例性实施例将通过附图进行详细描述，其中：
图1为本发明的横截面示意图；
图2为本发明的传感光纤与弹性增敏结构缠绕结构示意图；
图3为本发明的温度变化时传感光纤未缠绕时沿距离的光强积分效应示意图；
图4为本发明的温度变化时传感光纤缠绕时沿距离的光强积分效应示意图；
图5为本发明的空心弹性增敏结构示意图；
图6为本发明的含有金属支撑层的弹性增敏结构示意图；
图7为本发明的镀有金属增敏层的弹性增敏结构示意图。
其中，1外护套，2固化层，3传感光纤，4弹性增敏结构，401弹性支撑层，402空气层，403金属支撑层，5金属增敏层，6抗拉加强件。
具体实施方式
为使本公开实施例的目的、技术方案和优点更加清楚，下面将结合本公开实施例的附图，对本公开实施例的技术方案进行清楚、完整地描述。显然，所描述的实施例是本公开的一部分实施例，而不是全部的实施例。基于所描述的本公开的实施例，本领域普通技术人员在无需创造性劳动的前提下所获得的所有其他实施例，都属于本公开保护的范围。
除非另外定义，本公开使用的技术术语或者科学术语应当为本公开所属领域内具有一般技能的人士所理解的通常意义。本公开中使用的“第一”、“第二”以及类似的词语并不表示任何顺序、数量或者重要性，而只是用来区分不同的组成部分。“包括”或者“包含”等类似的词语意指出现该词前面的元件或者物件涵盖出现在该词后面列举的元件或者物件及其等同，而不排除其他元件或者物件。“连接”或者“相连”等类似的词语并非限定于物理的或者机械的连接，而是可以包括电性的连接，不管是直接的还是间接的。“上”、“下”、“左”、“右”等仅用于表示相对位置关系，当被描述对象的绝对位置改变后，则该相对位置关系也可能相应地改变。
图1～2和图5～7是本申请一些实施例所示的密绕光纤型超敏油井传感光缆的结构示意图，以下将结合图1～2和图5～7对本申请所涉及的密绕光纤型超敏油井传感光缆进行介绍。需要注意的是，图1～2和图5～7仅作为示例，并不对密绕光纤型超敏油井传感光缆的具体形状和结构形成限定。
参阅图1～2，在本实施方式中，密绕光纤型超敏油井传感光缆包括外护套1、固化层2、传感光纤3、弹性增敏结构4和抗拉加强件6；传感光纤3缠绕在弹性增敏结构4上并通过固化层2固定，传感光纤3由交错分布的密绕段和非密绕段构成。
在本实施例中，传感光纤3利用交错分布的密绕段和非密绕段结构间断紧密缠绕在弹性增敏结构4上，可在保证较长传感距离的同时，使缠绕部分单位长度上的光纤实际长度更长，受到外界扰动累积的散射光信号变化更强。且弹性增敏结构4受到外界环境影响产生形变及温度变化可进一步提升传感光纤3产生形变及温度变化，使得传感光缆的声压灵敏度及温度灵敏度能够得到数量级的提高。
其中，外护套1与抗拉加强件6用于对传感光纤3和弹性增敏结构4进行保护并增强光缆整体强度。具体的，抗拉加强件6为钢丝缠绕形成的铠装结构。
具体的，固化层2是胶水固化形成的。固化层2除用于加固传感光纤3与弹性增敏结构4的连接外，亦可对传感光纤3起到一定的保护作用。
在一些实施例中，传感光纤3的密绕段以100μm～1mm的螺距缠绕在弹性增敏结构上；传感光纤3的非密绕段以1mm～1000mm的螺距缠绕在弹性增敏结构4上。
在本实施例中，传感光纤3的缠绕方式如图2所示，传感光纤3一段以一定预应力以1mm～1000mm较大螺距缠绕于弹性增敏结构4上，一段以无缝隙紧挨横向缠绕或以100μm～1mm较小螺距缠绕于弹性增敏结构4上，往复如此。其中，传感光纤3密绕段紧密缠绕在弹性体增敏结构4上以增强传感光缆的声压及温度灵敏度，传感光纤3非密绕段以较大螺距缠绕于弹性增敏结构4上以防止光纤受弯曲影响断裂。
在一些实施例中，传感光纤3包括一根单模光纤，单模光纤内通过有两个不同波长的光信号，用于同时实现对声波和温度的分离测量。
在本实施例中，传感光纤3中同时传输两个不同波长的探测信号光，通过波分复用技术使得单根光缆可对多个参量同时进行测量，大大提高了传感光纤3的测量效率。此外，***探测到的温度信息除可实时监测外界环境变化外，还可用于对分布式声波传感***进行温度补偿。
此外，对于传感光纤3来说，在一些实施例中，亦可采用传感光纤包括两根单模光纤的结构，两根单模光纤分别用于声波和温度的测量。
其中，本实施例中所述的密绕光纤型超敏油井传感光缆其灵敏度提高的原理如下：
首先，光纤的声压灵敏度是指声信号引起的光纤的相位差与声场中心位置处的自由场声压的比值：
Figure PCTCN2021071275-appb-000001
其中，
Figure PCTCN2021071275-appb-000002
由于声压作用导致的传感光纤3中传输光束的相位变化可分为两部分，一部分是声压直接作用在传感光纤3上引起的相位变化
Figure PCTCN2021071275-appb-000003
另一部分是声压作用于弹性增敏结构4引起的形变带动传感光纤3产生相位变化
Figure PCTCN2021071275-appb-000004
可表示为：
Figure PCTCN2021071275-appb-000005
其中，L为光纤有效传感长度，β为光纤中的传播常数，n为光纤的纤芯折射率，D为 纤芯直径，V为归一化频率，V与光纤的归一化波导折射率b有一定的对应关系。ΔL 1为由光纤直接在外界压力作用下的长度变化，ΔL 2为弹性增敏结构4在声压作用下的形变引起的光纤长度变化。
通过计算可知，
Figure PCTCN2021071275-appb-000006
比
Figure PCTCN2021071275-appb-000007
高一个数量级，因此声压作用于弹性增敏结构4产生形变带动传感光纤3内光束的相位变化远大于声压单独施加在传感光纤3上引起的光束相位变化。因此，本发明中采用传感光纤3间断紧密缠绕于弹性增敏结构4的结构，可以显著提高传感光缆的声压灵敏度。
其次，在光纤中，斯托克斯光子数N s及反斯托克斯光子数N a为：
Figure PCTCN2021071275-appb-000008
其中，K s和K a分别为与斯托克斯光和反斯托克斯光截面有关的系数，S为后向散射因子，v s和v a分别为斯托克斯和反斯托克斯光的频率，α 0、α s、α a分别为入射光、斯托克斯散射光和反斯托克斯散射光的传输损耗，z为待测点距离，R s(T)和R a(T)分别为与光纤分子低能级和高能级上的布局数有关的系数。
根据已知的T 0时刻传感光纤3中的斯托克斯和反斯托克斯光子数，可以对外界温度变化进行传感，其光子数变化关系为：
Figure PCTCN2021071275-appb-000009
光纤分布式温度传感技术是将***空间分辨率范围内光纤中的拉曼散射光强度进行积分计算反演外界温度，如图3所示，当传感光纤3未缠绕时，拉曼散射光强仅在温度变化点处增强，若空间分辨率大于热辐射范围，***的计算结果与实际温度场将产生测量误差；而如图4所示，将传感光纤3缠绕于弹性增敏结构4上可提高单位长度内传感光纤3的实际长度，即在外界温度场发生变化时，即使空间分辨率大于热辐射范围，单位长度内DTS***积分计算的拉曼散射光强度仍准确，***精度及空间分辨率更高。在本实施例中，DTS***空间分辨率为20m，将传感光纤3紧密缠绕于外径15mm的弹性体上，则缠绕20m传感光纤3的实际距离为0.106m。根据上述公式可知，此时DTS的接收信号强度可提高22.76dB。
在一些实施例中，外护套1、弹性增敏结构4采用耐高温材料制成；传感光纤3表面涂覆有耐高温材料涂层。
具体的，在在本实施例中，可采用耐高温的聚醚醚酮材料制作外护套1，聚酰亚胺等耐 高温材料对传感光纤3进行涂覆，硅橡胶等低杨氏模量的耐高温材料制作弹性增敏结构4，使光缆具备耐高温特性，使其更适于在200～300℃高温环境的油气井中进行长久监测。
在一些实施例中，弹性增敏结构4为实心结构。实心结构的弹性增敏结构4机械强度高，但耗材多，光缆总体重量较重。
参阅图5，在一些实施例中，弹性增敏结构4为弹性支撑层401和空气层402构成的空心结构。
在本实施例中，空心结构的弹性增敏结构4灵敏度相对于实心结构更高，光缆总重量较轻，耗材少，但是机械强度略差。假设传感光纤3的纤芯杨氏模量为72GPa，泊松比为0.17，弹性增敏结构4中的弹性支撑层401的杨氏模量为500MPa，泊松比为0.465，外径为15mm，内径为6mm，通过计算可知传感光纤3的声压灵敏度为-184.45dB re rad/μPa，而经缠绕于弹性增敏结构4后传感光纤3的声压灵敏度为-155.39dB re rad/μPa。
参阅图6，在一些实施例中，弹性支撑层401和空气层402之间设有金属支撑层403。金属支撑层403可增强传感光缆的机械强度，以此在保证灵敏度的同时，克服空心结构弹性增敏结构4机械强度低的问题。假设传感光纤3及弹性增敏结构4中的弹性支撑层401的参数不变，金属支撑层403的杨氏模量为70.3GPa，泊松比为0.345，外径为8mm，内径为6mm，则此时缠绕后单模传感光纤301的声压灵敏度为-156.79dB re rad/μPa。
参阅图7，在一些实施例中，弹性增敏结构4外表面镀有金属增敏层5。
通过弹性增敏结构4镀有金属增敏层5，以提高传感光缆的温度灵敏度。
基于拉曼散射的DTS的采用反斯托克斯拉曼背向散射解调方法得到的温度灵敏度可表示为：
Figure PCTCN2021071275-appb-000010
其中，h为普朗克系数，k为玻尔兹曼常数，Δv为光纤声子频率，T 0为实时光纤温度，T为光纤某局域处温度变化量。而SiO 2的导热系数约为7.6W/mK，金属的导热系数约为30～300W/mK。当本发明中传感光纤3间断紧密缠绕于表面镀有金属增敏层5的弹性增敏结构4上时，密绕段传感光纤3局域温度变化量更大，光纤拉曼散射光子通量更多，则温度灵敏度更高。
优选的，金属增敏层5由铜构成。由于铜具有良好的导热性能，可以此提高弹性增敏结构4的导热性能，以提高传感光缆的温度灵敏度。
具体的，弹性增敏结构4直径为0.5cm～2cm。
如上即为本发明的实施例。上述实施例以及实施例中的具体参数仅是为了清楚表述发明的验证过程，并非用以限制本发明的专利保护范围，本发明的专利保护范围仍然以其权利要求书为准，凡是运用本发明的说明书及附图内容所作的等同结构变化，同理均应包含在本发明的保护范围内。

Claims (10)

  1. 密绕光纤型超敏油井传感光缆，其特征在于，包括抗拉加强件(6)、外护套(1)、固化层(2)、传感光纤(3)和弹性增敏结构(4)；
    所述传感光纤(3)缠绕在弹性增敏结构(4)上并通过固化层(2)固定，所述传感光纤(3)由交错分布的密绕段和非密绕段构成。
  2. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述传感光纤(3)的密绕段以100μm～1mm的螺距缠绕在弹性增敏结构(4)上；
    所述传感光纤(3)的非密绕段以1mm～1000mm的螺距缠绕在弹性增敏结构(4)上。
  3. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述传感光纤(3)包括一根单模光纤，所述单模光纤内通过有两个不同波长的光信号，用于实现同时对声波和温度的分离测量。
  4. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述传感光纤(3)包括两根单模光纤，两根单模光纤分别用于声波和温度的测量。
  5. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述外护套(1)、所述弹性增敏结构(4)采用耐高温材料制成；
    所述传感光纤(3)表面涂覆有耐高温材料涂层。
  6. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述弹性增敏结构(4)为实心结构。
  7. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述弹性增敏结构(4)为弹性支撑层(401)和空气层(402)构成的空心结构。
  8. 根据权利要求7所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述弹性支撑层(401)和空气层(402)之间设有金属支撑层(403)。
  9. 根据权利要求1所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述弹性增敏结构(4)外表面镀有金属增敏层(5)。
  10. 根据权利要求9所述的密绕光纤型超敏油井传感光缆，其特征在于：
    所述金属增敏层(5)由铜构成。
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