Optical fiber pressure gauge, array type optical fiber pressure monitoring device outside sleeve and temperature and pressure monitoring method

Abstract

The invention relates to an optical fiber pressure meter, an array type optical fiber pressure monitoring device outside a sleeve and a temperature and pressure monitoring method, the monitoring device comprises a plurality of groups of monitoring units, and each monitoring unit comprises an optical fiber pressure meter and optical fiber couplers arranged at two ends of the optical fiber pressure meter; and the multiple groups of monitoring units are connected in series with an in-well optical cable to form the array type optical fiber pressure monitoring device. According to the monitoring device, the array type optical fiber pressure gauge is fixed to the casing pipe, the temperature and pressure of all sections in casing pipe well cementation operation can be monitored, optical fibers have the technical characteristics of high temperature resistance, corrosion resistance, high stability and the like, and the device is slightly affected by the environment and is good in stability; the monitoring device and the in-well optical cable integrally go down to the well in a winch mode, and the time of repeated splicing of optical fibers and the risk of splicing of the optical fibers can be reduced during field operation; and the optical fiber coupler and the optical fiber pressure gauge are directly fixed on the outer side of the sleeve through the protective cover respectively, so that the service life of the monitoring device is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield development and production, and in particular relates to an optical fiber pressure gauge, an array optical fiber pressure monitoring device outside a casing, and a temperature and pressure monitoring method. Background Art

[0002] Cementing is an important part of the drilling process. It can isolate the formation, protect and support the casing in the oil and gas well, and ensure the safety and high production of the oil well. If the cementing quality is unqualified, it may lead to safety hazards such as oil well cracking and penetration, which will have a serious impact on oil field production. At present, cementing quality detection is mainly carried out through acoustic amplitude logging, variable density logging and well temperature logging. Due to the harsh downhole environment, high temperature, high pressure and corrosiveness, the accuracy of the existing detection device is greatly affected by the environment and has poor stability. Therefore, higher requirements are put forward for cementing quality detection devices.

[0003] Optical fiber has the technical characteristics of high temperature resistance, corrosion resistance, high stability, etc. In recent years, with the development of distributed optical fiber acoustic monitoring (DAS), distributed optical fiber temperature monitoring (DTS), and optical fiber pressure monitoring, it has provided an important means for real-time dynamic monitoring of oil wells. It has been successfully applied to injection and production profile monitoring, hydraulic fracturing monitoring, intelligent well production monitoring, and other fields, and has achieved good results.

[0004] In view of the advantages of optical fiber monitoring in the field of oilfield development and production technology, and the importance of real-time monitoring of parameters during casing cementing, it is particularly necessary to establish an array optical fiber pressure monitoring device outside the casing and a temperature and pressure monitoring method. Summary of the invention

[0005] In view of at least one of the problems in the above-mentioned prior art, the purpose of the present invention is to provide a fiber optic pressure gauge, an array-type fiber optic pressure monitoring device outside the casing, and a temperature and pressure monitoring method. The array-type fiber optic pressure gauge is fixed on the casing to monitor the temperature and pressure of each section in the casing cementing operation. The device is less affected by the environment and has good stability.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A fiber optic pressure gauge comprises an upper ferrule sealing joint, an upper sealing ring, an upper temperature-pressure cavity short section, a temperature-pressure sensing module, a pressure transmission short section, a lower temperature-pressure cavity short section, a lower sealing ring, and a lower ferrule sealing joint connected in sequence, wherein the temperature-pressure sensing module is arranged at one end of the pressure transmission short section and extends into the upper temperature-pressure cavity short section, a pressure transmission hole connected to the outside is opened in the pressure transmission short section, and the temperature-pressure sensing module senses the external temperature and pressure through the pressure transmission hole; the temperature-pressure sensing module is connected to the fiber core passing through the fiber optic pressure gauge.

[0007] A casing outer array optical fiber pressure monitoring device comprises a plurality of monitoring units, wherein the monitoring units comprise the above optical fiber pressure gauge and optical fiber connectors arranged at both ends thereof; the plurality of monitoring units are connected in series with the downhole optical cable to form an array optical fiber pressure monitoring device.

[0008] Preferably, the optical fiber pressure gauge and the optical fiber connector are connected via a steel tube optical cable.

[0009] Preferably, the steel tube optical cable comprises an outer steel tube, an inner steel tube and a fiber core which are wrapped in sequence from the outside to the inside. The steel tube optical cable at both ends of the optical fiber pressure gauge has the outer steel tube fixed to the upper sealing ring and the lower sealing ring respectively through the upper ferrule sealing joint and the lower ferrule sealing joint; the inner steel tube is fixed to the two ends of the optical fiber pressure gauge respectively through the upper sealing ring and the lower sealing ring, and the fiber core passes through the optical fiber pressure gauge and is connected to the temperature and pressure sensing module.

[0010] Preferably, a through hole is provided in the pressure transmission short section, and the fiber core passes through the through hole and penetrates the fiber optic pressure gauge.

[0011] Preferably, cavities are provided in both the upper temperature-pressure cavity short section and the lower temperature-pressure cavity short section, the inner steel pipe is respectively fixed at both ends of the upper temperature-pressure cavity short section and the lower temperature-pressure cavity short section, and the fiber core passes through the cavity in the upper temperature-pressure cavity short section, the through hole and the cavity in the lower temperature-pressure cavity short section in sequence.

[0012] Preferably, a fiber optic pressure gauge protective cover is provided outside the fiber optic pressure gauge, and a fiber optic pressure gauge card slot is longitudinally opened on the inner wall of the fiber optic pressure gauge, and the fiber optic pressure gauge card slot is clamped in the fiber optic pressure gauge protective cover for fixing the fiber optic pressure gauge on the casing. Preferably, a fiber optic connector cover is provided outside the fiber optic connector, and a fiber optic connector slot is longitudinally opened on the inner wall thereof, the fiber optic connector is clamped in the fiber optic connector slot, and the fiber optic connector cover is used to fix the fiber optic connector on the sleeve.

[0013] A method for monitoring temperature and pressure outside a casing is implemented based on the above-mentioned array optical fiber pressure monitoring device outside the casing, and comprises the following steps: Connecting multiple groups of monitoring units in series with the optical cables going into the well to form an array type optical fiber pressure monitoring device; The monitoring device and the optical cable for entering the well are integrally winched, and the performance of the optical cable is tested after connection; The optical fiber cable is lowered into the well according to the set lowering depth, and during the lowering process, the optical fiber pressure gauge and the optical fiber connector are fixed on the outside of the casing; After the downhole optical cable is lowered into place, the temperature and pressure in the casing cementing operation are monitored in real time by the optical fiber pressure gauge, and the data collected by the optical fiber pressure gauge is transmitted to an external control console through the downhole optical cable.

[0014] Preferably, in the step of fixing the optical fiber connector and the optical fiber pressure gauge on the outside of the casing, the optical fiber connector and the optical fiber pressure gauge are fixed on the outside of the casing by means of an optical fiber pressure gauge cover and an optical fiber connector cover, respectively.

[0015] The present invention adopts the above technical solution, which has the following advantages: 1. The optical fiber pressure gauge provided by the present invention can monitor the external temperature and pressure through the temperature and pressure sensing module, and transmit the information to the external control console in real time through the optical fiber.

[0016] 2. The array-type optical fiber pressure monitoring device outside the casing provided by the present invention fixes the array-type optical fiber pressure gauge on the casing, which can monitor the temperature and pressure of each section in the casing cementing operation. The optical fiber has the technical characteristics of high temperature resistance, corrosion resistance, high stability, etc. The device is less affected by the environment and has good stability.

[0017] 3. The casing external temperature and pressure monitoring method provided by the present invention is to lower the monitoring device and the optical cable into the well by an integral winch, which can reduce the time and risk of multiple optical fiber splicing during on-site operations; the optical fiber splicer and the optical fiber pressure gauge are directly fixed to the outside of the casing through protective covers, respectively, thereby increasing the service life of the monitoring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an outer casing array optical fiber pressure monitoring device provided by an embodiment of the present invention.

[0019] Figure 2 It is a structural schematic diagram of a fiber optic pressure gauge provided in one embodiment of the present invention.

[0020] Figure 3 It is a schematic structural diagram of a fiber optic pressure gauge shield provided by an embodiment of the present invention.

[0021] Figure 4 It is a schematic structural diagram of a fiber optic connector cover provided by an embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of the structure of an array-type optical fiber pressure monitoring device outside the casing provided by an embodiment of the present invention entering a well.

[0023] Figure 6 The figure is a schematic diagram of the structure of a well optical cable winch provided by one embodiment of the present invention.

[0024] Figure 7It is a flow chart of the casing external temperature and pressure monitoring method provided in the second embodiment of the present invention.

[0025] Markings in the accompanying drawings: 1 is a fiber optic pressure gauge, 101 is an upper ferrule sealing joint, 102 is an upper sealing ring, 103 is an upper temperature and pressure cavity short section, 104 is a temperature and pressure sensing module, 105 is a pressure transmission short section, 106 is a lower temperature and pressure cavity short section, 107 is a lower sealing ring, 108 is a lower ferrule sealing joint, 109 is a pressure transmission hole, 110 is a through hole, 2 is a fiber optic connector, 3 is a steel tube cable, 301 is an outer steel tube, 302 is an inner steel tube, 303 is a fiber core, 4 is a fiber optic pressure gauge shield, 401 is a fiber optic pressure gauge slot, 5 is a fiber optic connector shield, and 501 is a fiber optic connector slot. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "backward", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. The arrows in the accompanying drawings represent the flow direction of the substance.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "assembly", "setting", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention provides an optical fiber pressure gauge, an array optical fiber pressure monitoring device outside a casing, and a temperature and pressure monitoring method. The array optical fiber pressure gauge is fixed on the casing, which can monitor the temperature and pressure of each section in the casing cementing operation. The device is less affected by the environment and has good stability.

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Example 1 Please refer to Figure 2 The present embodiment provides an optical fiber pressure gauge 1, which includes an upper ferrule sealing joint 101, an upper sealing ring 102, an upper temperature-pressure cavity short section 103, a temperature-pressure sensing module 104, a pressure transmission short section 105, a lower temperature-pressure cavity short section 106, a lower sealing ring 107, and a lower ferrule sealing joint 108, which are connected in sequence. The temperature-pressure sensing module 104 is provided with one end of the pressure transmission short section 105 and extends into the upper temperature-pressure cavity short section 103. A pressure transmission hole 109 connected to the outside is opened in the pressure transmission short section 105. The temperature-pressure sensing module 104 senses the external temperature and pressure through the pressure transmission hole 109; the temperature-pressure sensing module 104 is connected to the core 201 passing through the optical fiber pressure gauge 1.

[0032] Specifically, the pressure transmission sub 105 is cylindrical, and has external threads at both ends. The pressure transmission hole 109 is an L-shaped hole, one end of which has an outlet on the outer wall of the pressure transmission sub 105, and the other end is connected to the temperature and pressure sensing module 104, and the temperature and pressure sensing module 104 can monitor the external temperature and pressure through the pressure transmission hole 109. A through hole 110 is opened in the pressure transmission sub 105, and the fiber core passes through the through hole 110 to penetrate the optical fiber pressure gauge 1.

[0033] The upper temperature and pressure cavity short section 103 and the lower temperature and pressure cavity short section 106 are both provided with cavities, and the interfaces where the upper temperature and pressure cavity short section 103 and the lower temperature and pressure cavity short section 106 are connected to the pressure transmission short section 105 are provided with internal threads, and the upper temperature and pressure cavity short section 103 and the lower temperature and pressure cavity short section 106 are respectively connected to the pressure transmission short section 105 through threads. The outer ends of the upper temperature and pressure cavity short section 103 and the lower temperature and pressure cavity short section 106 are both provided with external threaded studs extending outward, and the centers of the external threaded studs are provided with a central hole penetrating therethrough.

[0034] The two ends of the upper sealing ring 102 are respectively threadedly connected to the upper ferrule sealing joint 101 and the upper temperature and pressure cavity short section 103, and the three components are provided with holes suitable for the passage of optical cables. Similarly, the two ends of the lower sealing ring 107 are respectively threadedly connected to the lower temperature and pressure cavity short section 106 and the lower ferrule sealing joint 108, and the three components are also provided with holes suitable for the passage of optical cables, thereby being able to meet the requirements of the optical cable optical fiber pressure gauge 1.

[0035] In this embodiment, the upper ferrule sealing joint 101, the upper sealing ring 102, the lower sealing ring 107 and the lower ferrule sealing joint 108 are all made of metal and have metal sealing rings inside.

[0036] Please refer to Figure 1 and Figure 2 The present embodiment provides an array-type optical fiber pressure monitoring device outside the casing, comprising a plurality of monitoring units, wherein the monitoring units include the above-mentioned optical fiber pressure gauge 1 and optical fiber connectors 2 arranged at both ends thereof; the plurality of monitoring units are connected in series with the downhole optical cable to form an array-type optical fiber pressure monitoring device.

[0037] A single optical fiber pressure gauge 1 is equipped with two optical fiber connectors 2 as a group, and multiple groups are designed in series to form a downhole array pressure monitoring design to meet the downhole multi-point array pressure and temperature monitoring requirements.

[0038] In a specific application, the optical fiber pressure gauge 1 and the optical fiber connector 2 are connected via a steel tube optical cable 3, and the optical fiber connector 2 is a prior art product. The steel tube optical cable 3 includes an outer steel tube 301, an inner steel tube 302 and a fiber core 303 which are wrapped in sequence from the outside to the inside. The fiber core 303 is composed of multiple single optical fibers. The steel tube optical cable 3 at both ends of the optical fiber pressure gauge 1 has an outer steel tube 301 which is fixed on an upper sealing ring 102 and a lower sealing ring 107 through an upper ferrule sealing joint 101 and a lower ferrule sealing joint 108 respectively; the upper ferrule sealing joint 101 and the lower ferrule sealing joint 108 are both tubular structures, and one end of the inner side thereof is an internal threaded hole; the upper sealing ring 102 and the lower sealing ring 107 are also tubular structures, and one end of the outer side thereof is an externally threaded tube, and the upper sealing ring 102 and the lower sealing ring 107 are threadedly connected to the upper ferrule sealing joint 101 and the lower ferrule sealing joint 108 respectively; the inner ends of the upper sealing ring 102 and the lower sealing ring 107 are internally threaded holes, which are respectively connected to the upper ferrule sealing joint 101 and the lower ferrule sealing joint 108. The two ends of the upper temperature-pressure cavity short section 103 and the lower temperature-pressure cavity short section 106 are threadedly connected; the outer steel pipe 301 at the upper end extends into the upper sealing ring 102 through the upper ferrule sealing joint 101; the inner steel pipe 302 extends into the upper temperature-pressure cavity short section 103 through the upper sealing ring 102, and the fiber core 303 enters the cavity of the temperature-pressure cavity short section 103, an optical fiber in the fiber core 303 is connected to the temperature-pressure sensing module 104, and the other optical fibers pass through the pressure transmission short section 105; similarly, the fiber core 303 enters the lower temperature-pressure cavity short section 106; the inner steel pipe 302 at the other end enters the lower sealing ring 107 through the lower temperature-pressure cavity short section 106, and the outer steel pipe 301 passes through the lower ferrule sealing joint 108 through the lower sealing ring 107; the steel pipe optical cables 3 at both ends of the optical fiber pressure gauge 1 are connected to the optical fiber connector 2, and the optical fiber connector 2 is then connected to the downhole optical cable. In order to facilitate on-site construction, the monitoring unit needs to be prefabricated in the factory and then connected to the optical cable going into the well.

[0039] Please refer to Figures 3 to 5 In this embodiment, a fiber optic pressure gauge protective cover 4 is provided outside the fiber optic pressure gauge 1. The fiber optic pressure gauge protective cover 4 is a petal-type annular hoop, and a fiber optic pressure gauge card slot 401 is longitudinally opened on its inner wall. The fiber optic pressure gauge card slot 401 is a longitudinally penetrating groove. The fiber optic pressure gauge 1 is clamped in the fiber optic pressure gauge card slot 401. The fiber optic pressure gauge protective cover 4 is used to fix the fiber optic pressure gauge 1 on the casing. The fiber optic pressure gauge protective cover 4 can protect the fiber optic pressure gauge 1 and increase the service life of the fiber optic pressure gauge 1. In this embodiment, the optical fiber connector outer 2 is provided with an optical fiber connector cover 5, which has the same structure as the optical fiber pressure gauge cover 4, and is a petal-type annular hoop, and the inner wall thereof is longitudinally provided with an optical fiber connector slot 501, and the optical fiber connector slot 501 is a longitudinally penetrating groove, and the optical fiber connector 2 is clamped in the optical fiber connector slot 501, and the optical fiber connector cover 5 is used to fix the optical fiber connector 2 on the sleeve. The optical fiber connector cover 5 can protect the optical fiber connector outer 2 and improve the service life of the optical fiber connector outer 2.

[0040] Example 2 Please refer to Figure 7 The present embodiment provides a method for monitoring temperature and pressure outside a casing, which is based on the casing array optical fiber pressure monitoring device in Embodiment 1 and includes the following steps: S01, connecting multiple groups of monitoring units and downhole optical cables in series to form an array type optical fiber pressure monitoring device; S02, winch the monitoring device and the optical cable into the well as a whole, and perform a performance test on the optical cable after connection; S03, lowering the optical cable into the well according to the set running depth, and fixing the optical fiber pressure gauge 1 and the optical fiber connector 2 on the outside of the casing during the running process; S04. After the optical fiber cable is lowered into place, the temperature and pressure in the casing cementing operation are monitored in real time through the optical fiber pressure gauge 1, and the data collected by the optical fiber pressure gauge is transmitted to the external control console through the optical fiber cable.

[0041] For specific applications, please refer to Figure 6 According to the requirements of well monitoring, the optical fiber connector 2 and the optical fiber pressure gauge 1 are connected in series with the optical cable in the workshop in advance to form an array optical fiber pressure monitoring device, and the optical cable is integrally capstan. During field operations, the time for multiple optical fiber splicing and the risk of optical fiber splicing can be reduced.

[0042] In this embodiment, in the step of fixing the optical fiber pressure gauge 1 and the optical fiber connector 2 on the outside of the casing, the optical fiber pressure gauge 1 and the optical fiber connector 2 are fixed on the outside of the casing by the optical fiber pressure gauge cover 4 and the optical fiber connector cover 5 respectively, so as to protect the optical fiber pressure gauge 1 and the optical fiber connector 2.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical fiber pressure gauge, characterized in that: It includes an upper ferrule sealing joint, an upper sealing ring, an upper temperature and pressure cavity short section, a temperature and pressure sensing module, a pressure transmission short section, a lower temperature and pressure cavity short section, a lower sealing ring, and a lower ferrule sealing joint which are connected in sequence. The temperature and pressure sensing module is arranged at one end of the pressure transmission short section and extends into the upper temperature and pressure cavity short section. A pressure transmission hole connected to the outside is opened in the pressure transmission short section. The temperature and pressure sensing module senses the external temperature and pressure through the pressure transmission hole. The temperature and pressure sensing module is connected to the core passing through the optical fiber pressure gauge.

2. An array-type optical fiber pressure monitoring device outside a casing, characterized in that: It comprises a plurality of monitoring units, wherein the monitoring units comprise the optical fiber pressure gauge as claimed in claim 1 and optical fiber connectors arranged at both ends thereof; the plurality of monitoring units are connected in series with the downhole optical cable to form an array optical fiber pressure monitoring device.

3. The outer-casing array optical fiber pressure monitoring device according to claim 2, characterized in that: The optical fiber pressure gauge and the optical fiber connector are connected via a steel tube optical cable.

4. The outer-casing array optical fiber pressure monitoring device according to claim 3, characterized in that: The steel tube optical cable comprises an outer steel tube, an inner steel tube and an optical core which are wrapped in sequence from the outside to the inside. The steel tube optical cable at both ends of the optical fiber pressure gauge has the outer steel tube fixed to the upper sealing ring and the lower sealing ring respectively through the upper ferrule sealing joint and the lower ferrule sealing joint; the inner steel tube is fixed to the two ends of the optical fiber pressure gauge respectively through the upper sealing ring and the lower sealing ring, and the optical core passes through the optical fiber pressure gauge and is connected to the temperature and pressure sensing module.

5. The outer-casing array optical fiber pressure monitoring device according to claim 4, characterized in that: A through hole is provided in the pressure transmission short section, and the fiber core passes through the through hole and penetrates the optical fiber pressure gauge.

6. The outer-casing array optical fiber pressure monitoring device according to claim 5, characterized in that: The upper temperature-pressure cavity short section and the lower temperature-pressure cavity short section are both provided with cavities, the inner steel pipe is respectively fixed at both ends of the upper temperature-pressure cavity short section and the lower temperature-pressure cavity short section, and the fiber core passes through the cavity in the upper temperature-pressure cavity short section, the through hole and the cavity in the lower temperature-pressure cavity short section in sequence.

7. The outer-casing array optical fiber pressure monitoring device according to claim 2, characterized in that: The fiber optic pressure gauge is provided with a fiber optic pressure gauge protective cover outside the fiber optic pressure gauge, and a fiber optic pressure gauge card slot is longitudinally opened on the inner wall of the fiber optic pressure gauge. The fiber optic pressure gauge is clamped in the fiber optic pressure gauge card slot, and the fiber optic pressure gauge protective cover is used to fix the fiber optic pressure gauge on the casing.

8. The outer-casing array optical fiber pressure monitoring device according to claim 2, characterized in that: The optical fiber connector is provided with an optical fiber connector cover outside, and an optical fiber connector slot is longitudinally opened on the inner wall thereof. The optical fiber connector is clamped in the optical fiber connector slot, and the optical fiber connector cover is used to fix the optical fiber connector on the sleeve.

9. A method for monitoring temperature and pressure outside a casing, characterized in that: The outer-casing array optical fiber pressure monitoring device according to any one of claims 2 to 7 is completed, comprising the following steps: Connecting multiple groups of monitoring units in series with the optical cables going into the well to form an array type optical fiber pressure monitoring device; The monitoring device and the optical cable for entering the well are integrally winched, and the performance of the optical cable is tested after connection; The optical fiber cable is lowered into the well according to the set lowering depth, and during the lowering process, the optical fiber pressure gauge and the optical fiber connector are fixed on the outside of the casing; After the downhole optical cable is lowered into place, the temperature and pressure in the casing cementing operation are monitored in real time by the optical fiber pressure gauge, and the data collected by the optical fiber pressure gauge is transmitted to an external control console through the downhole optical cable.

10. The casing external temperature and pressure monitoring method according to claim 9, characterized in that: In the step of fixing the optical fiber connector and the optical fiber pressure gauge on the outside of the casing, the optical fiber connector and the optical fiber pressure gauge are fixed to the outside of the casing by means of an optical fiber pressure gauge cover and an optical fiber connector cover, respectively.

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