Sensing Device and Method for Monitoring Submarine Pipeline Subjected to Seabed Shear Stress

Abstract

The present invention discloses a sensing device and method for monitoring the shear stress of deep - sea pipelines by the seabed. The sensing device includes a housing, a differential pressure sensor, a sensing probe, and a connecting pipe. The beneficial technical effect of the present invention is that it proposes a sensing device and method for monitoring the shear stress of deep - sea pipelines by the seabed. This solution can eliminate the influence of the background static pressure caused by deep - sea water on the detection signal, enabling us to measure tiny shear stresses under the conditions of high water pressure in the deep sea.

Description

Technical Field

[0001] The present invention relates to a deep - sea pipeline safety monitoring technology, and particularly to a sensing device and method for monitoring the shear stress of a deep - sea pipeline by the seabed. Background Art

[0002] With the gradual advancement of ocean economic development towards the deep sea, the demand for monitoring deep - sea structures is increasing continuously. Typical application scenarios include: deep - sea oil and gas pipelines, floating production storage and offloading (FPSO) platforms for oil and gas exploitation and the steel catenary risers (SCRs) they use, underwater cables used in deep - sea or far - sea wind power platforms, etc. Under the influence of factors such as ocean currents and harsh weather conditions, pipelines laid on the seabed may gradually drift (for example, some pipelines are laid in a straight line, and under the long - term action of ocean currents, the pipeline may drift into an S - shape), ultimately leading to pipeline damage. When the pipeline drifts, it will displace relative to the seabed. By detecting the shear stress of the seabed on the pipeline, drift monitoring can be achieved. Therefore, it is necessary to monitor the shear stress of the deep - sea pipeline by the seabed.

[0003] In the prior art, for the pipeline safety monitoring in the deep - sea environment, the common means are regular inspection by remotely operated vehicle (ROV) and fiber - optic sensing. Although regular inspection by ROV does not require infrastructure construction, it cannot achieve online real - time monitoring, and the later manual and operation and maintenance costs are high. Although fiber - optic sensing can achieve online real - time monitoring, the construction and equipment costs are high. More importantly, the fiber - optic sensing system is greatly affected by vibration, cannot accurately measure the shear stress in a dynamic environment, and is easily affected by internal waves of ocean currents underwater, resulting in a high false - alarm rate.

[0004] The shear - force measurement means used on land mainly rely on piezoelectric materials or strain materials. However, in the deep sea with high hydrostatic pressure, the on - land detection means will be affected by the background water pressure and cannot measure tiny stresses. Summary of the Invention

[0005] In view of the problems in the background art, the present invention proposes a sensing device for monitoring the shear stress of a deep - sea pipeline by the seabed. The innovation lies in that: the sensing device includes a housing, a differential pressure sensor, a sensing probe, and a connecting pipe;

[0006] The differential pressure sensor is encapsulated in the housing;

[0007] The sensing probe is composed of a sensing rigid pipe and a pressure - guiding pipe; the sensing rigid pipe is composed of a main pipe and a plurality of sensing heads; the main pipe is a single - port pipe, and the port of the main pipe is connected to the outer port of the pressure - guiding pipe; when the axis of the main pipe is horizontally arranged, the sensing heads are arranged on the lower side surface of the main pipe, the axis of the sensing head is parallel to the radial direction of the main pipe, the sensing head is provided with a cavity inside and is communicated with the inner cavity of the main pipe, and the plurality of sensing heads are distributed in an array form on the lower side surface of the main pipe; the upper side surface of the main pipe is recorded as the installation surface;

[0008] The inner port of the pressure guiding pipe is communicated with the first input port of the differential pressure sensor; the sensing rigid pipe is placed outside the housing;

[0009] The sensing rigid pipe and the pressure guiding pipe are filled with a liquid pressure guiding medium; a first through hole matching the pressure guiding pipe is arranged on the housing, and the middle part of the pressure guiding pipe is connected with the first through hole through a first connector;

[0010] The inner port of the communicating pipe is communicated with the second input port of the differential pressure sensor, and the outer port of the communicating pipe is placed outside the housing; a second through hole matching the communicating pipe is arranged on the housing, and the middle part of the communicating pipe is connected with the second through hole through a second connector.

[0011] The function of the housing is to isolate seawater, bear the deep-sea pressure, and protect the differential pressure sensor. Specifically, when implemented, a material with a certain strength and seawater corrosion resistance should be used for production;

[0012] The sensing probe is fixed on the lower side of the deep-sea pipeline. When laying the deep-sea pipeline, the sensing probe sinks to the seabed together with the deep-sea pipeline. Multiple induction heads on the sensing probe will insert into the seabed sludge. When the deep-sea pipeline drifts, the induction heads will be forced to deform, thereby changing the pressure of the internal liquid pressure guiding medium;

[0013] The pressure guiding pipe is used to connect the sensing probe and the first input port of the differential pressure sensor;

[0014] The communicating pipe is used to connect the external environmental water body and the second input port of the differential pressure sensor;

[0015] The differential pressure sensor is used to obtain the pressure difference sensed by the first input port and the second input port.

[0016] The connector plays a role in sealing, connecting and supporting, and can be preferably selected from the prior art.

[0017] Preferably, the installation surface is an inner concave cylindrical surface, and the axial direction of the cylindrical surface is parallel to the axial direction of the main pipe. The cylindrical surface matches the outer shape of the deep-sea pipeline, which can improve the connection stability between the sensing probe and the deep-sea pipeline.

[0018] Preferably, the material of the sensing rigid pipe is titanium-based metal, high-silicon cast iron or vulcanized rubber.

[0019] Based on the foregoing sensing device, the present invention also provides a method for monitoring the submarine shear stress on a deep - sea pipeline. The hardware involved includes multiple sensing devices and a processing device; the structure of a single sensing device is as described above; the output parts of multiple differential pressure sensors are connected to the processing device through electrical cables; the specific method is as follows: The lower side of the deep - sea pipeline is in contact with the seabed. Along the direction of the deep - sea pipeline, a monitoring point is set at a certain interval on the lower side of the deep - sea pipeline. The method includes:

[0020] 1) A sensing device is set at each monitoring point; when setting a single sensing device, before laying the deep - sea pipeline, the main pipe is set on the lower side of the deep - sea pipeline at the monitoring point, the axial direction of the main pipe is parallel to the axial direction of the deep - sea pipeline, and the shell is fixed on the outer wall of the deep - sea pipeline; the sensing device is laid to the seabed together with the deep - sea pipeline;

[0021] 2) After putting into operation, the processing device periodically identifies the output signals of each differential pressure sensor. If the output signal of the differential pressure sensor exceeds the set threshold, it indicates that the deep - sea pipeline has drifted at the corresponding part.

[0022] Traditional shear - force measurement means mainly rely on piezoelectric materials or strain materials, which are not suitable for application in the deep - sea conditions of large depth and high static pressure. The main reasons are as follows: Under deep - sea conditions, the detection signals obtained by traditional means include the background static pressure caused by deep - sea water bodies, sensor noise, and actual strain force. Since the background static pressure caused by deep - sea water bodies is much greater than the actual strain force (usually, the drift process is relatively slow and the stress change is also relatively small), and the sensor noise is proportional to the background static pressure, this will cause the sensor noise to be similar to the actual strain force, thus seriously affecting the dynamic range and accuracy of the sensing device.

[0023] The idea of the present invention is: The main pipe is connected to the deep - sea pipeline and laid to the seabed synchronously with the deep - sea pipeline. After the deep - sea pipeline is laid, the sensing head on the main pipe will be inserted into the seabed silt; after a certain sensing device is put into operation, if there is no drift at the corresponding part of the pipeline, the relative position between the sensing head and the seabed will not change. The signal measured by the differential pressure sensor corresponding to the first input port is "background static pressure A + sensor noise A", and at the same time, the signal corresponding to the second input port is "background static pressure B + sensor noise B". Since the sensing rigid pipe, the pressure - guiding pipe, and the connecting pipe are all at the same depth position in the sea, the background static pressure caused by the water pressure is the same. Therefore, "background static pressure A = background static pressure B", and because it is the same differential pressure sensor, the sensor noise corresponding to the two input ports is the same. So, "sensor noise A = sensor noise B". At this time, through the processing of the differential pressure sensor, the signals corresponding to the two input ports cancel each other out, and the finally obtained output signal is "0";

[0024] When the corresponding part of the pipeline drifts, since the main pipe is connected to the deep-sea pipeline, the main pipe will move along with the deep-sea pipeline. And the sensing head, because it is inserted into the seabed silt and has a relatively small size, will deform under the blocking effect of the silt, resulting in the liquid pressure-conducting medium in the sensing rigid pipe being squeezed. At this time, the signal corresponding to the first input port measured by the differential pressure sensor is "background static pressure A + sensor noise A + sensing strain force" (the sensing strain force is the acting force generated by the squeezing of the liquid pressure-conducting medium), and the signal corresponding to the second input port is still "background static pressure B + sensor noise B". As mentioned above, since the background static pressure and sensor noise corresponding to the two input ports can cancel each other out, the final output signal of the differential pressure sensor at this time is the "sensing strain force". Based on the "sensing strain force" and its value, we can know whether the corresponding part has drifted and the severity of the drift, and finally can achieve online real-time monitoring of the deep-sea pipeline drift. After adopting the solution of the present invention, the background static pressure and sensor noise caused by the deep-sea high water pressure can be self-canceled, solving the problem that the prior art cannot measure the micro-deformation stress under the deep-sea high water pressure condition.

[0025] Preferably, the deep-sea pipeline is an oil pipeline, a gas pipeline, a steel catenary riser or an underwater cable.

[0026] The beneficial technical effect of the present invention is: a sensing device and method for monitoring the deep-sea pipeline subjected to the seabed shear stress are proposed. This solution can eliminate the influence of the background static pressure caused by the deep-sea water body on the detection signal, enabling us to measure the micro-shear stress under the deep-sea high water pressure condition. Description of the Drawings

[0027] Figure 1 、Schematic diagram of the structure of the sensing device;

[0028] Figure 2 、Schematic diagram of the usage state of the sensing device;

[0029] Figure 3 、Schematic diagram of the lower side of the sensing rigid pipe;

[0030] Figure 4 、Schematic diagram of the outer end face of the sensing rigid pipe;

[0031] The names corresponding to each mark in the figure are: housing 1, differential pressure sensor 2, sensing rigid pipe 3, main pipe 31, sensing head 32, pressure-conducting pipe 4, connecting pipe 5, seabed silt layer 6, deep-sea pipeline 7. Detailed Embodiment

[0032] A sensing device for monitoring the deep-sea pipeline subjected to the seabed shear stress, the innovation of which is: the sensing device includes a housing 1, a differential pressure sensor 2, a sensing probe and a connecting pipe 5;

[0033] The differential pressure sensor 2 is encapsulated in the housing 1;

[0034] The sensing probe is composed of a sensing rigid tube 3 and a pressure guiding tube 4; the sensing rigid tube 3 is composed of a main tube 31 and a plurality of induction heads 32; the main tube 31 is a single-port tube, and the port of the main tube 31 is connected to the outer port of the pressure guiding tube 4; when the main tube 31 is axially horizontally arranged, the induction heads 32 are arranged on the lower side surface of the main tube 31, the axis of the induction heads 32 is parallel to the radial direction of the main tube 31, the induction heads 32 are internally provided with cavities and are communicated with the inner cavity of the main tube 31, and the plurality of induction heads 32 are distributed in an array form on the lower side surface of the main tube 31; the upper side surface of the main tube 31 is denoted as the mounting surface;

[0035] The inner port of the pressure guiding tube 4 is communicated with the first input port of the differential pressure sensor 2; the sensing rigid tube 3 is placed outside the housing 1;

[0036] The sensing rigid tube 3 and the pressure guiding tube 4 are filled with a liquid pressure guiding medium; a first through hole matching the pressure guiding tube 4 is arranged on the housing 1, and the middle part of the pressure guiding tube 4 is connected to the first through hole through a connector I;

[0037] The inner port of the communicating tube 5 is communicated with the second input port of the differential pressure sensor 2, and the outer port of the communicating tube 5 is placed outside the housing 1; a second through hole matching the communicating tube 5 is arranged on the housing 1, and the middle part of the communicating tube 5 is connected to the second through hole through a connector II.

[0038] Further, the mounting surface is a concave cylindrical surface, and the axis of the cylindrical surface is parallel to the axis of the main tube 31.

[0039] Further, the material of the sensing rigid tube 3 is titanium-based metal, high-silicon cast iron or vulcanized rubber.

[0040] A method for monitoring the submarine shear stress on a deep-sea pipeline, the involved hardware includes a plurality of sensing devices and a processing device; a single sensing device includes a housing 1, a differential pressure sensor 2, a sensing probe and a communicating tube 5;

[0041] The differential pressure sensor 2 is encapsulated in the housing 1;

[0042] The sensing probe is composed of a sensing rigid tube 3 and a pressure guiding tube 4; the sensing rigid tube 3 is composed of a main tube 31 and a plurality of induction heads 32; the main tube 31 is a single-port tube, and the port of the main tube 31 is connected to the outer port of the pressure guiding tube 4; when the main tube 31 is axially horizontally arranged, the induction heads 32 are arranged on the lower side surface of the main tube 31, the axis of the induction heads 32 is parallel to the radial direction of the main tube 31, the induction heads 32 are internally provided with cavities and are communicated with the inner cavity of the main tube 31, and the plurality of induction heads 32 are distributed in an array form on the lower side surface of the main tube 31; the upper side surface of the main tube 31 is denoted as the mounting surface;

[0043] The inner port of the pressure guiding pipe 4 communicates with the first input port of the differential pressure sensor 2; the sensing rigid pipe 3 is placed outside the housing 1;

[0044] The sensing rigid pipe 3 and the pressure guiding pipe 4 are filled with a liquid pressure guiding medium; a first through hole matching the pressure guiding pipe 4 is provided on the housing 1, and the middle part of the pressure guiding pipe 4 is connected to the first through hole through a first connector;

[0045] The inner port of the communicating pipe 5 communicates with the second input port of the differential pressure sensor 2, and the outer port of the communicating pipe 5 is placed outside the housing 1; a second through hole matching the communicating pipe 5 is provided on the housing 1, and the middle part of the communicating pipe 5 is connected to the second through hole through a second connector;

[0046] The output parts of multiple differential pressure sensors 2 are connected to the processing device through electric cables;

[0047] Its innovation lies in that: the lower side of the deep-sea pipeline contacts the seabed, and along the direction of the deep-sea pipeline, a monitoring point is set at a certain distance interval on the lower side of the deep-sea pipeline; the method includes:

[0048] 1) A sensing device is set at each monitoring point; when setting a single sensing device, before laying the deep-sea pipeline, the main pipe 31 is set on the lower side of the deep-sea pipeline at the monitoring point, the axis of the main pipe 31 is parallel to the axis of the deep-sea pipeline, and the housing 1 is fixed on the outer wall of the deep-sea pipeline; the sensing device is laid to the seabed together with the deep-sea pipeline;

[0049] 2) After putting into operation, the processing device periodically identifies the output signals of each differential pressure sensor 2. If the output signal of the differential pressure sensor 2 exceeds the set threshold value, it indicates that the deep-sea pipeline has drifted at the corresponding position.

[0050] Further, the deep-sea pipeline is an oil pipeline, a gas pipeline, a steel catenary riser or an underwater cable.

Claims

1. A method for monitoring the submarine shear stress on a deep - sea pipeline, and the involved hardware includes multiple sensing devices and a processing device; a single sensing device includes a housing (1), a differential pressure sensor (2), a sensing probe, and a connecting pipe (5); The differential pressure sensor (2) is encapsulated in the housing (1); The sensing probe consists of a sensing rigid pipe (3) and a pressure - guiding pipe (4); the sensing rigid pipe (3) is composed of a main pipe (31) and multiple induction heads (32); the main pipe (31) is a single - port pipe, and the port of the main pipe (31) is connected to the outer port of the pressure - guiding pipe (4); when the main pipe (31) is axially horizontally arranged, the induction heads (32) are arranged on the lower side surface of the main pipe (31), the axis of the induction heads (32) is parallel to the radial direction of the main pipe (31), a cavity is arranged inside the induction heads (32) and is communicated with the inner cavity of the main pipe (31), and multiple induction heads (32) are distributed in an array form on the lower side surface of the main pipe (31); the upper side surface of the main pipe (31) is recorded as the installation surface; The inner port of the pressure - guiding pipe (4) is communicated with the first input port of the differential pressure sensor (2); the sensing rigid pipe (3) is placed outside the housing (1); The sensing rigid pipe (3) and the pressure - guiding pipe (4) are filled with a liquid pressure - guiding medium; a first through - hole matching the pressure - guiding pipe (4) is arranged on the housing (1), and the middle part of the pressure - guiding pipe (4) is connected to the first through - hole through a connector one; The inner port of the connecting pipe (5) is communicated with the second input port of the differential pressure sensor (2), and the outer port of the connecting pipe (5) is placed outside the housing (1); a second through - hole matching the connecting pipe (5) is arranged on the housing (1), and the middle part of the connecting pipe (5) is connected to the second through - hole through a connector two; The output parts of multiple differential pressure sensors (2) are connected to the processing device through electrical cables; Characterized in that: The lower side surface of the deep - sea pipeline contacts the seabed, and along the direction of the deep - sea pipeline, a monitoring point is set at a certain distance interval on the lower side surface of the deep - sea pipeline; the method includes: 1) Setting a sensing device at each monitoring point; when setting a single sensing device, before laying the deep - sea pipeline, the main pipe (31) is set on the lower side surface of the deep - sea pipeline at the monitoring point, the axis of the main pipe (31) is parallel to the axis of the deep - sea pipeline, and the housing (1) is fixed on the outer wall of the deep - sea pipeline; the sensing device is laid to the seabed together with the deep - sea pipeline; 2) After putting into operation, the processing device periodically identifies the output signals of each differential pressure sensor (2). If the output signal of the differential pressure sensor (2) exceeds the set threshold value, it indicates that the deep - sea pipeline has drifted at the corresponding part.

2. The method for monitoring the submarine pipeline subjected to the seabed shear stress according to claim 1, wherein: The deep - sea pipeline is an oil pipeline, a gas pipeline, a steel catenary riser or an underwater cable.

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