KR102096536B1 - Optical fiber sensor cable system for seismic profiling - Google Patents

Abstract

The present invention relates to an optical fiber sensor cable system for seismic survey, and provides a system capable of closely installing the optical fiber sensor to the ground surface. The optical fiber sensor can be closely attached to the ground surface to remove noise caused by cable waves, which improves the accuracy and reliability of seismic sensing and facilitates signal processing.

Description

Fiber optic sensor cable system for seismic survey {OPTICAL FIBER SENSOR CABLE SYSTEM FOR SEISMIC PROFILING}

The present invention relates to seismic exploration among physical exploration methods used for the detection of structures, properties, and deposits of the ground, and more particularly to seismic exploration technology using an optical fiber sensor cable.

Seismic exploration refers to exploration that identifies the physical characteristics of an underground geological structure or rock by recording a signal returned by an elastic wave generated or artificially generated on land or off the sea by reflection or refraction. It is used for exploring oil, gas, and mineral resources buried underground, or used for engineering purposes to explore cables buried underground.

1 is a view for explaining sea seismic exploration (top) and land seismic exploration (bottom).

Referring to Figure 1, the existing seismic probe is installed in a receiver or a geophone (geophone) or hydrophone (hydrophone) in a row or in the form of a matrix on the ground or sea level, artificially vibrating (source) at a specific point Generated and analyzed the signal received by the geophone or hydrophone to perform the exploration.

Recently, a method of using an optical fiber as a receiver in place of a geophone or hydrophone has been proposed. A schematic diagram of seismic survey using optical fiber is shown in FIG. 2.

Referring to FIG. 2, in the seismic survey using an optical fiber sensor, the optical fiber is installed in close contact with the ground, and an optical signal (laser) is transmitted through the optical fiber through a light source-optical modulator-circulator. The optical signal proceeds in the forward direction along the optical fiber, but at each point (continuous) of the optical fiber through which the light passes, there is a reflected signal that is reflected and returned in reverse by scattering of the light. That is, the light propagating the optical fiber collides with the molecules in the optical fiber and scatters to generate a reflected signal in the reverse direction.

 The circulator guides the reflected signal back to the photodetector. The analog signal is converted into a digital signal and analyzed by the processor.

In the steady state, the reflected signal shows a certain pattern. When an elastic wave is applied from the outside, the reflected or refracted elastic wave acts on the optical fiber, and the magnitude, frequency, and phase of scattering (Rayleigh scattering, etc.) change. It shows a different pattern from. That is, the pattern of the reflected signal appears differently by the application of elastic waves. In this way, the structure of the ground can be analyzed by using a point in which the pattern of the reflected signal is different according to the existence of the elastic wave, the amplitude of the elastic wave, and the frequency.

In the conventional seismic wave survey using a geophone or a hydrophone, as shown in FIG. 1, the receiver is arranged at a predetermined interval (multi-poiny array) to receive refracting and reflected waves only at the point where the receiver is located, but the optical fiber sensor By using it, reflection signals can be obtained at all points of the optical fiber. In other words, the same effect occurs that geophones or hydrophones are continuously arranged. Since the optical fiber sensor has a spatial resolution of at least 1 m, it is possible to obtain a more sophisticated exploration result than a geophone that has been intermittently deployed.

In addition, since the optical fiber sensor is not affected by electromagnetic interference, the signal-to-noise ratio (S / N ratio) is at least 20 dB (100 times) better than that of conventional coils and electromagnetic induction-type geophones. In addition, by using light, it is possible to collect signals on a wide scale up to 50 km, which is more economical and efficient than conventional seismic exploration.

Seismic exploration using an optical fiber sensor is an early stage, so there are many challenges to solve in order to apply it in the field. One of them is to fix the optical fiber sensor in close contact with the ground or the observation hole. This is because, when the optical fiber is in close contact with the ground, elastic waves that are reflected and refracted in the layer can accurately act on the optical fiber.

An object of the present invention is to provide an optical fiber sensor cable system capable of improving the accuracy of seismic survey by mounting the optical fiber sensor in close contact with the ground surface to solve the above problems.

On the other hand, other objects not specified in the present invention will be additionally considered within a scope that can be easily deduced from the following detailed description and its effects.

The optical fiber sensor cable system for seismic survey according to an example of the present invention for achieving the above object is installed on the ground surface, and once connected to the light source, light is scattered at each point when light is propagated in the forward direction. An optical fiber sensor in which the light reflection signal propagates in the reverse direction; A mounting member on which the optical fiber sensor is mounted; An expansion member capable of expanding and contracting according to injection and discharge of a fluid, so that the mounting member is in close contact with the ground surface during expansion; And one end is connected to the expansion member, the other end is connected to the pump fluid transfer pipe to which the fluid is transferred; characterized in that it comprises a.

According to the present invention, the mounting members are arranged to overlap each other in a state of being rolled in an annular shape, so that both ends can be deformed in a direction in which they are opened according to the expansion of the expansion member. And the mounting member is made of a rubber material.

In an example of the present invention, a mounting groove is formed in the mounting member along a lengthwise direction, and the optical fiber sensor can be installed by being fitted into the mounting groove. In addition, a clamp coupled to the mounting member and surrounding the optical fiber sensor to prevent the optical fiber sensor from being detached may be further provided.

According to the present invention, the expansion member is made of a silicone or rubber material, and an accommodating portion capable of sealing the fluid is formed therein.

In an example of the present invention, when the combination of the mounting member and the expansion member is referred to as one mounting unit, a plurality of the mounting units may be arranged at a predetermined distance along the optical fiber.

In order to interconnect a plurality of mounting units, a first connection tube and a second connection tube connected to the expansion member are respectively installed on one side and the other side of the mounting unit, and the second connection tube and the other side of the mounting unit disposed on one side. The first connection pipes of the mounting units disposed in each other are coupled to each other by a connector, so that the fluid moving through the fluid transfer pipes can be injected into a plurality of mounting units.

In an example of the present invention, the fluid injected into the expansion member may use any one of water, a fluid that is heavier than gas, and an oil containing a lubricant to press the optical fiber sensor downward.

In one example of the present invention, after the surface is excavated to form a trench concavely, the mounting member is installed in the trench.

Alternatively, the optical fiber sensor may be made of a flat plate-shaped body portion and an optical fiber installed in the body portion to be in close contact with the ground.

In the present invention, seismic exploration can be performed precisely using an optical fiber sensor cable. Since a sensor system with a spatial resolution of at least 1 m is constructed, the accuracy and reliability of seismic exploration can be increased. And the advantage of using fiber optics is that they can be explored over a wide area of 50 km or more.

First of all, in the present invention, since the optical fiber sensor is pressed and adhered to the ground, it maintains a compact spatial resolution as a distributed sensor and minimizes air waves received by cables that are not in close contact or noise propagating along the cable. can do. In other words, it is possible to improve the reliability of exploration as well as to facilitate signal processing by minimizing unwanted noise measured by a non-adherent cable and improving the signal-to-noise ratio (S / N ratio).

In the present invention, according to the injection and discharge of the fluid, the optical fiber sensor can be pressure-closed to the ground or released from the pressure, and thus there is an advantage that the installation and dismantling of the cable is very easy.

On the other hand, even if the effects are not explicitly mentioned herein, it is noted that the effects described in the following specification expected by the technical features of the present invention and the potential effects thereof are handled as described in the specification of the present invention.

1 is a schematic diagram for explaining the principle of seismic exploration.
2 is a schematic diagram for explaining the principle of seismic sensing using an optical fiber sensor.
3 is a schematic exploded perspective view of an optical fiber sensor cable system for seismic survey according to an example of the present invention.
FIG. 4 is a longitudinal cross-sectional view of the extended state in which the optical fiber sensor cable system for seismic survey shown in FIG. 3 is installed on the ground surface.
5 is a schematic cross-sectional view of the mounting member and the expansion member shown in FIG.
6 is a schematic cross-sectional view of a state in which the fluid is discharged and contracted in the state of FIG. 5.
7 is a view for explaining a state in which a plurality of mounting units are installed.
8 is a view for explaining a flat type optical fiber sensor.
※ The accompanying drawings indicate that they are exemplified by reference for understanding the technical idea of the present invention, and the scope of the present invention is not limited thereby.

The present invention relates to a fiber optic sensor cable system for seismic survey. In particular, the present invention relates to a system for performing seismic survey by installing an optical fiber sensor along a long surface.

Seismic exploration using an optical fiber sensor is currently in the early stages of research and development, and various attempts have been made to increase accuracy and efficiency.

If there is no separate mounting structure or if the fiber optic sensor cable is installed on the surface without landfill, the accuracy of the measurement cannot be guaranteed due to cable noise. That is, when vibration is generated using an acoustic wave source, the optical fiber sensor performs analysis by receiving a reflected wave or a refracted wave reflected by an underground layer or structure. However, if the ground is shaken by the seismic source, the fiber optic sensor cable is shaken together by the ground wave, resulting in noise, so-called cable noise. The generation of noise not only degrades the accuracy of seismic survey, but also remains a signal processing difficulty in removing noise through filtering.

In order to exclude the cable noise as above, the sensor cable must be in close contact with the ground surface.

In the present invention, by providing a system that can be close to the surface of the optical fiber sensor cable, it is intended to improve the accuracy of seismic survey using the optical fiber.

Hereinafter, an optical fiber sensor cable system for seismic survey according to an example of the present invention will be described in more detail with reference to the accompanying drawings.

However, when it is determined that the subject matter of the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description of the related known functions will be omitted.

3 is a schematic exploded perspective view of an optical fiber sensor cable system for seismic survey according to an example of the present invention, and FIG. 4 is a longitudinal cross-sectional view of the expanded optical fiber sensor cable system shown in FIG. 3 installed on the surface. .

3 and 4, the optical fiber sensor cable system (100, hereinafter referred to as 'optical fiber sensor cable system') for seismic probe according to an example of the present invention is an optical fiber sensor 10, a mounting member 20, expansion The member 30 is provided.

The optical fiber sensor 10 refers to an elongated and formed optical fiber itself, and is called a fiber optical sensor for convenience since sensing is performed using the optical fiber itself. The optical fiber sensor 10 is installed long on the surface of the surface, and once connected to a light source (not shown) to propagate light (laser) transmitted from the light source. However, light propagated through the optical fiber is scattered while colliding with molecules constituting the optical fiber in each part of the optical fiber, and transmits the scattered light in the reverse direction. Light scattered in the reverse direction (called a light reflection signal) is continuously generated in all regions of the optical fiber through which the light passes. The light reflection signal is received by a detector (not shown) by a circulator (not shown) or the like arranged at the rear end of the light source. The circulator serves to separate transmission and reception of optical signals.

When light is irradiated, the light reflection signal is continuously generated with a parallax, so the detector can estimate at what point of the optical fiber it is reflected by the arrival time of the light reflection signal. This is called spatial resolution, and is spaced at least in units of 1m. It is known that it can decompose. In other words, the same effect as that of the existing geophones continuously buried in at least 1 m units can be exhibited, which significantly improves the efficiency of seismic exploration. Sensing using such an optical fiber sensor is called a distributed system.

The optical fiber sensor 10 is mounted on the mounting member 20. The mounting member 20 is installed on the ground surface with the optical fiber sensor mounted. In this example, the mounting member 20 is formed in a shape that is substantially circularly rolled and both ends are superimposed on each other. And the expansion member 30 is installed inside the mounting member 20. In this example, the expansion member 30 is made of a silicone or rubber material, and an airtight space in which a fluid can be filled is formed. The expansion member 30 is connected to the fluid transfer pipe 40, the fluid may be injected or discharged into the closed space.

When the fluid is filled under pressure, the silicone expansion member expands along the radial direction as shown in FIG. 5. At this time, in the mounting member 20, both ends of the overlapping portion are expanded together. When both ends of the mounting member 20 are opened and expanded, the optical fiber sensor 10 that is in contact with the ground surface is in close contact with the ground surface by the weight of the expansion member. Conversely, when the fluid is discharged from the expansion member 30 through the fluid transfer pipe 40, it contracts to its original state. At this time, the mounting member 20 also overlaps each other as it is, and the load on the optical fiber sensor is also reduced.

In this embodiment, the mounting member 20 is made of a rubber material in order to increase the adhesion with the ground surface. In addition, the mounting member 20 is a double-sheet structure, the outer side is rough, but a rubber material having high adhesion, and the inner circumferential surface is not rough, and a rubber of relatively soft material can be used. Since the inner peripheral surface of the mounting member 20 is in contact with the expansion member 30, it is to protect the expansion member 30. In order to increase the adhesion between the mounting member 20 and the surface of the surface, the contact groove may be formed on the outer circumferential surface of the mounting member 20 in a horizontal direction or in a matrix pattern.

The optical fiber sensor 10 is fitted and installed in the mounting groove 21 formed in the mounting member 20. Of course, in another example, it may be directly attached to the outer peripheral surface of the mounting member without the mounting groove. However, in order to stably mount the optical fiber sensor and exclude external noise, it is preferable to be inserted into the mounting groove 21. In this example, a separate clamp 22 may be provided to prevent the optical fiber sensor 10 fitted in the mounting groove 21 from being detached. The central portion 221 of the clamp 22 is formed convexly so as to cover the optical fiber sensor 10, and flange portions 222 are formed on both sides thereof. A coupling means such as a screw (not shown) may couple the flange portion 222 and the mounting member 20 to each other.

On the other hand, the mounting member is the optical fiber sensor 10 is fitted and installed, for example, the central portion is formed thickest, and the thickness toward the both ends is formed thinner. The central portion should be relatively thick because the optical fiber should be installed and should be rigid, and the both ends should be thinner since it should be able to easily open as the expansion member expands.

So far, in the optical fiber sensor cable system 100, it has been described and illustrated that there is only one mounting member 20 and an expansion member 30, but if the range of surface exploration is wide, a plurality is required. When the mounting member 20 and the expansion member 30 are combined in one set, and when this is referred to as a mounting unit 60 for convenience, the mounting units 60 are spaced apart from each other along the arrangement of the optical fiber sensor 10. Can be prepared.

An example of this form is shown in FIG. 7. Referring to FIG. 7, it can be seen that the optical fiber sensor 10 is elongated in a row on the ground surface, and the mounting unit 60 is installed in the middle of the optical fiber sensor 10.

In addition, a first connection pipe 41 and a second connection pipe 42 are installed on one side and the other side of the mounting unit 60, respectively. Both the first connection pipe 41 and the second connection pipe 42 are interlocked with the inside of the expansion member. The first connector 41 and the second connector 42 are interconnected by a connector 49.

The fluid transfer pipe 40 is connected by a first connection pipe 41 and a connector 49 of the first disposed mounting unit 60. And the second connector 42 installed on the other side of the first disposed mounting unit 60 is connected by a connector 49 and the first connector 41 of the second disposed mounting unit. A plurality of mounting units 60 can be connected in the manner described above. Since the fluid transfer pipe 40 and the expansion member 30, the first connection pipe 41, and the second connection pipe 42 are all interlocked, when the fluid is injected and discharged, the plurality of mounting members 60 have slight parallax. And expand and contract together.

The optical fiber sensor cable system 100 having the above-described configuration mounts at least one mounting unit 60 to the optical fiber sensor 10 at a predetermined position while the optical fiber sensor 10 is installed on the ground surface. The mounting unit 60 is installed at the time of installation of the optical fiber sensor 10 and is disposed at a predetermined position on the ground.

When the optical fiber sensor is installed on the ground surface, two methods can be adopted to increase the adhesion.

The first method is a method of installing a mounting member having an approximately circular curved surface after forming a trench in a concave shape by excavating the surface slightly.

The second method is to use a flat type optical fiber sensor as shown in FIG. 8. The flat type optical fiber is provided with a flat plate-shaped body portion 11 and an optical fiber installed inside the body portion 11. Since it is flat, the contact area with the ground increases, so that the adhesion can be increased.

When the fluid (compressed air, water, oil, etc.) is injected through the fluid transfer pipe 40 in the above-described state, the expansion member 30 expands and becomes heavy, and the optical fiber sensor 10 is pressed against the ground. A pressure gauge 70, a valve 80, and a pump 90 are sequentially installed at the inlet of the fluid transfer pipe 40 to adjust the pressure of the injected fluid.

When the injection pressure of the fluid reaches a certain standard, the valve 80 is closed and the operation of the pump 90 is stopped to complete the installation of the optical fiber sensor cable system 100.

When the installation is completed, the optical fiber sensor is irradiated with light and an optical reflection signal is received to perform analysis. When vibration is applied through the acoustic wave source, the elastic wave is refracted and reflected by the strata, buried, and the like to act on the optical fiber sensor 10. The seismic probe is performed by analyzing the position, delay time, and size of the seismic signal reaching the optical fiber.

When exploration is completed, when the valve 80 is opened and the fluid is discharged, the expansion member contracts, and accordingly, the mounting member also overlaps in its original state. Thus, the fiber optic sensor cable can be easily dismantled.

As described above, in the present invention, it is possible to elaborate the seismic survey using an optical fiber sensor cable. Since a sensor system with a spatial resolution of at least 1 m is constructed, the accuracy and reliability of seismic exploration can be increased. And the advantage of using fiber optics is that they can be explored over a wide area of 50 km or more.

Above all, in the present invention, since the optical fiber sensor is pressed and adhered to the ground, cable waves due to ground waves can be removed. By removing the cable wave, not only is the signal processing easy, but also the reliability of exploration can be improved.

In addition, there is an advantage that it is very easy to install and dismantle the optical fiber sensor according to the injection and discharge of the fluid.

On the other hand, until now, when the fluid is injected into each mounting unit, it has been described and illustrated as continuously in series, but in another example, the fluid transfer pipe may be separately installed for each mounting unit to separately inject fluid.

Unexplained reference numeral g is the ground.

The scope of protection of the present invention is not limited to the description and expression of the embodiments explicitly described above. In addition, it is pointed out once again that the scope of protection of the present invention may not be limited by obvious changes or substitutions in the technical field to which the present invention pertains.

100… Fiber optic sensor cable system
10… Fiber optic sensor, 20… Mounting member
21… Mounting groove, 22. clamp
30… Expansion member 40. Fluid transfer pipe
60… Mounting unit, 70… Pressure gauge
80… Valve 90… Pump
g… Ground,

Claims (11)

It is installed on the surface,
Once the light source is connected to the light source and the light propagates in the forward direction, an optical fiber sensor in which the light reflection signal generated as light is scattered at each point propagates in the reverse direction;
A mounting member on which the optical fiber sensor is mounted;
An expansion member capable of expanding and contracting according to injection and discharge of a fluid, so that the mounting member is in close contact with the ground surface during expansion; And
One end is connected to the expansion member, the other end is connected to the pump is provided with a fluid transfer pipe for transferring the fluid;
The mounting member is arranged to be overlapped at both ends in a state of being rolled in an annular shape, so that both ends can be deformed in a direction in which they are opened according to the expansion of the expansion member,
The expansion member is an optical fiber sensor cable system for seismic survey, characterized in that disposed inside the annular mounting member. delete According to claim 1,
The mounting member is an optical fiber sensor cable system for seismic survey, characterized in that made of a rubber material. According to claim 1,
An optical fiber sensor cable system for seismic probes characterized in that a mounting groove is formed in the mounting member along a lengthwise direction, and the optical fiber sensor is fitted into the mounting groove. The method of claim 1 or 4,
The optical fiber sensor cable system for seismic survey, further comprising a clamp wrapped around the optical fiber sensor to prevent the optical fiber sensor from being detached and coupled to the mounting member. According to claim 1,
The expansion member is made of a silicone or rubber material and the optical fiber sensor cable system for seismic probes characterized in that a receiving portion capable of sealing the fluid is formed therein. According to claim 1,
When the combination of the mounting member and the expansion member is referred to as one mounting unit, a plurality of the mounting units are spaced apart a predetermined distance along the optical fiber sensor, the optical fiber sensor cable system for seismic survey. The method of claim 7,
First and second connecting pipes connected to the expansion member are respectively installed on one side and the other side of the mounting unit,
The second connection pipe of the mounting unit disposed on one side and the first connection pipe of the mounting unit disposed on the other side are mutually coupled by a connector, so that the fluid moving through the fluid transfer pipe can be injected into a plurality of mounting units Fiber optic sensor cable system for seismic probes. According to claim 1,
The fluid injected into the expansion member is any one of oil containing water and lubricating oil, which is a fluid that is heavier than gas so as to press the optical fiber sensor downward. According to claim 1,
After excavating the ground surface to form a trench concavely,
The mounting member is installed in the trench, the optical fiber sensor cable system for seismic survey. According to claim 1,
The optical fiber sensor is a flat plate-shaped body portion, and an optical fiber sensor cable system for seismic survey, characterized in that it is made of an optical fiber installed in the body portion.

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