Light power supply seismic center device and observation system using the same

Abstract

To provide a light power supply seismic center device that has a permanent power supply of an active source that is supplied with power using an optical fiber and made chargeable, and generates physical vibration with power from the permanent power supply, and an observation system using the same that performs observation of a physical change with an optical fiber sensor that does not require electric wiring.SOLUTION: A light power supply seismic center device drives a seismic generation unit with a drive control unit connected with a permanent power supply installed on the bottom of the sea, and generates an active quake. The light power supply seismic center has a charging function to perform light / power conversion of light power transmitted through a first optical fiber cable into electric energy, and charge the permanent power supply with the electric energy obtained through the conversion, a control function to perform light / power conversion of a control signal transmitted through a second optical fiber cable into an electric signal, and control the drive control unit with the electric signal obtained through the conversion, and a determination function to determine the charging state of the permanent power supply. On the basis of the determination made by the determination function, the light power supply seismic center device drives the seismic generation unit when the permanent power supply is sufficiently charged, and charges the permanent power supply when it is not sufficiently charged.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an optically powered seismic source device that supplies and stores electricity via optical fiber to a permanent power source installed in a remote location such as the seabed for active observation, and generates physical vibrations using the power from the permanent power source, as well as an observation system that uses the same to observe physical fluctuations using optical fiber sensors. [Background technology]

[0002] When exploring the subsurface structure and resources of the seafloor using a cabled observation system, as shown in Figures 1(A) and 1(B), an air gun 3 suspended from a transmitter rod 2 on a research vessel 1 at sea sends a vibrating sound field through seawater to the seafloor, and data is collected from multiple hydrophones 5 attached like fingers to a streamer cable 4, and analyzed by an analysis processing device on the research vessel 1 or on land. However, such observation systems have issues such as the high operating costs of the research vessel 1, which limits the number of observations, and they cannot be applied to applications requiring continuous real-time monitoring, such as CCS (Carbon dioxide Capture and Storage) monitoring, which is proposed as a measure against global warming.

[0003] CCS, for example, is an effective way to reduce large amounts of CO2 emissions in a short period of time by injecting large amounts of CO2 deep underground on the seabed via a pipeline 10 from an onshore injection well 11, as shown in Figure 2. CO2 injection methods include floating structures on the seabed and fixed offshore rigs. When CO2 is injected deep underground (seabed), CCS monitoring is required at multiple CO2 storage sites distributed over a wide area using observation sensors to prevent (predict) CO2 leakage and induced earthquakes and ensure environmental safety. CCS monitoring is typically performed using an ocean bottom cable (OBC)-based ocean bottom cable (OBC) observation system, as shown in Figure 3. Specifically, OBCs 31 are placed on the seabed in a finger-like fashion from a fixed offshore rig 30. The OBCs 31 are equipped with multiple triaxial seismometers and hydrophones, and detect and observe seismic waves emitted by a seismic vessel 33 traveling along a zigzag route 34.

[0004] Such active observations require many sensors, each of which requires power. Power is supplied from either the sea or land. However, when power is transmitted via electric cables, the distance from the power source to the sensors is considerable, necessitating high-voltage transmission. This necessitates measures to protect against seawater corrosion, pressure resistance, and insulation. When electric cables are used, measures to protect the cables from lightning strikes are also necessary. Furthermore, the cables are heavy and large, and the installation equipment is extensive. Furthermore, as shown in Figure 1, active observations require observation vessels 1 and air guns 3 as seismic sources, but these cannot be operated continuously. This poses challenges when continuous observations are required, such as CCS monitoring. While this can be solved by using permanently installed electrically driven seismic sources, a power supply is required, and the issue of electric cables remains. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7072838 [Patent Document 2] Patent No. 4851330 [Patent Document 3] U.S. Patent No. 7,696,901 [Patent Document 4] US Patent Application Publication No. 2007 / 0039776 [Patent Document 5] Japanese Patent Application Publication No. 7-151563 [Patent Document 6] Japanese Patent Application Publication No. 5-164574 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, when using a permanent seafloor seismic source for active observation, a challenge arises in the supply of power to the seismic source device, such as long-distance high-voltage transmission. The problems of power transmission via these electric cables are common to both seafloor and terrestrial observations, but seafloor observations in particular require measures such as high pressure and rust prevention, while terrestrial observations face the problem of lightning strikes on the power lines.

[0007] Furthermore, using electrical sensors for observation increases power consumption and does not work in highly radioactive areas, so there is a demand for optical fiber sensors that do not have electronic components and do not require electrical wiring.

[0008] The present invention has been made in light of the above-mentioned circumstances, and its object is to provide an optically powered seismic source device that uses optical fiber to supply power to the permanent power supply of an active seismic source, allowing it to be constantly charged, and that can generate physical vibrations continuously using the power of a fully charged permanent power supply, and an observation system that uses the same to observe physical movements using optical fiber sensors that do not have electronic components or require electrical wiring.

[0009] For active observations, if an optical power supply system is used to transmit power over long distances to the permanent power source (secondary battery) of the seismic source device installed on the seafloor, by performing optical / electrical (O / E) conversion from a power supply source installed on land or sea to supply power via optical fiber, and then performing electrical / optical conversion on the permanent power source side to charge it, high-voltage power transmission is not required, and power can be transmitted from the power source using only optical fiber, and the permanent power source can be charged.By converting the optical energy transmitted over long distances into electrical energy using optical / electrical conversion and charging the permanent power source (secondary battery), the seismic source device of the active seismic source can be constantly powered by the power from the permanent seismic source.

[0010] Furthermore, by using optical fiber sensors for observation, which do not have any electronic components and do not require electrical wiring, it is possible to perform active observations in real time, continuously, and with high reliability, while also reducing the power consumption of permanent power sources. [Means for solving the problem]

[0011] The present invention relates to a seismic source device that generates active vibrations by driving a seismic generator using a drive control unit connected to an optical power supply / control unit installed on land or sea by an optical fiber cable and connected to a permanent power source installed on the seabed or on land in a remote location, and the above-mentioned object of the present invention is to provide a device in which the permanent power source and the drive control unit are modular, and the device has a charging function that converts optical power transmitted from the optical power supply / control unit via a first optical fiber cable into electrical power within the module and charges the permanent power source with the converted electrical energy, a control function that converts control signals transmitted from the optical power supply / control unit via a second optical fiber cable into electrical power within the module and controls the drive control unit with the converted electrical signal, and a control function that determines the charging state of the permanent power source. and a judgment function for determining whether or not the power supply is sufficiently charged, the judgment result of which is transmitted to the optical power supply / control unit via the second optical fiber cable, the oscillation unit is driven when the charge is sufficient, and the permanent power supply is charged when the charge is insufficient. This object is more effectively achieved by providing a thermal / electrical conversion unit made of a Seebeck effect element in contact with the side of the housing of the component that performs the optical / electrical conversion, and by providing a heat dissipation fin on the opposing surface of the thermal / electrical conversion unit, so that the permanent power supply is charged with the power generated by the thermal / electrical conversion unit, or by configuring the first optical fiber cable and the second optical fiber cable to be a single optical fiber cable made of double-clad optical fiber that serves both as an optical power supply and a control unit.

[0012] Furthermore, the above-mentioned object of the present invention is achieved by arranging optical fiber sensors, which input and output laser light using an OBC (Ocean Bottom Cable), in a circular, star, snake or finger shape near the optically powered seismic source device, and by detecting active vibrations and performing physical exploration using the optical fiber sensors, where the optical fiber sensors are a three-axis acceleration sensor, an optical hydrophone and a DAS (Distributed Acoustic Sensing). [Effects of the Invention]

[0013] According to this invention, for CCS monitoring, a permanent power source installed on the seabed or elsewhere is made into a rechargeable secondary power source, and power is supplied to the permanent power source via optical fiber (OBC) that performs electrical-to-optical and optical-to-electrical conversion, so power can be transmitted from a power supply unit (base station) installed on land or at sea and the permanent power source can be charged using only optical fiber, and the seismic source device can be constantly driven for observation using power from the permanent power source on the seabed. Since it is easy to secure power, it is also possible to install multiple seismic source devices.

[0014] Since the wires and insulating elements required for power transmission are not required, cost reduction, weight reduction, and miniaturization can be achieved. Furthermore, in order to utilize the thermal energy generated by light-to-electricity conversion, the present invention uses a Seebeck effect element to convert heat to electricity to obtain electrical energy, which is then used to charge a permanent power source, thereby achieving efficient and stable charging.

[0015] Furthermore, by installing a large number of optical fiber sensors near the epicenter, which do not contain electronic components and do not require electrical wiring, and connecting them with optical fiber cables (OBC), it is possible to build a highly reliable, real-time, active, continuous seafloor observation system that does not require power supply via undersea cable wires. This has the great advantage of being able to observe physical changes on the seafloor at base stations without using electrical signals.

[0016] Optical OBC cables or downhole optical fiber cables are used as distributed acoustic sensors, playing a complementary role to optical 4C sensors. Optical 4C sensors are highly sensitive and capable of triaxial detection, equivalent to point sensors, while DASs are less sensitive than optical 4C sensors and only have sensitivity in the axial direction of the fiber, but they have the advantage of being able to observe continuously and distributedly at intervals of several meters.

[0017] The system of the present invention has the advantage that it can be applied to active exploration using artificial seismic sources and passive monitoring of natural earthquakes, induced earthquakes, etc. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are a schematic diagram showing an example of a general seabed exploration and a plan view of a streamer cable. [Figure 2] This is a schematic diagram showing an example of CO2 injection into the seabed. [Figure 3] A cross-sectional perspective view showing an example of an observation system using OBC. [Figure 4] 1 is an overall schematic diagram showing a first embodiment (series integrated type) of the present invention. [Figure 5] FIG. 1 is a block diagram showing a configuration example (two optical seismic sources / optical 4C sensor modules) of a first embodiment of the present invention. [Figure 6] FIG. 2 is a block diagram showing an example of the detailed configuration of a drive control unit and a transmitting / receiving unit. [Figure 7] FIG. 3 is a diagram showing an example of epicenter data stored in a control unit. [Figure 8] 1 is a perspective structural view showing an example of the mechanical configuration of an optical / electrical conversion unit according to the present invention. [Figure 9] 1 is a perspective view showing an example of a fiber cable that can be used in the present invention. [Figure 10] 1 is a flowchart showing an example of operation of the present invention (the seismic source system of the first embodiment). [Figure 11] 4 is a flowchart showing an operation example (sensor system of the first embodiment) of the present invention. [Figure 12] 10 is a flowchart showing a modified example of the operation example (seismic source system of the first embodiment) of the present invention. [Figure 13] 10 is a flowchart showing an example of an operation for detecting a failure of an optical 4C sensor. [Figure 14] FIG. 10 is an overall schematic diagram showing a second embodiment (series separation type) of the present invention. [Figure 15] FIG. 10 is a block diagram showing a configuration example (two optical seismic source modules and two optical 4C sensor modules) of a second embodiment of the present invention. [Figure 16] FIG. 10 is a schematic diagram showing another example of the arrangement of the optical seismic source module and the optical 4C sensor module. [Figure 17]FIG. 10 is an overall schematic diagram showing a third embodiment (completely separated type) of the present invention. [Figure 18] FIG. 10 is a block diagram showing a configuration example (two optical seismic source modules and two optical 4C sensor modules) of a third embodiment of the present invention. [Figure 19] FIG. 10 is an overall schematic diagram showing a fourth embodiment (completely separated type (DAS-VSP)) of the present invention. [Figure 20] 1A and 1B are a circuit diagram and a sound pressure waveform diagram for explaining a sparker; [Figure 21] FIG. 1 is an external configuration diagram showing an example of a boomer. [Figure 22] FIG. 2 is a characteristic diagram for explaining a laser wavelength used in the present invention. [Figure 23] 1 is a block diagram showing a first embodiment of an optical fiber sensor that is optimal for the present invention. [Figure 24] 24 is a flowchart showing an example of operation of the first embodiment of FIG. 23. [Figure 25] FIG. 10 is a block diagram showing a second embodiment of an optical fiber sensor suitable for the present invention. [Figure 26] 26 is a flowchart showing an example of operation of the second embodiment of FIG. 25. [Figure 27] FIG. 1 is a schematic diagram showing an overview of the ground-based seismic source device and observation system. [Figure 28] FIG. 10 is a connection diagram showing the results of a demonstration test of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] In this invention, for active observations such as CCS monitoring, a seismic source device installed on the seafloor is powered by a permanent power source. The permanent power source is a rechargeable secondary battery. Power supply for charging the permanent power source and communication of signals and data are performed using light instead of electricity, and optical fiber is used for both power supply and signal transmission. Furthermore, physical environmental changes due to earthquakes generated by the seismic source device are observed using optical fiber sensors that do not contain electronic components or require electrical wiring, and the optical fiber sensors are driven and observation results are transmitted and received using optical fiber. Since an optical fiber power supply system is used for long-distance power transmission to charge the permanent power source, there is no need for high-voltage power transmission or the risk of lightning strikes on power lines. Stable power transmission is possible from a power supply unit (power supply light source) installed on land or offshore using only optical fiber, and optical-to-electrical (O / E) conversion is performed on the seafloor (or underground) to charge the permanent power source. Since the permanent power source can be charged as needed remotely, replacement and maintenance of the permanent power source are also unnecessary.

[0020] Furthermore, by using optical fiber sensors that do not have electronic components and do not require electrical wiring as sensors for observing physical fluctuations, it is possible to achieve active observation that is continuous and highly reliable in real time.

[0021] Furthermore, in this invention, multiple modules integrating an optical seismic source and optical fiber sensor are connected in series with an OBC (Ocean Bottom Cable) to systematize the optical seismic source and optical fiber sensor for active observation, or multiple optical seismic source modules and multiple optical fiber sensor modules are separated and connected in series with an OBC to systematize the optical seismic source and optical fiber sensor.Furthermore, multiple optical seismic source modules are connected in series with an OBC, and multiple optical fiber sensor modules are connected in series with an OBC in a completely separate form to systematize the optical seismic source and optical fiber sensor for active observation.

[0022] The optical fiber sensor uses a modularized three-axis xyz optical acceleration sensor, optical hydrophone, and DAS.

[0023] In addition, since OBN (Ocean Bottom Node) cannot perform real-time observation, OBC is used in the present invention.

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0025] Figure 4 shows a schematic diagram of the overall configuration of the first embodiment (series integrated type) of the present invention. Multiple (seven in this example) photoseismic source / optical 4C sensor modules 100 are installed near the injection well 501, connected by OBCs. One is installed near the wellhead and six are installed in a circular configuration centered on the wellhead. The observation vessel 500 is also equipped with air guns, water guns, sparkers, and other devices for use. While the OBCs are shown in Figure 4 as being installed in a loop configuration, a single-ended configuration is also acceptable. Installing them in a loop configuration enables measurements from both ends, which is expected to improve the reliability and performance of the system. Furthermore, the photoseismic source within the photoseismic source / optical 4C sensor module 100 can be controlled externally (on land or at sea).

[0026] An example of the detailed configuration is shown in Figure 5. For convenience, two optical seismic source / optical 4C sensor modules 100-1 and 100-2 are shown in this example, but in reality, seven optical seismic source / optical 4C sensor modules are connected, as shown in Figure 4. The earthquake source vessel 500 is equipped with an optical hybrid system control / processing unit 510, which is composed of a CPU (Central Processing Unit), memory, interface input / output units, etc., as well as an optical power supply / control unit 520, an optical 4C sensor transceiver unit 530, and a DAS transceiver unit 540, and the optical hybrid system control / processing unit 510 is interconnected with the optical power supply / control unit 520, the optical 4C sensor transceiver unit 530, and the DAS transceiver unit 540. The optical hybrid system control / processing unit 510, the optical power supply / control unit 520, the optical 4C sensor transceiver unit 530, and the DAS transceiver unit 540 are installed on land or at sea.

[0027] The optical power supply / control unit 520 is composed of a power supply unit 521 that supplies power, an electrical / optical (E / O) conversion unit 522 that converts the electrical energy from the power supply unit 521 into optical (laser) energy, a control monitoring unit 523 that controls and monitors the optical source, and a transceiver unit 524 that transmits or receives optical information via a control optical fiber FB3. The power supply unit 521 and the electrical / optical (E / O) conversion unit 522 may be an integrated laser light source. The optical 4C sensor transceiver unit 530 is composed of a control monitoring unit 531 that controls and monitors the optical 4C sensor, a transmitter 532 connected to optical fiber FB4, and a receiver 533 connected to optical fiber FB5.

[0028] The optical 4C sensor 120 used in this invention is composed of a three-axis optical acceleration sensor (x, y, z axes) and an optical hydrophone, and the DAS (Distributed Acoustic Sensing) is a well-known distributed acoustic measurement system, and is configured with a non-reflective termination 140 at the final end of the OBC connection.

[0029] Optical seismic source / optical 4C sensor modules 100-1 and 100-2 have the same configuration, so here we will explain optical seismic source / optical 4C sensor module 100-1. Optical seismic source / optical 4C sensor module 100-1 is an integrated module of optical seismic source module 110, which generates an earthquake source, and optical 4C sensor 120. Optical seismic source module 110 is equipped with a permanent power supply (secondary battery) 113, and the power from permanent power supply 113 is used to drive seismic source unit 115, which generates acoustic or physical vibrations, via drive control unit 114. The optical seismic source module 110 is also provided with an optical / electrical (O / E) conversion unit 111 that converts optical energy from the optical power supply optical fiber FB1 into electrical energy, and a charging unit 112 that charges a permanent power supply 113 with power PW1 from the optical / electrical conversion unit 111, and is also provided with a transceiver unit 116 that transmits and receives optical signals via the control optical fiber FB3 between the drive control unit 114 and the optical power supply / control unit 520.

[0030] 6 shows a detailed configuration example of the drive control unit 114 and the transmitter / receiver unit 116. The optical signal LS1 (seismic source signal VSA) transmitted through the control optical fiber FB3 is received by the optical signal receiver 116-1 and converted into an electrical signal ES1 (seismic source signal VS) by the optical / electrical converter 116-2. The electrical signal ES1 is input to the controller 114-1, which stores hypocenter data. The controller 114-1 then activates the hypocenter unit 115 via the hypocenter driver 114-4 based on the selected hypocenter type. The charge determination unit 114-2 determines whether the permanent power supply 113 is sufficiently charged and transmits the charge status to the controller 114-1. The standby signal WT from the controller 114-1 and the charge status signal from the charge determination unit 114-3 are converted into an optical signal by the electrical / optical converter 114-3 and transmitted as an optical signal LS4 via the optical signal transmitter 116-3.

[0031] The control unit 114-1 stores data of sweep waveforms generated by the earthquake generating unit 115 as hypocenter types #1 to #n in a format such as that shown in Fig. 7. The hypocenter data includes an upper frequency limit Fu, a lower frequency limit Fd, time T, amplitude AP, and the number of times (countdown) N set for each hypocenter type #1 to #n. A sweep waveform is a waveform in which the oscillation frequency is continuously changed on the time axis, and the earthquake generating unit 115 can also be generated by pseudo-random wave data. Therefore, if the source earthquake generating signal VSA contains, for example, a signal to select hypocenter type #2, the earthquake generating unit 115 generates the upper frequency limit Fd via the earthquake generating drive unit 114-4. u2 , lower frequency limit F d2 The earthquake occurs based on the source data of time T2, amplitude AP2 and number of occurrences N2.

[0032] The optical / electrical conversion unit 111 generates heat due to photoelectric conversion, and in the present invention, a mechanism is provided to convert this heat into electricity in order to make effective use of it. Fig. 8 is a plan view of the structure, and a thermal / electrical conversion unit 111-1 made of a Seebeck effect element is provided in contact with the side of the optical / electrical conversion unit 111, and a heat dissipation fin 111-2 exposed to the outside of the permanent submarine housing 101 is provided on the opposite surface of the thermal / electrical conversion unit 111-1. The optical / electrical conversion unit 111, which is powered by an optical power feeding optical fiber FB1, generates electric power PW1, and the electric power PW1 charges the permanent power supply 113 via a charging unit 112. Furthermore, thermal / electricity conversion unit 111-1, which is made up of a Seebeck effect element, generates electricity based on a temperature difference, and therefore generates electric power PW2 using the high-temperature heat of optical / electricity conversion unit 111 and the low-temperature cooling of heat dissipation fins 111-2, and electric power PW2 also charges permanent power supply 113 via charging unit 112. In other words, permanent power supply 113 is charged by the logical sum of electric power PW1 from optical / electricity conversion unit 111 and electric power PW2 from thermal / electricity conversion unit 111-1.

[0033] The optical / electrical conversion unit 111 can use approximately 25% of the optical energy as electric power PW1, and generates the remaining approximately 75% as heat. The thermal / electrical conversion unit 111-1 can use approximately 10% of the thermal energy as electric power PW2, and the power saving effect of charging these electric powers PW1 and PW2 is significant.

[0034] In the above description, the optical fiber for optical power supply and the optical fiber for control are separate, but if a double-clad optical fiber FB as shown in Figure 9 is used, it is possible to supply power and send and receive signals simultaneously using a single optical fiber.

[0035] An example of the operation of such a configuration will be described with reference to the flowchart of FIG.

[0036] First, in response to a command from the optical hybrid system control processor 510, power is supplied from the power supply unit 521 of the optical power supply / control unit 520 to the electrical / optical converter 522. The optical power obtained by the electrical / optical converter 522 is input to the optical / electrical converter 111 in the optical seismic source / optical 4C module 100-1 via the optical power supply optical fiber FB1 and converted to electrical power (step S10). The permanent power supply 113 is charged via the charging unit 112 (step S11). Charging continues until the charging determination unit 114-2 determines that the charging is sufficient (step S12). When the permanent power supply 113 is sufficiently charged, it enters a standby state (step S13). A standby signal WT is output from the control unit 114-1, converted into an optical signal by the electrical / optical converter 114-3, transmitted via the optical signal transmitter 116-3 over the control optical fiber FB3, and further notified to the control monitor unit 523 via the transmitter / receiver 524 (step S30).

[0037] When the transceiver 524 receives the standby notification WT, it cooperates with the control monitor 523 to notify the optical hybrid system control processor 510 of the reception of the standby notification WT. Thereafter, the optical hybrid system control processor 510 transmits, as necessary, a ground-seismic signal VSA including one of the seismic motion types shown in Fig. 7 via the control monitor 523 and the transceiver 524 through the control optical fiber FB3 to the optical signal receiver 116-1 in the transceiver 116 (step S31). The ground-seismic signal VSA is received by the optical signal receiver 116-1 and converted into an electric signal ES1 by the optical / electrical converter 116-2, and input as the ground-seismic signal VS to the controller 114-1 (step S14). In response to the input of the seismic generation signal VS, the control unit 114-1 selects the hypocenter type included in the seismic generation signal VS from memory (step S15), generates hypocenter data ES3 that specifies the lower frequency limit Fd, upper frequency limit Fu, time T, amplitude AP, and number of times N (step S16), and inputs the hypocenter data ES3 to the seismic generation driver 114-4. The seismic generation driver 114-4 reconfirms whether the permanent power supply 113 is sufficiently charged (step S20), and if so, activates the seismic generation unit 115 to start seismic generation (step S21). The charge determination in the seismic generation driver 114-4 is performed via the charge determination unit 114-2 and the control unit 114-1.

[0038] If it is determined in step S20 that the charge is insufficient, no earthquake is generated (step S23). Although one charging unit 112 is shown above, multiple charging units (for example, two) may be provided, and one charging unit may be used to charge while the other is generating an earthquake, allowing earthquake generation to continue at all times. Note that the earthquake generation unit 115 may use a sparker (underwater discharge) or an underwater speaker (piezoelectric or induction type) as a non-explosive earthquake source, and sparkers, boomers, and underwater speakers will be described later.

[0039] The number of times that defines the number of times the earthquake generation unit 115 operates is included in the hypocenter data ES3 and is measured, for example, by a countdown of a time counter (not shown). When the countdown reaches zero (step S22), earthquake generation by the earthquake generation driving unit 114-4 stops (step S23) and the system goes into standby mode (step S24). When earthquake generation stops, the control unit 114-1 inputs a standby notification WT to the electrical / optical conversion unit 114-3, and the standby notification WT is converted into an optical signal and transmitted from the optical signal transmission unit 116-3 to the control monitoring unit 523 via the optical fiber FB3 via the transmission / reception unit 524 in the optical power supply / control unit 520 (step S32).

[0040] Next, an example of operation (in the case of an active type) of the optical 4C sensor 120 in the optical seismic source / optical 4C module 100-1 will be described with reference to the flowchart of FIG.

[0041] The control monitor 531 in the optical 4C sensor transmitter / receiver 530 determines whether the optical power supply / control unit 520 is performing a seismic activity and waits until the seismic activity is determined (step S41). When the seismic activity is determined, the control monitor 531 drives the built-in laser driver to activate the laser light source and emit light (step S42). The laser light is then transmitted to the optical 4C sensors 120 via the transmitter 532 and the optical fiber FB4 toward the optical 4C sensors 120 (step S43). The transmitted laser light is sequentially transmitted to the optical 4C sensors 120, and each optical 4C sensor 120 performs a predetermined detection (triaxial acceleration and ultrasonic sound field) (step S44). The detection signal is received by the receiver 532 via the optical fiber FB5 (step S45). The control monitor 531 or the optical hybrid system control processor 510 performs light reception processing, i.e., calculation processing for detection (step S46). The above operation is repeated until the standby signal WT is notified (step S47), and at the stage when the standby signal WT is notified, the laser light source stops emitting light and the operation ends (step S48).

[0042] 11 explains an example of the operation of an active-type optical 4C sensor 120 that works in conjunction with an optical earthquake source device, but in the case of a passive-type sensor that performs detection at all times regardless of the operation of the optical earthquake source device, the optical 4C sensor 120 performs detection at all times regardless of whether an earthquake occurs in step S41 or whether the standby signal is received in step S47. In other words, the sensor is in an operational state, emitting laser light at all times.

[0043] For DAS, this is performed by measuring the acoustic distribution of the optical fiber FB6 connected to the DAS transceiver 540 and the non-reflective termination 140 of the terminal.

[0044] In the above description, the control unit 114-1 creates and stores in advance the hypocenter data shown in Fig. 7, and selects the hypocenter type by the hypocenter generation signal that instructs the generation of a hypocenter. In this case, since it is inconvenient to not be able to generate a hypocenter using new hypocenter data that is not stored, it is also possible to transmit the hypocenter data shown in Fig. 7 from the control monitor unit 531 or the optical hybrid system control processor 510 each time a hypocenter generation command is issued, and cause the hypocenter generation unit 115 to generate a hypocenter.

[0045] Figure 12 is a flowchart showing an example of operation in this case, in which steps S15 and S16 in Figure 10 are omitted. In addition, in step S31A, epicenter data is transmitted together with the seismic signal VSA, and in step S14A, reception processing of the epicenter data (optical / electrical conversion) is performed together with reception processing of the seismic signal VSA. Other operations are the same as in Figure 10.

[0046] It is also possible to use a hybrid format in which some data is in the format shown in Fig. 10 and some data is in the format shown in Fig. 12. In other words, some of the hypocenter data is in the format shown in Fig. 7, and for data not included in that, priority hypocenter data is included in the seismic source signal VSA to generate a seismic source.

[0047] In the first embodiment of the above-mentioned series-integrated type, the seismic source 115 and the optical 4C sensor 120 are modularized into an integrated unit and arranged in close proximity, so that the epicenter of the seismic source 115 can be used to detect malfunctions (including abnormality detection) of the optical 4C sensor 120.

[0048] An example of operation in this case is shown in the flowchart of Figure 13. First, the optical 4C sensor 120 is driven using the method described above (passive or active) (step S50), and then seismic source data (sweep waves, pseudorandom waves, etc.) is transmitted to the optical seismic source module 110 (step S51). Based on the transmitted seismic source data, the seismic source unit 115 generates a seismic source via the control unit 114-1 and the seismic source driver 114-4 (step S52). The generated sound waves are detected and received by the optical 4C sensor 120 (step S53). The detected optical signal is transmitted to the control and monitoring unit 531 in the optical 4C sensor transceiver unit 530 or the optical hybrid system control and processing unit 510 for analysis (step S54). If the analysis reveals no malfunction, operation continues; if a malfunction is detected, a designated department is notified (step S56). Note that if the sensor malfunctions, the expected signal cannot be detected, or no signal is detected at all.

[0049] Next, a second embodiment (series separation type) of the present invention will be described.

[0050] Figure 14 shows a schematic diagram of the overall configuration of the second embodiment (series-separated type), in which multiple optical seismic source modules 110 (three in this example) and optical 4C sensor modules 130 (three in this example) connected by OBCs are installed in the vicinity of the injection well 501, connected in series in a circular configuration centered on the wellhead, with one optical 4C sensor module 130 located near the wellhead. In other words, the optical seismic source module 100 and the optical 4C sensor module 130 are separated and connected in series. As with the first embodiment, the optical seismic source 100 can be controlled externally, and active exploration using air guns or the like installed on the earthquake generation vessel 500 is also possible.

[0051] A detailed configuration example is shown in Figure 15, which corresponds to Figure 5. For convenience, this example shows two optical seismic source modules 110-1 and 110-2 and two optical 4C sensor modules 130-1 and 130-2, but if we match it to Figure 15, three optical seismic source modules and four optical 4C sensor modules are each connected in series.

[0052] In the second embodiment, the optical seismic source / optical 4C sensor module 100 in the first embodiment is separated into an optical seismic source module 110 and an optical 4C sensor module 130, each of which is modularized, and the optical seismic source module 110 and the optical 4C sensor module 130 are arranged alternately in series, and the operation is the same as in the first embodiment. That is, the optical fibers FB1 to FB5 are arranged in a single bundle in a circular shape from the wellhead and return to the wellhead, and in this second embodiment, the same operations as in Figures 10 to 12 are performed.

[0053] In the first and second embodiments described above, the optical seismic source / optical 4C sensor module 100, the optical seismic source module 110, and the optical 4C sensor module 130 are all arranged in a circle around the injection well, but they may also be arranged in a star shape as shown in Figure 16(A). They may also be arranged in a snake shape as shown in Figure 16(B) or in a finger shape as shown in Figure 16(C). A combination of these arrangements is also possible, but in any case, the optical 4C sensor module 130 is arranged at the wellhead.

[0054] Next, a third embodiment (completely separated type) of the present invention will be described.

[0055] Figure 17 shows the overall configuration of the third embodiment (completely separated type), which consists of multiple optical seismic source modules 110 (12 in this example) connected by OBC and arranged in a star configuration near the injection well 501, multiple optical 4C sensor modules 130 (6 in this example) arranged in a circle, and one optical 4C sensor module 130 arranged at the wellhead, and the optical seismic source module 110 can be controlled externally as desired, as in the first and second embodiments.

[0056] A detailed configuration example is shown in Figure 18, which corresponds to Figure 15.In this example, for convenience, two optical seismic source modules 110-1 and 110-2 and two optical 4C sensor modules 130-1 and 130-2 are shown, but if combined with Figure 17, 12 optical seismic source modules 110 are connected in a star shape, and seven independent optical 4C sensor modules 130 are connected at the wellhead and in a circular shape.

[0057] In the third embodiment, the optical seismic source module 110 and the optical 4C sensor module 130 in the second embodiment are completely separated and modularized, and each is arranged independently, but their operation is the same as in the first and second embodiments. That is, the optical seismic source module 110 operates as shown in Figure 10 or Figure 12, and the optical 4C sensor module 130 operates as either the active type or passive type shown in Figure 11.

[0058] In the third embodiment, the optical seismic source module 110 and the optical 4C sensor module 130 are separate, which has the advantage of increasing the degree of freedom in the installation location and allowing the reliability of the optical seismic source module 110 and the optical 4C sensor module 130 to be examined separately. Note that in Figure 17, the optical seismic source modules 110 are arranged in a star configuration and the optical 4C sensor modules 130 are arranged in a circle, but they can also be arranged in the configuration shown in Figure 16 or in other configurations. In either case, one of the optical 4C sensor modules 130 is installed near the wellhead. Furthermore, by adding an optical fiber for DAS within the OBC of the optical seismic source module 110 and performing distributed acoustic observations, vibrations on the seafloor can be measured in a distributed manner.

[0059] Next, a fourth embodiment of the present invention is shown in FIG. 19, corresponding to FIG. 17 of the third embodiment. In this fourth embodiment, a DAS is installed as a downhole receiver, and is called a DAS-VSP (Vertical Seismic Profile). In this fourth embodiment, since a sensor is installed in the downhole, the propagation distance of elastic waves from the surface is shortened, making seismic exploration possible even when the power of the seismic source is low. Apart from installing a DAS as a downhole receiver, the configuration and operation are the same as those of the third embodiment.

[0060] Next, a sparker that can be used as the vibration generator 115 of the present invention is described with reference to FIG. 20. FIG. 20(A) shows an example of its configuration. The sparker uses a spark discharge in seawater via the switch SW1 and a cable, generating a high-voltage charge stored in capacitor C1 via the starter 150 when switch SW2 is turned on. The resulting shock wave is used as a sound source. A characteristic of the sparker waveform is the generation of two pulses P1 and P2, as shown in FIG. 20(B). Pulse P1 is a shock wave generated when seawater is rapidly vaporized by heat, and pulse P2 is a shock wave generated when the generated bubbles contract and collapse again. The frequency of the waveform obtained by the sparker ranges from several hundred Hz to several kHz, and the frequency band and sound pressure level vary depending on the capacitance and voltage of capacitor C1 used and the ambient water pressure.

[0061] Similarly, a boomer that can be used as the vibration generating unit 115 of the present invention will be explained with reference to Figure 21. Like the sparker, the boomer also discharges the high voltage charge stored in capacitor C2. That is, when switch SW3 is turned on, a discharge current from capacitor C2 flows through a spiral coil 160, and eddy currents are induced in a metal disk 161 facing the coil 160. This generates an electromagnetic force, which causes the metal disk 161 to move, generating a shock wave.

[0062] Furthermore, an underwater speaker such as that disclosed in Japanese Patent Laid-Open Publication No. 8-205275 can be used as the vibration generating unit 115. A typical underwater speaker has a permanent magnet elastically attached to a diaphragm, facing a voice coil attached to the diaphragm, and the diaphragm vibrates underwater when pushed back from inside the underwater speaker with an elastic force equal to the water pressure. This characteristic ensures that the conversion efficiency is not affected by changes in external pressure, and the frequency characteristics are well maintained.

[0063] The light used in this invention is laser light, but as shown in Figure 22(A), the fed power attenuates according to the transmission distance (km). Also, Figure 22(B) shows an example of the wavelength-attenuation characteristics, and it can be seen that a wavelength of 980 nm is advantageous for transmission distances in the range of 1 km to 5 km. Therefore, in this invention, laser light with a wavelength of 980 nm, which has little attenuation, is used.

[0064] As an optical fiber sensor, it is also possible to measure the optical characteristics of the fiber using DTS (Distributed Temperature Sensing), DSS (Distributed Strain Sensing), or OTDR (Optical Frequency Domain Reflectometry), and the optical fiber sensor OFS using a 3x3 optical coupler described below can also be used as a three-axis acceleration sensor.

[0065] 23 shows a first embodiment of the optical fiber sensor OFS. A laser light source 350 and a 2x2 optical coupler 351 are connected via an SM fiber F1, and the 2x2 optical coupler 351 and a 3x3 optical coupler 352 are connected via an SM fiber F2. Two SM fibers F3, F4, and F4' that constitute an interferometer are connected to the 3x3 optical coupler 352. The SM fiber F3 constitutes a reference path, and the SM fibers F4 and F4' constitute a measurement path. FRMs 353 and 354 are connected to the tips of the SM fibers F3 and F4', respectively, via spatial coupling prisms. An acceleration sensor 360, serving as a measurement target, is disposed midway between the SM fibers F4 and F4' on the measurement path, and optically measures the relative displacement d of the acceleration sensor 360. The acceleration sensor 360 includes a prism mirror 361. Furthermore, an SM fiber F5 having a delay unit DL1 (for example, a delay time τ) and an SM fiber F6 having a delay unit DL2 (for example, a delay time 2τ) are connected in parallel between the 3×3 optical coupler 352 and the optical combining unit 355, and an SM fiber F7 is connected between the optical combining unit 355 and the 2×2 optical coupler 351. Furthermore, one SM fiber F8 serving as an output line is connected to the optical combining unit 355.

[0066] An example of the operation of such a configuration will be described with reference to the flowchart of FIG.

[0067] First, a laser pulse L1 is emitted from the laser light source 350 (step S100). The laser pulse L1 is transmitted through the SM fiber F1, passes through the 2×2 optical coupler 351, and is transmitted as a laser pulse L2 through the SM fiber F2 to the 3×3 optical coupler 352 (step S101). The laser pulse L2 is branched by the 3×3 optical coupler 352 into two-phase laser pulses L3 and L4 for interference (step S102), which are transmitted through the SM fiber F3 of the reference path and the SM fibers F4 and F4' of the measurement path, respectively. The reference laser pulse L3 is reflected by the FRM 353 at the end and is transmitted in the opposite direction through the same SM fiber F3 as a reference reflected laser pulse L5 (step S103). The branched measurement laser pulse L4 is transmitted through the measurement section of the acceleration sensor 360 (step S104), then reflected by the FRM 354 at the end of the SM fiber F4' (step S105), transmitted in the reverse direction through the SM fibers F4' and F4 as a measurement reflected laser pulse L6, and transmitted to the 3x3 optical coupler 352 through the measurement section of the acceleration sensor 360 (step S106).

[0068] The reference reflected laser pulse L5 and measurement reflected laser pulse L6 returned by the SM fibers F3 and F4, respectively, are transmitted to the 3×3 optical coupler 352, where they interfere with each other and are converted into three-phase laser pulses L7, L8, and L9 (step S110). Here, if the phase difference between the reference reflected laser pulse L5 and measurement reflected laser pulse L6 is φ, a constant representing the DC offset is C, and a constant representing the AC amplitude is B, the two-phase to three-phase conversion in the 3×3 optical coupler 352 is performed according to the following equation 1: (Number 1) L7=C+B·cos(φ) L8=C+B·cos(φ+2π / 3) L9=C+B·cos(φ-2π / 3) The converted first-phase laser pulse L7 is transmitted to the 2×2 optical coupler 351 through the SM fiber F2 (step S111), and further transmitted from the 2×2 optical coupler 351 through the SM fiber F7 as a laser pulse L7A (peak value X1) to the optical combining unit 355 (step S112). The converted second-phase laser pulse L8 (peak value X2) is transmitted through the SM fiber F5 (step S113), passes through a delay unit (delay time τ) DL1, and is transmitted to the optical combining unit 355 (step S114). The converted third-phase laser pulse L9 (peak value X3) is transmitted through the SM fiber F6 (step S115), and is transmitted to the optical combining unit 355 through a delay unit (delay time 2τ) DL2 (step S116).

[0069] The optical combiner 355 combines (logically ORs) the transmitted laser pulses L7A, L8, and L9 (step S120). Laser pulses L8 and L9 are shifted by delay times τ and 2τ, respectively, relative to laser pulse L7A, and therefore output pulse train PT1 from optical combiner 355 is in a time-division format (step S121). Output pulse train PT1 is input to an optical / electrical converter at the base station and converted into an electrical signal (step S122). A calculation unit or the like measures peak values ​​X1, X2, and X3 of each pulse, and calculates relative displacement d of acceleration sensor 20 (step S123).

[0070] Next, a second embodiment in which multiple measurement targets are measured simultaneously by time division multiplexing will be described with reference to Fig. 25. Although Fig. 25 shows three interferometers 3100, 3110, and 3120 as measurement targets, the present invention is not limited to this. Interferometers 3100, 3110, and 3120 have the same configuration, and are similar to the configuration of the sensor side (interferometer) in Fig. 23.

[0071] A laser light source 3101 that emits laser pulse L10 is connected to an optical coupler 3102 by an SM fiber F10, the optical coupler 3102 and interferometer 3100 are connected by an SM fiber F11, and the optical coupler 3102 is connected to an optical coupler 3103 by an SM fiber F12 via a delay unit DL10. The TDM output of the interferometer 3100 is connected to an optical combiner 3104 by an SM fiber F14, the optical coupler 3103 and interferometer 3110 are connected by an SM fiber F15, and the interferometer 3120 is connected to an SM fiber F18 via a delay unit DL11. The TDM output of the interferometer 3110 is connected to the optical combiner 3104 by an SM fiber F16, and the combined output of the optical combiner 3104 is connected to an optical combiner 3106 by an SM fiber F17. The TDM output of the interferometer 3120 is connected to the optical combiner 3106 via an SM fiber F20, and the combined output of the optical combiner 3106 is transmitted via an SM fiber F21.

[0072] An example of the operation of such a configuration will be described with reference to the flowchart of FIG.

[0073] First, a laser pulse L10 emitted from a laser light source 3101 is transmitted to an optical coupler 3102 via an SM fiber F10 (step S200), and is converted into two-phase pulses, a measurement pulse L11 and a delay pulse L12, in the optical coupler 3102 (step S201). The measurement pulse L11 from the optical coupler 3102 is transmitted to an interferometer 3100 via an SM fiber F11, and the interferometer 3100 performs the same operation as that described in the first embodiment (step S210), and a time-division pulse train PT10 is output from the interferometer 3100 and transmitted to an optical combiner 3104 via an SM fiber F14 (step S211). Furthermore, the delay pulse L12 from the optical coupler 3102 passes through the delay unit DL10 (step S202), and is transmitted to the optical coupler 3103 through the SM fiber F12 (step S203), where it is converted into two-phase pulses, a measurement pulse L13 and a delay pulse L14 (step S204). The measurement pulse L13 is transmitted to the interferometer 3110 through the SM fiber F15, where an operation similar to that described in the first embodiment is executed (step S220), and a time-division pulse train PT11 is output from the interferometer 3110 and transmitted to the combining unit 3104 through the SM fiber F16 (step S221).

[0074] In addition, the delay pulse L14 from the optical coupler 3103 passes through the delay unit DL11 (step S205) and is transmitted to the interferometer 3120 via the SM fiber F18, and the interferometer 3120 performs the same operation as described above (step S230), and a time-division pulse train PT12 is output from the interferometer 3120 (step S231).

[0075] In the optical combiner 3104, the pulse trains PT10 and PT11 are combined on the time axis (step S240), and a combined pulse train PT20 is formed (step S241), and the pulse train PT20 is transmitted to the optical combiner 3106 through the SM fiber F17.

[0076] The time-division pulse train PT12 from the interferometer 3120 is transmitted to the optical combiner 3106 via the SM fiber F20, where the pulse trains PT12 and PT20 are combined on the time axis (step S242), and the combined pulse train PT21 is output (step S243). The pulse train PT21 is transmitted to the optical / electrical converter of the base station 100 via the SM fiber F21 (step S244), where it is converted optically to electricity (step S245), and the relative displacement of the acceleration sensors of the interferometers 3100, 3110, and 3120 is measured by measuring the peak values ​​of the pulses in each pulse train (step S246).

[0077] 25 illustrates three objects to be measured (interferometers 3100, 3110, and 3120), but n (≧2) interferometers may be used as the objects to be measured. That is, this optical fiber sensor transmits measurement pulses to n (≧2) interferometers, each including an object to be measured, optically combines and outputs TDM pulse trains corresponding to the displacements of the objects to be measured from the n interferometers, and is provided with (n−1) optical couplers that convert laser pulses into two phases, a measurement pulse and a delay pulse, where the first-stage optical coupler inputs a laser pulse from a laser light source, the second- to (n−1)-th optical couplers input the delay pulse from the previous stage via a delay unit, and the n-th optical coupler transmits the delay pulse from the (n−1)-th optical coupler to the n-th interferometer and inputs it, and the TDM pulse trains output from the n interferometers are sequentially and additionally optically combined to output a multiplexed TDM pulse train.

[0078] Although the above describes the optical power feed from a permanently installed power source on the seabed, the seismic source device, and its observation system, it can also be applied to ground observation as shown in Fig. 27. That is, optical power is fed from a base station 400 via an optical fiber 401 to a permanent power source at an observation station 410 installed on land in a remote location, and vibrations of a seismic source 420 connected to the observation station 410 are observed by a sensor group 450.

[0079] 28 is a connection diagram showing the results of a demonstration test of the optical power supply of the present invention. Light from a light source (wavelength: 980 nm, output power: 22 W) was transmitted through a 2000 m long optical fiber (core: 105 μm, cladding: 125 μm) and input to an optical-voltage conversion element. As a result, an output power of 2.5 W (output voltage: 19 V, output current: 0.135 A) was obtained from the optical-voltage conversion element. By using this output, the power required to drive the seismic source can be supplied to the charging unit. [Explanation of symbols]

[0080] 1. Research vessel 2 Oscillating rod 3. Air guns 4 Streamer Cable 5 Hydrophone 10 Pipeline 11 Pressure well 30 Fixed Offshore Rig 31 OBC 33 Earthquake Ship 100 (100-1, 100-2) Optical Seismic Source / Optical 4C Sensor Module 101 Submarine permanent enclosure 110 Optical Seismic Source Module 111 Optical / electrical (O / E) conversion unit 111-1 Heat / electricity conversion section 111-2 Heat dissipation fin 112 Live parts 113 Permanent power supply (secondary battery) 114 Drive control unit 114-1 Control section 114-2 Charge determination section 114-3 Electrical / Optical (E / O) Conversion Unit 114-4 Seismic drive unit 115 Source 116 Transmitter / Receiver 120, 130 Optical 4C sensor module 140 Non-reflective termination 150 Starting section 160 Metal Disc 161 Coil 500 Earthquake Ship 501 Injection well 510 Optical Hybrid System Control Processing Unit 520 Optical power supply / control unit 521 Power supply section 522 Optical / Electrical (O / E) Conversion Unit 523, 531 Control and monitoring section 530 Optical 4C sensor transmitter / receiver 540 DAS transmitter / receiver

Claims

1. In a seismic source device that generates active vibrations by driving a seismic source unit with a drive control unit connected to an optical power supply / control unit installed on land or on the sea by an optical fiber cable and connected to a permanent power source installed on the seabed or on land in a remote location, The permanent power supply and the drive control unit are modular, a charging function of converting optical power transmitted from the optical power supply / control unit via a first optical fiber cable into electricity in the module and charging the permanent power supply with the converted electrical energy; a control function for optically / electrically converting a control signal transmitted from the optical power supply / control unit via a second optical fiber cable within the module and controlling the drive control unit with the converted electrical signal; a determination function for determining a charging state of the permanent power source; and transmitting the judgment result of the judgment function to the optical power supply / control unit via the second optical fiber cable, driving the vibration generating unit when the charge is sufficient, and charging the permanent power supply when the charge is insufficient.

2. An optically powered seismic source device as described in claim 1, in which a thermal / electrical conversion unit consisting of a Seebeck effect element is provided in contact with the side of the housing of the component that performs the optical / electrical conversion, and a heat dissipation fin is provided on the opposing surface of the thermal / electrical conversion unit, so that the permanent power supply is charged with the electricity generated by the thermal / electrical conversion unit.

3. An optically powered seismic source device as described in claim 1 or 2, wherein the first optical fiber cable and the second optical fiber cable are a single optical fiber cable of double-clad optical fiber that serves both optical power supply and control.

4. 3. The optically powered seismic source device according to claim 1, wherein the drive of said vibration generating unit by said drive control unit is controlled based on seismic source data including a lower limit of frequency, an upper limit of frequency, time, amplitude and number of times.

5. 5. The optically powered seismic source device according to claim 4, wherein the seismic source data is a sweep waveform.

6. An observation system characterized in that optical fiber sensors that input and output laser light using an OBC (Ocean Bottom Cable) are arranged in a circular, star, snake, or finger shape near the optically powered seismic source device described in claim 1 or 2, and that the optical fiber sensors detect active vibrations and perform physical exploration.

7. The observation system of claim 6 , wherein the OBC is a single-ended configuration.

8. 8. The observation system according to claim 6, wherein the optical fiber sensor is a three-axis acceleration sensor, an optical hydrophone, and a DAS (Distributed Acoustic Sensing).

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