JP2006046009A - Device and method of collecting hydrocarbon gas resources existing underground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently collect methane by transmitting heat energy without heat loss from the sea or land to a stratum where methane hydrate exists, to heat the methane hydrate. <P>SOLUTION: This device is provided with a laser oscillator 4 installed at a floating type marine structure A or on the ground; an optical fiber 1 for leading laser beams outputted from the laser oscillator 4 to the stratum B where methane hydrate exists; and a light/heat converting member 5 provided at the tip part of the optical fiber 1 to convert the laser beams into heat energy. The stratum B where methane hydrate exists, is heated with heat converted by the light/heat converting member 5 to decompose methane hydrate, to separate methane and to collect floating methane. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for collecting hydrocarbon gas such as methane gas from methane hydrate existing in the ground.

  Various underground resources such as oil are buried underground, but recently methane hydrate has attracted attention as an underground resource.

  In methane hydrate, a plurality of water molecules gather to form a dodecahedron, tetrahedron, or hexahedron cage, and the methane molecule is confined in the cage to form one molecule, which is crystalline or Randomly assembled.

  This methane hydrate exists deep underground in the world, such as in rocks beneath the seabed and in Siberia. It should be noted that even in the vicinity of Japan, it has been confirmed that it is widely present under the seafloor off Tokai, etc., and is expected as an energy resource.

  Methane hydrate is formed under a high pressure at a low temperature. As shown in the phase equilibrium curve diagram of FIG. Methane hydrate is formed in (left side of) and when the temperature is increased or the pressure is decreased (to the right side of the curve), it is separated into methane gas and water.

  In order to separate methane gas from methane hydrate, the state must be on the right side of the phase equilibrium curve shown in FIG. That is, at the same pressure, the temperature must be increased by several tens of degrees. Further, 79 cal of heat energy per gram of ice is required as latent heat to be dissolved from ice to water, and much heat energy is required to heat methane hydrate including the heat of dissolution.

As described in the following patent document, as a method of supplying thermal energy to methane hydrate existing in the ground and collecting methane gas, the seabed is drilled to the formation where methane hydrate exists. A well is opened, a laser beam is guided from the sea through an optical fiber inserted into this well, and the formation where methane hydrate is present is irradiated and heated to decompose the methane hydrate and separate the methane gas. A method has been proposed for collecting methane gas.
Japanese Patent No. 3506696

  According to this method, methane hydrate, particularly a laser beam with a wavelength absorbed by water, must be selected and irradiated as the laser beam to be used, so there are limitations on the selection of the laser light source, and an optical fiber that transmits the laser beam. The spectral transmission characteristics must also be considered.

  Therefore, the present invention has been conceived to solve such a problem, and transmits energy from the ocean or land to the formation where methane hydrate exists, with a small heat loss by a laser beam. It aims to collect methane gas efficiently by converting energy into heat energy and indirectly heating methane hydrate.

  The underground gas storage apparatus according to the present invention includes a floating ocean structure or a laser oscillator installed on the ground, an optical fiber that guides a laser beam output from the laser oscillator to a formation where methane hydrate exists, The optical fiber has a light / heat conversion member that converts laser light into heat energy at the tip of this optical fiber, and heats the formation where methane hydrate is present by the heat converted by the light / heat conversion member. It is a device that decomposes and separates methane gas and collects methane gas that rises.

  According to the method for collecting underground gas resources according to the present invention, a laser beam output from a floating marine structure or a laser oscillator installed on the ground is guided to a formation where methane hydrate is present by an optical fiber, and is applied to the tip of the optical fiber. Laser light is converted into thermal energy by the installed light / heat conversion member, the formation where methane hydrate exists is heated by this thermal energy, methane hydrate is decomposed to separate methane gas, and floating methane gas is collected It is a method to do.

  According to the underground methane gas resource collection apparatus of the present invention, a laser beam is transmitted to a deep formation where methane hydrate exists by using an optical fiber, that is, energy for heating is transmitted with high efficiency. Therefore, it is possible to efficiently collect methane gas from methane hydrate, and the economic and practical effects are extremely large.

  Since methane hydrate is indirectly heated by a light-to-heat conversion member, there is no need to select a laser beam of a wavelength that is absorbed by methane hydrate, and it is only necessary to consider the wavelength of the laser beam to be used and the spectral transmission characteristics of the optical fiber. Various laser light sources and optical fibers can be selected.

  The drilling pipe is lowered from the floating offshore structure (offshore facility) to the bottom of the sea, and the formation below the bottom of the sea is drilled to the formation where methane hydrate exists, forming a well. The formation of this well can be formed by the same technique as that of oil drilling.

  As shown in FIG. 1, the underground existing gas resource collecting apparatus of the present invention includes a floating marine structure A, and the floating marine structure A includes an apparatus for lowering a pipe 3 to an excavated well. A device for lowering the flexible tube 2 through which the optical fiber 1 has been inserted in advance into the pipe 3, a reel 7 for winding the flexible tube 2, a laser oscillator 4 for sending a laser beam through the optical fiber 1, and a pipe 3 A levitated material processing apparatus 8 that separates methane gas from levitated matter that has levitated via a flow path between the flexible tube 2 and a pump 6 that sucks the levitated matter and pumps it in the opposite direction.

  As shown in FIGS. 2 and 3, a light / heat conversion member 5 that converts the transmitted laser beam into heat energy is coupled to the distal end of the flexible tube 2. The light / heat conversion member 5 includes a heat converter 51 and a radiator 53.

  The light / heat converter 51 has an inverted frustoconical shape, and has a space 52 therein. The light / heat converter 51 protects the tip of the optical fiber 1 and diffuses a transmitted laser beam (not shown). The light / heat converter 51 is heated by diffusing the laser beam by this concave lens and irradiating the inner wall surface. The inner wall surface of the light / heat converter 51 is preferably made of a material close to a black body that absorbs radiation of all wavelengths, but a material having an absorption spectrum at the wavelength of the laser beam to be used is selected.

  The heat radiator 53 has a tapered hole 54 into which the light / heat converter 51 is fitted, and a heat conductor 55 to be fitted into the earth retaining pipe 9 which is driven to the formation B where the methane hydrate exists is provided. ing. The heat conductor 55 is composed of ring-shaped blades or blades arranged in a radial manner, and conducts heat generated by the light / heat converter 51 to the earth retaining pipe 9 to heat the surrounding methane hydrate.

  As the material of the radiator 53, copper having good heat conductivity is suitable. Note that if the bottom of the taper hole 54 is passed through without closing, even if dirt or sand enters the taper hole 54, the light / heat converter 51 can be correctly fitted to the taper hole 54. .

  The earth retaining pipe 9 is driven to the vicinity of the lowermost part of the formation B where methane hydrate exists. A number of holes or slits 91 are formed in the earth retaining pipe 9 over a range corresponding to the thickness of the formation B where methane hydrate exists.

  As shown in FIGS. 2 and 3, a plurality of centering springs 34 bent in an arc shape are attached in the vicinity of the distal end of the flexible tube 2 through which the optical fiber 1 is inserted. When the tip of the tube reaches the tip of the pipe 3, the tip of the flexible tube 2 is guided to the center of the pipe 3, and the tip of the flexible tube 2 is projected below the pipe 3.

  In the floating offshore structure A, the upper end of the pipe 3 is closed by a valve 36 inserted through the flexible tube 2, and the levitated object that has been sucked up by the pump 6 and moved up in the pipe 3 is levitated through the valve 21. It couple | bonds so that it may lead to the material processing apparatus 8. FIG. In addition, it is not necessary to operate the pump when the floating object contains a lot of gas and the specific gravity is light and self-injection.

  Further, the pump 6 is operated in the reverse direction, and the warm water or seawater accumulated in the pipe 3 may be sent back to the formation B where the methane hydrate exists to stir the dissolved methane hydrate. It is.

  As shown in FIG. 4, in the floating offshore structure A, the flexible tube 2 through which the optical fiber 1 has been inserted in advance is wound around the reel 7 by the expected length, and the optical fiber 1 and the flexible The tube 2 is coupled to the laser oscillator 4 via a swivel joint 71 that coaxially couples the tube 2.

  As the laser oscillator 4, an iodine laser device (abbreviated as COIL) that chemically generates a laser beam having a wavelength range (1.0 to 1.3 μm) with low transmission loss of quartz fiber, or A YAG laser device that generates laser light by electric energy is suitable. That is, as is apparent from the characteristic curve of FIG. 5 showing the spectral characteristics of transmission loss of quartz fiber, the laser beam having a wavelength (1.3 μm) output from the iodine laser device and the wavelength (1. 06 μm) can be transmitted over long distances with little loss.

  It has been experimentally proven that a laser beam (energy) of 4 kW or more can be transmitted using a 0.6 mm diameter quartz fiber, and a laser beam of 10 kW or more can be sufficiently transmitted using a 1 mm diameter quartz fiber. When several quartz fibers are bundled, it is possible to transmit a laser beam of several tens of kW or more to a formation where methane hydrate is separated by 1000 m or more.

  Next, a process of collecting methane gas using the underground existing hydrocarbon gas resource collecting apparatus configured as described above will be described.

  The earth retaining pipe 9 is driven into the well drilled to the vicinity of the bottom of the formation B where methane hydrate exists. As shown in FIG. 3, the radiator 53 of the light / heat conversion member 5 is fitted into the lower end portion of the retaining pipe 9. Next, the pipe 3 is lowered from the floating offshore structure A. The pipe 3 has its tip lowered to the vicinity of the uppermost part of the formation B where methane hydrate exists.

  Since the pipe packer 35 is attached in the vicinity of the tip of the pipe 3, the pipe packer 35 is expanded by remote operation to seal the gap between the pipe 3 and the retaining pipe 9. Further, the gap between the earth retaining pipe 9 and the formation can be sealed by the pipe packer.

  The light / heat converter 51 of the light / heat conversion member 5 is attached to the tip of the flexible tube 2 through which the optical fiber 1 wound on the reel 7 is inserted, and the flexible tube 2 is pulled out while being inside the pipe 3. Descent. Since a plurality of centering springs 43 bent in an arc shape are attached to the outer periphery of the distal end portion of the flexible tube 2, the distal end of the flexible tube 2 is guided to the center of the pipe 3. The tip of the flexible tube 2 is projected below the pipe 3, and the light / heat converter 51 is guided to the tapered hole 54 of the radiator 53 and fitted.

  When the laser oscillator 4 is operated and a high energy laser beam output from the laser oscillator 4 is diffused by a concave lens from the tip of the optical fiber 1 and irradiated on the inner surface of the light / heat converter 51, the light / heat converter is heated. Since the temperature of 51 rises, the lower part of the earth retaining pipe 9 is heated through the radiator 53 to decompose the methane hydrate present in the surrounding area into moisture and methane gas.

  The types of rocks that coexist with methane hydrate are sandstone, limestone, shale, etc., which are finely crushed into sand, but are conductively heated and separated into rock, water, and methane gas. Over time, the rocks settle, so the water-only space expands, and the water with increased temperature convects and decomposes a wider range of methane hydrate.

  Methane gas decomposed together with water enters the pipe 3 through the hole 91 of the retaining pipe 9 and rises. Small rocks (sand) that entered the earth retaining pipe 9 are guided to the levitated material treatment device 8 installed in the floating offshore structure A together with fluid (water, seawater, gas), and separated to collect methane gas. Is done.

  In the embodiment described above, the method of collecting methane gas from the formation B in which methane hydrate exists using the floating offshore structure A has been described. Can be collected. Further, it is possible to collect methane gas while excavating the formation B in which methane hydrate exists by applying petroleum drilling technology.

Schematic diagram showing an embodiment of marine or ground facilities used in the underground methane gas resource collection device of the present invention, The longitudinal cross-sectional view which shows embodiment of the front-end | tip part of the flexible tube which penetrated the pipe lowered | hung to the formation where methane hydrate exists, and the optical fiber, A longitudinal sectional view showing a state before the light / heat converter attached to the tip of the flexible tube through which the optical fiber is inserted is fitted into the tapered hole of the radiator, Cross-sectional view showing reels at sea or above ground facilities, A characteristic curve showing the spectral characteristics of transmission loss of quartz fiber, It is a phase equilibrium curve figure of methane hydrate.

Explanation of symbols

A Floating marine structure B Geologic layer with methane hydrate 1 Optical fiber 2 Flexible tube 3 Pipe 4 Laser oscillator 5 Light / heat conversion member 6 Pump 7 Reel for winding flexible tube 8 Floating object processing device 9 Earth retaining pipe
51 Light-to-heat converter
53 Heatsink
54 Taper hole 54
55 Thermal conductor

Claims (4)

A laser oscillator installed on a floating marine structure or on the ground, an optical fiber that guides the laser beam output from the laser oscillator to the formation where methane hydrate exists, and converts the laser beam into thermal energy at the tip of the optical fiber Methane gas that has a light-to-heat conversion member that heats a formation in which methane hydrate is present by heat converted by the light-to-heat conversion member, decomposes methane hydrate to separate methane gas, and floats An underground existing gas resource collection device characterized by collecting gas. The underground existing gas resource collecting apparatus according to claim 1, wherein a radiator for expanding a heat transfer area is provided outside the light / heat conversion member. 2. The underground existence gas according to claim 1, wherein the laser oscillator is a laser device that outputs a laser beam having a wavelength capable of transmitting a low-loss fiber such as a COIL laser or a YAG laser that chemically generates a laser beam. Resource collector. The laser beam output from the floating offshore structure or the laser oscillator installed on the ground is guided to the formation where methane hydrate exists by the optical fiber, and the laser beam is heated by the light / heat conversion member provided at the tip of the optical fiber. Converting to energy, heating the geological layer where methane hydrate is present with the above-mentioned thermal energy, decomposing methane hydrate to separate methane gas, and collecting floating methane gas Collection method.

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