Abstract: Warm water is pumped up by a pump from an underground aquifer present 1000 to 1500 m below the seabed, geothermal energy is caused to flow through a permeable layer below a methane hydrate layer, a dissociation boundary surface of an un-dissociated area of the methane hydrate layer is dissociated to generate methane gas, the methane gas is led into a production well from peripheral areas and through a gas inlet screen and caused to rise so that the methane gas is collected on the sea.

Abstract: An object is to provide a method capable of boring a borehole even when quartz glass or silicon dioxide is deposited as molten dross by laser irradiation. A laser irradiation position of a workpiece is irradiated with a laser having wavelength of 1.2 ?m or longer and a high factor of absorption into liquid, for example, a CO2 laser, from a laser oscillator through liquid. By high pressure generated in an advancing microbubble flow occurring in the liquid, molten dross is scattered. Thus, the processing, such as boring, of the rock is performed.

Abstract: An excavation technique for a stratum capable of excavating a submerged stratum such as a layer containing an underground resource by using laser irradiation in liquid is provided. In this technique, a laser beam transmitted through laser transmission means 20 is irradiated in liquid 90 in form of a laser beam having a wavelength with high absorptance of the liquid 90 by laser-induced bubble generation means 35, generating a bubble flow 36, thus excavation of a submerged stratum may be carried out by using a laser-induced destruction effect. Moreover, a laser beam 41 having low absorptance of the liquid 90 is irradiated by laser irradiation means 39 and passed through the bubble flow 36, thereby applying a thermal effect to a stratum to destroy rock and excavate the stratum. The destruction effect and the thermal effect also may be cooperatively worked.

Abstract: An object is to provide a method capable of boring a borehole even when quartz glass or silicon dioxide is deposited as molten dross by laser irradiation. A laser irradiation position of a workpiece is irradiated with a laser having wavelength of 1.2 ?m or longer and a high factor of absorption into liquid, for example, a CO2 laser, from a laser oscillator through liquid. By high pressure generated in an advancing microbubble flow occurring in the liquid, molten dross is scattered. Thus, the processing, such as boring, of the rock is performed.

Abstract: An excavation technique for a stratum capable of excavating a submerged stratum such as a layer containing an underground resource by using laser irradiation in liquid is provided. In this technique, a laser beam transmitted through laser transmission means 20 is irradiated in liquid 90 in form of a laser beam having a wavelength with high absorptance of the liquid 90 by laser-induced bubble generation means 35, generating a bubble flow 36, thus excavation of a submerged stratum may be carried out by using a laser-induced destruction effect. Moreover, a laser beam 41 having low absorptance of the liquid 90 is irradiated by laser irradiation means 39 and passed through the bubble flow 36, thereby applying a thermal effect to a stratum to destroy rock and excavate the stratum. The destruction effect and the thermal effect also may be cooperatively worked.

Abstract: A method for boring a well with a laser beam is provided, the method comprising: shining the laser beam into a conduit, wherein the laser beam is guided through the conduit by the internal reflectivity of said conduit; and extending the conduit into the well, so that the laser beam exiting the conduit shines onto an area in the well to be bored. A system for boring a well with a laser beam is also provided, the system comprising: a means for shining the laser beam into a conduit; wherein the laser beam is guided through the conduit by the internal reflectivity of said conduit; and a means for extending the conduit into the well, so that the laser beam exiting the conduit shines onto an area in the well to be bored. An apparatus is provided as well, comprising a conduit that is extendable into the well, and an inner surface inside of the conduit, wherein the inner surface is reflective to the laser beam.

Abstract: By using a reaming machine which arranges a plurality of hydraulic hammer driven drill bits in parallel on a cross section to be reamed, a horizontal or gently inclined pilot hole is reamed. A pressurized water introducing drill pipe and a drill pipe as a discharge pipe are connected to the reaming machine, a seal which forms a sealing between the drill bits and a reamed hole is provided, and a passage for feeding drilling water into the drill pipe is provided, whereby the reaming machine can be propelled while discharging cuttings with a small amount of water through the drill pipe.

Abstract: A dual hoist derrick system for deep sea drilling, capable of elevating a very long and massive heavy object involved in a drilling for deep sea, is provided with a normal drilling hoisting system and a heavy load hoisting system arranged on a single derrick in parallel. The derrick is mounted on a skid movable in a horizontal direction. The skid is provided with a cut broader than a blow-out prevention device, so that the skid may travel to a position of the blow-out prevention device to lift up the blow-out prevention device. The system contributes to speeding up in hoist speed of offshore drilling units for deep sea, reducing working hours and improvement in safety.

Abstract: Disclosed is a buoy which comprises a high density polyethylene foam as a buoyant member, and an outer skin covering the surface of the foam. The buoy has excellent resistance against external force and the loss of the buoyancy by the reduction of the volume is minimized.