Disclosed are a device and a method of drilling a hydrate micro-borehole and performing fast completion, which belongs to the technical field of a hydrate extraction device and a hydrate extraction method. The method includes a continuous operation machine, a power control mechanism, a high pressure water jet pump, a guider, a continuous pipe, a parent pipe and a child pipe, the parent pipe is connected with the continuous operation machine, and an end of the child pipe is connected with a water jet nozzle; the working method basically includes the following: firstly, a large main borehole is formed by drilling to a destination layer at one time with a large size drill bit; secondly, a horizontal micro-borehole is drilled in a natural gas hydrate reservoir by a high pressure water jet device formed by the child and parent pipes and then the child pipe is heated to enable its skin to fall off and leave a screen; finally, the child and parent pipes are disconnected to perform well completion. The present disclosure is applicable to different natural gas hydrate extraction manners. In this way, well drilling and completion is integrated, sand production is effectively inhibited, and the production of the hydrate reservoir is increased with a small effect on the hydrate reservoir. Thus, drilling is accelerated.

In a gas collecting method for collecting gas yielding from source material on a sea bottom, [1] releasing a collecting membrane into water, a fixture being connected with a lower end of the collecting membrane and the collecting membrane being flared downward from its top; [2] keeping a three-dimensional position of the fixture at a target position with its autonomous navigation by a position maintainer provided in the fixture; [3] based on vertical water temperature distribution, setting the lower end at a position that is higher than the sea bottom and shallower than a water depth where the source material separates from its solid state into water and gas and setting the top at a deeper position than a water depth where bubbles of the gas disappear due to mixture of the gas with seawater; and [4] collecting the gas released from the sea bottom by the collecting membrane.

A hydrate solid-state fluidization mining method and system under an underbalanced reverse circulation condition are used for solid-state fluidization mining on a non-rock-forming weak-cementation natural gas hydrate layer in the ocean. Equipment includes a ground equipment system and an underwater equipment system. The construction procedure includes an earlier-stage construction process, pilot hole drilling construction process, reverse circulation jet fragmentation process, underbalanced reverse circulation fragment recovery process and silt backfilling process. Natural gas hydrates in the seafloor are mined through an underbalanced reverse circulation method. Problems such as shaft safety, production control and environmental risks faced by conventional natural gas hydrate mining methods such as depressurization, heat injection, agent injection and replacement are effectively solved. By using the method, the weak-cementation non-rock-forming natural gas hydrates in the seafloor can be mined in environment-friendly, efficient, safe and economical modes, more energy resources can be provided, and energy shortage dilemmas are solved.

The present invention discloses a pressurized test device and method for in-situ mining natural gas hydrates by jets, relating to the field of exploitation of marine natural gas hydrates. The device comprises an injection system, a jet breakup system, an annular pressure system, an axial pressure system, a backpressure system, a vacuum system, a simulation system, a collecting and processing system and a metering system, all of which can operate independently by controlling pipe valves on pipelines. The loading of the confining pressure of the device is independent of the loading of the axial pressure, without interference to each other. Meanwhile, the jet breakup process of natural gas hydrate-containing sediments can be observed in real time by a video camera.

A real-time monitoring apparatus for seafloor deformation during hydrate exploitation, includes a main frame, a detecting device, and a sensing and wireless data transmitting device. The detecting device includes at least two detecting straight rods in different directions; the detecting straight rods are connected to the main frame through the movable sleeves; and at least two fixing supports are configured below each detecting straight rod, perpendicular to and uniformly distributed along the detecting straight rod. A movable lever is configured above each detecting straight rod, the movable lever is connected to the main frame through the lever-fixing rod, and a stretchable and compressible spring is configured at an upper end of the movable lever. The sensing and wireless data transmitting device includes at least two tension and compression force sensors in different directions, a gyroscope sensor, a wireless data transmitter, and a power source, all mounted in the main frame.

Disclosed is a new drilling casing, including a casing wall and several sand control apparatuses disposed on the casing wall in a spacing, wherein each sand control apparatus includes a sand control net, a sealing steel sheet and a sealing rubber plug, a plurality of mutually-paralleled sand control meshes are disposed on the sand control net, the sand control mesh exactly faces the sealing steel sheet, and the sand control net is connected with the sealing steel sheet through a steel pin. Further a method of performing fast drilling and completion of a large-borehole multilateral well by using the new drilling casing is disclosed. a main borehole is formed by drilling to a destination well depth at one time with a large size drill bit, a lateral borehole is then drilled in a natural gas hydrate reservoir by using the new drilling casing, and then, the drill bit is taken out for completion. The method is applicable to various natural gas hydrate extraction manners. The method greatly increases production and recovery rate of a hydrate well by integrating well drilling and completion in a shorter drilling and completion period, thereby saving lots of labor and materials, and ensuring effective sand control.

A method and equipment for harvesting natural gas from seabed hydrates are disclosed. The preferred equipment includes a mobile riser, a water injection nozzle, a gas collector, a gas separator, a gas compressor, a water pump, and a water boiler. A fraction of produced gas is used to heat water which is in turn injected to seafloor for dissociating gas hydrates. The preferred method of the invention comprises producing natural gas from seabed hydrates using a production ship with a moving riser installed. This method eliminates the need of drilling wells and thus cuts cost of gas production tremendously.

The present invention discloses a silty marine natural gas hydrate gravel stimulation mining method and a mining device. The mining method appropriately relaxes the sand retention accuracy of a wellbore, so that the fine sand and muddy components of the stratum can flow into the wellbore, and after a certain period of production, the coarse gravels are injected into the extra-pipe stratum of the production well to fill the deficit caused by the production of the fine components of the stratum and the hydrates, and then the well is opened for production. The method achieves the triple objectives of improving the productivity of the silty reservoir, preventing the large-area deficit in the stratum and extending the effective period of the sand retention of the wellbore, by way of the alternation of the rounds of the gravel injection and the hydrate reservoir fluid extraction.

A natural gas hydrate pressure-retaining corer includes an outer tube assembly and an inner tube assembly installed inside the outer tube assembly. The inner tube assembly includes a first inner tube assembly and a second inner tube assembly. The first inner tube assembly includes a spearhead, a latching device, a suspension plug, a hydraulic piston tube, a piston short limit short section, a limit copper pin, a sealing head, a middle tube, a weight tube drive mechanism and a pressure-retaining ball valve closing sealing mechanism which are sequentially connected from top to bottom. The second inner tube assembly includes a piston compensation balance mechanism, a single-action mechanism, an accumulator mechanism, a sealing mechanism and a core barrel connected sequentially from top to bottom.

Disclosed is a device for solid-state fluidized mining of natural gas hydrates in a shallow seabed, including: a sea surface support system, a pipeline delivery system, and an undersea drilling system. The sea surface support system includes a hydrate drilling vessel floating on seawater. The pipeline delivery system includes a continuous double-layer oil pipe, a recyclable conduit installed in a sediment cover, an open-hole steering packer installed outside the recyclable conduit. The undersea drilling system includes a hydrate slurry separator, a single screw pump, a hydraulic motor, a jet head and a differential pressure sliding sleeve close to the hydrate drill bit. The present invention has the following beneficial effects. The device achieves a multi-directionally horizontal drilling and production in the hydrate reservoir with a single well head, improving the drilling efficiency and single well production.