A self-entry exploitation device and method for marine natural gas hydrates is provided. The exploitation device includes a self-entry structural body (1), a sand control device (2) and a gas-liquid lifting system. The self-entry structural body (1) is a gravity anchor. The sand control device (2) and the gas-liquid lifting system are mounted on the self-entry structural body (1). At least one cavity (21) is formed between the self-entry structural body (1) and the sand control device (2), and the cavity (21) is communicated with at least one channel. The sand control device (2) allows liquid and gas to pass through to enter the cavity (21) and is able to filter out silt. The gas-liquid lifting system includes at least one lifting power device (31) and has an end connected to the cavity (21) and an end extending out through a pipeline. By adoption of the exploitation device, drilling is not needed, the self-entry structural body (1) can enter a natural gas hydrate reservoir or a free gas layer below the natural gas hydrate reservoir, so that depressurizing exploitation can be realized, an exploitation system can be withdrawn, and the exploitation cost of natural gas hydrates can be greatly reduced.

A safety drilling system for preventing collapse of water-sensitive formation in the upper part of a high-pressure saltwater layer, which includes a wellhead equipment, a downhole drilling tool, a first injection pipeline, a second injection pipeline, a first return pipeline and a second return pipeline. Upon encountering a high-pressure saltwater layer while drilling, the system injects heavy mud into the annulus of a wellhead through the first injection pipeline to form a heavy mud cap, such that a fluid column pressure in the annulus balances the pressure of the high-pressure saltwater layer. In this case, a fluid column pressure in a drill string is lower than the pressure of the high-pressure saltwater layer.

A natural gas hydrate solid-state fluidization mining method and system under an underbalanced positive circulation condition, used for performing 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 has an earlier-stage construction process, underbalanced hydrate solid-state fluidization mining construction process and silt backfilling process. Natural gas hydrates in the seafloor are mined through an underbalanced positive circulation method.

A pressure-control temperature-control hypergravity experimental device includes a high pressure reactor, a hydraulic oil station, a manifold board, a hypergravity water pressure control module, a hypergravity mining control module, a kettle body temperature control module, and a data collection box. The hydraulic oil station is connected to the manifold board and then two paths are formed. The two paths are respectively connected to the high pressure reactor via the hypergravity water pressure control module and the hypergravity mining control module. The kettle body temperature control module is connected to the high pressure reactor. The high pressure reactor, the manifold board, the data collection box, the hypergravity water pressure control module and the hypergravity mining control module are disposed on a hypergravity centrifuge air-conditioning chamber. The hydraulic oil station, a computer and the kettle body temperature control module are disposed outside the hypergravity centrifuge air-conditioning chamber.

A method for monitoring hydrate formation in an interior of a tube may include deploying a first hydrate controller device at a first location on an exterior surface of the tube. The method may include deploying a second hydrate controller device at a second location on the exterior surface of the tube. The method may include transmitting, by the first hydrate controller device, first acoustic signals towards the interior of the tube. The first acoustic signals may include a first frequency value and a first amplitude value associated to a transmission power level. The method may include receiving, by the second hydrate controller device, the first acoustic signals. The method may include measuring, by the second hydrate controller device, a reception power level of the first acoustic signals.

[Problem] In the production of sand reservoir type methane hydrate, there are problems, such as compaction of reservoir or production of sand in the mine, and the effect of existing methods to counter the production of sand is inadequate.

[Solution] The present invention can prevent the fluidization of sand occurred when methane hydrate is decomposed by injecting a grouting agent capable of adequately adhere sand particles into gaps (pore gaps) within sand particles which are unsolidified or weakly solidified and constitute the reservoir to be developed. In addition, provided is a technique capable of suppressing the production of sand in the mine, contributing to the stable production of gas, by injecting a filling material into the target reservoir around a mine well and thus constructing a porous grouting body having sufficient strength and good permeability. Further, the present invention also performs permeability restoration measures such as hydraulic fracturing or chemical treatment on the reservoir which has been subjected to the abovementioned grouting, thereby achieving both of stabilization of the reservoir and productivity of gas.

The present invention relates to the field of natural gas production, and discloses a well structure for natural gas hydrate production, which comprises: a natural gas production well (12); an injection well (4) capable of extending into a geothermal reservoir and injecting a heat-carrying fluid; a high curvature connecting well (7), the inlet end of the high curvature connecting well (7) is connected to the outlet end of the injection well (4); a hydrate production horizontal well (10), which may be arranged in a shallow hydrate reservoir (9), the high curvature connecting well (7) and the hydrate production horizontal well (10) are connected by an ascending well section (8), and connected with the natural gas production well (12). With the above technical scheme, the high curvature connected well connecting the horizontal well and the vertical well can be located in the bottom layer below the hydrate reservoir, enhancing the stability and production efficiency of the gas hydrate production well.

A safety drilling system for preventing collapse of water-sensitive formation in the upper part of a high-pressure saltwater layer includes a wellhead equipment, a downhole drilling tool, a first injection pipeline, a second injection pipeline, a first return pipeline and a second return pipeline, and further includes a drilling method, wherein after encountering a high-pressure saltwater layer while drilling, heavy mud is injected into the annulus of a wellhead through the first injection pipeline to form a heavy mud cap, such that a fluid column pressure in the annulus balances the pressure of the high-pressure saltwater layer; in this case, a fluid column pressure in a drill string is lower than the pressure of the high-pressure saltwater layer.

A hydrate remediation system and method utilizing a concentric coiled tubing downline is provided. The concentric coiled tubing downline includes an outer coiled tubing and an inner coiled tubing, the inner coiled tubing disposed within the outer coiled tubing and extending at least partially through the outer coiled tubing. The concentric coiled tubing downline may be deployed from a single surface reel housed on a surface vessel. A bottom hole assembly (BHA) including a subsea connector is disposed at a distal end of the concentric coiled tubing. The subsea connector of the BHA is configured to be connected to the subsea interface that will be depressurized via the concentric coiled tubing downline. The concentric coiled tubing downline may provide two flow paths. Pressurized gas flows down one flow path, and effluent from the hydrate remediation flows up to the surface via the other flow path.

The present invention discloses an exploiting structure for a natural gas hydrate reservoir, comprising: a drilling well located in the natural gas hydrate reservoir; and a fractured fracture provided in communication with the drilling well, which is located in the natural gas hydrate reservoir and in which a gas containing calcium oxide powder is provided. In the present invention, the calcium oxide powder is filled with the fractured fracture by means of the gas. Then, the natural gas hydrate in the fractured fracture is decomposed, and the water generated from the decomposition reacts with the calcium oxide to release a large amount of heat, and a high-porosity calcium hydroxide filler can be formed. The exploiting method provided in the present invention is simple and easy to operate, and has low exploitation costs, and is suitable for commercial promotion and application.