An offshore methane hydrate production assembly (1), having a tubing (41) extending into a subsea well (5) that extends down to a methane hydrate formation (7) below the seabed (3). A submersible pump (45) is arranged in the tubing (41). A methane conduit (35,35) extends down from a surface installation (49). A well control package (15) landed on a wellhead (13) is positioned at the upper end of the subsea well (5). Moreover, an emergency disconnection package (25) is arranged between the methane conduit (35,135) and the well control package (15). The tubing (41) is suspended from the well control package (15). Other aspects of the invention are also disclosed.

A drilling casing includes a casing wall and several sand control apparatuses disposed on the casing wall in a spacing. 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. 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 the drilling casing includes forming a main borehole by drilling to a destination well depth at one time with a large-size drill bit, drilling a lateral borehole in a natural gas hydrate reservoir by using the drilling casing, and taking out the drill bit for completion. The method is applicable to various natural gas hydrate extraction manners.

The present invention provides an automatic jet breaking tool for solid fluidization exploitation of natural gas hydrate, which mainly includes an upper joint, an outer cylinder, an inner sliding sleeve, a lockup sliding sleeve, a thrust bearing, a spring, a jet joint, a telescopic jet sprinkler, a plug block and an extrusion seal ring. The present invention mainly adopts the principle of throttling control pressure to control the position of the inner sliding sleeve by controlling a flow rate of a drilling fluid, so as to turn on and turn off the jet breaking tool. The application of the present invention can realize automatic jet breaking of solid fluidization exploitation of the natural gas hydrate, reduce procedures of a round trip operation, and effectively improve the efficiency and safety of the exploitation operation of the natural gas hydrate.

The present invention relates to a combined crushing super-variable-diameter drill bit for natural gas hydrate exploitation, including a joint, an outer cylinder connected to the joint by thread, a nozzle I mounted in the outer cylinder, a mechanical locking mechanism, a blade telescoping mechanism, an end cap connected to the outer cylinder by thread, a seal ring IV mounted to the end cap, and a nozzle II mounted in the end cap by threaded connection. The present invention achieves integrated operation of conventional drilling and draw-back expanding, which can effectively solve the problems that the existing hydrate drill bit cannot drill a large borehole, cannot mechanically lock an extending position of the blade to stabilize the size of the borehole, and a single crushing method is inefficient.

An active control method and system for wellbore pressure in open-cycle drilling in marine natural gas hydrates. The system comprises a drilling system, a drilling fluid injection system, and a data processing system for conducting the drilling operation.

The invention is related to a system which has been developed to obtain gas from the gas hydrate formations that are found under the frozen layers of earth in the cold regions or sea floor/slopes and comprises a drilling machine (3) that performs drilling by means of a drilling bit (33) after being lowered into the drilled well, drilling machine lowering and controlling equipment (1) which allow said drilling machine (3) to be lowered into the well and supply power and control to the system (A), and a stripped production tubing (4) with plugs (41) in which the water level and water level dependent pressure and gas pressure are controlled, which allows for the dissociation of the formation into gas and water and forming a cavern (6), and in which the gas separated from the gas hydrate formation reaches the surface; and to the method presented by using said system (A).

The invention discloses an experimental device for natural gas hydrate solid-state fluidized mining and crushing, the experimental device comprising a power liquid supply module, a hydrate suction module, a pipeline conveying module, a hydrate fluidized crushing module, a secondary processing module and an experimental data information collection and processing module. An experimental method for the experimental device comprises: turning on the power liquid supply module, the hydrate suction module, the pipeline conveying module, the hydrate fluidized crushing module and the secondary processing module, and collecting pressure and flow data at a plurality of locations by the experimental data information collection and processing module. The present invention has the following beneficial effects: a jet solid-state fluidized mining process is simulated, and a plurality of pressure and flow detection points and sampling ports for crushed samples are provided at the same time so as to facilitate parameter collection; a plurality of component parameters are flexibly variable, including changing a drag-back speed of a moving slider, shape parameters of jet nozzles, and a pressure and flow of a power liquid; a spray head is designed to simplify the experimental device, and a dynamic process of jet crushing may be observed from a side surface of an experimental tank.

A methane gas production facility or the like capable of efficiently producing a methane gas from a wide range of a methane hydrate layer. In a methane gas production facility that produces a methane gas from a methane hydrate layer MHL, a first horizontal well is provided along the methane hydrate layer MHL and injection water supply units supply injection water obtained by dispersing a carbon dioxide gas in water to the first horizontal. well. A second horizontal well is provided along an area in which methane released from methane hydrate by replacement with carbon dioxide rises, a decompression and suction unit decompresses the inside of the second horizontal well by pumping water and sucks water containing methane, and a gas-liquid separation unit separates a methane gas from the sucked water.

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.

An active control method and control device for wellbore pressure in the open-cycle drilling of marine natural gas hydrates comprises following steps: (1) optimized design of drilling parameter; (2) carry out open-cycle drilling according to the designed drilling parameters; (3) utilize the APWD to monitor the bottom-hole temperature and the bottom-hole pressure in real time for real-time correction of the wellbore annulus temperature and pressure calculation models; determine whether a hydrate decomposition has occurred in the annulus and then infer whether a shallow gas intrusion has occurred in the bottom hole; (4) Intelligent active control: control and adjust the mixed density of drilling fluid, the injection displacement of drilling fluid as well as the injection temperature of drilling fluid and the pump pressure in wellhead automatically during the well killing based on the real-time treatment results of the computer terminal for the signal fluctuations detected by the APWD.