An offshore drilling system includes a drilling tower, a tubular string hoisting device with a crown block and a travelling block suspended from the crown block in a multiple fall arrangement. A heave compensation system is adapted to provide heave compensation of the travelling block. The heave compensation system includes a hydraulic sheave compensator. The system further includes a mobile working deck which is movable with respect to the drilling tower within a motion range including a heave compensation motion range. The heave compensation system is further adapted to provide heave compensation of the mobile working deck by a hydraulic deck compensator, which is hydraulically connected via a hydraulic conduit to the hydraulic sheave compensator, such that in operation the deck compensator moves synchronously with the sheave compensator of the heave compensation system.

A wellbore intervention tool conveyance system includes an upper pipe injector disposed in a pressure tight housing. The upper injector has a seal element engageable with a wellbore intervention tool and disposed below the injector. The upper housing has a coupling at a lower longitudinal end. A lower pipe injector is disposed in a pressure tight housing, the lower housing has well closure elements disposed above the lower pipe injector. The lower housing is configured to be coupled at a lower longitudinal end to a subsea wellhead. The lower housing is configured to be coupled at an upper longitudinal end to at least one of (i) a spacer spool disposed between the upper pipe injector housing and the lower pipe injector housing, and (ii) the lower longitudinal end of the upper pipe injector housing.

A jetting system for an undersea trencher has jetting conduits extending aftward of its trench-cutting jetting swords. Jetting conduit nozzles direct liquid radially from their jetting conduits into the trench after the trench is excavated by the jetting sword cutting nozzles. The jetting conduits direct sufficient liquid into the trench to maintain the mix of trenched soil and water in the trench along the length of the conduits at not more than a super-critical density, extending the distance in which the product being laid in the trench is able to descend in the trench and increasing the likelihood that the product will be buried at the intended trench depth.

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.

An abrasive suspension eroding system has an eroding unit (11), which can be lowered into an existing drilled hole (1), in order to generate a high-pressure erosion jet for the abrasive suspension eroding of material (6, 20) in an existing drilled hole (1). The eroding unit (11) can be connected to a drilling fluid line (9) and is configured to generate a high-pressure erosion jet from a drilling fluid abrasive suspension device.

The invention discloses a suction cylinder exploitation device and method for marine natural gas hydrates. The exploitation device comprises an exploitation cylinder, a water pump, a sand control device, a liquid-gas filling system and the like. Through the specially-designed exploitation cylinder and mating devices thereof, the exploitation cylinder can sink below a seabed surface to exploit natural gas hydrates deep below the seabed surface and can be withdrawn. A series of problems such as high well drilling and completion cost of traditional deep-sea drilling exploitation methods, and damage, collapses and sand generation of plain concrete wellbores under the effect of formation pressure are solved, and the limitations that traditional capping depressurization methods can only exploit submarine superficial hydrates and are low in exploitation efficiency are overcome. The invention can greatly reduce the exploitation cost of natural gas hydrates deep below the seabed surface and is of great significance for commercial exploitation of marine natural gas hydrates.

A resource collection device of a resource collection system has a resource collection pipe, a protection pipe, and a coiled tubing device. The protection pipe is disposed around the resource collection pipe and protects the resource collection pipe. The coiled tubing device is fed from a winding reel disposed on the sea surface or inside the protection pipe by way of a feeding device and penetrates a side wall of the protection pipe to extend from the interior to the exterior. The resource collection system cracks the sea floor layer by way of: supplying undiluted solutions of foaming material, fuel gas, and air containing oxygen into the sea floor layer through the coiled tubing device; mixing the undiluted solutions of foaming material together to expand in an atmosphere that includes fuel gas and air; and causing the fuel gas accumulated in the hollows of the foaming material to explosively combust.

A resource collection device of a resource collection system has a resource collection pipe, a protection pipe, and a coiled tubing device. The protection pipe is disposed around the resource collection pipe and protects the resource collection pipe. The coiled tubing device is fed from a winding reel disposed on the sea surface or inside the protection pipe by way of a feeding device and penetrates a side wall of the protection pipe to extend from the interior to the exterior. The resource collection system cracks the sea floor layer by way of: supplying undiluted solutions of foaming material, fuel gas, and air containing oxygen into the sea floor layer through the coiled tubing device; mixing the undiluted solutions of foaming material together to expand in an atmosphere that includes fuel gas and air; and causing the fuel gas accumulated in the hollows of the foaming material to explosively combust.

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.

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.