Decompression marine natural gas hydrate mining method and submarine mining system

Abstract

The invention relates to a decompression marine natural gas hydrate mining method and a submarine mining system. The submarine mining system comprises a semi-submersible offshore platform, a mining well with multiple shower holes, a wellhead gas and water acquisition tree, a gas and water mixed delivery system, a submarine gas and water separating device, a gas delivery system, a pipeline system, a power and communication system and an auxiliary device. The decompression marine natural gas hydrate mining method and the submarine mining system have the advantages that submarine natural gas hydrate reservoirs can be safely, efficiently and economically mined; the submarine mining system is complete, and various portions of the submarine mining system are high in modularization, low in manufacturing cost and short in manufacturing cycle and can be reused; most devices are positioned in submarine environments and are controlled via the offshore platform, only natural gas is delivered offshore, and accordingly the submarine mining system is low in extra energy consumption; owing to a technology for forming the multiple shower holes in the mining well, missed mining regions can be effectively reduced, and the gas yield can be effectively increased owing to multiple horizontal wells; the submarine mining system has functions of well blocking prevention, well blowout prevention, hydrate secondary generation and the like, and accordingly safety production can be guaranteed; various main devices can flexibly move and are used with one another, and accordingly movable regional production operation can be implemented.

Description

technical field [0001] The invention relates to a natural gas hydrate resource exploitation technology, in particular to a depressurization type natural gas hydrate exploitation method and system, which is especially suitable for efficient exploitation of seabed natural gas hydrate resources. Background technique [0002] Natural Gas Hydrate (NGH for short) is a solid substance formed by the interaction and crystallization of natural gas and water under high pressure and low temperature conditions. In the tundra. According to modern geological survey and research, it is found that NGH has a wide distribution range, large scale, and high energy density. It is one of the most promising new high-efficiency clean energy sources. natural gas), which has huge commercial exploitation value. [0003] The exploitation of natural gas hydrate is mainly by destroying its phase equilibrium conditions to promote its decomposition into natural gas. The common extraction methods at this s...

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Problems solved by technology

[0004] However, the storage conditions of natural gas hydrates are more complicated. Compared with conventional energy sources such as oil and natural gas, the situation is special. It is much more difficult to drill when solid-state reservoirs are formed. During the production process, the phase changes into a gaseous state, which poses a great challenge to the reservoir structure.

Moreover, marine hydrate pools are generally distributed on the seabed more than 1,000 meters away from the sea surface and under rock layers more than 300 meters away. They are thin-layered and interbedded with sediments, and have the characteristics of high pressure, low permeability, and extreme inhomogeneity. Exploitation is obviously different from the exploitation of conventional oil and gas reservoirs, and factors such as cost, efficiency and safety need to be considered comprehensively. Therefore, there is currently no effective system solution for natural gas hydrate exploitation. The technical solutions for NGH trial exploitation in Japan and other countries are only Combination or deformation matching of conventional mining methods, so the mining technology and scheme of natural gas hydrate has great research and development space

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