Mining device and method for continuously exploiting marine natural gas hydrates

Abstract

The invention relates to a mining device and method for continuously exploiting marine natural gas hydrates, and belongs to the field of natural gas hydrate exploitation. The mining device comprises an offshore auxiliary device, a two-channel continuous pipe drilling device, a decomposition separation device and a waste backfill device. A two-channel continuous pipe is used as a drill pipe, crushing is carried out along a natural gas hydrate layer through directional drilling and high-pressure jetting, and a slurry mixture is formed; the two-channel continuous pipe correspondingly provides channels for transportation of high-pressure fluid and upward-returning of the slurry mixture; the slurry mixture is transported to the decomposition separation device through a slurry conveying channelinside the two-channel continuous pipe; and after the slurry mixture is decomposed and separated, natural gas is collected and used, and liquid waste and solid waste are backfilled into the mined-outarea by the two-channel continuous pipe. The method has the advantages of integrated drilling and mining, continuous mining, and controllable direction, at the same time, the liquid waste and the solid waste are backfilled in time, and the possibility of occurrence of geological disasters is reduced.

Description

technical field [0001] The invention relates to a mining device and method for continuously mining marine natural gas hydrate, belonging to the field of natural gas hydrate mining. Background technique [0002] Gas hydrates are distributed in marine sediments or permafrost on land, and are ice-like crystalline substances formed by natural gas and water under high pressure and low temperature conditions. The content of methane in natural gas hydrate is high, the combustion pollution is much smaller than that of coal and oil, and its reserves are abundant. It may become another energy source with huge reserves after shale gas and coalbed methane. [0003] Since the gas hydrate reserves in the ocean are far greater than those on land, the ocean will become the main area for the development of gas hydrate resources in the future. Among them, seabed sandstone-type natural gas hydrate has good permeability and high saturation, and the mining difficulty is relatively small. Howev...

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Problems solved by technology

The thermal activation method is to heat the formation by injecting steam, hot water, hot brine or other methods, but this method has the disadvantages of large heat loss, low efficiency and high energy consumption

In the process of natural gas hydrate exploitation by depressurization method, due to the decomposition and absorption of heat by natural gas hydrate, the temperature will drop, and secondary natural gas hydrate or ice will be formed in the pores, which will block the circulation channel and reduce the production efficiency. At the same time, the production well is usually designed If it becomes a low-pressure well, it is necessary to formulate strict sand control measures

The chemical reagent method decomposes natural gas hydrate by changing the phase equilibrium conditions of natural gas hydrate, but when it is applied to on-site mining, it has the disadvantages of high cost and environmental pollution

The replacement method uses carbon dioxide to replace methane in natural gas hydrate, and at the same time plays the role of mining methane and sequestering carbon dioxide, reducing the greenhouse effect. However, this method involves a complex phase transition process and is affected by formation properties and temperature and pressure conditions. further research needed

[0005] In the process of mining hydrates, the above method has a limited range of natural gas hydrate formations, and at the same time, because the original state of natural gas hydrates is changed, natural gas hydrates are decomposed, resulting in a decrease in the effective stress of the formations, resulting in geological disasters such as submarine landslides The occurrence of natural gas hydrate will even cause the decomposition of a large amount of natural gas hydrate on the seabed, and the methane gas produced will lead to the greenhouse effect

At the same time, the above method cannot achieve effective exploitation of the marine muddy silt type natural gas hydrate with the largest amount of resources.

In the patent document "A Device and Method for Solid Fluidization Exploitation of Non-diagenetic Natural Gas Hydrate in Submarine Shallow Layer" with application number 201710249143. The method needs to set up a water-resisting conduit in the surface layer of the seabed, and at the same time, the broken solid hydrate particles need to be transported to the hydrate collection ship through a transfer station. Therefore, a new technical solution is urgently needed in the prior art to solve the above technical problems

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