Device and method for safely and efficiently exploiting ocean natural gas hydrate through depressurizing decomposition

Abstract

The invention discloses a device and a method for safely and efficiently exploiting an ocean natural gas hydrate through depressurizing decomposition. The device comprises a sand production preventing device, a gas-water separation device and a safety protection device, and can be provided with a secondary hydrate generation preventing device. The method for safely and efficiently exploiting the ocean natural gas hydrate through the depressurizing decomposition by using the device comprises the following steps that gas, water and sands, which are formed by decomposition, flow to a shaft, the mud and the sands of a deposition layer are blocked, and the gas and the water enter the shaft; under the extraction action of a water pump, the gas and the water flow upwards along the shaft, are separated to enter respective pipelines, and are lifted to an exploitation platform or an exploitation ship finally; well pressure is detected in real time; once a hydrate layer is abnormally self-isolated, the gas pipeline and the water pipeline are turned off, and gas production is temporarily stopped. According to the device and the method, the flowing sands formed by the decomposition of the hydrate can be well prevented from entering the shaft, gas-water separation is realized in the shaft, secondary generation of the hydrate in the shaft is prevented, and the ocean natural gas hydrate can be safely and efficiently exploited.

Description

technical field [0001] The invention belongs to the technical field of marine oil and gas reservoir exploitation, and relates to a safe and efficient marine natural gas hydrate decompression and decomposition exploitation device and method. Background technique [0002] Natural gas hydrate is widely distributed in seabed sediments and terrestrial permafrost. It is a clean energy with huge reserves and is expected to become the main energy to replace oil and coal. The production methods of natural gas hydrates are roughly divided into depressurization method, heat injection method and chemical inhibitor injection method. The main purpose of these three types of production methods is to change the stable environment of natural gas hydrates and make them decompose to generate flowing gas and After the water is mined. The heat injection method needs to provide a large number of heat sources, and the economy is poor; the chemical inhibitor injection method may cause pollution to...

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Problems solved by technology

[0003] The depressurization method is the most economical natural gas hydrate mining method at present, but there are many problems in its implementation, such as: only relying on the energy of the natural gas hydrate layer itself, and there is no external energy supply for mining. Gas production rate, but as the natural gas hydrate decomposes and absorbs heat, the formation energy gradually decreases, which slows down the hydrate decomposition rate, and even causes formation water to freeze, and the secondary generation of natural gas hydrate will completely stop gas production; at the same time, After the hydrate is decomposed, the sediment particles lose their support, and under the action of formation pressure, compaction and flow effects occur, which greatly reduces the permeability of the formation. In severe cases, the pipeline will even be blocked and production will be interrupted.

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