Combustion ice mining method

Traditional Mining (1) Thermal Excitation Mining The thermal excitation mining method directly heats the natural gas hydrate layer, so that the temperature of the natural gas hydrate layer exceeds its equilibrium temperature, thereby promoting the decomposition of natural gas hydrate into a water and natural gas mining method. This method has experienced the development of direct injection of hot fluid heating, fire flooding, downhole electromagnetic heating, and microwave heating into the natural gas hydrate formation. The thermal excitation method can realize the cyclic heat injection, and the action method is faster. The continuous improvement of heating methods has promoted the development of thermally stimulated mining methods. However, this method has not yet solved the problem of low heat utilization efficiency and can only perform local heating. Therefore, this method still needs further improvement.

(2) Decompression mining The decompression mining method is a mining method that promotes the decomposition of natural gas hydrates by reducing the pressure. There are two main ways of pressure reduction: 1 Use low-density mud drilling to achieve the purpose of decompression; 2 When there is free gas or other fluid below the gas hydrate layer, lower the free gas or other fluid under the gas hydrate layer to lower The pressure of the gas hydrate layer. The decompression mining method does not require continuous excitation and has a low cost and is suitable for large-area mining. It is especially suitable for the exploitation of natural gas hydrate reservoirs in the presence of underlying free gas layers. It is the most promising technology for traditional gas hydrate extraction methods. . However, it has special requirements for the nature of natural gas hydrate reservoirs. Only when the natural gas hydrate reservoir is located near the temperature-pressure equilibrium boundary, the decompression mining method is economically viable.

(3) Chemical reagent injection and mining The chemical reagent injection and mining method injects certain chemical reagents such as salt water, methanol, ethanol, ethylene glycol and glycerin into the natural gas hydrate layer to destroy the phase balance of the gas hydrate reservoir. Conditions promote the decomposition of natural gas hydrates. Although this method can reduce the initial energy input, the defect is obvious. It requires expensive chemical reagents, has a slow effect on the natural gas hydrate layer, and also brings some environmental problems. Therefore, this method is used in this method. There is relatively little research.

New Mining (1) CO2 Replacement Mining. This method was first proposed by Japanese researchers, and the method is still based on the pressure conditions of the gas hydrate stabilization zone. Under certain temperature conditions, the pressure required to maintain the stability of natural gas hydrates is higher than that of CO2 hydrates. Therefore, in a certain pressure range, natural gas hydrates will decompose, and CO2 hydrates are easy to form and remain stable. If CO2 gas is injected into the natural gas hydrate reservoir at this time, the CO2 gas may generate CO2 hydrate with water that is decomposed by the natural gas hydrate. The heat released by this action allows the gas hydrate decomposition reaction to continue.

(2) Solid mining method. The solids extraction method initially collects solid hydrates from the seabed and pulls the gas hydrates into shallow water for controlled decomposition. This method has evolved into a hybrid mining method or mining mud mining method. The specific steps of the method are: firstly, the natural gas hydrate is firstly decomposed into a gas-liquid mixed phase in situ; a mixed mud containing mixed gas, liquid and solid hydrate is collected; and then the mixed mud is introduced into a sea surface operation ship or a production platform for processing. , to promote the complete decomposition of natural gas hydrates, in order to obtain natural gas.