CO2 emulsion and method for reforming and exploiting natural gas hydrate reservoir by injecting CO2 emulsion

Abstract

The invention discloses a CO2 emulsion and a method for reforming and exploiting a natural gas hydrate reservoir by injecting the CO2 emulsion. The CO2 emulsion comprises liquid CO2, at least two kinds of surface active agents, a hydrate generation accelerant and water. Di(2-ethylhexyl) sodium sulfosuccinate is at least included in the surface active agents. The mass percent concentration of the di(2-ethylhexyl) sodium sulfosuccinate ranges from 0.5% to 3%, and the mass percent concentration of the other components of the surface active agents ranges from 1% to 3%. The mass concentration of the hydrate accelerant ranges from 0.05% to 1%. The volume percentage of water in the emulsion ranges from 10% to 70%, and the volume of the liquid CO2 accounts for 30%-90% of the volume of the emulsion. By means of the exploiting method, the characteristics that the CO2 emulsion has good diffusibility in porous media and generated hydrates have ultralow permeability are utilized, the remarkable production increase function is achieved on exploitation of natural gas hydrates, meanwhile, the seabed CO2 sealing effect can be enhanced, and the exploitation safety coefficient of the natural gas hydrates can be improved.

Description

technical field [0001] The invention belongs to the field of natural gas hydrate exploitation; 2 Emulsion and injection thereof are used to modify and exploit natural gas hydrate reservoirs. Background technique [0002] Natural gas hydrate is a solid crystalline non-quantitative compound formed by water and natural gas under low temperature and high pressure conditions. Natural gas is mainly composed of methane, so it is also called methane hydrate. Under standard conditions, one cubic meter of methane hydrate decomposes to produce a maximum of 164 cubic meters of methane gas and 0.8 cubic meters of water. The energy density of methane hydrate is very high, which is 2-5 times that of conventional natural gas, and its combustion value is very high, and it hardly produces any residue after combustion. It is a rare clean energy. [0003] Although gas hydrate reserves are huge and have broad application prospects, due to the complexity of the environment in which it occurs a...

AI Technical Summary

Problems solved by technology

However, when injecting pure liquid carbon dioxide for reservoir transformation, there will be the following problems: 1. Due to its poor diffusivity, it cannot effectively cover the gas hydrate reservoir when injected into the sediment, which is not conducive to the formation of low-permeability caprock ; 2. Due to the extremely harsh reservoir conditions, carbon dioxide is very easy to block the wellbore due to the formation of hydrates during the injection process; 3. The hydrates generated based on liquid carbon dioxide are thermodynamically unstable, and due to the remaining Low water saturation, resulting in CO 2 The hydrate saturation is low, and the carbon dioxide hydrate cap rock is prone to instability and collapse during the depressurization operation of the reservoir

However, due to different mining methods, the emulsion cannot be directly applied to reservoir stimulation and depressurization mining, so it is necessary to prepare a new type of CO 2 Emulsion, instead of the existing injection of pure CO 2 Transformation process

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