Volume 34: CCUS Technologies for the Carbon Neutrality: Part II

Research status of CO2 as cushion gas in underground natural gas storage Du Siyu, Bai Mingxing, Zhang Zhichao, Liu jingyuan

Abstract

CO2 as cushion gas of underground natural gas storage can not only effectively save the initial capital investment, but also slow down the greenhouse effect and realize the geological burial of CO2. It has important strategic significance and social value for the development and construction of underground natural gas storage. Based on a large number of literature research at home and abroad, this paper summarizes and combs the differences in physical properties between carbon dioxide and natural gas, the mixing mechanism of carbon dioxide as cushion gas and natural gas in natural gas underground storage, the influence of multiple rounds of injection and production in the operation of natural gas underground storage and the influence on the capacity and stability of gas storage under fluid solid coupling, so as to provide reference for the implementation of CO2 as cushion gas in natural gas underground storage. In addition, it also puts forward the deficiency of theoretical understanding of cushion gas in CO2 as natural gas underground storage, including: ①High-speed non Darcy seepage of gas, the movement law of displacement phase front and the distribution characteristics of mixing zone under the action of alternating load; ②The accuracy of three-dimensional three-phase oil, gas and water injection production dynamic multi physical field coupling model is improved; ③For geological activities in the early stage of natural disasters, which may lead to gas leakage, specific measures shall be taken to deal with emergencies; ④The geological conditions of gas storage construction are more complex, and its development is more difficult. In addition, the mathematical model of injection production operation evaluation in the whole life cycle of natural gas underground storage operation is established.

Keywords Underground natural gas storage, Cushion gas, Mixing mechanism, CO2 deep burial, Permeation-diffusion