Abstract
Gas hydrate is a new clean energy resource with polar molecule. However due to the change of temperature and pressure during extraction process, there will be secondary formation of gas hydrate, which usually occurs in reservoirs or pipelines near the wellhead. It is significance to prevent secondary formation of hydrate because of safety issues or production rate reduction caused by it. Theoretically, microwave heating can accelerate the decomposition of gas hydrate. Therefore, it is possible to use microwave radiation to prevent secondary formation of hydrate. In this paper, a microwave antenna with special shaped coaxial-slots was designed. Based on electromagnetics and antenna transmission theories, the key parameters of the coaxial-slot antenna were calculated. The frequency is 2.45 GHz, the impedance is 50 ohms, and ratio of outer to inner conductor radius is 3.32. The slots were designed as ‘H’-shape with the width is 2 mm, the radial length is 12mm, the axial length is 14 mm and the interval is 35 mm. Teflon was used as filling material and the radome. Then the software HFSS and ANSYS were used to analyze the electromagnetic field and temperature field to further optimize the parameters. It will be proved that the microwave antenna can heat gas hydrate and prevent the secondary formation.
Highlights
Natural gas hydrate is a non-stoichiometric crystalline solid, which is formed by water and small molecular gases under low temperature and highpressure conditions [1]
The electromagnetic heating method can quickly heat as needed, and it has demonstrated its effectiveness in heavy oil [8,9,10,11,12,13,14,15,16,17,18,19]
The thermodynamic power required for the decomposition of hydrates can be provided, which is beneficial to inhibit the secondary formation of hydrates or promote the decomposition of secondary hydrates, and improve productivity [28,29,30,31]
Summary
Natural gas hydrate is a non-stoichiometric crystalline solid, which is formed by water and small molecular gases (such as H2, CH4, H2S, etc.) under low temperature and highpressure conditions [1]. Microwave heating is a kind of body heating, which does not depend on the power system It means that the temperature can be increased in a short time so that the energy conversion rate is high and the heat loss is small. In this case, the thermodynamic power required for the decomposition of hydrates can be provided, which is beneficial to inhibit the secondary formation of hydrates or promote the decomposition of secondary hydrates, and improve productivity [28,29,30,31]. The dimension of antenna was optimally designed, which provides a theoretical basis for the removal of secondary hydrates during the exploitation of natural gas hydrates
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