Dynamics Research on Natural Gas Storage and Transportation by Gas Hydrates

At present, pipeline natural gas (PNG) and liquefied natural gas (LNG) are the main technologies for natural gas storage and transportation. But it is not economic to explore those scattered, remote and limited high well-pressure gas fields by PNG and LNG technologies. So the new technology should be investigated. Natural gas hydrate (NGH) approach is expected to resolve these problems. In this paper, the effects of ultrasonic power, temperature, pressure, and hydrate reaction history on the induction time of NGH (mol percent of methane, ethane and propane are 91.89 %, 5.04 %, 3.07%, respectively) were investigated. The experiments were carried out in a high- pressure system with ultrasonic (the frequency 20 kHz, an adjustable power 0~150 W). The experimental results show that in the ultrasonic system the longest induction time is 2.5 days and the shortest is 0.14 days. While in the quiescent system the longest induction time is 8.5 days and the shortest is 4.9 days. Under the same conditions the induction time decreases with the pressure increase or ultrasonic power increase. And when the ultrasonic power keeps constant, the induction time increases linearly with the temperature increase. In order to investigate the influence of hydrate reaction history on the induction time the re- hydrate experiments is done after melt for one night. It is found that the induction time is very short and random, the longest of which is 4 minutes and the shortest is less than 1 minute in the ultrasonic field.