Progress of shallow hydrate exploration and production test in Japan

Compared to the marine pore-filling hydrates which have been extensively investigated and tested for gas production, the exploration and production test (EPT) of shallow hydrates with predominant component of seabed surface and near-seafloor sediments existea in near cold seeps, mud diapirs and mud volcanoes, has a long way to go. As one of the earliest countries to implement gas hydrate EPT, Japan has made significant progress in resource survey and evaluation of shallow hydrates, marine regional geological and environmental survey, development technology investigation and evaluation, and production system construction since fiscal year 2013. Based on the literature research, the authors in this paper summarized the development process of Japan's hydrate EPT and the overall deployment of shallow hydrate EPT, and introduce the main work cartied out by Japan in the fields related to the shallow hydrates EPT. The analysis shows that Japan's practical experience and theoretical understanding in the following four aspects are worthy of reference for the systematic deployment of shallow hydrate exploration and production test in China: regional resource and environmental survey centered on the Sea of Japan; resource evaluation demonstrations in a small-scale areas; refined resource and environmental surveys for optimizing production test sites; evaluation and establishment of the production system design principle of “based on the large-scale vertical mining method using a large-diameter drill bit, giving priority to the two key technologies of gas lift recovery method and shipboard separation method to form an optimal combination”.