This book is a compilation of selected papers from the Fourth International Technical Symposium on Deepwater Oil and Gas Engineering & The Third International Youth Forum on Gas Hydrate, held in Qingdao, China in December 2021. The work focuses on the advancement of techniques for the deepwater oil and gas exploitation and natural gas hydrate exploitation. The book introduces new ideas for exploring deepwater oil and gas hydrate in a safe and efficient way. Advances of the natural gas hydrate pilot production in South China Sea, in oil and gas flow assurance and emerging technologies based on clathrate hydrate will be presented. It is a valuable resource for both practitioners and academics working in the field of deepwater oil and gas engineering.