Recent Advances on Natural Gas Hydrate Exploration and Development in the South China Sea

Because of the urgency of energy transition for a net-zero society, the world's gas demand is rapidly increasing. Natural gas hydrate (NGH) is regarded as the next alternate energy resource to meet the demand, thanks to its high energy density and enormous reserves. As two successful production trials and a series of relevant drilling expeditions were implemented in the northern slope of the South China Sea (SCS), it may now be the most promising district for NGH exploitation in the world. The objective of this work is to review the recent research advances on hydrate exploration status, reservoir geological features, hydrate-bearing sediment geophysical properties, and hydrate exploitation techniques related to the hydrate reservoirs in the SCS. Geological surveys, well logging and core sampling were performed and helped the analysis of hydrate occurrence, gas origin, and accumulation mechanism. It is inferred that both microgenic and thermogenic gas present in SCS hydrate reservoirs and the hydrate accumulation is primarily controlled by the structure of the gas chimney. The characteristics of high porosity, low permeability, weak diagenesis, weak strength, and complex hydrate dissociation behaviors of the gas hydrate-bearing sediments from the SCS determined that innovative exploitation approaches are required. Different well configurations and reservoir stimulation techniques were proposed to enhance the production efficiency and evaluated through simulation and laboratory experiments. As the NGH development process in the SCS progresses continuously, it attracts more and more research interests from academic and engineering communities. We are convinced that, with constant diligence and effort, China will achieve the goal of safe and efficient commercial exploitation in the near future.