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

Abstract

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.

Virtual Special Issue of Recent Research Advances in China: Unconventional Gas

“…summarizes the natural gas hydrate flow assurance research in China. There are six reviews covering a wide range of aspects related to methane hydrates targeting resource potential, production methods (depressurization and CH 4 /CO 2 exchange), exploration activities, sand management, and hydrate properties . The original research articles pertaining to the topic of hydrates cover a wide spectrum of areas, from numerical modeling, ,,, hydrate properties and characterization, ,,,, hydrate equipment ,,, to fluid production analysis, ,− ,, etc.…”

Undrained Mechanical Properties of Overlying Soils of Gas Hydrate Reservoirs in the South China Sea

“…20 Lee et al conducted a sequence of laboratory tests on the mechanical characteristics and physical parameters of sediments on the Costa Rican continental margin and found that effective stress and porosity are the main factors influencing their mechanical and physical properties in this region. 21 In recent years, China has successfully conducted two trial productions of NGHs in SCS, 22 providing technical reserves and accumulating valuable experience for the commercial development and utilization of NGHs. This has sparked extensive research by numerous scholars into the mechanical characteristics of hydrate reservoirs in SCS.…”

Numerical study of response behaviors of natural gas hydrate reservoir around wellbore induced by water jet slotting

“…In the 1960s, NGH was found in nature and was considered a potential alternative energy source (Makogon, 1965). Subsequently, the United States, Japan, and China have implemented a series of NGH research and development plans (Liu and Li, 2021). More than 230 NGH occurrence areas have been detected in coastal slopes, polar regions, and permafrost zones (Makogon, 2010;Liu and Li, 2021;Wu et al, 2022), with estimated total reserves reaching 3,000-20,000 trillion cubic meters, twice that of traditional fossil fuels (Yin et al, 2019).…”

“…Subsequently, the United States, Japan, and China have implemented a series of NGH research and development plans (Liu and Li, 2021). More than 230 NGH occurrence areas have been detected in coastal slopes, polar regions, and permafrost zones (Makogon, 2010;Liu and Li, 2021;Wu et al, 2022), with estimated total reserves reaching 3,000-20,000 trillion cubic meters, twice that of traditional fossil fuels (Yin et al, 2019). The total reserves of NGH in China are estimated to be approximately 84 trillion cubic meters; the prospective NGH resources on the northern slope of the South China Sea (SCS) alone amount to tens of billions of tons of oil equivalent (Liang et al, 2020).…”