The new scenario involving the rapid energy supply transition from oil-based to natural gas-based undoubtedly affects the future carbon capture and storage (CCS) and offers an opportunity for the use of natural gas hydrates (NGHs). NGHs account for one-third of the mobile organic carbon on Earth, acting as a carbon storage reservoir in the carbon cycle. Hydrate-based technologies including CO₂ capture, CO₂ separation, and natural gas storage and transportation can also be used to reduce greenhouse gas (CO₂, CH₄) emissions and have excellent application potential. However, the implications of the energy supply transition, NGH extraction, and hydrate-based technologies for future climate change mitigation have not been deeply recognized. This paper comprehensively discusses the global energy supply and environmental challenges and transitions, and NGHs and their role in the energy supply, carbon cycle, and historical and future climate change, and summarizes the state-of-the-art developments in hydrate-based technologies and NGH exploitation methods and their potential environmental impacts, thereby providing a perspective on the roles of NGHs and their related technologies in the future energy supply and climate change mitigation. In all of these areas, we focus on identifying future CCS challenges and the technological development risk imposed by a natural gas-based global economy and NGH utilization, which should be highlighted in the next several decades.

The Shenhu Area is located in the Pearl River Mouth Basin, the northern continental slope of the South China Sea. In 2007, gas hydrate samples were recovered during the scientific expedition conducted by the China Geological Survey in the area. Using numerical simulation and currently available data from site measurements, including the water depth, thickness of the hydrate-bearing layer (HBL), sediment porosity, salinity, and pressures and temperatures at key locations, we developed preliminarily estimates of the production potential of these hydrates as gas-producing resource. We used measurements of ambient temperature in the sediments to determine the local geothermal gradient. Evidence from this and other field studies showed that the initial pressure distribution followed the hydrostatic gradient. Direct measurements from core samples provided estimates of the initial hydrate saturation and of the intrinsic permeabilities in the various strata of the system. The hydrate accumulations in the Shenhu Area appear to be hydrate deposits involving a single HBL within fine-textured sediments and boundaries (overburden and underburden layers) which have the same intrinsic permeabilities with the HBL. We investigated gas production from the Shenhu hydrates by means of depressurization and thermal stimulation using a single horizontal well placed in the middle of the HBL. The simulation results indicated that the hydrates dissociate along cylindrical interfaces around the well and along horizontal dissociation interfaces at the top and bottom of the HBL. Production is invariably lower than that attainable in a confined system, and thermal stimulation is shown to affect only a limited region around the well. The sensitivity analysis demonstrates the dependence of production on the level of depressurization, the initial hydrate saturation, the intrinsic permeability of the HBL, the temperature of the well, and the initial temperature of the HBL. A general observation is that gas production is low and is burdened with significant water production, making the hydrate accumulations at the Shenhu Area unattractive production targets with current technology.