Advances in microscopic testing techniques and applications for natural gas hydrates

Abstact: Natural gas hydrates, as an important strategic resource, exhibit highly complex dynamic aggregation and dispersion processes within sediments, involving numerous scientific questions that necessitate a microscopic perspective for resolution. Microscopic testing techniques enable the acquisition of information on the state and evolution of research subjects at millimeter, micrometer, or even nanometer scales, making them essential tools for fundamental research on natural gas hydrates. This paper systematically reviewed the microscopic testing technology system for natural gas hydrates, which has been established using advanced techniques such as X-ray computed tomography (X-CT), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), low-field nuclear magnetic resonance (LFNMR), Raman spectroscopy (RM), scanning electron microscopy (SEM), and high-pressure differential scanning calorimetry (HPDSC). It mainly focused on the characteristics and advancements of each technique, as well as the applications and recent developments of these microscopic testing techniques in the quantitative characterization of the microstructure of hydrate-bearing sediments and the characterization of micro-scale permeability features. At last, this paper also proposed research directions and trends in the field of natural gas hydrate microscopic testing technology and applications, with the aim of providing more insights for in-depth research on natural gas hydrates.