The drilling recovered high-concentration methane hydrates (maximum 26–48%) in a disseminated form in silty clay sediments in Shenhu area of Pearl River Mouth Basin, South China Sea. Combining the geochemical data, the gas hydrate-bearing sediments are 10 m to 43 m in thickness and located just above the base of the gas hydrate stability zone. The methane content is 96.10–99.91% with small amount of ethane and propane. The baseline chlorinity of pore waters shows 10% lower than that of shallow sediments below and inside the gas hydrate zone. The methane/ethane ratios are higher than 1000 above the gas hydrate zone and less than 1000 at the interval of gas hydrate zone. The depth of sulphate methane interface varies from site to site as 17 to 27 mbsf. These results show that the methane of gas hydrate was mainly originated from microbial activity and the upward methane flux is minor. This is evidenced by the δC13CH4 values of headspace gases from the gravity piston cores and released gases from pressure cores, which range from −74.3‰ PDB to −46.2‰ PDB, with the majority less than −55%‰ PDB. The hydrate deposit is a distributed gas hydrate system in Shenhu area.

The process of extracting natural gas from gas hydrate‐bearing sediments (GHBS) may yield significant sand influx due to the metastable nature of GHBS. Selecting appropriate sand control media is vital to addressing the challenges caused by excessive sand production. This study proposes a protocol called holding coarse expelling fine particles (HCEFP) for sand control design. The protocol aims to provide a new optimization method for screen mesh size selection for clayey silt hydrate reservoirs. Detailed optimizing procedures of proper candidate screen mesh sizes in hydrate exploitation well in clayey silt hydrate reservoirs are depicted based on the HCEFP. Then, the site W18, which is located in the Shenhu area of the northern South China Sea, is taken as an example to illustrate the optimization procedure for screen mesh size selection. The results reveal that complete solid retention via a standalone screen is rarely beneficial as high clay contents can adversely affect wellbore productivity due to excessive plugging. Screen aperture size selection for clayey silt hydrate wells should strike a balance between retaining coarser particles and avoiding screen blockage by the relatively fine particles. Furthermore, longitudinal heterogeneity of the PSDs also increases the difficulties associated with sand control design. Multistage sand control optimization is necessary in hydrate production wells. For Site W18, we recommend that the entire production interval can be divided into two subintervals for multistage sand control operations.

The characteristics of the hydrate-bearing layer are important parameters for gas hydrate exploration and exploitation, which can be provided by laboratory analysis. We have carried out a systematic analysis of modern instruments, including the laser grain size analyzer, X-ray computed tomography, scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, gas chromatography, and isotope mass spectrometry, on the hydrate-bearing sediment samples recovered from the Shenhu area in the South China Sea in 2016. We focused on the structure, hydration number, and gas composition of the gas hydrate samples. We also evaluated the effects of sediments on the occurrence and distribution of gas hydrate. Our results showed that the sediments are much finer than those recovered from the Shenhu area in 2007. Some samples are found to contain calcareous microfossils and foraminifera, which are beneficial for dispersed gas hydrate formation. Whereas the only visible hydrate sample (FC4) has not found any bioclast in the sediments. Based on the Raman data and the XRD analysis, the gas hydrates demonstrate typical structure I (sI) hydrates, with cage occupancies of methane molecules higher than 99.3% in large cages and 81.5%–91.4% in small cages, respectively. The crystal lattice parameter is 11.89 Å with the hydration number being approximately 6.0. Methane is obviously the dominant component, ranging from 97.6% to 99.95% in these samples. Comprehensive study of carbon and hydrogen isotopes suggests that the hydrate-bound gases are from biogenic and thermogenic gases in the study area.

How natural gas hydrates nucleate and grow is a crucial scientific question. The research on it will help solve practical problems encountered in hydrate accumulation, development, and utilization of hydrate related technology. Due to its limitations on both spatial and temporal dimensions, experiment cannot fully explain this issue on a micro-scale. With the development of computer technology, molecular simulation has been widely used in the study of hydrate formation because it can observe the nucleation and growth process of hydrates at the molecular level. This review will assess the recent progresses in molecular dynamics simulation of hydrate nucleation and growth, as well as the enlightening significance of these developments in hydrate applications. At the same time, combined with the problems encountered in recent hydrate trial mining and applications, some potential directions for molecular simulation in the research of hydrate nucleation and growth are proposed, and the future of molecular simulation research on hydrate nucleation and growth is prospected.