Since the beginning of the 2000s, many gas hydrate exploration projects have been implemented in the permafrost and marine environments all around the world. Important technological developments have been made in the drilling, well logging and coring of the gas hydrate-bearing sediments (Merey and Zhu, 2022; Xie et al., 2022; Zhu et al., 2021), which are important steps for reaching the gas hydrate production test stage. Currently, the gas hydrate industry can drill and core gas hydrate-bearing sediments, but the main obstacles are at the gas hydrate production trial stages (Chen and Merey, 2021). In production stages, high water production rates, geomechanical risks, sand production and declining production efficiency are the main problems that need to be solved to reach feasible gas production from gas hydrate-bearing sediments. In March 2023, the longest gas hydrate production test duration was 60 days, conducted in the Shenhu area of the South China Sea in 2017 (Li et al., 2018). As in many areas, COVID-19 postponed many gas hydrate field projects in the last few years. However, recently in 2023, many field scale gas hydrate projects have continued, and others are being planned for 2024. For example, in the Alaska North Slope there is currently preparation underway to conduct a one-year gas hydrate production test (Haines and Collett, 2022). Similarly, China is planning to conduct their third gas hydrate production test in the South China Sea (Xu, 2023). As well as production tests, gas hydrate exploration and core sampling projects (i.e., in the Gulf of Mexico) are planned in 2023 (Flemings, 2023).
Overall, 2023–2024 will be active years in terms of field-scale gas hydrate projects. Many scientific studies about gas production from gas hydrates, gas hydrate characterization and geomechanical and environmental analysis about gas hydrates will be essential. This special issue ‘Geoenvironmental issues related to gas hydrates, part II’ presents six articles that contribute to these topics. In the first article of this issue, Kang et al. (2023) characterized the gas hydrate reservoir in the Shenhu area by using resistivity images. These evaluations are important for deciding whether gas hydrate reservoirs are appropriate for production tests or not. In the second article of this issue, Feng et al. (2023) simulated gas production from the gas hydrate reservoirs with the conditions of the Nankai Trough, Japan using well-known simulator TOUGH+HYDRATE. These simulations are important for production design. Zhang et al. (2023) investigated in the third article of this issue the effect of multi-well production systems with the conditions of the Nankai Trough, Japan. In the fourth article of this issue, Kong et al. (2023) explored the geomechanical behaviour of hydrate-bearing sediments by using the modified Cam-Clay model. Similarly, Liu and Jiang (2023) applied a DEM simulation to gas hydrate-bearing sediments to understand the mechanical behaviour of these sediments. In the last article of this issue, Zhu et al. (2023) visualized fluid migration with gas hydrate dissociation experimentally. This article revealed important results about submarine slides related to gas hydrates, which are crucial in environmental perspectives.
We hope the six articles published in this themed issue on gas hydrates in Environmental Geotechnics are able to generate a significant impact in the gas hydrate research field for years to come. Environmental Geotechnics acknowledges the authors and reviewers for contributing to the themed issue.
