Recent Advances in Methods of Gas Recovery from Hydrate-Bearing Sediments: A Review
Zhiyuan Wang, Yangyang Zhang, Zhenyu Peng, Zhengfeng Shan, Baojiang Sun, Jinsheng Sun
Abstract
Safe, efficient, and economical gas recovery from hydrate-bearing sediments (HBS) is a severe issue that determines if natural gas hydrate (NGH), as an alternative energy in the future as fossil fuels approach depletion, is applied. Researchers worldwide are committed to developing a safe, efficient, and economical method of gas recovery from HBS. However, until now, most methods are still being validated and not have not been identified to exploit NGH commercially. Therefore, it is appropriate and significant to discuss researchers’ achievements to exploit NGH and summarize their potential benefits and challenges. This paper introduces nearly all the conventional and latest NGH exploitation methods and reviews field trials’ development characteristics. On the basis of laboratory experiments and field trials, key challenges restricting safe and efficient NGH development, and the existing research gaps reflecting these challenges, are also presented from the gas production, security, and economic aspects. The unfavorable situation mainly comprises the insufficient sensible heat, extremely low thermal conductivity, and ultralow permeability of HBS, lower gas production rate and its intense fluctuations, higher water-to-gas ratio (WGR), geological deformation, and subsidence of HBS attributed to excessive sand production, driving the consideration of some possible solutions. Given this, a new method for enhanced gas production from HBS based on the combination of depressurization (DP) and an in-situ heat generation method is proposed. Benefiting from multiple theoretical enhancement mechanisms such as replenishing energy to HBS with in-situ heat generation powders, cementing and strengthening the HBS skeleton, improving the gas permeability in HBS, decreasing the WGR based on blocking water, and removing gas characteristics of hydration products, this method could be expected to achieve promising long-term performance of gas production, which will be theoretically and practically significant to study commercial gas production.