Research on the anisotropy of gas hydrate reservoirs in South China Sea
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ORIGINAL RESEARCH PAPER
Research on the anisotropy of gas hydrate reservoirs in South China Sea Xiangchun Wang1 · Wuyunbateer Bai1 · Yanpeng Zheng2 Received: 5 June 2020 / Accepted: 19 September 2020 © Springer Nature B.V. 2020
Abstract The leakage-type hydrate is filled in the fractures, with steep and directional dips characteristics and the reservoir is basically anisotropic. The fractures characteristics are the key factors for reserve estimation and making of the production plan, and it is also the challenge and difficulty of the seismic exploration. Here we use the existing data recorded from ocean-bottom seismometers in the northeastern slope of South China Sea to carry out the research on whether the hydrate reservoir has the seismic anisotropy characteristics, and the results show that the seismic anisotropy characteristics is very obvious. The thickness and position of HTI medium lies between the time of 1550 ms and 1600 ms. On the basis of HTI anisotropy, combined with the geological situation of the region, it is assumed that vertical fractures exist in the region and the leakage-type hydrate exists. Also the research on parameters extracted from the fracture strike is carried out. The symmetry axis and the fracture directions of fractures are estimated. The results show that 60° and 240° correspond to the fractures symmetry axis, and 150° and 300° are the fractures trend. The recognition is very important for the estimation of the gas hydrate’s saturation. Keywords Hydrate · Leakage type · Fractures · Anisotropy · Ocean-bottom seismometer
Introduction Natural gas hydrate is a new energy with huge reserves that has not yet been commercially produced (Sha et al. 2015a, b). As a crystalline compound of methane gas and water at a certain temperature and pressure, the important role of gas channeling system and migration mode in the gas hydrate reservoir has been concerned by many scholars. According to the controlling factors of gas migration, four kinds of gas hydrate accumulation are summarized, which are fault structure type, mud volcano type, stratum controlling type and structure stratum type (Milkov et al. 2002; Tréhu et al. 2004). Also there are some scholars (Fan et al. 2004; Su 2008) who divided gas hydrate deposits into two types of systems: diffusion type and leakage type according to the way of gas channeling. * Xiangchun Wang [email protected] 1
School of Geophysics and Information Technology, China University of Geosciences (Beijing), Beijing 100083, China
Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China
2
South China Sea is located on the convergence zone of the Eurasian Plate, the Filipino Plate, and the Indian Ocean Plate. Owing to the interaction of these plates, the South China Sea evolved a marginal sea basin with a complex sedimentary structure and unique regional tectonic geological characteristics (Yang et al. 2014). Shenhu area is geographically situated in the central north continental slope of the So
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