Characterization of Thin Gas Hydrate Reservoir in Ulleung Basin with Stepwise Seismic Inversion

• Published in: Energies (Basel) Vol. 14; no. 14; p. 4077
• Main Authors: Yi, Bo-Yeon, Yoon, Young-Ho, Kim, Young-Jun, Kim, Gil-Young, Joo, Yong-Hwan, Kang, Nyeon-Keon, Kim, Jung-Ki, Chun, Jong-Hwa, Yoo, Dong-Geun
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2021
• Subjects: 3D seismic survey; acoustic impedance; Acoustics; Climate change; Data analysis; Datasets; Drilling; gas hydrate; Reservoirs; saturation; Sediments; stepwise seismic inversion; Velocity
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en14144077

Natural gas hydrates (GHs) filling sand layer pores are the most promising GHs that can be produced via conventional mechanisms in deep-sea environments. However, the seismic tracking of such thin GH-bearing sand layers is subject to certain limitations. For example, because most GH-bearing sand layers are thin and sparsely interbedded with mud layers, conventional seismic data with a maximum resolution of ~10 m are of limited use for describing their spatial distribution. The 2010 Ulleung Basin drilling expedition identified a relatively good GH reservoir at the UBGH2-6 site. However, the individual GH-bearing sand layers at this site are thin and cannot therefore be reliably tracked using conventional seismic techniques. This study presents a new thin layer tracking method using stepwise seismic inversion and 3D seismic datasets with two different resolutions. The high-resolution acoustic impedance volume obtained is then used to trace thin layers that cannot be harnessed with conventional methods. Moreover, we estimate the high-resolution regional GH distribution based on GH saturation derived from acoustic impedance at UBGH2-6. The thin GH layers, previously viewed as a single layer because of limited resolution, are further subdivided, traced, and characterized in terms of lateral variation.