Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

View/ Open
Date
2011-05-25Author
Wang, Xiujuan
Concept link
Hutchinson, Deborah R.
Concept link
Wu, Shiguo
Concept link
Yang, Shengxiong
Concept link
Guo, Yiqun
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/4642As published
https://doi.org/10.1029/2010JB007944DOI
10.1029/2010JB007944Keyword
Gas hydrate; Saturation; Shenhu area; Fine-grained; Gas chimneyAbstract
Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.
Description
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B05102, doi:10.1029/2010JB007944.
Collections
Suggested Citation
Journal of Geophysical Research 116 (2011): B05102Related items
Showing items related by title, author, creator and subject.
-
Hydrate morphology : physical properties of sands with patchy hydrate saturation
Dai, Sheng; Santamarina, J. Carlos; Waite, William F.; Kneafsey, Timothy J. (American Geophysical Union, 2012-11-14)The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate ... -
Archie's saturation exponent for natural gas hydrate in coarse‐grained reservoirs
Cook, Ann E.; Waite, William F. (John Wiley & Sons, 2018-02-17)Accurately quantifying the amount of naturally occurring gas hydrate in marine and permafrost environments is important for assessing its resource potential and understanding the role of gas hydrate in the global carbon ... -
Estimating pore-space gas hydrate saturations from well log acoustic data
Lee, Myung W.; Waite, William F. (American Geophysical Union, 2008-07-09)Relating pore-space gas hydrate saturation to sonic velocity data is important for remotely estimating gas hydrate concentration in sediment. In the present study, sonic velocities of gas hydrate–bearing sands are modeled ...