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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 115,
B02102,
11 PP., 2010
doi:10.1029/2008JB006160
Acoustic properties of gas hydrate–bearing consolidated sediments and experimental testing of elastic velocity models
Key Laboratory of Biogeology and Environmental Geology of the Ministry of Education, Faculty of Earth Sciences, China University of Geosciences, Wuhan, China
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, China
Qingdao Institute of Marine Geology, Qingdao, China
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, China
Qingdao Institute of Marine Geology, Qingdao, China
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, China
Qingdao Institute of Marine Geology, Qingdao, China
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, China
Qingdao Institute of Marine Geology, Qingdao, China
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, China
Qingdao Institute of Marine Geology, Qingdao, China
Key Laboratory of Biogeology and Environmental Geology of the Ministry of Education, Faculty of Earth Sciences, China University of Geosciences, Wuhan, China
Although elastic velocities (Vp, Vs) can be used to assess the distribution and concentration of marine gas hydrates in situ and several existing models relate hydrate saturation to acoustic velocity, the accuracy of these models is uncertain because of the difficulty in determining hydrate saturations and velocities of intact hydrate-bearing sediments. In this paper, the acoustic properties of gas hydrate–bearing consolidated sediments were investigated experimentally. Hydrate saturation (Sh) and acoustic velocities were measured in one system by time domain reflectometry and ultrasonic methods, respectively, during gas hydrate formation and subsequent dissociation in a water-saturated artificial core. Acoustic velocities change little at low hydrate saturations (0% to ∼10%), whereas they increase rapidly when hydrate saturation is between 10% and 30%. We verified two commonly used models, i.e., the weighted equation (WE) and the Biot-Gassmann theory modified by Lee (BGTL). In the 0% to 40% hydrate saturation range, the WE model is consistent with the measured Vp data, while a combination of the WE and the Vp/Vs ratio in the BGTL predicts Vs corresponding to the observed data. As hydrate saturation is more than 30%, however, the BGTL is more suitable for predicting both Vp and Vs. This suggests that gas hydrate may be treated as a component within a matrix of consolidated sediments when hydrate saturation exceeds 30%. However, when Sh is less than 30%, the hydrate locates in the pore fluid or partly adheres to the sediment frame.
Received 16 October 2008; accepted 21 September 2009; published 20 February 2010.
Citation: (2010), Acoustic properties of gas hydrate–bearing consolidated sediments and experimental testing of elastic velocity models, J. Geophys. Res., 115, B02102, doi:10.1029/2008JB006160.
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