8. Reservoir Characterization
Measuring Elastic Wave of Porous Media in the Freezing and Thawing Process of Methane Hydrate
Kyosuke Onishi, Kazuhiko Tsukada, Toshifumi Matsuoka and Yasuhiro Yamada
Kyoto University, Japan.
Abstract
For the stock assessment and the improvement of production efficiency of methane hydrate under the seabed, the process concentrating methane hydrate in sediments has to be investigated and prospecting techniques which can specify the concentrated region with high reliability have to be developed. Thus, we measured elastic wave of porous media in the freezing and thawing process of methane hydrate using a high pressure vessel. Wave velocity and amplitude of porous media including methane hydrate in the pores are useful to improve the estimation of concentrated area of methane hydrate using seismic waves. Moreover, the time-series measurement of the distribution of wave velocity and amplitude in specimens realizes to monitor the behavior of the freezing and thawing process of methane hydrate in porous media. We made an apparatus, which can construct the high pressure condition up to 10.5MPa and keep low temperature about 2 degree of Celsius. Methane hydrate was frozen and thawed in rock specimens in several times. A specimen was used CIPS which is a man-made rock and is made to be cemented by calcite. Elastic wave was continuously measured by ultrasonic transducers set on the side of specimens. The central frequency of the employed small transducers is 1MHz. Velocity and amplitude of elastic wave is measured to decrease at the time of generating methane gas. Velocity increase and amplitude recovery are observed along with the generated amount of methane hydrate in pores. The influence on the matrix and the change of physical properties of the CIPS specimen are measured in the freezing and thawing process of methane hydrate.
Last modified: Thu May 25 16:10:42 2006