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Seismic Attenuation in Fluid-saturated Rock: Experimental Evidence of a Gas Dissolution-exsolution MechanismNormal access

Authors: S.A. Chapman, N. Tisato, B. Quintal and K. Holliger
Event name: 77th EAGE Conference and Exhibition 2015
Session: Rock Physics - Applications and Case Studies
Publication date: 01 June 2015
DOI: 10.3997/2214-4609.201412560
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.5Mb )
Price: € 20

Summary:
Laboratory measurements of seismic attenuation were performed on a synthetic rock sample using the forced oscillation method. Studying first the effect of partial water saturation, significant and frequency-dependent attenuation was only observed at near full water saturation and at low pore fluid pressures (≤0.6 MPa). Increasing the confining pressure and fluid pressure equally, thus keeping the effective stress unchanged, caused a significant decrease in attenuation. For fluid pressures >2.5 MPa attenuation was negligible and frequency independent. Additional measurements at different effective stresses showed that the mechanism responsible for the observed frequency-dependent attenuation is not sensitive to the effective stress. The physical mechanism that can potentially explain these results is wave-induced-gas-exsolution-dissolution (WIGED) occurring in response to fluid pressure variations, rather than wave-induced fluid flow (WIFF).


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