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Physical Modelling Studies of the Effect of Fracture Thickness on P-wave AttenuationNormal access

Authors: A. M. Ekanem, J. Wei, X. Y. Li, M. Chapman and I. G. Main
Event name: 72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010
Session: Seismic Modelling 2 (EAGE)
Publication date: 14 June 2010
DOI: 10.3997/2214-4609.201401104
Organisations: SPE, EAGE
Language: English
Info: Extended abstract, PDF ( 222.76Kb )
Price: € 20

The seismic physical approach was used to investigate the effect of fracture thickness on P-wave attenuation, using a laboratory-scale model of two horizontal layers. The first layer is isotropic while the second layer has six fractured blocks, each consisting of thin penny-shaped chips of 3mm fixed diameter and same thickness to simulate a suite of aligned vertical fractures. The chips’ thicknesses vary according to the blocks while the fracture density remains the same in each block. 2D data were acquired with the physical model submerged in a water tank in a direction normal to the fracture strikes using the pulse-transmission method. The seismic quality factor, Q was estimated from the pre-processed CMP gathers using the QVO method, which is an extension of the spectral ratio method of measuring attenuation. The results of our measurements show a direct relationship between attenuation and fracture thickness. The induced attenuation was observed to increase systematically with fracture thickness, implying more scattering of the wave energy in the direction of increasing thickness. This information may be useful to differentiate the effect caused by thin micro cracks from that of large open fractures.

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