Table of Contents
ISRN Geophysics
Volume 2014 (2014), Article ID 241279, 8 pages
http://dx.doi.org/10.1155/2014/241279
Research Article

Effect of Fracture Aperture on P-Wave Attenuation: A Seismic Physical Modelling Study

1Department of Physics, Akwa Ibom State University, PMB 1167, Mkpat Enin, Nigeria
2School of Geosciences, University of Edinburgh, Edinburgh EH9 3JW, UK
3British Geological Survey, Murchison House, Edinburgh EH9 3LA, UK
4CNPC Geophysical Key Laboratory, China University of Petroleum, Beijing 102249, China

Received 14 August 2013; Accepted 24 December 2013; Published 11 February 2014

Academic Editors: E. Del Pezzo, E. Liu, F. Luzon Martinez, A. Stovas, and T. Tsapanos

Copyright © 2014 Aniekan Martin Ekanem et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We used the seismic physical modelling approach to study the effect of fracture thickness or aperture 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 3 mm fixed diameter and same thickness to simulate a set of aligned vertical fractures. The thickness of the chips varies according to the blocks while the fracture density remains the same in each block. 2D reflection data were acquired with the physical model submerged in a water tank in a direction perpendicular to the fracture strikes using the pulse and transmission method. The induced attenuation was estimated from the preprocessed CMP gathers using the QVO method, which is an extension of the classical spectral ratio method of attenuation measurement from seismic data. The results of our analysis show a direct relationship between attenuation and the fracture thickness or aperture. The induced attenuation increases systematically with fracture thickness, implying more scattering of the wave energy in the direction of increasing aperture. This information may be useful to differentiate the effect caused by thin microcracks from that of large open fractures.