Elastic wave propagation in media with parallel fractures and aligned cracks
A model of parallel slip interfaces simulates the behaviour of a fracture system composed of large, closely spaced, aligned joints. The model admits any fracture system anisotropy; triclinic (the most general), monoclinic, orthorhombic or transversely isotropic, and this is specified by the form of the 3 x 3 fracture system compliance matrix. The fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy. To compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 x 3 matrices. When the fractures are assumed on average to have rotational symmetry (transversely isotropic fracture system behaviour) and the background is assumed isotropic, the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters (in addition to the two isotropic parameters of the isotropic background). Dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints,i.e. there are two additional parameters due to the presence of the microcracks which play roles in the stress-strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints. Thus, knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation.
- Research Organization:
- Schlumberger-Doll Research, Ridgefield, CT (US)
- OSTI ID:
- 6434283
- Journal Information:
- Geophys. Prospect.; (United States), Journal Name: Geophys. Prospect.; (United States) Vol. 36:6; ISSN GPPRA
- Country of Publication:
- United States
- Language:
- English
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