Laboratory estimation of fracture compliance of a fluid-filled fracture using AVO response of a nonwelded interface

Abstract

We explore the potential of multi-angle AVO inversion of P-P and P-S reflections from a fracture to estimate fracture proper- ties. Although AVO analysis of welded interface like geologi- cal layer boundaries is common, the use of AVO variations for nonwelded boundaries like fractures is yet to be investigated. We conduct laboratory experiments to measure reflection re- sponses of dry and wet fractures. The observed P-P reflec- tions of the fracture and the fracture aperture are very well pre- dicted by the nonwelded interface model. We invert the angle- dependent P-P reflectivity of the fracture to estimate both nor- mal and tangential fracture compliances. The estimated value of the normal compliance is accurate, and it is also possible to obtain the value of the non-zero tangential compliance. We find that supplementing the information of converted P-S re- flections in the AVO inversion greatly improves the estimate of the tangential compliance. The calculated compliance ra- tio clearly shows the existence of fluid in the fracture. This finding can be crucial for new applications in a wide range of scale - from earthquake seismology, deep and shallow seismic exploration, to nondestructive material testing.