Experimental Studies of Reflections from Single and Multiple-Fractures Using Lucite Models

摘要

Laboratory acoustic measurements are performed with Lucite fracture models to understand the reflection characteristics of a seismic wave in a fracture zone. The fracture models include single fracture, dual fracture, and fracture zones having different fracture geometries. First we check the acoustic measurement system without fractures so we can identify the surface waves and the characteristics of the acoustic source and receiver. We then measure P-waves reflected and scattered by the different fracture models using a suite of illumination directions and receiver positions. The acoustic waves are reflected from the top of the fractures and their arrival times, frequencies and amplitudes are related to the depth and width of the fracture. We compare the acoustic waves reflected from dual fracture with those reflected from the single fracture and observe the effects of multiple scattering between the two fractures. In the fracture zone model, the scattered waveforms vary in different acquisition directions, which can help determine the fracture orientation. Variations in the scattering characteristics from the top and base of the fractures may provide information on fracture geometry, spacing, and orientation.