Experimental study on the effect of fracture scale on seismic wave characteristics

摘要

In fractured reservoir beds,fracture characteristics affect seismic wave response.Fractured models based on the Hudson's fractured medium theory were constructed in our laboratory by a backfilling technique.For the same fracture density,the variations of the velocity and amplitude of the primary wave and shear wave parallel and perpendicular to the fracture were observed by altering the diameter (scale)of the penny-shaped fracture disk.The model test indicated that an increase of fracture scale increased the velocity and amplitude of the primary wave by about 2%.When the shear wave propagated parallel to the fracture,the velocity of the fast shear wave hardly changed,while the velocity of slow shear wave increased by 2.6% with increasing fracture scale.The results indicated that an increase of fracture scale would reduce the degree of anisotropy of the shear wave.The amplitudes of slow shear waves propagating parallel and perpendicular to fractures decreased with increasing fracture scale.