Estimation of wave propagation characteristics around fracture using simulation techniques: T. Kikuchi & M. Abe, Geothermal Science & Technology, 5(1–2), 1995, pp 53–62

Abstract

Fractures play an important role in a geothermal system because they are not only conduits of hot water but reservoirs themselves. Therefore, it is important to estimate positions and permeability of fractures from the view point of reservoir evaluation. To estimate fracture properties, the method using seismic waves is one of the most effective. In this paper, simulations are carried out to clarify the wave propagation around a fracture, with the aim of developing a method to estimate the apertures and permeability of fractures. The fractures are simulated as two parallel plates up to the present. However, the real fracture is more complicated and has many contact points. Therefore, we have attempted to simulate the real fracture using the staggered grid finite-difference method. The horizontal and vertical displacement components around a fracture with contact points were calculated. Stoneley wave was found to exist under the following conditions, (1) if the aperture of the fracture is 0.1 m, (2) the dominant frequency of the source is about 175Hz, (3) the source is located in the fluid of the fracture or on the surface of the fracture. Stoneley wave reflects at the point of contact under conditions mentioned earlier.