The effect of fluid flow in the longitudinal fracture along a borehole axis on Stoneley wave propagation

Abstract

The characterization of fractures is essential to increase the production of hydrocarbon and geothermal resources. In this study, we investigate the effect of fluid flow in the longitudinal fracture along a borehole on the dispersion and attenuation behavior of Stoneley waves using numerical experiments. Generally, incorporating a fracture with the aperture of several tens to hundreds of micrometers into 3D seismic modeling is challenging with high calculational costs. We develop a novel numerical scheme that includes a 2D fluid flow simulation embedded into a 3D wave propagation modeling to address this problem. We devise an approach for capturing the effects of fluid flow in fractures of arbitrary aperture widths, which could be much thinner than the grid spacing of 3D wave propagation simulation. A comparison of the numerical results from our scheme with the analytical solution shows good agreement, supporting the method's validity. This developed scheme is applied to coupled simulation between Stoneley wave propagation along the borehole axis and induced fluid flow inside a longitudinal fracture with different fracture apertures, fluid viscosity, and dynamic hydraulic conductivity. The modified matrix pencil algorithm applied to the recorded waveforms estimates the dispersion and attenuation of Stoneley mode. The numerical results reveal the effect of the fracture aperture and fluid viscosity on the dispersion and attenuation behavior of the Stoneley waves. Based on the results, we propose our scheme as an innovative method for estimating the aperture of fracture and viscosity of the fluid by analyzing the dispersion and attenuation properties of the Stoneley waves.