Reservoir fracture characterization from seismic scattered waves

Abstract

Fracture characterization in an oil or gas reservoir is very important for field development and exploration because natural fracture systems can dominate the fluid drainage pattern in a reservoir. Traditional seismic methods for fracture characterization, such as amplitude variations with offset and azimuth and shear wave birefringence, are based on the equivalent medium theory with the assumption that fracture dimensions and spacing are small relative to the seismic wave length, so a fractured unit is equivalent to a homogeneous anisotropic medium. However, fractures on the order of the seismic wavelength are also very important for enhanced oil recovery, and they are one of the important subsurface scattering sources that generate scattered seismic waves. In this paper, we present an approach for detecting fracture direction through computing the fracture transfer function using surface recorded seismic scattered waves. The applicability and accuracy of this approach is validated through both laboratory experiment and numerical simulation. Our results show that fracture direction can be robustly determined by using our approach even for heterogeneous models containing complex non-periodic orthogonal fractures with varying fracture spacing and compliance.