A new method to quantify elastic anisotropy of a transversely isotropic medium

Elastic anisotropy of vertically transversely isotropic (VTI) rocks has been increasingly investigated in the past two decades due to the key role of shales in exploration of oil and gas conventional and unconventional reservoirs. In this presentation we introduce a new anisotropy parameter: “hydrostatic strain ratio” (designated by Ω). It is defined as the ratio between bedding-normal and bedding-parallel contraction in hydrostatic compression, and analyzed based on Hooke’s law for VTI rocks. The Ω parameter is examined here using static and dynamic measurements of dry organic-rich chalk core samples from the Shefela basin, and dynamic data of eight other organic-rich rock formations published by Vernik and Liu (1997). Using the anisotropy results of the examined organic-rich rocks, we propose relationships between Ω and Thomsen’s anisotropy parameters (ε and γ). The anisotropic behavior of the examined organic-rich rocks is found to be very consistent according to the strong connection between Ω and Thomsen’s parameters, and to the similar dependency on organic matter content. We argue that the Ω is advantageous because it can be extracted from static and dynamic measurements, and because it provides a link between elastic VTI rock properties.