In this paper we propose a new rock physics workflow which uses a combination of the Hashin-Shtrikman bounds (Hashin and Shtrikman, 1962) and the Joint Self Consistent Approximation (Bruggeman, 1935; Landauer, 1952; Berryman, 1995) and Differential Effective Medium model (Bruggeman, 1935; Sen et al., 1981) to estimate the horizontal and vertical resistivity of a clastic anisotropic rock. This model has been developed such that it is suitable for both sands and shales. We assume that anisotropy is caused by the collapse of the pore space as the rock is buried and the rearrangement of grains (layering and fracture induced anisotropy is not considered). The aspect ratio of the inclusions is estimated from the effective porosity of the rock. Shallow soft and stiff rocks have a more disordered microstructure and high effective porosity and therefore have high effective aspect ratios. Deep soft rocks (which are dominated by shales) have a more ordered microstructure and therefore lower aspect ratios which are aligned. Stiff deep rocks, where effective porosity is better preserved as they are buried, have higher aspect ratios. By linking the effective aspect ratio to the effective porosity we can model both sands and shales with the same model without changing the input parameters.
Presentation Date: Monday, October 15, 2018
Start Time: 1:50:00 PM
Location: 202A (Anaheim Convention Center)
Presentation Type: Oral