Permeability anisotropy and resistivity anisotropy of mechanically compressed mudrocks

Abstract

Permeability anisotropy (the ratio of the horizontal to vertical permeability) develops in mudrocks at the macroscale due to heterogeneities such as layering and at the element scale (i.e., within a single homogeneous layer or unit) due to decreasing porosity and increasing platy particle alignment. This work describes new experimental methods and results from a laboratory program using cubic specimens to investigate the evolution of mudrock permeability and resistivity at the element scale. A systematic study analyzes the evolution of the permeability anisotropy and electrical resistivity anisotropy using resedimented Boston blue clay (RBBC) over a stress range of 0.4–40 MPa; additional measurements are presented for three other mudrocks within varying clay fraction and clay mineralogy within the stress range 1.2–10 MPa. The permeability anisotropy and the conductivity anisotropy (inverse of the resistivity anisotropy) of all four mudrocks studied ranges from 1 to 2.2 over the porosity range 0.55–0.30. A nearly 1:1 correlation between the electrical conductivity anisotropy and the permeability anisotropy is observed to be independent of clay fraction or clay mineralogy.

Pore‐Scale Explanation of the Archie's Cementation Exponent: Microstructure, Electrical Anisotropy, and Numerical Experiments

“…For C y , ΔC y will synchronously increase with the ΔC p according to equation (13), resulting a high change rate, correspondingly. The data obtained from laboratory experiments (Adams et al, 2016) shows a similar trend of anisotropy exponent changing with porosity as shown in Figure 4c.…”

“…However, the simulated results shown in Figure d indicate that the m x > m y , which is opposite to the conclusion deduced from conventional observations. The data obtained from laboratory experiments (Adams et al, ) show a similar trend of formation factor changing with porosity, as shown in Figure e. The laboratory data were measured by experiments on a cubic rock sample, which was constructed by resedimenting both Boston Blue Clay and quartz platy particles.…”

“…(a) Anisotropic primary model with C x 0 < C y 0 , (b) digital model with redistributed grains, (c) isotropic model at critical porosity, (d) F ‐ ϕ in the x and y directions, obtained by LGA, and (e) F ‐ ϕ obtained by laboratory experiments (Adams et al, ).…”

An Experimental Study of Matrix Dissolution and Wormhole Formation Using Gypsum Core Flood Tests: 1. Permeability Evolution and Wormhole Geometry Analysis

“…The ECMS adopted the electric conductivity measurement design proposed by Ramsay () and Adams et al. (). The Kelvin sensing method (four‐terminal sensing method) was used to measure the electric impedance of the effluent ( R eff ).…”

Hydration behavior by X-ray diffraction profile fitting of smectite-bearing minerals

“…Original pore pressure, core, and geomechanics based studies tested much of this material's in situ behavior. After the cores lost their original water contents, they were ground and homogenized to produce a standard material for laboratory testing using resedimentation techniques (14)(15)(16).…”