Anisotropy in capillary invasion and fluid flow through induced sandstone and shale fractures

• The capillary pressure curve is independent of invasion direction.
• The sandstone fracture displays a higher anisotropy in hydraulic and electrical conductivities than the shale fracture.
• The anisotropy in flows of brine and electrical current in fracture is correlated with the directional roughness, harmonic mean, and range of fracture aperture.

Understanding the physics of flows in a single fracture is the basis for modeling subsurface transport problems in fractured media. Capillary pressure curve and equivalent aperture have been accepted as tools for characterizing capillary invasion and single-phase flow in a single fracture. Numerical modeling is used to determine the capillary pressure curve and the equivalent aperture for different flow directions in sandstone and shale fractures. Invasion percolation method is used to model the invasion process of dense non-aqueous phase liquid in a water saturated sandstone fracture from different directions. Finite element method is applied to model the flows of brine and electric current in the fractures along different directions. The numerical results are calibrated against the experimental data including capillary pressure measurement and single-phase flow tests in the fractures. Results from the invasion percolation modeling show that the capillary pressure curve is independent of invasion direction. The study on the flows of brine and electric current in the fractures illustrates that the sandstone fracture displays a higher anisotropy in hydraulic and electrical conductivities than the shale fracture. Furthermore, it is found that the anisotropy is correlated with the directional roughness, harmonic mean, and range of fracture aperture.