Transport in rough self-affine fractures

Area of Science:

• Geophysics
• Fluid Dynamics
• Computational Physics

Background:

• Understanding fluid flow in fractured rock is crucial for subsurface resource management and contaminant transport.
• Characterizing the complex geometry of fractures and its impact on flow is a significant challenge.

Purpose of the Study:

• To investigate the transport properties of three-dimensional self-affine rough fractures.
• To evaluate the accuracy of effective-medium approximation for predicting fracture permeability and flow behavior.
• To analyze the influence of fracture surface geometry and relative displacements on flow and dispersion.

Main Methods:

• Effective-medium analysis
• Numerical simulations using the Lattice-Boltzmann method
• Analytic and numerical investigation of tracer particle dispersion

Main Results:

• Effective-medium approximation accurately predicts scaling behavior of permeability and velocity fluctuations for small surface separations.
• Fracture permeability can be bounded by two-dimensional fracture permeability, depending on surface displacements.
• Channel-like structures in the velocity field develop with varying relative displacements.
• Geometric dispersion, driven by velocity fluctuations and correlations, dominates tracer dispersion at very small surface separations.

Conclusions:

• Effective-medium theory provides a valid framework for understanding transport in rough fractures under specific conditions.
• Fracture geometry and surface interactions significantly influence fluid flow and solute transport.
• Velocity fluctuations and their spatial correlations are key factors in dispersion within fractures.