In sparsely fractured crystalline rock, aperture variability exhibits
significant control of the flow field through the fracture network.
However, its inclusion in models is hampered due to a lack of field
measurements and adequate numerical representation. A model for aperture
generation is developed based on self-affine methods which includes two
key parameters, the Hurst exponent and a scaling parameter, and which
accounts for relative anisotropy and correlation between the adjacent
surfaces forming the fracture. A methodology for analysing and
extracting the necessary parameters from 3D surface scans of natural
rock fractures is also developed. Analysis of the Hurst exponent and
scaling parameter space shows that input combinations following a linear
upper bound can be used to generate aperture fields which accurately
reproduce measurements. It is also shown that the Hurst and scaling
parameters are more sensitive than the correlation between the upper and
lower fracture surfaces. The new model can produce an aperture ensemble
that closely corresponds with the aperture obtained from the surface
scans, and is an improvement on previous methods. The model is also
successfully used to up-scale fracture apertures based on measurements
restricted to a small sub-section of the sample. Thereby, the aperture
fields generated using the model are representative of natural fracture
apertures and can be implemented in larger scale fracture network
models, allowing for numerical simulations to included representation of
aperture internal heterogeneity.