Inference of field-scale fracture transmissivities in crystalline rock using flow log measurements

Characterization of transmissivity for crystalline rock is conducted through simulation by conditioning against borehole flow rates obtained from high-resolution, in situ field measurements during extraction pumping. Full three-dimensional discrete fracture network simulations are carried out according to specifications obtained from site characterization data in a stochastic Monte Carlo setting. A novel method of conditioning is thereby introduced and applied using nonparametric comparison tests, which provide quantifiable measures of accuracy enabling evaluation of simulated results against field measurements. The assumption of a constitutive relationship ( perfect correlation) between fracture size and transmissivity is adopted. The method is evaluated against both single and multiple realizations, various domain size, and fracture length configurations and shown to be robust for the cases considered. When the introduced method of conditioning is applied, transmissivity parameterization can be inferred to a narrow range with a quantifiable accuracy in terms of a probability value. Results indicate that elementary interpretation of transmissivity based on homogenization of a porous medium will generally underestimate transmissivity. Further implications on advective transport for natural flow conditions are briefly evaluated, indicating advective breakthrough times can be overestimated up to a factor of about 10 in the median.