Effective porosity estimation from tracer testing in low-permeability fractured rock

Two key issues must be addressed to reduce uncertainty in effective porosity (&phis;_e) calculations from tracer testing in low-permeability fractured rock: (1) what effect do fracture network statistics have on the estimation of effective porosity and (2) which tracer test configuration is best suited to capture the “true” effective porosity?; A numerical model (FASTFLOTRAC) was used in a Monte Carlo framework to assess the uncertainty in effective porosity estimates derived from analytical solutions. Specifically, fracture network parameters and hydraulic designs were systematically varied to quantify their influence on &phis;_e estimates.; The results of this research provide a methodology to properly incorporate effective porosity estimates into a Monte Carlo framework. Also, with little prior site characterization, the results provide a method to design future tracer tests such that the uncertainty in &phis;_e can be minimized.