Cement grout propagation in two-dimensional fracture networks: Impact of structure and hydraulic variability

Abstract

Analysis of cement grout propagation in water-saturated two-dimensional discrete fracture networks is presented in this study. A two-phase flow model for Bingham fluids flow in a single saturated fracture is extended to simulate cement grouts propagation in saturated networks. Using this extended model, the impacts of network structure and hydraulic variability, i.e., network geometry and aperture distribution, on the propagation process are investigated through numerical simulations. Cement grout propagation in 50 realizations of a two-dimensional discrete fracture network (2D DFN) are simulated with different cases of aperture variability, i.e. constant aperture, uncorrelated and length-correlated heterogeneous apertures following a truncated lognormal distribution. The results indicate that network structure and hydraulic variability significantly affect the grout propagation in 2D DFN systems. The randomized network structure and uncorrelated heterogeneous apertures significantly delay the propagation rate and largely increase the variability range of the propagation volume fraction. In contrast, in the case with length-correlated heterogeneous apertures, the propagation rate increases, while the variability range and rate of change of the propagation volume fraction decreases. The extended two-phase flow model for fracture networks and the simulation results presented in this work are useful for basic understanding of the processes relevant for design, monitoring and execution of rock grouting.