Simulating the Filtration Effects of Cement-Grout in Fractured Porous Media with the 3D Unified Pipe-Network Method

Abstract

In grouting process, filtration is the retention and adsorption of cement-grout particles in a porous/fractured medium. Filtration partly/even completely blocks the transportation channels in the medium, greatly decreasing its permeability. Taking into account filtration effects is essential for accurately estimating the grout penetration region. In this paper, the 3D unified pipe-network method (UPM) is adopted for simulating 3D grout penetration process in a fractured porous medium, considering filtration effects. The grout is assumed to exhibit two-phase flow, and the filtration effects depend on not only the concentration and rheology of the grout but also the porosity and permeability of the fractured porous medium. By comparing the model with the experimental results, we firstly verify the proposed numerical model. Then sensitivity analysis is conducted, showing the influences of grout injection pressures, the water–cement ratios of grout (W/C) and the grout injection rates on filtration effect. Finally, the grout filtration process in a complex 3D fractured network is simulated, indicating that the size of the grout penetration region is limited due to filtration.

Evaluation of Effectiveness of CO2 Sequestration Using Portland Cement in Geological Reservoir Based on Unified Pipe-network Method

“…The Unified Pipe-Network Method based on the Control Volume Finite Element (CVFE) is proposed by Ren [49,50,76,77]; for a detailed description of this model, see [78,79]. In the UPM frame, the above mentioned two governing equations for both rock matrix and fractures are discretized as:…”

“…The simulation results of the homogeneous chemical reaction D (aq) + M (aq) → P (aq) are contrasted with analytical solutions of reaction in a free fluid. Moreover, additional models in the above UPM-based mix model (fluid flow problem and hydraulic-transport coupling problem) have been validated in [78,79]. Due to the quasi-implicit method used in our model, a convergence test is conducted to consider the influence of time step on the final results.…”

“…In the 3D UPM the rock matrix is reconstructed by tetrahedral element and the fracture is reconstructed by triangle element as shown in Figure 1 of Paper [78]. The pressures and concentrations within each tetrahedral element can be approximated by using the linear shape function as that in FEM:…”

Evaluation of effectiveness of CO₂ sequestration in geological reservoir based on Unified Pipe-network Method

“…The Unified Pipe-network Method based on the Control Volume Finite Element(CVFE) is proposed by Ren [49,50,76,77],for a detail description of this model see reference [78,79]. In the UPM frame, the above mentioned two governing equations for both rock matrix and fractures are discretized as:…”

“…In the 3D Unified Pipe-Network Method, the rock matrix is reconstructed by tetrahedral element and the fracture is reconstructed by triangle element as shown in Figure 1. of Paper [78]. The pressures and concentrations within each tetrahedral element can be approximated by using the linear shape function as that in FEM:…”