Thermal–hydraulic–mechanical–chemical coupling with damage mechanics using ESCRIPTRT and ABAQUS

We present a method to couple the thermal (T), hydraulic (H) and fluid–rock chemical (C) interaction capabilities of ESCRIPTRT with a rate-dependent mechanical (M) formulation of the finite element method including continuum damage mechanics for geomaterials implemented using Abaqus/Standard™. The resulting code builds on the modular architecture of ESCRIPTRT to solve sequentially these coupled THMC mechanisms and a number of feedback mechanisms including shear heating and damage. Damage in the host rock is linked to porosity evolution which in turn affects permeability, and this permeability-damage dependency is validated against published results. The motivation behind the development of this code is to improve our understanding of the formation of hydrothermal ore deposits, and we illustrate the use of this numerical tool with a simple geologic scenario involving shear zone development and albitisation. This application example focuses on the effects of damage on permeability enhancement and resultant fluid flow. Using damage mechanics allows for the localisation of narrower shear zones and reproduces the logarithmic pattern of rock pulverisation observed in nature on the sides of shear zones. The damage induced permeability evolution creates fluid pathways which may play a major role in forming hydrothermal ore-deposits.

► New thermal–hydraulic–mechanical–chemical code by coupling two existing codes. ► Damage mechanics linked to permeability evolution through porosity. ► Simulation of seal fracturing allowing fluid flow to overlying sequences and chemical reactions. ► Application to albitisation scenario.