Thermal simulation of millimetre wave ablation of geological materials

This work is concerned with the numerical simulation of ablation of geological materials using a millimetre wave source. To this end, a new mathematical model is developed for a thermal approach to the problem, allowing for large-scale simulations which account for the strong temperature dependence of material parameters. The model is implemented within an adaptive meshing framework, such that resolution can be placed where needed to further improve the computational efficiency of large-scale simulations. This approach allows the rate of penetration and the shape of the resulting borehole to be quantified, and is validated against experimental results, which indicate that temperatures and temperature gradients within the rock can be accurately predicted. The validated model is then exercised to obtain results demonstrating its capabilities for simulating millimetre wave drilling processes. The effects of the conditions at the surface of the rock are investigated, including simulations carried out both for isotropic rock, and also for a multi-strata configuration. It is found that for strata between similar rock types, their differing absorptive properties pose little problem for uniform drilling. However, larger variations in material parameters are shown to have strong implications on the evaporation behaviour of the wellbore, and hence the resulting structure.

Automated summary

This study focuses on the simulation of ablation of geological materials using millimeter wave source. A new mathematical model is developed to address the thermal approach to the problem, allowing for large-scale simulations with temperature-dependent material parameters. The model is implemented in an adaptive meshing framework, which improves computational efficiency. It is validated through experimental results and used to demonstrate its capabilities for simulating millimeter wave drilling processes. The effects of surface conditions and material variations on wellbore evaporation behavior and resulting structure are investigated.