Thermal simulation of millimetre wave ablation of geological materials: Fid-Bau Portal

Thermal simulation of millimetre wave ablation of geological materials

Zhang, A.Z. / Millmore, S.T. / Nikiforakis, N.

Abstract 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.