Investigate PPGD-spallation and cuttings removal / fluid management

In contrast to traditional subsurface rotary drilling methods, where the cuttings are in the mm size range, the cuttings produced by PPGD, and similar electro/plasma-pulse drilling methods, are with up to 20- 30 mm significantly larger. Removing such large cuttings from 5-10 km deep boreholes requires the development of a specifically designed fluid management system for PPGD. Furthermore, the fluid that is circulated during PPGD currently is demineralized water (required to enable electric arc (i.e. plasma) formation through the rock (Figure 17) and not as a short circuit from electrode to electrode  directly through the water). Thus, the demineralized water will need to transport the rock cuttings from the borehole bottom at 5-10 km depth all the way to the land surface.

This SP 11 has the following tasks/goals:

1. Improve the understanding of the PPGD spalling process
2. Investigate the grain size distribution of the PPGD produced rock cuttings for various PPGD parameters 3. Investigate how the rock cutting grain sizes affect their removal by the  fluid circulation system
4. Investigate the effects of the borehole cementing/casing on the hydraulic properties of the fluid management/circulation system
5. Estimate the power requirement to transport the rock cuttings to the land surface, based on nu-merical and physical models

Projektpartner:

ETH Zürich
SI KIBAG AG
Geotherm AG
SwissGeoPower AG
Basler und Hofmann AG
Amberg Group AG 
Sika Services AG