Abstract
Drilling expenses constitute a significant share of the upfront capital costs and thereby the associated risks of geothermal energy production. This is especially true for deep boreholes, as drilling costs per meter increase significantly with depth.
Thermal spallation drilling is a relatively new drilling technique, particularly suited to the hard crystalline (e.g., basement) rocks in which many deep geothermal resources are located. The method uses a hot jet-flame to rapidly heat the rock surface, which leads to large temperature gradients in the rock. These temperature gradients cause localized thermal stresses that, in combination with the in situ stress field, lead to the formation and ejection of spalls. These spalls are then transported out of the borehole with the drilling mud. Thermal spallation not only in principle enables much faster rates of penetration than traditional rotary drilling, but is also contact-less, which significantly reduces the long tripping times associated with conventional rotary head drilling.
We present numerical simulations investigating the influence of rock heterogeneities on the thermal spallation process. Special emphasis is put on different mineral compositions, stress regimes, and heat sources.
Thermal spallation drilling is a relatively new drilling technique, particularly suited to the hard crystalline (e.g., basement) rocks in which many deep geothermal resources are located. The method uses a hot jet-flame to rapidly heat the rock surface, which leads to large temperature gradients in the rock. These temperature gradients cause localized thermal stresses that, in combination with the in situ stress field, lead to the formation and ejection of spalls. These spalls are then transported out of the borehole with the drilling mud. Thermal spallation not only in principle enables much faster rates of penetration than traditional rotary drilling, but is also contact-less, which significantly reduces the long tripping times associated with conventional rotary head drilling.
We present numerical simulations investigating the influence of rock heterogeneities on the thermal spallation process. Special emphasis is put on different mineral compositions, stress regimes, and heat sources.
| Original language | English |
|---|---|
| Publication status | Published - 2017 |
| Externally published | Yes |
| Event | Fall Meeting of the American-Geophysical-Union 2017 - New Orleans, United States of America Duration: 11 Dec 2017 → 15 Dec 2017 |
Conference
| Conference | Fall Meeting of the American-Geophysical-Union 2017 |
|---|---|
| Country/Territory | United States of America |
| City | New Orleans |
| Period | 11/12/17 → 15/12/17 |