| Title | Review of Rock Testing in Brittle-Ductile Transition Conditions and Implications on Wellbore Stability in Ultra-Deep Drilling |
|---|---|
| Authors | Angel Sanchez-Barra, Anna Rogers, Juan Arias |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | As global energy consumption continues to rise, the development of scalable and sustainable energy solutions is imperative to ensure that total energy supply can meet future demands. Ultra-deep geothermal energy offers a promising alternative by enabling localized, autonomous power generation at nearly any location on Earth. However, unlocking this potential requires drilling into ultra-deep conditions, where elevated temperatures and in situ stresses induce complex geomechanical behavior. In these ultra-deep regimes, rock deformation mechanisms transition from brittle fracturing to semi-brittle and ultimately ductile flow, challenging conventional approaches to drilling and wellbore stability predictions. This study investigates the evolution of deformation mechanisms across the brittle-ductile transition (BDT) using a comprehensive review of literature data and previous experiences spanning microstructural observations, core-scale laboratory experiments, and field-scale measurements, including insights from the IDDP-2 geothermal project in Iceland, the KTB exploration borehole in Germany, Gravberg-1 in Sweden, and other relevant cases. Particular emphasis is placed on identifying how failure modes evolve with increasing stress-temperature conditions, the role of time-dependent creep in semi-brittle regimes, and the implications of these processes for borehole convergence and stress redistribution. By synthesizing data across scales and conditions, this work identifies future areas of research that will better inform geomechanical models and enable ultra-deep geothermal development. |