Geological Risk Associated with Drilling Into Magma at Krafla Caldera, Iceland: Preliminary Evaluation

Abstract

Magma has been encountered unexpectedly when drilling in several volcanic regions in the world, one being in Iceland. In 2009, drilling of Iceland Deep Drilling Project’s IDDP-1, intended to reach supercritical conditions at a depth of 4 – 5 km beneath Krafla caldera, ended abruptly when ~900°C rhyolitic magma was intersected at a depth of 2.1 km. The aim of Krafla Magma Testbed (KMT) is to drill into shallow magma at Krafla to advance our understanding of magmatic systems and their coupling to hydrothermal reservoirs. It is unprecedented to purposefully drill into magma at these depths and this unusual objective raises the question of associated risks. Here we aim to identify and assess the geological risks and discuss mitigating measures. The active Krafla volcanic system, with its fissure swarm and caldera volcano had a volcano-tectonic episode in 1975-84 featuring nine eruptions. It is also a geothermal energy production site for the past 40 years. The current evaluation of risks is underpinned by existing geological, volcanological and geophysical knowledge of the Krafla volcanic system, experience from the IDDP-1 project, as well as experiences from drilling into magma in Menengai, Kenya and Puna, Hawaii. Identified risk factors include: i) upwelling of magma into the borehole and other movement of magma within the bedrock, ii) magmatic eruptions of rhyolitic or basaltic origin, iii) increase in seismic activity, iv) changes in the chemical composition of groundwater or hydrothermal fluid, and v) harmful gas emissions. There is also need for assessing how these factors could impact the ongoing energy production at the site. At both IDDP-1 and Puna, it is inferred that magma upwelled about 10 metres up into the borehole. Therefore, risk associated with magma upwelling is of particular concern and needs to be evaluated in detail.