Introduction

Since the preparation and publication of the first edition of Geology of the Netherlands in 2007, the world has changed considerably. In the early 21st century natural gas was the main hydrocarbon and energy source for the Netherlands — and it still is. Since 2018 however, the reduced gas production from the enormous Groningen gas field and the decline in production from small gas fields have made the Netherlands a net importer of natural gas. For the first time in many decades, the security of energy supply has emerged as a significant concern, imperilled by ongoing wars and global political conflicts. This concern has significantly boosted the new energy transition that focuses on sustainable energy resources. A transition that also affects the global search for (critical) raw materials and comes with geopolitical implications. To ensure access to a secure and sustainable supply of critical raw materials and reduce the dependence of the European Union on other states, the Critical Raw Materials Act has been implemented. The energy transition leads to a growing component of renewables in the energy mix of the Netherlands. On sunny and windy days there is even a surplus production of electricity, which currently cannot be stored adequately. Hence the growing demand for (subsurface) energy storage solutions.