Within the Netherlands, 24 geothermal systems have been realized of which 18 added to production of 3.7 PJ of heat in 2018. The main application domain is horticulture. The ambition of the Dutch government is to increase the production of geothermal energy in the Netherlands to 15 PJ in 2030, subsequently 110 PJ in 2050 and to expand the application domain to district heating and industry. Kramers et al. (2012) published an article on the direct heat resource assessment stating that the recoverable heat amounts to just over 63000 PJ, assuming a reinjection temperature of 35 °C. This resource estimate combines all direct heat projects regardless of their maturity. A state-of-the-art resource assessment can support the Dutch government policy to realize its ambition by classifying the resources based on project maturity, including reference to the obstructing issues in the maturation of projects such as technical, financing, licensing and/or social and environmental complexities. In January 2019, 78 exploration licenses are active or have been applied for. At least one geothermal project is defined in each of these licenses, at different levels of advancement. Outside the existing licenses and licenses applied for, The Netherlands provides ample space for geothermal development by geothermal projects, yet in a conceptual stage. At the moment, there are no tools or practical methodology to integrate all the available information in a coherent and automated manner. Furthermore, a method to quantify the geothermal energy resources of projects ‘not yet realized’ using the United Nations Framework Classification (UNFC) resource classification system, would help policymakers to decide upon the most appropriate measures to relieve the obstruction issues to reach the 2030-2050 geothermal ambitions. In this study, we show the results of a resource assessment and classification system for geothermal energy while incorporating environmental and social issues in the classification, as required by the UNFC-2009. As basis for this resource assessment, we use the webtool ThermoGIS. ThermoGIS which uses information on the Dutch subsurface derived from the regional mapping by the Geological Survey and which is updated by incorporating newly gained insights and data, provides a comprehensive overview of the geothermal potential for a selected set of aquifers. The resource estimate, including the uncertainty range related to these figures, at the status date 1-1-2019 of the Dutch geothermal “project portfolio” is classified using UNFC, resulting in a set of resource figures per resource class according to project maturity: commercial, potentially commercial, non-commercial and exploration projects. Furthermore, some additional development options are introduced like installing heat pumps on relevant projects and stimulation on projects with poor productivity to increase the resource potential. Next level analysis envisages that future projects are given an attractivity attribute reflecting, amongst others, proximity to areas of favourable heat demand, proximity to heat network, which will guide the order of the exploration drilling sequence. An estimate on the geothermal portfolio maturation speed will then reflect on the minimum number of wells to be drilled to reach the geothermal ambition. @en

In the past 10 years the mature hydrocarbon province the West Netherlands Basin has hosted rapidly expanding geothermal development. Upper Jurassic to Lower Cretaceous strata from which gas and oil had been produced since the 1950s became targets for geothermal exploitation. The extensive publicly available subsurface data including seismic surveys, several cores and logs from hundreds of hydrocarbon wells, combined with understanding of the geology after decades of hydrocarbon exploitation, facilitated the offtake of geothermal exploitation. Whilst the first geothermal projects proved the suitability of the permeable Upper Jurassic to Lower Cretaceous sandstones for geothermal heat production, they also made clear that much detail of the aquifer geology is not yet fully understood. The aquifer architecture varies significantly across the basin because of the syn-tectonic sedimentation. The graben fault blocks that contain the geothermal targets experienced a different tectonic history compared to the horst and pop-up structures that host the hydrocarbon fields from which most subsurface data are derived. Accurate prediction of the continuity and thickness of aquifers is a prerequisite for efficient geothermal well deployment that aims at increasing heat recovery while avoiding the risk of early cold-water breakthrough. The potential recoverable heat and the current challenges to enhance further expansion of heat exploitation from this basin are evident. This paper presents an overview of the current understanding and uncertainties of the aquifer geology of the Upper Jurassic to Lower Cretaceous strata and discusses new sequence-stratigraphic updates of the regional sedimentary aquifer architecture.

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Within the Netherlands, 24 geothermal systems have been realized of which 16 are operational, together producing 3.4 PJ of heat in 2018 (status date 1-1-2019). The main application domain is horticulture. The ambition of the Dutch government is to see production of geothermal energy increase in the Netherlands to 50 PJ in 2030, subsequently 200 PJ in 2050 and also to expand the application domain to district heating and industry. A state of the art resource assessment can support the Dutch government policy to realize its ambition. By classifying the resources based on project maturity including reference to the obstructing issues in the maturation of projects such as technical, financing, licensing and or social and environmental complexities targeted policy can be drafted. As of January 2019, 51 exploration licenses have been granted, and 31 more have been applied for (MEA2019). At least one geothermal project is defined in each of these exploration licenses, at different levels of advancement. Outside the boundaries of existing licenses and licenses under application, the Netherlands provides ample space for geothermal development. At the moment, there are no tools or practical methodologies to integrate all available information in a coherent and automated manner. As such, a method to quantify the geothermal energy resources of projects ‘not yet realized’ using the United Nations Framework Classification (UNFC) resource classification system would help policymakers to decide upon the most appropriate measures to remove obstructions for reaching the 2030-2050 geothermal ambitions. In this study, we show the initial results of a resource assessment and classification system for geothermal energy while incorporating environmental and social issues in the classification, as required by the UNFC2009. As basis for this resource assessment, we use the web tool ThermoGIS-v2.1 (Vrijlandt et al. 2019). ThermoGIS-v2.1 using information on the Dutch subsurface derived from the regional mapping by the Geological Survey. It is updated through incorporation of newly gained insights and data and provides a comprehensive overview of the geothermal potential for a selected set of aquifers. The resource estimates, including the uncertainty range related to these figures, at the status date 1-1-2019 of the Dutch geothermal “project portfolio” are classified using UNFC, resulting in a set of resource figures per resource class according to project maturity: commercial, potentially commercial, non-commercial and exploration projects. @en

The primary challenge for efficient geothermal doublet design and deployment is the adequate prediction of the size, shape, lateral extent and thickness (or aquifer architecture) of aquifers. In the West Netherlands Basin, fluvial Lower Cretaceous sandstone-rich successions form the main aquifers for geothermal heat exploitation. Large variations in the thickness of these successions are recognised in currently active doublet systems that cannot be explained. This creates an uncertainty in aquifer thickness prediction, which increases the uncertainty in doublet lifetime prediction as it has an impact on net aquifer volume. The goal of this study was to improve our understanding of the thickness variations and regional aquifer architecture of the Nieuwerkerk Formation geothermal aquifers. For this purpose, new palynological data were evaluated to correlate aquifers in currently active doublet systems based on their chronostratigraphic position and regional Maximum Flooding Surfaces. Based on the palynological cuttings analysis, the fluvial interval of the Nieuwerkerk Formation was subdivided into two successions: a Late Ryazanian to Early Valanginian succession and a Valanginian succession. Within these successions trends were identified in sandstone content. In combination with seismic interpretation, maps were constructed that predict aquifer thickness and their lateral extent in the basin. The study emphasises the value of palynological analyses to reduce the uncertainty of fluvial hot sedimentary aquifer exploitation.

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