Characterization for the Upper Slochteren Formation for the Province of Utrecht to Research the Potential for Deep Geothermal Energy
A.W. Heye (TU Delft - Civil Engineering & Geosciences)
D.F. Bruhn – Mentor (TU Delft - Reservoir Engineering)
Karl-Heinz Wolf – Graduation committee member (TU Delft - Applied Geophysics and Petrophysics)
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Abstract
With the help of the Dutch Seismic Acquisition Program for Geothermal Exploration (SCAN),
there is a growing nationwide interest in the exploration and development of Deep Geothermal
Energy (DGE) by the geothermal industry. One geological target in the Dutch subsurface
that could be suitable for harnessing DGE is the Upper Slochteren Formation of the Early Permian.
Previous studies have revealed the geological property distributions of the formation in
the densely populated Province of Utrecht. However, the facies distribution of the formation
across the area has not explored yet. The thesis is objective is to gather information on the
facies distribution of the Upper Slochteren Formation in the Province.
For this purpose, available core slabs from several wells in the region were studied and interpreted
for their facies groupings. Each classified facies group is characterized by a specific
range in porosity values. Additionally, seven well logs were analyzed for this thesis to evaluate
the porosity, net sand, and permeability distributions of the Upper Slochteren Formation. By
utilzing the resulting porosity borehole profile values and the 2D SCAN seismic sections, five
facies units (aeolian dune (AD), interdune (ID), sandy sheet (SS), fluvial channels (FS), and
flood sheet (SF)) were indentified and traced throughout the entire study area. The resulting
facies distribution and corresponding geological property distributions are discussed to gain
insight into the study area is paleogeographic setting and depositional environment during the
Early Permian.
Firstly, for the area north of Amersfoort, the formation is characterized by favorable geological
properties (average demonstrated permeability of 149.73 [mD]), making this area a highpotential
geothermal case. Secondly, the facies maps reveal that the area mainly consisted of
aeolian sandy sheet (SS) facies, ephemeral flood sheet (SF) facies, and ephemeral fluviatile
channel (FC) facies units. The results also indicate that their distribution was irregular across
the study area, with increased quantities of sandy sheet (SS) facies in the northeastern (northwestern
Gelderland) and southwestern (Southeast Province of Utrecht) parts of the research
area. Furthermore, the results show that at the beginning of the Early Permian period, the
quantities of ephemeral flood sheet (SF) and fluviatile channel (FC) facies units were higher,
while the amount of sandy sheet (SS) facies units was lower, in contrast to the end of the
Early Permian period. Similarly, aeolian dune (AD) and aeolian interdune (ID) facies units
were absent from the deposition area of the study region during the Early Permian period.
To better constrain the DGE potential for the Upper Slochteren Formation in the Province
of Utrecht, it is recommended to retreive a 3D seismic cube for the high-potential case area.
Additionally, it is advised to gather a large quantity of core plugs and core slabs from the
Upper Slochteren Formation during future geothermal exploration drilling.
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