L.N. Barlet

Master thesis (1)

Student report (1)

2 records found

The Impact of varying thermal and hydraulic properties on HT-ATES systems

A Study Based on Sediments of the Maassluis Formation with a focus on thermal properties

Master thesis (2025) - L.N. Barlet (author) , JM Bloemendal (graduation committee member) , P. J. Vardon (graduation committee member) , S.T.W. Beernink (mentor)

To address the gap of constant heat supply by geothermal doublets and the varying demand throughout a year, High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems have attracted a growing amount of research interest as a way of storing the excess heat produced in ...

The performance of seasonal heat storage systems in confined shallow aquifers depends on several (hydro)geological and design parameters.

The storage aquifer and sealing aquitard characteristics are subject to uncertainty and spatial heterogeneity. The present study examines the variability of hydrological and, in particular, thermal properties in cores taken from boreholes of the Maassluis formation in four different locations in the Western Netherlands. Because the uncertainty of thermal properties is rarely implemented in (HT-)ATES models, it is the main focus of this research.

In a laboratory study, the hydraulic conductivity and thermal properties of the cores and smaller-scale core plugs are measured to create a database of those parameters for the Maassluis formation, which is a promising heat storage target.

The samples are classified according to their grain size and evaluated with respect to their spatial variability. Results yield thermal conductivities ranging from 1.35W/mK to 2.37W/mK for clay samples and from 2.05W/mK to 2.94W/mK for sands.

These thermal conductivities are subsequently utilized to populate a numerical model of a potential HT-ATES system at the TU-Delft campus, using the SEAWAT code. The present study aims to assess the impact of the expected range of thermal conductivity in the aquifer and sealing layers on two key aspects: firstly, the recovery efficiency over the lifetime of the system, and secondly, the thermal impact on the subsurface.

Simulation outcomes demonstrate that recovery efficiency differences are marginal for varied thermal conductivities. In contrast, the vertical hydraulic conductivity of the aquifer exerts a significant influence, resulting in absolute recovery efficiency differences of up to 7% in the modeled scenarios.

Varied thermal conductivity of the sealing layer modeled can have a noticeable thermal impact on the subsurface around the system, while the horizontal spread of heat into the aquifer is predominantly influenced by buoyancy flow, caused primarily by larger vertical hydraulic conductivities.

The overall impact of the uncertainty of thermal sediment properties on system performance is minor when compared to other uncertainties However, the effect of thermal plume spread could be significant, depending on the surrounding environment.

RINGEN Geothermal Project Development MDP

Student report (2023) - S.A. Akkermans (author) , J. Sass (author) , L.N. Barlet (author) , E.E. Zijlstra (author) , A.K. Jha (author) , A Amiri Simkooei (mentor) , D. F. Bruhn (mentor)

In this multidisciplinary project several aspects of geosciences are combined. The regional geology background was summarized and linked to the borehole data.
Multiple tests were conducted on the well to answer several questions. The slug test indicated that the fracture is still open and essentially confirmed that it is a shear fracture, however it is unclear to what extent that the fracture is open. The fracture seems to be hydraulically connected to a permeable unit or shallow aquifer. Unfortunately, the length of the fracture could not be determined with the data collected from the test.
Electrical resistivity tomography (ERT) and seismics were both applied to a location near the borehole to acquire lateral information of the subsurface. The ERT results showed that the layers were horizontally continuous and indicated layers with different compositions based on resistive properties.
Seismic refraction tomography conducted along a part of the same profile showed similar results as the ERT for that part of the profile. P-wave velocities indicate a horizontally layered subsurface in the upper 40m. Additionally surface wave analysis of the same setup utilizing active and passive measurements resulted in a vertical s-wave velocity profile that can be used for future implementation of the planned Borehole Thermal Energy Storage (BTES) system.
The last geophysical method was using gravity data on the region around the site. A map was made by using available data on changes in gravity in the region and plotting the results. On this map the location of remnants of volcanos and the Litoměřice deep fault can be recognised.
Thermal properties of cores were analyzed using a Hot Disk and an optical scanner. Unfortunately the drilling of a new well from which the cores were to be analyzed was delayed, and cores from an uranium mine were used. This way the advantages and disadvantages of both measuring devices could be argued and used for future research.
Past analysis of geothermal regions have shown that exploration of geothermal energy causes surface displacement. It can also be observed during the drilling phase. Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS) are valuable tools to monitor land surface changes. Measurement of surface deformation being one of its many applications. For this study, the above tools have been used to measure surface displacement in the region of Litoměřice.