PhD groundwater wells for heat storage: Methods for drilling and completio

Motivation.

The EU aims to have a net-zero greenhouse gas (GHG) economy by 2050. At present, heating and cooling represent around 50% of the final energy use in Europe and are mainly supplied by fossil fuel derived energy. Because sustainable heat is mainly available in summer and demand is in winter, large scale seasonal heat storage is a key strategy to decarbonize heating in order to achieve EU ambitions. TU Delft leads a large European project that will showcase and develop full-scale application of heat storage (up to 90°C) in geothermal reservoirs using three different technologies: Aquifer, Borehole and Mine Thermal Energy Storage (ATES, BTES, MTES), at 6 different sites in Europe which together represent a relevant range of geological conditions across Europe. In this PhD project you will develop and test methods for drilling and completion of ATES wells with a focus on high temperature (>60-100°C) levels. You will contribute to a demonstration site, where technology will be investigated at field scale.

New drilling and completion methods to reduce costs and risks.

ATES systems use 2 or more wells for the injection and extraction of water to carry heat to and from reservoirs or aquifers. Drilling is typically undertaken using (reverse circulation) rotary drilling with diameters of between ~300mm and ~1000mm for ATES systems. Depths for ATES wells are typically down to 200m, sometimes deeper. While for low temperature (<25°C) ATES systems design criteria already have been developed, these are only in part transferable to high temperature (HT)-ATES wells due to e.g. the impact of higher temperatures on material suitability and on the reservoir and well flow dynamics. Therefore, in this research, you will develop key advances for such wells by lab and field experimentation using various casing materials (vacuum, Glass-fibre Re-enforced Epoxy (GRE), stainless steel), different well designs (regular and expanded diameter (>2m)). In the HT-ATES demonstration site at Delft, two of the hot wells are intended to be equipped with new GRE casing and 1 with a vacuum casing to test/verify heat radiation reduction in penetrating layers. Two of the warm wells will be made with an expanded diameter gravel well (EDGW) to allow for higher flow rates and longer lifetime. Monitoring of well performance will provide crucial insights on optimal well design and completion for low cost and robust HT-ATES wells for future HT-ATES projects.

Objectives and methods.

You will assess, develop and demonstrate various drilling and completion methods for installing ATES wells:

• The EDGW is based on a new drilling technique that allows to significantly expand borehole diameters at depth and is one of the key well technologies you will develop further. Main research questions relate to: borehole stability preconditions during drilling and completion, cleaning of borehole wall after drilling and during maintenance, effect on particle mobilisation in relation to flow rate and temperature. You will use coupled temperature, hydraulic and mechanical (THM) models to asses these aspects, you will prepare drilling based on findings in simulations and monitor/control these during drilling of the EDGWs, furthermore you will evaluate performance of the EDGW’s once they are operational.
• You will evaluate the benefits of different types of materials for casing of ATES wells: vacuum, GRE, stainless steel. Main research questions relate to: the easy and quality of installation, quality (stability, losses, longevity) and costs. You will make general evaluation/benchmark using LCA or similar methods. Temperature and pressure monitoring allows you to evaluate performance, together with simulations.
• Evaluate the potential of casing while drilling together with drilling company.