Task 3.1: Geo-energy technologies

Research partners: Department of Mechanical and Process Engineering (D-MAVT) at ETHZ

Research objectives
Statistical data tell us that with today’s Rotary Drilling process from oil & gas, we are approximately only utilizing a third of the rig time on bottom making productive hole cutting progress. Two thirds of the contracted rig time is spent on changing worn bits, stabilizing or recovering the borehole, running/cementing casing, taking logs, repairing the rig or waiting on equipment or decisions. One approach investigated to access the reservoir without damaging the formation is spallation drilling at higher temperatures. This method is at the pilot stage. Hydrothermal flame systems in supercritical water have been studied at ETH Zürich for more than 14 years. Experimental and theoretical studies have been conducted concerning heat transfer, transport of spalls and flame operating conditions at operating conditions of above 25 MPa bars and at temperatures up to 1600° C. A demonstration of this technology is been constructed at ground level and is operated with different rock samples. An ambient pressure spallation plant is under construction. Theoretical and experimental work of the spallation dip side shall define optimal conditions for the spallation process and allow the transfer to industrial application.

Research partners: Institute for Building Materials (IfB) at ETHZ

Research objectives
The BP Deep Horizon oil spill in the Gulf of Mexico was due to oil escaping outside the casing as result of defective cementing of the casing to the host rock. The cementing of deep wells presents many technological challenges. These include: rheology and its evolution in time, setting and hardening kinetics in addition to the expected in service functions as mechanically supporting the metallic well casing pipes and in mitigating its corrosion. All of this is rendered substantially more challenging because of the high temperature and pressures encountered in deep wells. Well cementing operations are typically dealt with on a case-by-case basis, owing to local specificities and to the high cost of the operation. A bad cementing job can compromise the whole operation, so that very high technological expectances exist in this area. Specialized service companies have a very large expertise and practical experience in these systems. However, they regularly state that interactions among chemical additives as dispersants, set retarders and accelerators often lead to unexpected behavior and loss of performance. We will research cement properties at the extreme conditions of temperature and pressure encountered in deep geothermal well; as steel corrosion in concrete is another relevant issue, we will also examine the ability of modified well cements to protect the steel pipes from corrosion.

Research partners: Department of Mechanical and Process Engineering (D-MAVT) at ETHZ, Lucerne University of Applied Sciences and Arts, EPFL-CCE

Research objectives
Several thermodynamic cycles can be developed for the conversion of the geothermal heat into electricity. The different cycles configurations have to be adapted to the conditions of the geothermal heat availability and of the different possible usage of the harvested heat (combined heat and power schemes). We will work on three aspects of heat conversion:

  • The first technology development will be a modeling platform for the design of thermal cycles to convert geothermal heat into electricity. A systemic approach will be used, considering the different aspects of the system integration: heat exchanger fouling, variability of the operating conditions (heat demand, cold source availability, depletion of the geothermal heat source with time), selection of the appropriate fluids and cycle configurations.
  • Hybrid geothermal power generation is of high interest for geothermal reservoirs below T=300°C, by coupling with steam superheated by a different source of high-T heat and enabling to operate a more efficient steam-based Rankine cycle instead of a low-efficiency ORC.
  • The transfer of heat in the heat exchangers is prone to precipitation and crystallization fouling, corrosion (e.g. electrochemical oxidation disintegrating the heat exchanging walls) and abrasive wear of the heat exchanger walls due to particles in the fluid, leading to plugging or defects of the exchangers. The superposition of these mechanisms reduces the heat exchange efficiency and shortens the service live of the heat exchangers. The goal of this field of research is the development of efficient, reliable, economic and fouling resistant heat exchangers.

Research partners: University of Applied Sciences and Arts Western Switzerland (HES-SO)

Research objectives
The goal is to develop a new generation of borehole sensors suitable for operation under high temperatures and pressures, to measure properties which might include local physical and chemical properties, conditions of the well (casing integrity, corrosion, altitude), parameters to monitor induced seismicity, dynamic changes in rock conditions related to energy harvesting process operation, safety systems. Operating electronic circuits at very high temperatures is a challenge. We shall develop a two-step approach, where available active circuits for operation up to 200°C are placed in an intermediate cabinet at 2-3km depth, and a passive front-end capable of operating over a distance of up to 2km is designed for specific measurement systems. Activities will include the definition of measurement tasks, specifications, concepts, materials, devices and systems, casing and packaging; the evaluation of technologies and materials; technological infrastructure for the fabrication of harsh environment sensors; demonstrated sensor concepts and packaging in lab and first field trials.