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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - SURE (Novel Productivity Enhancement Concept for a Sustainable Utilization of a Geothermal Resource)

Teaser

Summary

Within the project SURE the radial water jet drilling (RJD) technology will be investigated and tested as a method to increase inflow into insufficiently producing geothermal wells. Radial water jet drilling uses the power of a focused jet of fluids, applied to a rock through a coil inserted in an existing well. This technology is likely to provide much better control of the enhanced flow paths around a geothermal well and does not involve the amount of fluid as conventional hydraulic fracturing, reducing the risk of induced seismicity considerably. RJD shall be applied to access and connect high permeable zones within geothermal reservoirs to the main well with a higher degree of control compared to conventional stimulation technologies. The jetting process as well as the controlling parameters will be investigated in order to allow for a prediction of the applicability of the jet drilling process in different geological settings as well as an optimization of the siting of such enhanced flow paths around existing wells.
The overall objective of the SURE project is to increase the number of economically viable geothermal wells, and thereby reducing the environmental impact associated with the provision of geothermal energy.

Work performed

Within the first reporting period, work started in all work packages. Below, you find a short summary of the activities:

WP 3 State-of-the-Art:

Objectives: Within SURE, different technologies to enhance a geothermal system (EGS) will be discussed. A special focus will be on the benefits and drawbacks of the water jet drilling technology in comparison to the more established stimulation treatments. As the possible length of the drilled laterals is currently limited to approximately 100 m, the RJD technology has a potential benefit in highly heterogeneous reservoirs, where strong and eventually even anisotropic permeability variations can be observed in the vicinity of the main bore.

Work Performed: A review of different stimulation technologies as well a state-of-the-art assessment of the radial water jet drilling technology was written.

WP4 - Micro-Scale Investigation

Objectives: The properties of various potential geothermal reservoir rock types will be determined and processes related to flow and to the jetting of the rocks will be investigated at the laboratory scale. One of the crucial questions addressed is the way in which the micro-scale processes, controlling the flow and heat transfer will behave at a larger scale. It is of critical importance to better understand the physical, mechanical and chemical properties and their dependency on mechanical and chemical reservoir conditions of the tested reservoir rocks. To generate these data and derive the necessary information detailed laboratory and numerical studies will be performed at micro (laboratory)-scale, with and without the drilled laterals.

Work Performed: Within the first reporting period, several rock samples have been characterized. Experimental set-ups for the measurement of the jetted laterals stability in the ambient stress field as well as fracture conductivity measurements were established.

WP5 - Meso-Scale Investigation

Objectives: The objective of this work package is to achieve a most complete understanding of the water jet/tooling-rock-interaction for a large variety of sedimentary and crystalline rocks, in order to introduce a drilling technology for EGS that is not limited only to one single geological setting but will be applicable all over Europe in low to high enthalpy reservoirs. Thus, it is necessary a) to prove the existing water jet-technology for different rock characteristics in laboratory and field scale experiments, b) to detect and understand the gaps, c) to improve the design when possible, d) to investigate if additional information about the geological structure is obtainable while drilling and finally e) to iteratively develop an enhanced jetting technology for rock properties that the existing water jet-tooling is not applicable to.

Work Performed: Within the first reporting period, data was gathered on the jet-ability of different rock types at ambient conditions. In addition, first experiments were performed to assess the jet-ability of rock samples under load. A field trial in a quarry was conducted to investigate the radial water jet drilling operation in a field scale environment. Currently, data is being analyzed.

WP6 - Macro-Scale Investigation

Objectives: Based on the knowledge gained from the experiments at the micro (WP4) and meso-scale investigations (WP5), the aim of the planned field application is to confirm the conclusions drawn from these tests as well as results from the integration work package (WP7) and to verify the possibility to improve the wellbore performance of a geothermal well at in-situ conditions. Therefore, two field experiments will be performed in two representative geothermal reservoir types - a sedimentary (The Netherlands) and a magmatic (Iceland) environment.

Work Performed: Within the first reporting period, two sites were selected as candidate sites for the RJD operation downhole. Required geological, geophysical as well as geotechnical data was assembled for each well. Based on t

Final results

SURE has a significant impact on the development of geothermal systems. Specifically, the impact relates to:

Replicability
By testing the jet-ability of representative reservoir rocks from major geothermal reservoirs in Europe, SURE aims at providing information about the applicability of the RJD technology in different geological settings. Additional field tests will ensure the replicability of the technology for various European geothermal sites.

Socio-economics
The application of this new stimulation concept for geothermal wells can significantly increase the development of industrial capacity â€“ both for the service industry as well as the geothermal energy companies. Therefore, SURE can contribute to strengthen the European industrial technology base, thereby creating growth and jobs in Europe. Furthermore, the applicability of RJD technology with its inherent very low environmental footprint will increase the societal acceptance of geothermal energy provision.

Environment
The proposed technological concept aims to significantly decrease the environmental footprint of a stimulation treatment while reducing simultaneously the amount of applied fluid volumes compared to established stimulation methods, the number of applied chemicals with environmental impact, and the risk of induced seismicity.