WP 3 State-of-the-Art:
Within the SURE project, a review of different stimulation technologies to enhance a geothermal system (EGS) was performed. A special focus lied on the benefits and drawbacks of the water jet drilling technology in comparison to the more established stimulation treatments.
WP4 - Micro-Scale Investigation
The physical properties of various potential geothermal reservoir rock types were determined and processes related to the jetting of these rocks were investigated at the laboratory scale. One of the crucial questions addressed was the way in which micro-scale processes, controlling the flow and heat transfer will behave at a larger scale. Therefore, experimental set-ups for the measurement of the jetted laterals stability in the ambient stress field as well as fracture conductivity measurements were established and experiments were performed to analyse the behaviour of various rocks at ambient stress conditions.
WP5 - Meso-Scale Investigation
The objective of this work package was to achieve a most complete understanding of the water jet/tooling-rock-interaction for a large variety of sedimentary and crystalline rocks. Thus, it was necessary a) to prove the existing water jet-technology for different rock characteristics, 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.
Therefore, a thorough understanding of the physical processes controlling the jet-ability of various rock types was gained through an extensive testing program at a) ambient laboratory conditions with saturated and unsaturated rock samples, b) varying pore pressure conditions, as well as c) true-triaxial stress conditions. In addition, a jetting experiment was performed in a quarry with field scale jetting equipment to bridge the gap between laboratory and field scale conditions. Based on the experiments in this workpackage, improved jet-assisted drilling nozzles were tested and qualified.
WP6 - Macro-Scale Investigation
Based on the knowledge gained from the experiments at the micro (WP4) and meso-scale investigations (WP5), two radial jet drilling stimulations were planned. The aim of the planned field application was to confirm the conclusions drawn from laboratory tests as well as results from the integration work package (WP7). Furthermore, the stimulations were intended to showcase the performance increase for a geothermal well at in-situ conditions in a sedimentary and a magmatic environment, respectively.
Unfortunately, it was not possible to successfully test the RJD stimulation technology. In this framework, however, a workflow was developed to assess and design a RJD stimulation treatment. Based on the field experience, important technical adjustments to the state-of-the-art stimulation technology were investigated. Also, a post-stimulation workflow is proposed and different tools, e.g. a low-cost downhole geophone and a sensor to investigate the lateral's geometry were developed.
WP7 - Integration
In order to enable the operator to evaluate the potential benefit from a RJD stimulation treatment, the experimental results of the previous work packages were numerically analyzed and used to calibrate physical models. As a result, WP7 provides predictive modelling capability to interpret experimental results for WP4-6. These numerical tools can be used to plan and optimize the RJD stimulation design as well as to evaluate the results of a stimulation treatment. As economic aspects are considered, numerical results can be evaluated in the light of levelized cost of energy.
All results of the SURE project are documented and publicly available. Experimental set-ups and numerical tools were developed and are available for advancing the knowledge about RJD stimulation treatments together with partners in industry and science. A list of the most recent publications can be found on www.sure-h2020.eu.
