Short summary of the project: The aim of the project is to develop, develop and demonstrate as a pilot project cost-effective technologies that are much more advanced than those applied in the current Hungarian practice, which will enable the realisation of sustainable geothermal energy production by re-injection of thermal water extracted from unconsolidated upper-pannon (FP) sandstones with high geothermal potential into the same water station in accordance with legislation. The project’s industrial research results are two validated geothermal injection mechanisms. Based on this, the experimental development result is two geothermal repressive well-training technology, database and service development, which can be used internationally. The main tasks of the project are: FP sandstones characterised by unconsolidated, loose sediments, with high thickness and watering capacity, have a significant geothermal potential, but this can be achieved in a sustainable manner by re-injection of cooled thermal waters beyond the heat recovery into the same water tax, which is also a legal obligation (Act LVII of 1995 and related regulations) at the current level of technology or at an uncompetitive price. Many repressive wells have been installed on FP sandstone storage sites, but because of the outdated well-training technology, the success of the injection is questionable. A current and previous R & D project is experimenting with the development of geological modeling and the construction of larger diameter wells (TECH_08_A4, GINOP-2.1.1-15-2016-00970), but it is clear that technological developments that fundamentally determine the re-injection are also needed, which, if successful, will also support these tenders. The aim of this project is to implement complex technological and methodological developments that result in water injection into FP sandstones in a sustainable way. MECSEKÉRC Zrt. The R & D project “Developing a well-training technology for sustainable geothermal energy use-I” (GOP 1.1.1-11-2012-0033), successfully implemented and completed between 2012 and 14, is the direct precedent of the project to be implemented. In the course of this, the measurement of the rock mechanical and rock physics characteristics of the FP sandstones, the development of measurement technology and method, the design, production and installation of two laboratory tools for the development of injection-well-training technologies (gravel-bed filter and Frac&Pac), and the development of laboratory infrastructural and human resources have been carried out, thus preparing for the second phase of the project, which means the present project. The project consists of 7 research and development sub-tasks: 1. Examination and treatment of damage to the plateau 2. GP well training tests 3. Development of an environmentally friendly F&P methodology optimised for water injection into FP sandstones 4. Rock mechanical changes and F&P hydraulic fracturing modelling 5. The construction of a new GP-training well and the retraining of an existing geothermal well into a return well with F&P technology FP sandstones 6. Core tests 7. Conducting a long-term injection experiment in the FP injection well trained with two developed technologies The project consortium leader is MECSEKÉRC Zrt, consortium partners: ROTAQUA Kft., Stone Metering Ltd., University of Pécs. Duration of the project: 48 months. Building the professional tasks of the project on each other: The R & D task is essentially the parallel implementation of two methodological developments, i.e. the development of a GP and a F&P injection-well training technology and the long-term testing in pilot projects. The project is divided into R & D sub-tasks, which are combined by project management and are partly run in parallel and are built on each other. Sub-task 1 is the execution of complex laboratory strata damage tests, covering all factors that may affect the success of injection. The tests shall include testing of thermal water, applied well-technological fluids and materials, solid and suspended materials capable of migration, and the impact of bacteria on rock and on each other under partly static and partly dynamic conditions, including treatments to eliminate layer damage. Their results also play a role in the selection and parametrisation of the layer damage model. As many experiments need to be carried out and insufficient FP sandstone samples are available, it is necessary to produce and qualify artificial samples with natural binders with corresponding rock physical properties for the target environment. The result of the sub-task is two well-technological fluids and an appropriate quantity of artificial sample bodies, which form the basis of the subsequent subtasks, and the development of a recommendation on the process of reclaimed and waste generation