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GEMex: Cooperation in Geothermal energy research Europe-Mexico for development of Enhanced Geothermal Systems and Superhot Geothermal Systems

Periodic Reporting for period 3 - GEMex (GEMex: Cooperation in Geothermal energy research Europe-Mexico for development of Enhanced Geothermal Systems and Superhot Geothermal Systems)

Periodo di rendicontazione: 2019-04-01 al 2020-05-31

The GEMex project was an international cooperation between a European and a Mexican consortium on deep geothermal energy, with the aim to speed up the development of unconventional geothermal systems. So far, the use of geothermal energy for electricity production in Mexico has been restricted to conventional geothermal systems indicated by surface manifestations such as hot springs and fumaroles, where high temperatures suitable for exploitation and electricity production are reached at relatively shallow depths. GEMex investigated two types of unconventional resources: 1) Enhanced Geothermal Systems (EGS), where sufficiently high temperatures are found but either the permeability of the rocks is too low or there are no geothermal fluids available at all; and 2) Superhot geothermal systems (SHGS), where temperatures above 350 °C require specific safety measures for drilling and materials to withstand the harsh conditions of the fluid.
The project was based on four pillars
1. Resource assessment for the EGS site near Acoculco and for a superhot resource near Los Humeros. The focus of this part was on understanding the tectonic evolution, the fracture distribution and hydrogeology of the respective region, and on predicting in-situ stresses and temperatures at depth.
The resource assessment provides the basic geological knowledge on the two research sites. Fieldtrips were dedicated to collecting new data and take rock, fluid and gas samples. Integrated geological and volcanological models have been developed. The knowledge gained in this part of the project was subsequently used by the project partners as a-priori information for the models and inversions. The geological fieldwork as well as the modelling were both performed in collaboration with the Mexican team in an equal partnership.
2. Reservoir characterization using techniques and approaches developed at conventional geothermal sites, including novel geophysical and geological methods to be tested and refined for their application at the two project sites: passive seismic data were collected to apply tomography and ambient noise correlation methods; newly collected electromagnetic data were inverted and used for joint interpretation with the seismic data. For the interpretation of these data, high-pressure/ high-temperature laboratory experiments were performed to derive the parameters determined on rock samples from Mexico or equivalent materials.
Geophysical fieldwork in Los Humeros was finished within 2018 and data analysis was ongoing until the end of the project starting with preliminary and successively updated models with constraints from other methods. Sample analysis for physical rock properties contributed to the reservoir models. An extensive database of physical rock properties is published. Reservoir modelling was performed with different approaches. Geophysical fieldwork has benefitted from enormous support by the Mexican team, who did the major part of the geophysical surveys, even though survey planning and data analysis were carried out in an equal partnership.
3. Concepts for Site Development: all existing and newly collected information was applied to define drilling targets, to recommend a design for well completion including suitable material selection, and to investigate optimum stimulation and operation procedures for safe and economic exploitation with control of undesired side effects. These steps include appropriate measures and recommendations for public acceptance and outreach as well as for the monitoring and control of environmental impact.
The concept development was mainly carried out in the final period of the project. For the potential EGS site, various stimulation approaches have been evaluated, based on the data collected and derived in the project. On the basis of these stimulation approaches, productivity scenarios were evaluated. A specific workflow for a stimulation test in one of the two existing wells in Acoculco was proposed. Furthermore, the environmental risks were evaluated (soil pollution and seismic risk). Finally, an in-depth study on social acceptance and public engagement strategies resulted in a conceptual model for public engagement. For the superhot site in Los Humeros, a number of different modelling approaches have been developed in order to select a suitable location and drill path for a superhot well. A downhole material test in Los Humeros was performed and suitable materials for the completion of a superhot well have been proposed. A review of failure modes of superhot drilling projects has been completed and laboratory experiments for non-Portland cement have been performed.
4. The work package for dissemination internal communication (WP2) has enabled and supported the dissemination of project results throughout the lifetime of the project. Internal communication has been supported by the Virtual Research Environment, which was used by both, the Mexican and the European consortia. 60 scientific papers have been published or are currently under review. 244 conference contributions have been presented or are foreseen in the near future. Additionally, GEMex engaged with industry stakeholders through 2 stakeholder workshops, a series of three online-seminars and participation to two industry exhibitions. A patent has been filed on a high-temperature tracer.
The two GEMex partner projects brought together the extended Mexican know-how of discovering, developing, and deploying conventional geothermal energy systems with a variety of European expertise from superhot geothermal energy systems (Italy, Iceland etc.) and in developing EGS technology. The synergies of competencies was used to develop concepts for extended future deployment of geothermal energy in Europe and Mexico.
In particular, the relationship between recent volcanism, regional structures and the current geothermal potential were newly defined for Los Humeros. By using the strongly multidisciplinary approach the work performed in GEMex has defined new areas outside the currently exploited locations where superhot geothermal resources are likely. In addition, the material testing approach has clearly constrained the candidate steels and metal alloys for future well completion in such highly aggressive geothermal environments.
The lack of data for Acoculco was alleviated by extensive field campaigns to constrain the local fracture network and derive as much information as possible on the local stress field.
The concepts for site development provided by GEMex present a major step forward for the regional geothermal operations and future deployment. Beyond the regional progress, the systematic approach applied by GEMex provides a blueprint for the investigation of superhot geothermal systems and their potential development in the future. Their exploitation would lead to a significantly higher electricity generation from drilled wells such that fewer wells would need to be drilled to produce even more geothermal energy than from conventional geothermal systems. Even though there is currently no installation producing energy from such resources in the world, international interest in exploiting such economically highly promising resources has grown significantly in the last years, leading to numerous projects investigating them, for example in the Iceland Deep Drilling Project IDDP. GEMex is a major contribution towards the development of these resources in the future.