DErisking Exploration for geothermal Plays in magmatic ENvironments

High resource risk and high upstream exploration costs are key barriers to scaling up of geothermal energy development globally. Reducing the upstream risk has, for a long time, been a priority area of the sector on several fronts. The DEEPEN project is intended to contribute to this goal through increasing the probability of success when drilling for geothermal fluids in magmatic systems. This will be achieved by developing improved exploration methods and improved framework for joint interpretation of exploration data using the Play Fairway Analysis (PFA) methodology. The development of the PFA methodology is among the more notable developments towards reducing geothermal resource risk in the recent years. This methodology, which is inspired by best practices in the oil and gas industries, allows estimation of the combined probability of encountering high-temperature fluids, their producibility and recharge, in a sub-volume of the crust through joint inversion of a number of geoscientific exploration data sets. To date, the PFA methodology has been applied with significant success to several different geothermal play types but much remains to be done to refine it for application to magmatic environments. Developing the PFA methodology for magmatic environments is a priority area for the sector as most geothermal resources, currently under production, belong to this play type. Improved understanding of subsurface conditions in these environments would improve success rate of drilling and thus have a direct positive impact on economic viability of geothermal power projects through reduced drilling cost. Furthermore, mounting evidence suggests that harvestable energy from magmatic geothermal reservoirs could be increased significantly by exploiting the bottom of convective geothermal reservoirs, towards the top of the magmatic heat sources, where superhot conditions prevail. In order to reach supercritical fluids (SCF) by deep drilling in an economically viable way the methodology for defining well targets needs to be improved. The PFA methodology, as a framework to interpret a diverse portfolio of geoscientific data, could be a key tool to define drilling targets in the roots of magmatic geothermal systems. The DEEPEN project will: 1) develop a PFA methodology specific to magmatic plays that includes the root zones of geothermal systems in magmatic environments by combining the PFA methodology (developing training sites, statistical analysis of exploration data, fairway analysis) with the development of generalized conceptual models and numerical models for multiple plays within a single magmatic system, 2) develop new tools that will help with the subsurface imaging of deep and hot bodies, building on the results of the FP7-IMAGE project, and 3) demonstrate the PFA methodology at two magmatic systems, at Hengill, Iceland and at Newberry Volcano, in the U.S. Cascades. The DEEPEN consortium consists of a group of industrial, academic, and national laboratory partners from Iceland, United States, Norway, Germany and Switzerland. The consortium includes Reykjavik Energy, an established geothermal developer in Iceland; National Renewable Energy Laboratory (NREL), U.S., the pioneers of the PFA methodology for geothermal, EQUINOR (formerly Statoil), an energy company with deep roots in the oil and gas sector and a strong tradition of joint inversion of multiple geoscientific exploration data sets, and seven research institutions with a long track record geothermal research: Iceland GeoSurvey (ÍSOR), Iceland; University of Iceland (UoI), Iceland; Norwegian Seismic Array (NORSAR), Norway; Lawrence Berkeley National Laboratory (LBNL), U.S.; Das Deutsche GeoForschungsZentrum (GFZ), Germany; Eidgenössische Technische Hochschule Zürich (ETHZ), Switzerland; and IFP Energies Nouvelles (IFPEN), France.

The overall DEEPEN project outcome provides a scientific basis and an approach for for applying the Play Fairway Analysis (PFA) methogology in "superhot" magmatic plays. In the DEEPEN project, geological elements of magmatic plays and indicators for multiple plays in magmatic systems have been defined for two DEEPEN use cases, the Hengill volcanic system on Iceland, and the Newberry volcano in Oregon, USA, representing hydrothermal/hybrid and EGS-type magmatic plays, respectively. These geologic elements were used as a basis for developing a generalized fairway analysis of multiple plays in a single magmatic system. They were further used to identify indicators for the presence of natural supercritical fluids in magmatic settings, as well as applicable exploration methods. The DEEPEN project has developed exploration methods to be used for subsurface imaging of deep and hot bodies, covering different methodologies comprising geochemical tools for targeting superhot fluids, assessment of supercritical fluid composition and utilization, tools for fracture analysis based on seismic and EM anisotropy, MT network design for deep targets, benchmarking of seismic velocity models using well logs, and multi-geophysical inversion. A high quality seismic dataset was used to detect and image deep and hot bodies and fault zones around the IDDP-3 target region at high resolution using microseismic event analysis, tomographic methods, DAS acquisitions, 2D/3D modelling, and inversion of magnetic data. Methodologices were developed for seismic event detection, seismic imaging, and source parameter estimations to assess the suitability of mapping superhot and supercritical target regions. Methods for resource assessment and technical economical analysis for superhot and supercritical systems were adapted from conventional geothermal system analysis. For the Hengill case, the volumetric resource method of USGS was demonstrated in a Monte Carlo simulation framework. For the Newberry case study, resource assessment and TEA was performed using the Geophires and GETEM tools developed by NRE.

Most high-temperature geothermal resources are found in magmatic plays. In this project we will develop methodology for de-risking of magmatic geothermal systems, including super-critical plays. First, we will develop a toolbox of geophysical, geochemical and geological tools, for mapping and characterization of magmatic systems and faults in non-sedimentary rocks, from regional scale to prospect scale. This includes methods traditionally used in geothermal exploration and methods adapted from the oil and gas industry. Cross-disciplinary integration will be performed by means of Play Fairway Analysis, with focus on the three risk elements (1) heat source, (2) recharge and (3) producibility. The methodology will be demonstrated on exploration cases in Iceland and the U.S.