Geothermal Play Typing - Current Development and Future Trends of a Modern Concept for Geothermal Resources Assessment

The play type is a common concept to streamline the exploration for subsurface natural commodities and is a fundamental part of the resource assessment practice. A play type describes the generic geological environment that might host an economic accumulation of a given commodity. The identification of a certain play type has therefore implications for exploration and extraction strategies. In geothermal exploration, a systematic worldwide play type concept has been recently published. The aim of geothermal play typing is to economize the exploration process, to define the play risk, and the chances of reservoir discovery by appropriate targeting and exploration methods, which are ideally geosystem specific. However, the play type concept needs further definitions and specifications to integrate geothermal plays into the assessment process for geothermal resources. A worldwide usable language for the geothermal assessment process remains elusive. First attempts have been made on a geothermal play type workshop under the umbrella of the IEA-Geothermal meeting in Vienna in May 2018. The recent nucleus for systematic research and development of a conceptual framework is the research project PlayType that aims to find a standardized and broadly applicable methodology for play typing (funded by the German Federal Ministry of Economy and Energy - BMWi). Preliminary results reveal the common interest in geothermal play type concepts but also the lack of clear definitions and play sub-categories. The play-based assessment process requires the integration of surface criteria including user demand, infrastructure and land access, and subsurface criteria such as geosystem, play focus and prospect scale play levels. Ultimately, play based exploration as a goal of geothermal resources assessment can only be achieved by continuous efforts on an international level.