Probabilistic Assessment of Geothermal Resource Bases (original) (raw)
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Geothermal resource assessment: Combining uncertainty evaluation and geothermal simulation
Geothermal resource assessment faces the problem of high degrees of uncertainties for both subsurface geometries and material parameters. We present novel methods for geothermal resource evaluation and their integration into one common framework. This combination enables quantitative assessment of uncertainty and hypothesis testing based on the following four components: 1) Integrated workflow for geological modeling and geothermal simulation; 2) Novel techniques for the spatial analysis of geothermal resource estimations; 3) Spatial map of potential recovery factors; 4) Uncertainty evaluation and hypothesis testing for geological scenarios;
Methods of Early Geothermal Energy Resource Assessment - A Modern Conceptual and Mathematical Model
2015
Early in a geothermal field development the owners and financiers want to know the number of MWe capacity of the plant that can be sustained by the new field although very limited information about the field has been gathered. In the past 50 years 3 methods of early assessment have been developed, each based on different concepts, mathematics, and statistics. Models are based on a conceptual model of the field. The “Volumetric method” was implemented more than 40 years ago, when no history or data from many fields and thousands of boreholes were available. It is basically a static energy calculation and the method can provide an early estimate of MWe capacity, normally greater than the natural real one. The “Monte Carlo Simulation” method produces a wide range of possible solutions, and then a statistical probabilistic value can estimate the final geothermal field estimate of MWe. The application to real cases (e.g. Iceland) proved that the resulting estimates are still above the tr...
2009
Conventional geothermal settings are convective and advective in nature, related to heat transfer by the physical motion of fluids and steam within volcanic and shallow magmatic environments. Early EGS development in Europe has also encountered convective conditions. However, Australia is largely a conductive geothermal setting. The embryonic Australian geothermal sector has looked towards the established European and US geothermal sectors for learnings, but little attention has been paid to the distinctly different nature of heat transfer (convection versus conduction) in these settings and what this may mean for resource estimation. The Geothermal Reporting Code governs the declaration of Geothermal Resource estimates by public companies in Australia. Whilst the Code allows flexibility in the methods of estimation for an Inferred Geothermal Resource, the use of dynamic reservoir modeling methods at the resource estimation stage, as commonly applied in European and US geothermal pr...
Classification and Reporting Requirements for Geothermal Resources
Growing awareness and interest in renewable resources has raised the need to homogenise the reporting requirements for geothermal resources so that they can be applied worldwide. As no globally agreed standards, guidelines or codes exist, there remains too much latitude in geothermal assessment, which leads to increased resource uncertainty, more investment risk and less confidence in development. Reconciling the various reporting of geothermal resources is a major challenge as it is difficult to define what the target actually is: the source, the reservoir, the fluids, the stored heat, the recoverable volume, the recoverable heat, the recoverable power, or the net profit. Formulating an agreed procedure to classify geothermal resources is further complicated by changing environmental, policy and regulatory constraints around the globe. Present day techniques of computing geothermal resources provide only ballpark estimates at best. This paper addresses the existing gaps in standardising geothermal resources assessment and reporting by capturing: current methods used to identify potential geothermal projects; current practices in classifying and reporting geothermal resources and reserves; key decision parameters for operators, investors, governments and insurance companies; and current obstacles to a common and transparent way to secure investment in geothermal energy.
Geothermal Systems Assessment—Identification and mitigation of EGS exploration risk
The conventional view in Australia (and many other places) is that achieving optimal temperature is the critical risk in exploration for conductive geothermal resources. This view has often resulted in other areas of risk being overlooked. A Geothermal Systems Assessment (GSA) investigates and ranks four largely independent critical risk areas-heat source, thermal/hydraulic insulation, reservoir potential, and working fluid. These four factors determine the probability of encountering an economic conductive geothermal resource. The GSA approach is synonymous with risk methodologies used in Petroleum Systems Analyses.
2014
Globally, geothermal energy is utilised within active volcanic regions. The state of Queensland in Australia has few areas of recent volcanic activity, but has large volumes of identified hot granites at 3 to 5 km depth, most of which are located in the far south-west of the state, beneath the Cooper and Eromanga basins. This is potentially a vast source of thermal energy that can be tapped by Engineered Geothermal System technology for power generation purposes. However, their distance from potential markets and the existing national electricity grid, prevent economic viability of the resources in the near term. The Queensland Government designed the Coastal Geothermal Energy Initiative program to investigate additional sources of hot rocks close to major population centres and existing infrastructure. The program targeted a variety of geological settings along the state’s north and east coasts in a structured drilling and heat flow investigation program to collect new, pre-competi...
Regional and Country-level Assessments of Geothermal Energy Potential Based on UNFC Principles
2019
The United Nations Framework Classification for Resources (UNFC) is a universally acceptable and internationally applicable scheme for the sustainable management of all energy, mineral and anthropogenic resources. As of 2016, the UNFC is also applicable togeothermal energy resources. Prescribing quantification methods for resource estimates goes beyond the scope of the UNFC, as multiple best practices, as well as analytical and numerical tools already exist, which encompass the significantly wide range of geothermal geological settings, heat recovery and conversion technologies and socio-environmental contexts. Nevertheless, the Project concept embedded in the UNFC, together with the need to define the associated level of confidence in the potential recoverability of the quantities, requires users to link different types of geothermal resources with corresponding viable project development schemes. This facilitates the choice of suitable quantification methods (probabilistic, scenar...
Technical-economic estimation of geothermal resources
Geothermics, 1970
Tremendous underground heat resources and simplicity of geothermal installations attracts ever more attention of pow& engineers in many countries of the world. To determine conditions and possible scale of earth heat effective utilization it is necessary to compare thoroughly geothermal sources with other energy sources.
The terrestrial energy current flowing from the mantle to the surface of the Earth is more intense at plate boundaries than within the tectonic plates. At the surface of the Earth, the most obvious manifestations of this energy current are active volcanoes and high temperature geothermal fields. Geothermal assessments have only been carried out for a limited number of countries or regions, while the distribution of active volcanoes in the world is fairly well known. As the volcanoes and the high temperature geothermal fields are manifestations of the same energy current, the distribution of active volcanoes should reflect the geothermal potential of the world. An empirical relation between the number of active volcanoes and the technical potential of high temperature geothermal fields in 8 regions of the world has been established in the paper. This relation is consequently used to estimate the technical potential of high temperature geothermal fields in the world as a whole. The result is that the most likely value for the technical potential of geothermal resources suitable for electricity generation is 240 GW e .