Revisiting the Classification of Geothermal Resources

Transcription

1 Revisiting the Classification of Geothermal Resources Colin F. Williams, USGS, Menlo Park, CA U.S. Department of the Interior U.S. Geological Survey

2 Outline Background/Motivation Classification Project - Objectives and Dates Desired Characteristics Examples of Classifications Assessment Confidence Temperature and other thermodynamic properties Convective/Advective vs. Conductive Geologic Setting Community Input and the Next Steps

3 Geothermal Manifestations

4 Direct Use Spas

5 Direct Use - Greenhouses

6 Geothermal Power The Geysers Photo by J. Donnelly-Nolan, USGS

7 Background and Motivation Resource classification is a key element in the characterization, assessment and development of energy resources, including geothermal energy. Stakeholders at all levels of government, within the geothermal industry, and among the general public need to be able to use and understand consistent terminology when addressing geothermal resource issues such as location, quality, feasibility of development, and potential impacts. This terminology must encompass both the fundamentally geological nature of geothermal resources and the practical technological and economic aspects of resource exploitation while remaining understandable to the broad community of nonspecialists. In the United States, the classifications applied to geothermal resources are primarily the legacy of resource assessment and characterization studies conducted in the 1970s during a time of rapid development and new interest in geothermal energy. That many of the standards developed during that time are still in use today is a testament to the quality of the original work.

8 Background and Motivation However, developments over the past 30 years, especially advances in geothermal technology, have expanded the scope of exploitable geothermal resources beyond the earlier classifications. As part of its ongoing work to improve the assessment of geothermal resources, the USGS is working with DOE to engage the geothermal industry and academic partners in developing a new geothermal resource classification system approach that will reflect the current state of knowledge regarding geothermal technology and serve as a effective means of characterizing, quantifying, assessing and communicating important aspects of geothermal energy potential. There will always be diversity in the characterization of geothermal resources, and we are not attempting to impose a single approach. The main goal is to provide facilitate clear and consistent communication within and outside the geothermal community. A key component of this effort will be the development of tools to translate between different approaches, both current and past.

9 Outline Background/Motivation Classification Project - Objectives and Dates Communicate Project Goals to Community This meeting; Stanford workshop paper and presentation with Reed and Anderson (Feb.) Report on draft classification system and translation tools (June/July) Public meeting and presentation at GRC (October) Formally engage the international community Desired Characteristics Examples of Classifications Community Input and the Next Steps

10 Outline Background/Motivation Classification Project - Objectives and Dates Desired Characteristics Is simple and logical for effective communication and understanding Is valid from scientific and technical perspectives Meets clearly identified need Is easily translated to other systems Avoids misconceptions that adversely affect commercial activities Eliminates gaps or overlap between categories Avoids unnecessary predictions Examples of Classification

11 Outline Background/Motivation Classification Project - Objectives and Dates Desired Characteristics Examples of Classifications Assessment Confidence Temperature and other thermodynamic properties Convective/Advective vs. Conductive Geologic Setting Community Input and the Next Steps

12 USGS Resource Assessment Concepts Reserve Geothermal energy that can be extracted legally and economically. Resource Geothermal energy that is technically recoverable and can be added to Reserves at some future time. Resource Base Thermal energy in the crust in specific area.

13 Australian and Canadian Protocol Terms AGEA (2008)

14 Example Geothermal Resource Categories Identified Undiscovered Producing Confirmed Potential Prospect Measured Indicated Inferred Proven Inferred Speculative Equivalent numerical schemes

15 Electricity Generation from Geothermal Energy Hot water flash Steam Binary Source: USGS Circular 1249

16 Examples of Temperature/Enthalpy Classes In addition to temperature and enthalpy, exergy (E) is also useful for classifying resources (Lee, 2001) and can be calculated using public domain software. B&C (1990) = Bendritter and Cormy (1990); A&G (2000) = Axelsson and Gunnlaugsson (2000)

17 Convective vs. Conductive Heat Transfer

18 Idealized Basin and Range Geothermal Power Plant Fluid upflow and outflow can involve all rock types, including sediments

19 Conductive, sediment-hosted resources Image courtesy of Alison LaBonte (DOE)

20 Geothermal Resources by Geologic Setting from Paul Brophy, EGS Inc. Defining resources by geologic setting is critically important for exploration and assessment.

21 Outline Background/Motivation Classification Project - Objectives and Dates Desired Characteristics Examples of Classifications Community Input and the Next Steps Share your opinions, priorities and needs Opportunities to evaluate translation tools Future communication through the IGWG? Stanford paper and presentation in February

22 Acknowledgements Arlene Anderson (DOE) and Marshall Reed (USGS) USGS Energy Resources Program, DOE Geothermal Technologies Program, Bureau of Land Management Every person who contributed a figure or information

23 Thank You