GRRM/How To/LevelOfInformation

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Applying the Methodology to Geothermal Projects




Level of Information

The following table provides the criteria to select the appropriate level of information associated with a geothermal project's research and development. Select the category/term that best corresponds to the current stage of the project.

Level of Information: Qualifying Criteria and Barriers
Proposed Terms Description Stage of Modeling Qualifying Criteria
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Proven The reservoir’s production has been evaluated with more than one successful commercial well, and is supported by extensive evidence from geophysical, geochemical, and geologic surveys. Very Advanced Conceptual, Advanced Reservoir – Includes multiple estimates of reservoir volume and temperature, includes local variations and multi-well drawdown effects For a resource to be considered ”Proven", all of the following criteria must be met:
  • Multiple, full-scale production and injection wells have been drilled and are capable of being placed online.
Well field built out and capable of producing expected flow
Confirmed The reservoir’s production has been evaluated with more than one successful commercial well, and is supported by extensive evidence from geophysical, geochemical, and geologic surveys. Very Advanced Conceptual, Intermediate Reservoir – Includes multiple estimates of reservoir volume and temperature, includes local variations and multi-well drawdown effects For a resource to be considered "Confirmed," all of the following criteria must be met:
  • Two or more full-scale wells must be drilled and flow tested
Multiple full-diameter wells drilled
Demonstrated Both of these requirements must be met:
  • The reservoir has been evaluated with successful flow tests (from slim holes and/or 1 successful production well), and
  • there are time series of supporting geophysical and geochemical data.
Advanced Conceptual, Basic Reservoir - Includes multiple converging estimates of reservoir temperature and volume, and initial estimates of reservoir degradation/ longevity. For a resource to be considered Demonstrated, all of the following criteria must be met:
  • At least one full-diameter well has been drilled
  • The reservoir permeability has been evaluated with at least one of the following methods:
    • flow tests and/or
    • packer test
  • Conceptual model has been refined using time series of supporting geophysical and geochemical data.
Full-diameter well / well test
Potential There are reliable estimates of temperature and volume for the reservoir from geophysical, structural, and geochemical evidence, but no successful flow tests have been completed to date. Intermediate Conceptual - Includes converging estimates of reservoir temperature and volume. For a resource to be considered Potential, all of the following criteria must be met:
  • Temperature is measured at the reservoir level using at least one of the following methods:
    • Downhole probe in slimhole(s) drilled into the reservoir
  • Temperature is corroborated using at least one of the following methods:
    • Downhole geothermometry
    • Assessment of lithology and mineral assemblages taken from cores and/or cuttings
  • Conceptual model is refined using downhole geophysics
Drill slim/core hole
Inferred Estimates of temperature and volume for the reservoir are based on minimal estimates and/or surficial geophysical, structural, and geochemical evidence. Rudimentary Conceptual- few converging estimates of reservoir temperature and volume, but use of the volume method. For a resource to be considered Inferred, both of the following criteria must be met:
  • Temperature is estimated using at least one of the following methods:
    • a well-executed geothermometry
    • thermal gradient holes
  • Conceptual model of the reservoir is supported by data from surface geophysical surveys
Field testing/sampling
Undiscovered Estimates of temperature and volume of the geothermal resource are largely theoretical, i.e. without specific research studies - interpolated from the visible existence of surface manifestations and/or fracturing, and/or from analogous structural and hydrological settings. Not enough information exists on the resource to construct a reservoir model – theoretical calculation of heat-in-place alone. For a resource to be considered Undiscovered, the potential is estimated by at least one of the following activities:
  • field mapping - structural, surface manifestations, etc.
  • shallow heat flow studies
  • extrapoloation of third-party data
  • remote sensing


For those familiar with other reporting standards, the following table attempts to show an approximate correspondence of the GRRM terminology to other terms. This matching is not to be taken as an exact cross-walk between terminologies, but simply as a reference point to better select the appropriate GRRM term.

Correspondence of RRM terminology with other reporting standards
Proposed Terms McKelvey
(1972)
USGS Circular 831
(1980)
USGS Circular 790 & 2008 Assessment PRMS
(SPE et al, 2011)
Australian Geothermal Code
(AGEA/AGEG, 2010)
Indonesian Geothermal Reserves Classification
(Brophy, 2012)
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Proven Proved C
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Measured I
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Producing Proved Resource Proven Resource Proven Resource
Well field built out
Confirmed Confirmed Measured
Multiple full-diameter wells
Demonstrated Probable Indicated (none) Discovered Indicated Probable Reserves
Full-diameter well / test
Potential Potential Prospect Possible Reserves
Drill slim/core hole
Inferred Possible Inferred (none) Play Inferred Hypothetical Resource
Field testing/sampling
Undiscovered Undiscovered Undiscovered Hypothetical/

Speculative

Undiscovered Undiscovered (none) Speculative Resource