Applying the Methodology to Geothermal Projects

Execution Indices for Estimated Volume

The following tables provide the details to select the appropriate execution index values for the GRRM attribute of volume. For each technique used within the calculation of volume, select the 1 - 5 index value of the category that most closely reflects the understanding of how the analytical method and technique were followed that collected the project's data.

Note: If more than 1 technique is used, select as many execution index values as techniques. If multiple sources of data are used (such as literature searches and independent sampling), record an execution index value for each source.

	Core Stratigraphy	MT (Magneto Telluric)	Magnetic Surveys
5	Well cuttings and core are complete enough to map fine relationships between intrusive complexes, aureoles of hydrothermal alteration, and geologic structures (faults). Surface geologic mapping has been completed in sufficient detail to correspond with structures at depth. Analysis conducted both during and after drilling. Includes combination of visual inspection by binocular microscope, petrographic thin sections, XRD clay analysis, and selected fluid inclusion measurements.	Local resistivity anomalies are known, and have been used to manually correct the telluric shift (e.g. through inversion of TEM results) Minimal incidents of signal noise (such as cultural interference) Measurements are taken over several hours at each site. Frequency of the signal is appropriate to the depth being probed (e.g. 0.00001 - 10 Hz for deep crustal investigations and 10 - 1000 Hz for upper crust features).	On-the-ground measurements are spaced in parallel profiles or grids at high resolution for the features under investigation. Survey lines are tailored in detail to follow geologic strike. Aeromagnetic surveys of large scale features are available to compliment on-the-ground results – particularly in sedimentary basins. Location can be corroborated with other methods (e.g. gravity) to within centimeters.
4	Well cuttings and core are complete enough to confirm major relationships between intrusive complexes, aureoles of hydrothermal alteration, and geologic structures (faults). Surface geologic mapping has been completed in sufficient detail to estimate structures at depth. Includes combination of visual inspection by binocular microscope, petrographic thin sections, and XRD clay analysis.	Local resistivity anomalies are fairly well known, and have been used to manually correct the telluric shift. Some incidents of signal noise (such as cultural interference) Measurements are taken over several hours at each site. Frequency of the signal is appropriate to the depth being probed.	On-the-ground measurements are spaced in parallel profiles or grids at an appropriate resolution for the features under investigation. Survey lines follow geologic strike, where known. Location cannot be corroborated with other methods, but contains GPS corrections to within 5 meters. Data gaps due to land access issues /steep terrain were overcome by fixed-wing aeromagnetic surveys.
3	Well cuttings and core are not complete enough to confirm major relationships between intrusive complexes, aureoles of hydrothermal alteration, and geologic structures (faults). Surface geologic mapping has not been completed in sufficient detail to estimate structures at depth. Includes combination of visual inspection by binocular microscope and petrographic thin sections.	Local resistivity anomalies are not well known, and corrections to the telluric shift are assumed. Some significant incidents of signal noise Measurements are taken for the minimum time possible at each site. Frequency of the signal not fully appropriate to the depth being probed.	Land access issues /steep terrain only allow intermittent sampling. Measurements of local structures are inferred from lower-resolution aeromagnetic surveys. Local structure investigations on the ground are pieced together to infer deeper intrusions, without an aeromagnetic survey. Location cannot be corroborated with other methods, and conditions force GPS correction accuracy > 5 meters. Survey lines are north-south, without consideration of geologic strike
2	Results taken from previous third-party studies of the area (either literature or contractors) with little or limited information on survey methods, replication, or error.
1	Assumed from studies of analogous geothermal settings, or extrapolated from studies of nearby areas.

	Gravity Surveys	Subsurface Temperature Probe	Active seismic reflection
5	The line direction is positioned perpendicular to the dominant geologic strike. Sampling includes > 5 magnetic measurements per anomaly. Intervals are spaced finely enough to individually characterize all anticipated anomalies. Precise measurements of altitude, rock mass, and local topography used to inform corrections.	Probe allowed to equilibrate Cuttings and/or geophysics confirms measurement within the reservoir (i.e. downhole alteration mineralogy consistent with reading)	Used in areas primarily dominated or overlain by sedimentary formations. Depth penetration reaches reservoir and clay cap. Geophones are appropriately grounded and secured. Survey array provides high resolution coverage in areas of desired feature discovery.
4	The line direction is positioned perpendicular to the dominant geologic strike. Sampling includes > 5 magnetic measurements per anomaly. Intervals are spaced finely enough to individually characterize all anticipated anomalies. Precise measurements of altitude, and rock mass, are used to inform corrections. Local topographic maps are used, but are of unknown quality/ not recently updated.	Probe allowed to equilibrate Cuttings and/or geophysics have not confirmed measurement within the reservoir (i.e. downhole alteration mineralogy not consistent with readings)	Depth penetration indicates clay cap, but no significant reach into the reservoir itself. Geophones are appropriately grounded and secured, although in loose soil in some areas. Survey array adequately corresponds to desired feature discovery.
3	Use of precise values for altitude, rock mass, and/or topography, thereby estimating free-air, Bouguer, and/or terrain corrections. Intervals spaced to capture some (but not all) anomalies. Sampling includes only one measurement per anomaly. Line direction is not fully perpendicular to dominant geologic strike (or strike is not known).	Probe not allowed to equilibrate Cuttings and/or geophysics have not confirmed measurement within the reservoir	Used in areas primarily dominated by highly fractured crystalline rock types (i.e. high uncertainty in interpretation). Depth penetration does not reach reservoir or clay cap. Geophones have not been checked for security or grounding, or are within very loose soil. Survey array is sparse, with little correspondence to desired feature discovery.
2	Results taken from previous third-party studies of the area (either literature or contractors) with little or limited information on survey methods, replication, or error.
1	Assumed from studies of analogous geothermal settings, or extrapolated from studies of nearby areas.

	TEM (Transient Electro Magnetic)	Field Mapping	Flow meter tests
5	Depth of survey is specifically adjusted to the resistivity of the area (e.g. few hundred meters in low resistivity) Current is applied to the transmitter loop for a sufficient time Current is shut off abruptly. Measurement windows/ sampling “gates” are high resolution to capture detailed changes in signal amplitude Conducted in area of minor external noise and interference. Loop size is more than adequate.	Analyst interpreting results has >5 years field experience interpolating deformational and faulting characteristics in the subsurface from surficial outcrops or scarps. Field studies include comprehensive fault kinematics and stress, overlying stratigraphy, and location of surficial manifestations	Impeller flowmeters used for velocities of > 5 ft/min, and heat-pulse or electromagnetic flowmeters used for velocities of less than 0.1 ft/min. Tests run at three or more pumping rates and at zero. Results correlated with temperature and pressure logs at all wells.
4	Depth of survey is appropriate to resistivity of area (few hundred meters in low resistivity, up to 1 km in high resistivity) Current is applied to the transmitter loop for a sufficient time Current is shut off abruptly. Measurement windows/ sampling “gates” are adequate to capture relevant changes in signal amplitude Conducted in area of some – minor external noise and interference. Loop size is appropriate for area.	Analyst interpreting results has >2 years field experience interpolating deformational and faulting characteristics in the subsurface from surficial outcrops or scarps. Field studies include comprehensive stratigraphy, fault geometry, and location of surficial manifestations, but minimal study of fault kinematics.	Impeller flowmeters used for velocities of > 5 ft/min, and heat-pulse or electromagnetic flowmeters used for velocities of less than 0.1 ft/min. Tests run at two pumping rates and at zero. Results correlated with temperature and pressure logs at some, but not all, test wells.
3	Effective exploration depth is not appropriately adjusted to resistivity of area (e.g.1 km in low resistivity) Current is not applied to the transmitter loop for a sufficient time Current is not shut off abruptly. Measurement windows/ sampling “gates” are too wide to capture relevant changes in signal amplitude Conducted in area of significant external noise and interference. Loop size is too small for area.	Analyst has minimal background ( 6 months – 2 years) field experience interpreting deformational and faulting characteristics in the subsurface from surficial outcrops or scarps. Field studies include cursory stratigraphic and fault geometry review, adequate location of surficial manifestations, and no fault kinematics.	Impeller flowmeters used for velocities less than 5 ft/min. Test run at one pumping rate and at zero. Results not correlated with temperature and pressure logs.
2	Results taken from previous third-party studies of the area (either literature or contractors) with little or limited information on survey methods, replication, or error.
1	Assumed from studies of analogous geothermal settings, or extrapolated from studies of nearby areas.

GRRM/How To/Execution/Volume

Geothermal Resource Reporting

GeoRePORT

Applying the Methodology to Geothermal Projects