DoubletCalc is a programme for calculating the indicative power of a geothermal doublet.
It can generate the probability graphs required to be submitted with the application for the SDE+ and/or the Guarantee Scheme for Geothermal Energy.

Download the DoubletCalc v1.4.3 software (17 December 2014 version, including Java 7 script) (not mandatory for the SDE+ and Guarantee Scheme applications).
This version has extra functionality relating to output. The output screen shows more results and the information in the "base case details" export has been expanded.
Download the DoubletCalc v1.4.3 manual (TNO 2014 R11396, 1 October 2014)

Download the DoubletCalc v1.4 software (25 February 2014 version) 
Download DoubletCalc v1.4 manual
Download the DoubletCalc v1.3 software (30 November 2009 version)

The most important addition to version 1.4 is that extra variables can be input:

  • The tubing scheme of producer and injector (along hole depth, true vertical depth, inner diameter and roughness)
  • The penetration angle in the reservoir for the producer and injector
  • The salinity distribution (min - median - max)

DoubletCalc source code
The DoubletCalc Java/JavaFX source code can be downloaded here.

DoubletCalc 2D

DoubletCalc 2D v1.0 (DC2D) is a software tool developed by TNO. Using this software it is possible to calculate the temperature and pressure around two or more geothermal wells, in two dimensions (2D) and over the course of time. The software has been developed to bridge the gap between simple 1D simulation tools such as TNO's DoubletCalc v1.43 (DC1D, Mijnlieff et al. 2014), and advanced 2D and 3D reservoir simulators such as Eclipse.

Manual DoubletCalc 2D V1.0 (DC2D) (pdf)


To support the search for suitable locations for geothermal energy, TNO has developed a free geothermal information system: ThermoGIS™ (see This system gives everyone access to a preliminary rough estimate of the geothermal potential of a certain location and to a wealth of information on geothermal energy in the Netherlands.

Salinity calculations

TNO has developed an Excel spreadsheet for calculating the salinity of formation water in ppm NaCl equivalents. When the composition of the water is input, it gives the salinity value. This can be used when determining the input values for DoubletCalc. The finishing touches are currently being made to the spreadsheet. The file will be made freely available when the QC has been completed.

Calculating the skin value of horizontal wells

DoubletCalc cannot be used to calculate the geothermal power if the design of the geothermal project assumes horizontal wells. Instead, an indication of the geothermal capacity can be obtained by using analytical methods such as those published in the public domain to calculate the improvement in productivity resulting from a horizontal production trajectory. TNO has implemented these methods in an Excel spreadsheet, in order to capture the productivity improvement in a skin value. An alternative way of determining the flow and hence the geothermal capacity when using a horizontal well is to use a reservoir simulator.

Manual for equivalent skin horizontal well (pdf)
Equivalent skin horizontal well (xls)

Spreadsheet to determine indicative injection pressure space 

The Geomech_V2.xlsx spreadsheet and its accompanying manual TNO manual for GeoMech can be used to ascertain the relationship between the injection pressure applied in the injection well and the various gradients:
State Supervision of Mines maximum injection pressure gradient

  • Lithostatic pressure gradient
  • Hydrostatic pressure gradient
  • Minimal horizontal tension gradient (Shmin)
  • Minimal horizontal tension gradient, taking account of the thermal effects of injection water on the rock (Shmin thermal)


For more information, see memorandum.