Add eCalc

@jsolaas @jorgenengelsen @TeeeJay

README.md

@@ -773,6 +773,7 @@ energy system designs and analysis of interactions between technologies.
 - [Pyra](https://github.com/tum-esm/pyra) - Automated EM27/SUN Greenhouse Gas Measurement Software.
 - [EMIT-Data-Resources](https://github.com/nasa/EMIT-Data-Resources) - Built to help scientists understand how dust affects climate, the EMIT can also pinpoint emissions of the potent greenhouse gas.
 - [Integrated Methane Inversion](https://github.com/geoschem/integrated_methane_inversion) - Contains the source code for setting up and running the Integrated Methane Inversion with GEOS-Chem.
+- [eCalc](https://github.com/equinor/ecalc) - A software tool for calculation of energy demand and greenhouse gas emissions from oil and gas production and processing.
 
 
 ## Industrial Ecology