Update README.md

Author: alex11818

README.md

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 ### (Screening Tools for SUBsurface CO2 storage in petroleum reservoirs on the NCS)  
 
 The repository contains codes, tools and data for screening CO2 storage potential of petroleum reservoirs on the Norwegian Continental Shelf (NCS) developed in [WP6 of the CSSR](https://cssr.no/research/fa3/wp-6/), namely:
-1.  an open database of 134 fields on the NCS compiled from:
+1.  an open database [*data/_main.csv*](https://github.com/alex11818/SubCSeT/blob/main/data/_main.csv) of 134 fields on the NCS compiled from:
     * [FactPages of the Norwegian Offshore Directorate](https://factpages.sodir.no/)  
     * [Public portal of DISKOS database](https://www.diskos.com/) 
     * more references are to be found in the main.ipynb