The 3D geological modelling training for GeoTwinn Work Package 1 was held on 1^st – 5^th April 2019, at BGS-UKRI offices in UK. The training was led by Andrew Newel, Bruce Napier, Stephen Thorpe, Martin Nayembil and Leanne Hughes, BGS-UKRI experts in 3D modelling. The training was attended by five HGI-CGS scientists that partake in WP1: Nikola Belić, Vlatko Brčić, Krešimir Petrinjak, Pavle Ferić and Dea Brunović.

Day one – 1^st April 2019

The first day was devoted to the arrival of HGI-CGS employees and their familiarisation with BGS-UKRI working environment and staff working in 3D geological modelling. The tour included a visit to the Core Store, which is the largest core facility in the UK and has space for over 18 000 pallets of drill-core and 80 000 trays of samples (https://www.bgs.ac.uk/collections/corestore_kw.html).

Office training started in the early afternoon with introduction to geological modelling (Power Point Presentation about essentials of geological modelling), preparation of geological modelling data and an initial look over SKUA-GOCAD™ (Software Suite by Emerson E&P Software).

Day two – 2^nd April 2019

The training was dedicated to 3D Geological modelling of the Zagreb area. It covered geological data import, data display and the creation and editing of data in a 3D environment, as well as construction of fault and horizon surfaces using explicit and implicit approaches. Exercises concerning fitting horizons to well markers and controlling errors were also included. Preparation of the geological models database was done using MAD.

Day three – 3^rd April 2019

The third day training continued with 3D Geological modelling of the Zagreb area. The focus of the training was on creating 3D grids from faults and horizon surfaces. To examine different types of 3D grid (regular versus stratigraphic) and understand why, when and how to use them. The use of geophysical logs in 3D geological modelling, extraction of the facies information from logs and introduction to grid-based stochastic geological modelling were also covered.

Day four – 4^th April 2019

Further progress in 3D Geological modelling of the Zagreb area was performed on the fourth day of the training. The trainees were working on export of geological models and learned more about the usage of the data in other applications and reinforcement of the modelling methods.

Day five – 5^th April 2019

The fifth day of the training was also the last day of the training itself. The day was dedicated to the final refinements to the model and export of generated data. Some model images were exported for the reports and further analyses.