The last version of Geosoft Desktop Applications to include ArcEngine was 8.5 back in 2015. Version 8.5 included ArcEngine 10.3.
ArcEngine is used within Oasis montaj and Target to read ArcMap Documents (MXD) and Layer files (LYR). Geosoft Version 9.* no longer includes an ArcEngine install by default. This change is due to Geosoft's move to a true 64-bit architecture and changes to Esri's direction and licensing of ArcEngine.
If you are installing Oasis montaj or Target on a computers without ArcGIS desktop installed, you will not be able to read ArcMap Documents (MXD) and Layer files (LYR) within Oasis montaj and Target.
This limitation can be resolve by either purchasing ArcMap from Esri or contacting Seequent to purchase a subscription for ArcEngine.