I have migrate a lot of Odoo with OpenUpgrade, and dont expect it to work on the first run, you will have to make modification on your database before most version upgrade (14, 15, 16).  Dont even think about migrating in 17.0 with openupgrade before the release of 18.0 and depending on the module selection you have had to you database, this can make the process harder.

Each new version add feature to Odoo, and in many case, feature we did add with and Oca module (Knowledge for example) so you will also have to remove a few module will migrating because they are now covered by new Odoo module.

And obviously porting all you custom code (and some other module not port by the original authors) can be a lot of work if the object they are extending have change a lot.

As Odoo Partner, we can assist you with that kind of migration but I strongly recommended to check all the feature of the Enterprise and all the cost saving it can generate, cause most of the time, those saving are bigger than the cost per seat of Odoo Enterprise

Hi 

You can use open upgrade scripts provided by OCA for database migration 

OpenUpgrade

OCA upgrade scripts are not fully ready for Odoo 17, 

Upgrade Database using OpenUpgrade

Regards