Hi HomerJ,
What you re experiencing is a known issue with QC 10 and Oracle DBs specifically. The user schemas you are seeing are (or at least should be) associated with no projects (if they are then this may not apply to you for those schemas), but thy were created during upgrade/ migration attempts and during certain activities such as project creation. They are temporary schemas created during the action in process and should normally be cleaned up and removed/ deleted during the routine housekeeping actions run by the system automatically on the predefined system schedule in the background. For some reason on QC10 (and QC10 only) running Oracle DBs the routines were not completed fully and the user schemas purged from the system, and they remained after the housekeeping completed.

It is fine to just delete these user schemas from the DB, or in your case they will not need to be migrated along with the other schemas (however as is always recommended, you should create a ful back up of everything, including these schemas, prior to such actions in the odd event that they should be needed and can then be recovered. Generally they are not needed and just extras left over that can be deleted without recourse).

Hope this helps,
Dan