Connect Oracle database using AD account via OID
Sounds like what you looking for is an implementation EUS (Enterprise User Security). 

As of now, EUS will only work with OID and OUD (Oracle Unified Directory). This is because of it's requirement of the LDAP protocol, which AD can not provide. However, there is a way to configure an OUD Proxy, connected to a Active Directory (ultimately making AD more LDAP compliant), and the implement EUS.

The other option is to synchronize user accounts on AD to users on OID (after you configured OID for EUS with your database). However, this can be troublesome with AD's strict protection with the passwords. 

Hope this helps!