I followed this document:
The only to comment (FRUSTRATED the hell out of me)
1) Add the bi libraries to your portal before you embark on the above guide : http://rsriv.blogspot.com/2011/10/obiee-11g-integration-with-webcenter.html
2) I kept getting an error:
Caused by: javax.naming.NamingException [Root exception is oracle.bi.presentation.soap.connection.BISoapException: javax.xml.ws.soap.SOAPFaultException: Authentication error. An invalid User Name or Password was entered.]
For some reason (I still need to investigate) the security does NOT work without impersonation for me. So I had to create my users on the bi server before everything could work.