By Oracle Primavera do you mean P6 EPPM or Contract Management?
In any case you have to develop your own integration solution using integration APIs, web services or Primavera Gateway. Alternatively you can use one of the Oracle Partners solution (https://solutions.oracle.com/scwar/sc/Partner/SC2PP-PROJECTP.html#solutions).
You do not need Oracle Project Management for the integration. You can integrate directly with Oracle Project Costing.