Both BIDS(Business Intelligence Development Studio) and Data Tools, BI development tools, in design phase, cannot co-work with 64BIT Oracle drive. Why? As you may notice, even what you installed is 64bit SQL Server, but these two BI tools are still a 32 bit application. With this reason, when you develop the SSIS package, in BIDS/DT, the package cannot recognize 64bit oracle drive.
The solution is to install 32bit oracle drive when you develop the SSIS packages. With 32 bit drive, you can debug the package and run the package in BIDS/DT. Does it mean when moving the package to other environments like QA/PD…you still need to use 32bit oracle drive? No. When you use SQL Agent job to wrap up the finished SSIS packages, it is highly recommended to use 64bit oracle dirve because SQL Agent Services is a 64bit applcaition. It works well with 64 bit drive. Can it(SQL Agent Job) work with 32 bit oracle drive? Yes, but you need specifically setup your jobs running in 32 mode? What is the down side if it is running in 32 bit mode? There is restriction to leverage the memory resources on server.
So, the conclusion is , in development phase, you have to install Oracle 32bit drive. When it pushes to QA/PD, it is recommended to have 64bit in place as your SQL Agent job can work well with it.
Hope it helps!