Hi Raj,
This does not sound like a very happy assigment and I hope that things will soon change.
In the meantime, it would be a very unusual change project that had no user requirements. If your project does have user requirements then you MUST have the opportunity to elicit those requirements from relevant users or you CANNOT complete the analysis of user requirements. This is not a 'nice to have' thing, you MUST have it.
If you are being restricted and told you cannot have user access you should
1. raise the issue that you are not being given the resources to do your job
2. raise the very high impact and very high liklihood risk that the project will fail to deliver any benefits as you are not able to uncover the user requirements that will deliver the benefits
These should be escalated to the Project Manager and/or sponors as the issue threatens to fatally damage the project.
If this is not done then when the project fails (and it almost certainly will be 'when' and not 'if' unless the issue is resolved), sponsors will want to know why the requirements weren't right.
While rasing the issue and risk, by all means use the documents to identify potential requirements that you can get users (when you have access to them!) to change and verify as neccessary.
I hope this helps!
Guy