Gachsaran Oli field
 

How do i disarm the bomb on the oil rig? i get there in time, and the thing goes "BOOM"

When you first approach the oil rigs you get attacked from the left. Kill all these bad guys first. Then proceed to the right towards the oil rigs and deal with these bad guys. You gotta be quick with both sets of bad guys, then the SAS guy will disarm the bomb for you. Then watch for the suicide bombers in the VBL's.

Hope that helps