I was looking into the impact of Chavez's recent move to cut-off supplies to Exxon's downstream operations and came across two documents on the web which seem to imply there will be little to no impact on Exxon's ops.
According to the EAI 80% of Venezuelan crude imported by the US/ Virgin islands is process by 11 refineries. Exxon has a stake in only one of these refineries, located in Chalmette LA, which is actually a joint venture between Exxon and PDVSA.
According to the Houston Chronicle article PDVSA said in its statement that its decision regarding Exxon Mobil will not affect "contractual agreements related to joint investments overseas."
It's not clear whether this includes the JV in Chalmette. But with a capacity of 185,000 barrels per day (50% owned by PDVSA and 50% owned by Exxon) it's a drop in the bucket to Exxon's refinery throughput of 5.7 mmbpd (Q4 2007).
Go Chavez, way to stick it to those capitalist swine!