"Initially I thought the oil companies only did spill response training.

I was presently surprised to find out the training they have their employees conduct usually also include spill prevention training

Here is an example of just some of the courses and companies I could find online, all of which cover spill prevention in addition to spill response.

Spill Response  - Acute Trianing

Spill Prevention and Response | atlanticcanadaoffshore.ca

Spill Prevention, Contingency and Countermeasures for Oil and Gas Operations

After the Valdez spill Exxon implement and deployed a significant operational reform and new management system globally to prevent further accidents. Here is summary of the change they made.

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This is download from Quaro,and we find that Emergency Response Program is very improtant to the oil companies.