Here's the abstract for the original article in
Geology. I don't feel like buying the article itself.
Anyway, as you can see from reading the abstract it merely hypothosizes that drilling is the cause of reduced seepage in that area (I've no idea if seepage in Santa Barbara Channel is remotely standard). That's a long way from "off shore drilling will likely reduce pollution in the ocean."
Maybe that has been supported over the last decade, but I can't find anybody pointing to such support and I'm certainly not doing a full citation search tonight.
Also, it is worth pointing out that the press release states that most of the seepage is natural gas which is different than what would be introduced into the water if there were a pipeline spill.