Effects of global oil rig failure and/or pipeline failure

If there was a cataclysmic event that wiped out most of the population and sent technology back to basic mechanics (electronics destroyed), what would potentially happen to the existing oil rigs?

I am assuming they will eventually start to leak due to corrosion and zero maintenance.

If a pipe was breached and oil began to spew, roughly how long would it take to naturally dissipate? Is there any chance for marine life to survive?

Take for instance the BP oil spill. It was estimated 62,000 barrels were released every day. If it was connected to a 1 billion-barrel reservoir, my simple calculation says it would take 44 years to finish leaking into the ocean; assuming most of it gets pushed out and the ocean water eventually takes its place in the reservoir.

Now, I'd imagine the oil would naturally start to evaporate early on in the leak (the first year), but I am just not sure how long that actually takes under perfect conditions. Since I am sure the amount of water in the ocean plays a huge factor -- assume this is Earth or a class M planet half the size of Earth.

Even if the oil rigs were fail-safe, imagine the event caused a fracture in the sea floor where an untouched oil reservoir was located. I am trying to produce black seas that still has some marine life for fishing 40+ years after the event.

• These kinds of systems have safeties on them (the BP spill went bad because the safety malfunctioned). If you are starting to talk about a magical cause of all electronics failing, the safeties might all malfunction, but any physical cause would lead rapidly to the safeties activating. Aug 25, 2015 at 5:16
• Even if the safeties activated, wouldn't the pipes eventually corrode if not maintained? I am trying to figure out how an entire ocean would be contaminated. Say the electronics were working, if the oil rig was unmanned for x years, I'd assume it would eventually lose power and any backup power that safety system needed in order to monitor for issues (unless low power actually triggered the system which I am ignorant on what actually happens when it is triggered). Aug 25, 2015 at 5:30

Given enough time, all pipes will corrode and fall apart. Pipe breaking can also occur very quickly due to hurricanes, earthquakes, etc. The petroleum industry deals with corrosion on a daily basis. Pipes are not designed to last for hundreds of year in marine environments without maintenance as this would be considerably more expensive than designs for the useful life of the wells. So I would expect many if not most pipe failures with the first 50 years.

Given that the largest oil reserves are deep water (and thus cold water) I would expect the shallow wells to be most likely to fail in the early years, but these sites tend to be smaller (they were easier to pump out)

The Deepwater Horizon spill (DHS) was huge - few rigs have the potential to be a spill anywhere near this large. As of this week there are 851 active offshore rigs globally. I expect that this is far fewer than most people would guess. The total possible spill rate post catastrophe is of course impossible to answer, but the global offshore production is about 25 million barrels per day, or 29,377 barrels per day for each rig. Note that without active pumping, the release rate from the wells would be considerably lower. I can't imagine the total past catastrophe leaking matching 100 DHS spills. So, let imagine the damage of 6 million barrels per day.

The DHS did not turn the Gulf of Mexico black. The maximum spill area I could find was 68,000 square miles. A little bigger than Florida. The total ocean surface area is about 140 million square miles. This is over 2000 times larger than the maximum extend of the DHS.

You would have a huge environmental mess, but you don't really have enough to turn the oceans black.

Lots of oil seeps into the ocean from natural oil seeps. These long-running natural seeps are home to vast colonies of petroleum eating bacteria. I would expect that with the increased oil abundance, these bacteria would flourish worldwide serving to reduce the overall oil in the oceans.

• Thanks a lot for the info and input. Looks like I will need to rethink my idea for oil as it doesn't appear to cause the effects I was looking for. However, with this information, it may have given me another idea.... =) Aug 25, 2015 at 15:21