How many barrels of oil does an average oil tanker carry and how does this compare to the April 2010 oil well platform spill in the Gulf of Mexico?

Answer 1

Your question is quite simple. However, there is no average tanker or tanker oil spill. Nor is there an average oil well blow out. Both are relatively rare events.

Capacity ranges of tankers ranges from 10,000 to 500,000 deadweight tonnes. Now, their carrying capacity is in terms of weight. However using a standard of West Texas Crude (39.7 degrees API) I can convert 1 metric tonne to 7.6 barrels, so this becomes a capacity range of 76,000 barrels to 3.8 million barrels. A pretty large range.

As stated in the related link on oil tankers, a very large crude carrier, (VLCC), capacity is approximately 2 million barrels of oil. Now, this doesn't mean that an accident with a VLCC will release this volume of oil. As shown in the attached link on oil spills, there have been only 3 huge tanker accidents in the last 43 years (since 1970), with spills in the range of 252,000 to 287,000 DWT (approx. 1.9 to 2.2 million barrels).

The highly publicized Exxon-Valdez at 10.9 million gallons or 260,000 million barrels, is comparatively much smaller than the huge and rare tanker spills

Most tanker oil spills are very small (less than 7 tonnes or 53 barrels) due to operational errors. In the last 43 years, there has been a declining trend in the number of oil tankers spills. (see related link). The worst accident in 20 years, spilled 62,000 tonnes.

Now, the quantity of oil spilled from a blown out (or wild) well, may be difficult to quantify. For the April 2010 blow out, the total quantity discharged into the gulf will be unknown until the well is killed. But, let us suppose (no harm in this), that the containment dome fails, and we have 120 days of flow at 5,000 barrels per day, then 600,000 barrels will enter the Gulf, more than twice the volume that Exxon-Valdez discharged, but hardly a record spill when compared with tanker spills.

The volume spilled is of course important. In making comparisons, I would think it is equally important to look at where the spills occurred, (near or far from natural important coastal habitats) how successful skimming, containment, and other control actions were, and if in the end, better safety procedures could be implemented to prevent spills.

My point is that spills are difficult to generalize. Sorry for such a long explanation. See related links.