The Supertanker

How can oil companies both supply their refineries with oil from overseas and meet the world’s constant demand for oil? 

One answer is the supertanker.

As I discussed in the previous section, Sunoco -- like many American oil companies -- bought and imported its oil from West Africa. In order to supply Philadelphia’s 335,000-barrel-a-day refinery with a constant supply of crude, Sunoco would theoretically have had to import over 1 million barrels of oil every three days. While I am uncertain whether a supertanker like the Tedorigawa roared into Girard Point on a bi-weekly basis, I know that understanding the nature of any oil refinery means understanding the transportation networks that underlie its operations. 

For this reason, I think it’s worth taking a moment to investigate the (rather horrifying) way in which many of the world’s oil companies have come to reconcile the demand problem with the ocean problem. 

So, back to the Tedorigawa. 

The Tedorigawa belongs to a class of supertanker called VLCC, or ‘very large crude carrier.’ Ships of this class are generally around 1,100 feet long and have capacities between 200,000 and 320,000 deadweight tons (DWT).

(‘Deadweight tonnage,’ by the way, is a measurement of a ship’s total weight capacity, which includes fuel, passengers, freight, fresh water, ballast water, and provisions.) 

How much is 320,000 DWT? At maximum capacity, all 1,114 feet of the Tedorigawa’s 68-foot draft (the red part of the hull) would be entirely submerged. Oil tankers can carry as much as they can because they are designed to leave only a small portion of their total volume above water. The total depth of the Tedorigawa’s hull, for example, is only twenty three feet more than its draft. I know that’s all hard to visualize, so I’ve done my best to make this more clear in Figure 2.

I am using this particular ship as an example because it is a VLCC, and VLCCs are the type of tanker -- or “supertanker” -- that can ship the amount of oil PES would need every three days to refine at full capacity. The class above VLCC - yes, there is actually a higher class - carries way more than PES would need every three days. 

The largest tankers are called ULCCs, or ‘ultra large crude carriers.’ With capacities ranging between 320,000 and 550,000 dead weight tons (equalling 2 to well over 3 million barrels of oil), they can carry over nine times as much oil as PES can refine in a day. The name “supertanker” applies to VLCCs and ULCCs. Why? Because they are herculean. They are, in fact, the two largest classes of shipping vessel in the world (with ULCCs taking the cake as the absolute largest). ULCCs are so large they can’t fit through  the Suez or Panama Canals.

Now, working back to how we got here, think about a VLCC’s-worth of oil arriving at PES every three days. Now, try connecting that realization to the fact that every refinery in the world requires a near-constant supply of oil, and that PES is just one node in that massive network. How massive? Well, for a starter, here’s a graphic depiction of every ship at sea at this moment (July 26, 2019, 11:35AM EST). 

The red ones are ships carrying fossil fuels.