Q&A: How much oil has spewed into the gulf?

One of the most confounding issues about the Deepwater Horizon explosion and resulting oil leak is that after more than a month and a half, no one can say for certain just how much oil has gushed into the Gulf of Mexico.

Teams of scientists have employed various methods to calculate the flow rate, and with each study, they have revised estimates upward. Meanwhile, others are working to pinpoint where the oil has gone and where it might head next.

Based on the best available data, here’s what we know:

How much oil has the blown-out well leaked into the gulf?

Probably between 1 million and 2 million barrels, according to the latest estimates. That converts to 42 million to 84 million gallons of oil in the gulf, with the lowest estimate nearly four times the size of the 1989 Exxon Valdez spill.

Federal officials announced last week that scientists have calculated flow rates ranging from 20,000 to 40,000 barrels a day for the period beginning April 22, the day the Deepwater Horizon oil rig sank, through June 3, when a containment dome was placed over the leak and began collecting some of the oil.

The new estimates put the spill total between 840,000 and 1.6 million barrels. But the leak didn’t stop on June 3. In fact, the flow accelerated after robotic devices cut the well’s leaking pipe and before the containment dome was installed.

Where has all that oil gone?

Cleanup crews and engineers have removed some of it, including more than half a million barrels of oil-and-water mix skimmed from the surface as of Friday, more than 125,000 barrels incinerated in controlled burns and about 100,000 barrels collected by the containment dome.

The remaining oil has spread through the gulf, on and below the surface.

Massive slicks of surface oil are hovering largely off the Louisiana coast; smaller slicks have advanced onto the coasts of Mississippi, Alabama and Florida. The federal government’s response efforts include daily updates on the positioning and movements of those slicks.

The oil beneath the surface, broken down by chemical dispersants, is more difficult to track. University and federal scientists have confirmed that a large amount lurks beneath the waves, in what researchers now describe as “clouds” of oil that form and break up periodically.

Where will it all end up?

It’s impossible to tell at this point. Deep and surface ocean currents could continue to push the oil ashore in gulf states. Some estimates suggest it could clear the tip of Florida and drift up the Eastern Seaboard, washing up in Mid-Atlantic or even New England states.

Weather could play a huge factor. The gulf has just entered a hurricane season that experts predict could be particularly fierce and could push vast quantities of oil onto land or to other parts of the gulf, such as the Texas coast.

jtankersley@latimes.com