Just heard that the “static kill” operation – pumping mud, possibly followed by cement, into the Macondo well via one of the valves on the blowout preventer – is now under way.
The new spill-rate estimate provided by government scientists yesterday got us thinking:
- How much of the oil, spilled 5,000′ down at the seafloor from BP’s Macondo well, never floated up to the surface, or sank back below the surface after being sprayed with dispersant?
- How much oil may remain in Gulf waters, possibly thousands of feet below the surface?
- What are the impacts of that “unseen” oil, and how long will it have toxic effects?
Time for some math: SkyTruth’s estimate of the spill rate (26,500 barrels per day), calculated way back at the end of April with help from Dr. Ian MacDonald at Florida State University, was based entirely on the oil we could see and measure at the ocean’s surface (8.9 million gallons, based on a Coast Guard map of the oil slick for April 28, 8 days into the spill).
Our spill-rate estimate is 43% of the 62,000 barrels-per-day rate that scientists now claim for the early days of the spill. But surely some of the “missing oil” in our estimate was consumed in the fire that raged on the Deepwater Horizon rig before it sank on April 22; so let’s optimistically say 2 days worth of flow from the well was totally burned up, bumping SkyTruth’s estimated daily flow rate up to 35,317 barrels per day – 57% of the new government rate. No oil was being diverted from the well at that time, and skimming operations probably weren’t collecting much at that point either, but dispersants were being used to break up the slick.
This suggests that at least 43% of the oil that leaked from the well remained under water or was driven back under water by dispersants, out of sight to satellite images and Coast Guard observers. Given a total spill of 172.2 million gallons, if we extrapolate from that first week we can conclude that at least 43% of that oil – 74 million gallons – may still be lurking beneath the surface in the Gulf.
That’s our attempt at answering the first question. As for the second question, biodegradation should be steadily breaking down this oil, but we don’t know at what rate, or what the byproducts of that breakdown might be. And we have no idea how to answer the third question.
Getting these answers will require a concerted, sustained, publicly transparent science effort. So we can be better prepared the next time something like this happens, and make better-informed plans for how we use our nation’s ocean resources in the future.
Well, we warned ya. That estimate didn’t last very long.
Yesterday the government released new estimates of how much oil was spewing on a daily basis from BP’s Macondo well into the Gulf of Mexico, based on much better data and hi-def video. It’s worse than we thought: initially the well was gushing oil at a rate of 2.6 million gallons (62,000 barrels) per day. At the time, BP and the Coast Guard claimed the spill rate was 62 times smaller than that — 42,000 gallons (1,000 barrels) per day.
Eight days into the spill, NOAA got involved and raised the estimate to 210,000 gallons (5,000 barrels) per day. BP grudgingly accepted this, and it remained the official estimate of the spill rate – more than 10 times too small, we now know – until May 27, more than a month after the disaster began.
Working with BP as a consultant back in the 1990s, I interacted with some of the smartest geologists and reservoir engineers I’ve known. How could they get this so very wrong, knowing the bottomhole pressure of the well, the size of the reservoir, and the relative percentage of oil to natural gas? And how could the US Coast Guard – the agency that responds to oil and hazardous materials spills of all kinds and sizes – not know that they were dealing with a spill 10 times larger than the official estimate?
As the well leaked oil and natural gas, pressure in the reservoir below gradually lessened, so the flow rate of oil declined to 2.2 million gallons (53,000 barrels) per day. The well was capped on July 15, totally shutting off the flow of oil and gas.
Bottom line: using these new government numbers, and the estimate in a previous Washington Post article that about 33.6 million gallons were diverted from the leaking well and never entered the Gulf, we come up with a total spill of 172.2 million gallons (4.1 million barrels) – more than 15 times the official size of the Exxon Valdez oil spill in 1989.
Turns out the pipeline that failed in Michigan last week, spilling a million gallons of oil into the Kalamazoo River that’s still threatening to reach Lake Michigan, was installed in 1969. Still no word on why it failed but corrosion is a constant battle for pipeline operators like Enbridge.
Most oil, gas, and refined-products pipeline, onshore and offshore, is owned and operated by companies you’ve probably never heard of (without the brand name or deep pockets of a company like BP or Exxon). Enbridge is a Canadian company that claims to operate the world’s largest pipeline network – 15,000 miles of pipe in the US and Canada. They also have a rap sheet of recent, major spills and fatal incidents (although we don’t know if their record is any worse than most other pipeline operators).
There are about 25,000 miles of active oil and gas pipeline on the seafloor in the Gulf of Mexico, connecting 3600 platforms and tens of thousands of wells to coastal storage, processing and distribution facilities. Much of this infrastructure is getting old – drilling began offshore in the Gulf in the 1940s. Are pipeline operators doing a better job inspecting, maintaining and replacing the pipes offshore than they are onshore?
Keeping an independent eye on this vast, aging infrastructure is yet another reason we think Gulf-wide satellite monitoring should be a routine activity, not a service limited only to emergencies like the BP / Deepwater Horizon spill.
The Macondo well is still tightly capped; the “static kill” effort to shut it down by pumping mud, then cement, into the well through the containment cap may begin as soon as tonight. This would be followed up by a “bottom kill” procedure, hopefully in August, that would use a relief well to pump more cement into the well at a point about 13,000′ below the seafloor.
So, folks are asking – just how big was this spill?
Big enough to – at one time or another – cover 68,000 square miles of Gulf waters with oil slick or sheen, based on our ongoing analysis of satellite images. But that’s just the part we could see at the surface. Lots of oil remained in the water column, beneath the surface, out of sight on the satellite images we’ve been able to acquire.
The Washington Post published a calculation on July 29 (article and useful graphic) that as much as 218 million gallons (5.2 million barrels) leaked out of the well over the duration of the spill from April 20 – July 15. That assumes the government team’s high-end leak rate estimate of 2.52 million gallons (60,000 barrels) per day for 87 days. Subtracting 33.6 million gallons (800,000 barrels) the Coast Guard and BP claim to have kept out of the water — by siphoning oil directly from the leaking well — yields a high-end spill estimate of 184.4 million gallons (4.4 million barrels).
SkyTruth’s estimate on May 1 that the well was gushing at a rate of at least 1.1 million gallons (26,500 barrels) per day turned out to be on the low end of the later scientific estimates made by the government-assembled Flow Rate Technical Group. Our conservative number generates a total flow of 96.8 million gallons (2.3 million barrels) from the leaking well over 87 days. Subtracting the 33.6 million gallons supposedly diverted from the leaking well – we have no way to confirm that number – yields a low-end total spill estimate of 63.2 million gallons (1.5 million barrels) directly into Gulf waters.
How does this compare with our previous sad benchmark, the Exxon Valdez spill in 1989? The official estimate — a number that, we should note, is disputed as being far too small — is that 11 million gallons were spilled when the Exxon Valdez supertanker ran aground in Prince William Sound, Alaska.
That would make the BP / Deepwater Horizon oil spill in the Gulf anywhere from 6 to 17 times as large as the official Exxon Valdez spill. But don’t lock these numbers in just yet: they may change as the investigation proceeds and new information is brought to light in coming months.
We’ll have to work hard, and stay on guard, to make sure this is one sorry new record that will never be broken.