With the ill-fated Deepwater Horizon rig sunken in the Gulf, there are now two similar rigs, along with the Discoverer Enterprise, a drilling ship; the Viking Poseidon, which knows how to install things on the sea floor; four mother ships for remotely operated underwater vehicles; various barges and supply vessels; and the Q4000 ( built by our KeppelAMFELS yard in 2002, see below for more detail about this rig ), a rig that specialises in repairing and closing wells. If the well that the Deepwater Horizon was in the process of closing off four weeks ago continues to spray oil into the sea for months to come, it won’t be for a lack of expensive, sophisticated and improbable-looking hardware a mile up above it.
Deployment of vessel and WI rig to plug the leak -
It is that mile which is the problem. The oil industry has been fixing blowouts for more than a century. The challenge is doing it under 150 atmospheres of pressure ( i.e. 5000ft below sea level ) with the tools and lights of a robot mini-submarine that gets its power and instructions by way of a cable. Under such environmental conditions, even the well orchestrated planned can come hit a snag, as it did when icy methane hydrates that form when natural gas gets mixed up with cold water at high pressure foul the plan to funnel the leaking oil up to Discoverer Enterprise. The hydrates did not just clog the pipes, they also buoyed up the 125-tonne cofferdam that had been lowered over the leak, lifting it right off the sea bed. [ Well, this phenomenon was not even in the eyes or expectation of all the experts BP has supposedly mobilised to study the viability of the cofferdam method it seems ! ]
On May 16th, though, oil did start to be collected by applying a subtler intervention. Oil is currently escaping from two leaks, one at each end of the well’s riser. The riser connected Deepwater Horizon to its blowout preventer, a stack of valves on the sea floor which marked the top of the well proper. When the rig sank, the riser broke near the top while remaining attached to the blowout preventer at the bottom, bending itself like a pretzel in its subsequent collapse. Some oil is now flowing from where the riser and the blowout preventer meet; most is coming from the broken end of the riser, which has ended up about 300 metres away on the sea floor. It is from a tube slipped into that distal end that oil is now being pumped up to Discoverer Enterprise and its attendant barges.
The insertion device, about a fifth of the diameter of the riser itself, is not supposed to block the flow of oil completely. If it did, the pressure of the oil would blow it out of the riser like a cork in a hose. Instead it sucks at the oil flowing around it, but gauging how hard to suck is tricky. Without enough suction more oil than necessary would continue to leak out; too much and it will let in water which will make the formation of those pesky hydrates more likely. Other anti-hydrate measures include a small pipe feeding methanol, an antifreeze, into the maw of the riser, and hot water circulating through a sleeve to warm the pipe bringing the oil to the surface. According to Kent Wells, vice-president of BP, the oil company in overall charge of the project, the amount of oil coming up through the pipe had risen to 2,000 barrels a day by May 17th.
The next step is to try to staunch the flow proper with drilling mud, a mixture of water and clay minerals. The well is gushing because of the pressure the oil is under in its reservoir 4,300 metres below the sea bed. If drilling mud can be forced into the well under even greater pressure—a technique called “top kill”—it will eventually reach a depth where the weight of the column of drilling mud exerts enough pressure to stop any oil flowing upwards. [ More about well kill when I start to upload from my archives ...]
To do this, BP has been replumbing and rewiring the blowout preventer, paying particular attention to its choke pipe and the kill pipe. These provide access to the central bore of the well underneath most of the heavy valves which should have closed off the flow of oil, but for some reason did not. The two pipes, which originally went up to the Deepwater Horizon, have been reconnected with heavyweight hoses to a metal framework called a manifold that has been installed nearby. Above it the Q4000 rig and three attendant vessels have 50,000 barrels of peculiarly heavy drilling mud and pumps capable of providing 30,000 horsepower ( ie. from the High pressure mud pumps ) with which to muscle that mud into the well.
Q4000 Well Intervention Rig
The blowout preventer’s control pod, which was also originally connected to the lost rig, has been taken up to the Q4000, where it has been tested and attached to new cables. The pod should soon be on its way back down for reattachment to the preventer. The Q4000 will then have control over the valves that connect the choke and kill lines to the well proper. One reason why all this is taking time is that there are now up to 14 remotely operated underwater vehicles working around the well. A “simultaneous operations” unit is needed to choreograph the complex dance of vessels, submersibles and rigs.
Once the control pod has been reinstalled on the blowout preventer and the manifold is attached to the Q4000, the top kill could start. The control pod ( refer to my earlier blog article or do a quick search on this word ) will open the valves that allow the drilling mud to be forced into the well. At that point the fluid-dynamics equivalent of a titanic arm-wrestling match will get under way, with the surface vessels’ pumps trying to push the mud down the well while the rising oil tries to push it out.
If the oil wins, then the team will try a “junk shot”. The manifold has two containers full of various sorts of rubber and plastic that are particularly good at gumming things up. Open and close a few valves on the manifold and the drilling mud from the surface can squirt one of these junk shots down the pipes and into the blowout preventer. The oil pressure will force it up into the heart of the stack of valves. There, by making it harder for anything to get out of the top, the junk will give the drilling mud a better chance in a second bout of arm wrestling. The second container of junk provides another shot.
If both barrels fail there is the possibility of putting a new blowout preventer on top of the old one. That would mean cutting the existing riser, but now that the siphon inserted into it is bringing oil up to the barges it means risking a serious setback. So it may be wiser to wait for the relief wells that are being drilled to get down to the point, 4,000 metres below the sea bed, where they will intersect the existing well. At that depth stopping the flow with a deadweight of drilling fluid could create few problems, once the exceedingly difficult challenge of hitting the well is met. So far, the first relief well is only about 1,000 metres or so below the sea bed, and the second has only just been started.
Underwater spraying by ROV -
Not all the remotely operated vehicles at the site have been involved in replumbing kill lines, hooking up manifolds and supporting the relief wells. Some have been swanning around spraying chemical dispersants into the oily waters. If the top kills do not work this spraying may also help limit the damage done by the oil before the relief wells are finished.
Spraying dispersants in new ways, rather than using new formulations, may make more of a difference. BP thinks spraying dispersants into the oil plume where it leaves the riser may be 20 times more effective than waiting until it reaches the surface. If so, the 45,000 gallons so far sprayed at depth may have done more good than all the spraying at the surface. Three trials of this technique have been made by the EPA ( Environment Protection Agency ), the first two being inconclusive due to logistical difficulties.
There will be plenty of lessons to learn from the Deepwater Horizon disaster. Once the leaks have been stopped, the operation may try to get the failed blowout preventer to the surface so that it is at last possible to see what really went wrong. It is not just the engineering response to future oil spills that will be affected, but also working practices, safety systems and regulation. The future safety of offshore drilling for both the roughnecks and the environment will be shaped by what happens a mile below.
[ And also the subsequent legal proceedings, if every of those involved wishes to wash their hands and pointing to the culprit of the cause....... ]
EVERY oil spill has a silver lining—if you are a lawyer, that is. More than 70 related lawsuits were filed in the two weeks after oil started leaking into the Gulf of Mexico on April 20th, most of them class actions that claim damages on behalf of many similar victims. Trial lawyers are dreaming of one of the biggest paydays since they feasted on tobacco litigation. Even more certain are the bumper fees for law firms defending BP, Halliburton and other firms involved. The most notable winner is Kirkland & Ellis, which will represent the British oil giant.
No one doubts that the BP lawsuits will dwarf those that followed the Exxon Valdez spill in Alaska in 1989.
However, actual damages could run into billions, even before fees. Less comforting is the $75m cap on liability for economic damages under the Oil Pollution Act (OPA) of 1990. Regardless of what happens to efforts in Congress to raise this cap to $10 billion, this legislation may not constrain tort lawsuits under state or common law. The point of the OPA was not to limit tort law but to supplement it. Legal damages could thus be in addition to other compensation that is paid voluntarily to victims by BP and others, an amount that has been estimated at anything from $3 billion to $8 billion.
A crucial contest is looming between BP and the trial lawyers over the extent to which various lawsuits will be consolidated, and where the trial will happen. The trial lawyers fancy Louisiana, with its long history of generosity to class-action litigants; BP would prefer oil-friendly Texas.
Litigation over the oil spill is helping to reverse a downward trend in class-action suits against business. The BP case may be just the sort of disaster that tort law exists to address. But the justification is less clear for some other high-profile litigation.
Cleaning the oil spill and impact to the Gulf environment and wildlife :
030610 Oil Spill Impact
Cleaning the oil spill and impact to the Gulf environment and wildlife :
030610 Oil Spill Impact