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There were several interrelated tragedies stemming from the Macondo well blowout, each leading to the other. First, the primary event—the failure of cement to contain the hydrocarbons in the formation—has been studied post-mortem and is fairly well understood.
The second event was the gas kick that sent mud and gas shooting up the drill pipe with tremendous force. The subsequent explosion and fire may or may not have been avoidable, but crucial decisions had to be made in moments.
Third, a conflagration, continuously fed by fresh hydrocarbons, consumed and destroyed the rig over the next several hours. And finally, after the Deepwater Horizon capsized and sank, oil and gas continued to flow unabated into the sea for weeks, an industrial, environmental (and public relations) nightmare.
Safety systems of last resort. Of all the “what if” scenarios, the one that reeks the least of armchair generalship is the question, What if the rig had been able to separate from the wellhead? We know that seven minutes after the fire began, the Subsea Supervisor attempted to activate the emergency disconnect system (EDS). The system works by sending signals from the rig via multiplex (MUX) communication cables to the blowout preventer and lower marine riser package (BOP/LMRP), where pod receptacles de-energize and retract, choke-and-kill lines disconnect, the blind shear ram (BSR) is triggered, and the LMRP separates from the BOP below. If everything works, the well is sealed and disaster is averted. (For a detailed discussion, see “Why did the Macondo BOP fail,” page 51.)
The primary purpose of the EDS is to prevent damage to the riser if the rig goes off-station, for whatever reason. A dynamically positioned rig like the Deepwater Horizon depends on power and control to stay put over the well, and failure of either one of these can send the rig wandering. In the case of a blowout and fire, the EDS is called upon to save the rig. Once fire and explosion damage the MUX cables, there is no way to separate the rig from the well. The system’s fatal weakness is communications.
Separate quicker, with a bang. Recently, Shell unveiled several new safety concepts at their Technology Center in Rijswijk, The Netherlands. One of the most interesting is the emergency separation tool (EST), a device that can sever pipe with explosive charges, allowing it to drop down through the BOP stack out of the way. The BOP can then be closed conventionally without shear rams.
Curtis Wilie, well testing superintendent at Shell and inventor of the EST, told World Oil that the device was developed not so much in response to the Macondo tragedy, but because Shell decided that the industry had to do more to avoid a dependency on BSRs. In the normal course of drilling and completions, it is inevitable that sometimes there are non-shearable components across the BOP stack.
“Historically, what the industry has done is make bigger and bigger shear rams,” Wilie said. “Now we are approaching the limit of how big a shear ram we can build. The EST will cut anything from 16-in. casing to 9½-in. drill collars. There are zero moving parts, and it utilizes existing technology you can get off the shelf today. We simply reconfigured it for a new format.”
The device contains rings of explosive charges, doubled for redundancy, that are triggered from the surface to sever the pipe. In early tests, linear explosives were used. Such systems are often utilized in decommissioning, for cutting off platform legs under water. But in order to cut a 9½-in. drill collar, up to 10 kilos of explosive were required. The designers reverted to shaped charges, which are more focused and directive.
“By using a band of 56 shaped charges, we were able to cut the explosive weight down to just 2.1 kilos,” Wilie said. “That allowed us to shrink everything, including the housing. Our goal is to maintain the integrity of the riser—we never want to breach the riser itself.”
Lose the cables. The EST system can be triggered by any of three wireless methods. The primary one is from the rig via direct-sight sonar. An encrypted acoustic signal is sent to a sonar beacon, and the sonar beacon transfers the signal to a receiver on the tool, which activates the detonator. Another available method is open-water, via boat. A vessel in the general location of the well drops a dunker in the water, which can pick up the signal and transmit it to the EST. The third method is via offsite transmission.
“We put a beacon offsite in an area outside the debris field,” Wilie said. “We can either place it on the sea floor or on a sea buoy so we could communicate with the system via satellite. It all depends on the level of redundancy you want. But all three methodologies will be utilized.”
Shell has a functioning prototype of the EST in testing now, with the goal of having it operational on a rig by the second quarter of 2012. A similar tool called the collapsible insert device (CID) is deployed downhole to collapse pipe in an emergency, either shutting off or greatly reducing hydrocarbon flow. Both tools are activated acoustically and can be triggered in 10,000-ft water depths. Open-water acoustic transmission is old technology, and has been used by the U.S. Navy to communicate up to 14 miles, so 10,000 ft is no problem.
Wilie stressed that the technology will be available for all subsea oil and gas operators. “This is a Shell invention, but we’re not going to keep it in the Shell portfolio. We are fully funding and developing the EST, but our goal is to see it utilized throughout the industry.”
When it comes to deep waters, the best safety systems are the ones that are used by everybody. If they aren’t, the smartest ideas in the world don’t help one bit. 
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