Factbox: How BP’s containment cap works, next steps

(BestGrowthStock) – BP Plc has placed a containment cap with a seal on jagged remnants of a pipe at the wellhead of an oil leak in the Gulf of Mexico.

The move is part of an effort to contain most of the leak by capping the opening left after the leaking pipe that connects to the wellhead was sheared off.

Here is an explanation of how the cap is supposed to work, as well as other technologies BP is employing to attempt to bring the well under control:

CONTAINMENT CAP

* BP placed the cap with a seal on the pipe remnant jutting from the top of a lower marine riser package, or LMRP, which sits atop a failed blowout preventer at the wellhead.

* Oil and gas continued to gush out from under the cap because vents are open as BP pumps nitrogen and methanol into the cap through a pipe attached to a drillship a mile above at the ocean’s surface.

* The chemicals are intended to stabilize pressures and combat cold temperatures as the pumping action helps expel seawater from the cap.

* The aim is to prevent seawater from mixing with the gas, which can form ice-like hydrates and block the eventual flow of oil and gas to the drillship.

* About 1,000 barrels a day of oil were flowing to the drillship as of early Friday. Daily recovery rate reached 10,500 barrels on Saturday.

* If the nitrogen lowers pressure as intended, the vents will close, the flow to the drillship will increase, and the amount of oil gushing from the cap should decrease.

* U.S. government scientists estimated that the leak’s flow could increase by 20 percent before the seal operates as intended. They are analyzing data to determine if that estimate turned out to be right.

* BP Chief Operating Officer Doug Suttles said on Friday the cap could corral 90-plus percent of the oil. That is higher than previous estimates of about 80 percent.

* Oil that is channeled to the drillship will be stored for later processing at a refinery ashore; the natural gas will be flared.

* The cap effort is, in theory, similar to a much larger 98-ton containment dome placed at the end of the broken pipe in early May. That dome also was connected to the ship by pipe and was intended to corral and channel oil and gas to the surface.

* That containment dome failed because too much seawater got inside and formed hydrates that blocked oil from flowing up to the drillship.

BACKUP CAPS/DOMES

* If the first containment cap doesn’t work, BP has several backup caps with and without seals of varying sizes at the seabed, on the way or being manufactured.

ENHANCEMENT TO LMRP CAP PLAN

* BP will use seabed equipment installed for a previous failed effort to block the leak known as “top kill” to enhance the containment cap system.

* The top kill involved pumping heavy drilling fluid into the failed blowout preventer to try to smother the leak. Mud was pumped from a ship to a service rig, down to a manifold, which routed the fluid to “choke and kill” hoses connected to the blowout preventer.

* BP will try to reverse direction and pull oil and gas from the blowout preventer through the hoses and manifold to a vessel at the water’s surface.

*That system is expected to be ready by mid-June.

HURRICANE PREPAREDNESS

* BP also is planning a system to allow the drillship connected by pipe to the containment cap to suspend operations and move if a hurricane approaches.

* BP will install a pipe that extends about 300 feet below the drillship. Then a hose would connect the pipe to the containment cap.

* Described by BP as a “long-term option,” the system would allow BP to disconnect the hose from the pipe and move the ship out of a storm’s path, then return when weather calms to resume the operation.

* BP has not yet worked out how it would cap or corral the leak while the storm passes and the hose is disconnected from the pipe.

* The system is expected to be implemented in late June or early July.

* The Atlantic hurricane season began last Tuesday.

THE RELIEF WELLS

* Drilling continued on a relief well begun May 2 intended to intercept and cap the leaking well beneath the seabed. Drilling was suspended last week on a second relief well begun May 16 while the top kill was in progress, but that rig resumed drilling last Sunday. Both wells are expected to be finished in August.

BLOWUP PREVENTER:

* BP suspended drilling of the second well so that rig’s blowout preventer could be on standby to place atop the failed blowout preventer and plug the well if the containment cap system fails. BP said on Tuesday that option had been sidelined “at the moment” with the focus on the cap and enhancement because the company lacked sufficient information about the state of the failed blowout preventer.

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(Reporting by Kristen Hays; Additional reporting by Bruce Nichols; Editing by Peter Cooney)

Factbox: How BP’s containment cap works, next steps