UPDATE 4-BP says capturing 11,100 bpd of Gulf oil leak

* Oil collected by cap system ramping up

* BP readying second seabed system to siphon more oil

* Preparing system that can be interrupted during storms (Adds details of hurricane-ready system, quotes)

By Kristen Hays

HOUSTON, June 7 (Reuters) - BP Plc (BP.L) said its cap system at an oil leak in the Gulf of Mexico captured 7,541 barrels of oil in the 12 hours through noon on Monday, which could bring the daylong total to more than 15,000 -- the company's highest capture rate yet.

BP said on Monday it would begin providing oil capture updates every 12 hours rather than 24, as the company had done. If the 7,541-barrel rate continues, the total would reach 15,082 barrels -- higher than the previous 24-hour total of 11,100 barrels.

The company said it aims to raise the amount to 20,000 barrels. The next update is slated for 9 a.m. CDT (1300 GMT).

If the latest capture rate holds, BP could capture about 79 percent of the high end of an estimate by U.S. scientists that the leak on the seabed is spewing 12,000 to 19,000 barrels a day. It also would be more than 60 percent of the highest government estimate of 25,000 barrels a day.

BP said it expects to increase collection "over the next few days."

Forty-nine days into the disaster, U.S. Coast Guard Admiral Thad Allen told a news conference in Washington the cap effort was "going fairly well" but the ramp-up will establish how much oil the cap can contain and how much will keep leaking.

"I don't think we ever ought to be comfortable with the containment system," Allen said. "I think we need to be ruthless."

As BP ramps up the containment cap system, the energy giant is moving to siphon more oil through other seabed equipment.

By late this week, BP intends to start reusing a setup that pumped heavy drilling fluid into a failed blowout preventer in an unsuccessful "top kill" attempt to plug the leak in May.

That system will pull oil and gas through the same equipment and channel it to the same service rig at the surface that was used for the top kill, BP said.

HURRICANE PREPARATIONS

Both the containment cap and seabed systems are short-term efforts while BP prepares another that will allow the drill ship to disengage and move if a hurricane approaches. The Atlantic hurricane season officially began on June 1.

That system will involve replacing the containment cap with a larger, tighter cap and sealing valve, said Kent Wells, BP's senior vice president of exploration and production.

Unlike the current containment cap, which was shoved onto the remnants of a pipe, the new cap will fit over more of a lower marine riser package, or LMRP, that sits atop the failed blowout preventer.

"It will be more of a sealing valve on top ... to get a more permanent connection," Wells said.

He said the new cap will be connected via hose to seabed equipment connected to a pipe that will stretch upward to about 300 feet (90 metres) below the surface. Another hose will connect the pipe to the drillship to bring oil and gas to the surface.

If a storm comes, the ship can disconnect the hose, move out of its path and reconnect when the weather calms.

Allen said the leak would spew unchecked while the system is disconnected. Wells said BP is trying to figure out a way to minimize the flow if the system must disconnect "but we're just not there yet."

Mobile drilling units routinely disconnect from undersea pipes and move out of the way when hurricanes loom but that routine includes shutting off wells with working equipment at the wellhead.

That equipment failed at the leaking well, leaving nothing to corral the flow if containment efforts are interrupted.

Allen said scientists are working on a more accurate leak rate and that BP hoped to bring in 20,000 barrels per day from the well -- a comment indicating government estimates of a daily flow of 12,000 to 19,000 barrels were low.

The slow ramp-up in collection, which includes oil billowing from under the bottom of the cap as well as out of the top through vents, is part of BP's effort to maintain warm temperatures and keep seawater out.

If cold seawater gets inside and mixes with natural gas escaping with the oil, the extreme temperatures and pressures can cause ice-like hydrates to form, which could block oil from traveling through a pipe to the drillship.

Hydrates foiled BP's attempt nearly a month ago to cover the leak with a box-shaped containment cover that filled with seawater. (Editing by John O'Callaghan and Cynthia Osterman)