Factbox: BP's technological options to seal the well

(Reuters) - BP Plc is mid-stride in a key procedure known as "top kill" to choke off a blown-out oil well a mile beneath the Gulf of Mexico. BP'S chief executive on Friday noted "some success" but said BP won't be able to access the plan's effectiveness until Sunday.

Here are some of the technologies BP is employing to attempt to bring the well under control:

THE TOP KILL

The top kill involves pumping drilling "mud," or fluids heavier than oil that can contain barite, clay and water from a ship to a rig and then to a failed blowout preventer. From there, the mud is intended to go into the leaking well and smother the flow of oil and gas beneath the seafloor. A drillship at the surface stocked with mud can pump up to 50 barrels a minute.

THE JUNK SHOT

In the early hours of May 28, BP and injected a "junk shot" of heavier materials, such as shredded rubber and golf balls, into a series of valves and pipes at the top of the blown-out well in a bid to block it off.

THE RELIEF WELL

* Drilling continued on a relief well begun May 2 intended to intercept and cap the leaking well beneath the seabed. Transocean Ltd Chief Executive Steven Newman said on May 28 that drilling on a well begun May 16 had been suspended while the top kill was in progress, and that rig was ready to resume drilling if needed.

BP spokesman David Nicholas said the company stopped that drilling so that rig's blowout preventer could be retrieved from the seabed to be ready to place on top of the failed one if the company decides to do that. Each drilling rig uses a blowout preventer at the wellhead.

OTHER OPTIONS

* If the top kill fails, BP will immediately move to cut the pipe from the top of a lower marine riser package, or LMRP, on top of the failed blowout preventer. Then a cap with a seal would be placed on the opening and connected to a drillship so leaking oil could be channeled to the surface.

* Another option involves placing a new blowout preventer atop the failed one to seal the well. BP said planning "is being advanced" for deploying the second blowout preventer if necessary.

(Reporting by Kristen Hays)