Top Kill

May 25 (Reuters) - As early as Wednesday, BP aims to try to stop the massive oil leak in the Gulf of Mexico with a procedure known as a "top kill."

 Here is how the procedure is designed to work, as explainedby Kent Wells, BP's senior vice president of exploration andproduction. He said the procedure could be delayed as BP

conducts tests to gauge its chances of success:

 * Drilling "mud," or fluid heavier than oil that cancontain barite, clay and water, will be pumped from a ship to aconstruction and well-servicing rig and then down a drill pipeto the seabed a mile (1.6 km) below the surface. The ship canpump 50 barrels (7,950 liters) of mud a minute and is stockedwith 11,000 barrels (1.75 million l). Three other ships stocked

with mud are nearby. * The mud will go through the pipe into hoses connected to

a manifold on the sea floor, which routes the fluid to anotherset of hoses known as "choke and kill." * The choke and kill hoses lead the fluid through valves onthe failed blowout preventer. * Once inside the blowout preventer, the fluid travels intothe well beneath the seabed. If successful, the "hydrostatichead" of the fluid, or the force exerted by the fluid at rest,will resist and overcome the flow of oil and "kill" the well.

 * If the fluid cannot stop the flow alone, BP (BP.L) caninject a "junk shot" of solid materials like golf balls andshredded rubber to help get more mud down the well.

 * The entire procedure can take from a half day to twodays.