BP technicians are in final tests to determine whether to proceed with the plan to pump heavy drilling mud into the Macondo well. Tests today involved slow injections of mud into the well to make sure the pumped mud will reach the oil reservoir from the column of pipes and valves that sit on top of it. It that works out, BP will begin pumping the mud and possibly cement into the well, an operation known as static kill. Alternatively, engineers may decide to wait for a relief well to be completed before pumping cement in. There is also a chance that they will pump mud both ways, to ensure the well is fully sealed.
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While the static kill may only plug the center well pipe, the relief well will penetrate both the central pipe and the portion of the well between the inner piping and the outer casing. That area — called the annulus, and akin to the space between a straw inserted in a tumbler of water and the glass itself — probably will not be reached by the mud and cement injected by the static kill.