Drilling the relief wells

(CNN) -BP has said it hopes to have a relief well in place in August to permanently cut off the oil gushing into the Gulf of Mexico. The company has said the operation is the best sure-fire way of plugging the massive oil leak.

A relief well is a well drilled into the existing well, intercepting the flow and allowing a specialized heavy liquid to be pumped into the flowing well to bring it under control.

BP began drilling the first relief well on May 2 and started drilling a second one two weeks later. The wells are being dug to a depth of about 18,000 feet, just above the oil reservoir.

Once one hits the original pipe, just 7 inches in diameter, drilling mud will be shot into it to stop the spewing oil. Cement will then be used to permanently seal it.

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