Porter Ranch Gas Leak Update: Company finds underground position of leaking well

After two months of  trying to shut down a leaking natural gas well north of Porter Ranch, Southern California Gas Co. reported it has pinpointed the underground position of well SS-25 — a first step to plugging it.

"When these wells are drilled, they’re not always exactly, exactly straight down. They may veer off slightly from straight," said SoCal Gas spokeswoman Melissa Bailey.

Plotting the underground coordinates of the well accurately enough to drill a second and third well to intercept and plug it nearly 8,000 feet underground is a challenge.

Oil and gas wells tend to veer farther off a straight line the deeper the drilling goes, she said. The energy industry has a name for that tendency: "the ellipsoid of uncertainty."

Experts hired by SoCal Gas lowered a tool down the new well that generates a magnetic field to detect the underground location of the leaking well. "Active magnetic ranging" was also used to locate and plug BP's massive ruptured oil well in the Gulf of Mexico.

The yellow dots show locations where residents have complained of smells coming from a leaking natural gas well in the Aliso Canyon gas storage field.

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Southern California Air Quality Management District

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The well has been leaking since Oct. 23 - and it could be months more before it's plugged and nearby residents return home. More than 2,000 families to relocate to temporary homes outside the area at the company's expense. Two Los Angeles Unified School District  campuses are also to be relocated after the winter break until the leak is stopped.

The process involves digging two rescue wells. The first is 3,800 feet deep, and is expected to continue drilling to 8,000 feet below earth so brine, gravel and other materials can be sent down to stop the leak. Drilling of a second well is set to begin in January.