(CNN) -- Workers are pumping mud into a well in the Gulf of Mexico, south of Louisiana, to try to stop a natural gas leak that is also leaving a sheen on top of the water, federal officials said Wednesday.
The wellhead is about 70 feet above the ocean's surface, at a platform about 74 miles southeast of Port Fourchon, Louisiana.
It was leaking a combination of natural gas, water, and condensate -- a liquid form of raw natural gas, according to the federal Bureau of Safety and Environmental Enforcement, which is monitoring the well-plugging efforts along with the Coast Guard.
While the natural gas dissipates into the air, the lightweight condensate falls to the ocean's surface, where it forms a "rainbow sheen." That sheen appears to be evaporating, the BSEE said.
Energy Resource Technology Gulf of Mexico, the energy company that owns the well and the platform it's on, says about 3.6 barrels of light condensate is leaking every 24 hours, based on the size of the sheen.
On Tuesday, the sheen measured four miles wide by three-quarters of a mile long, according to the Coast Guard, which flew over the leak. The size on Wednesday wasn't known.
The BSEE did not say when it expects the leak to be plugged.
Energy Resource Technology was in the process of permanently plugging and abandoning the well when the leak started Sunday. The company reported the leak to the Coast Guard and BSEE and plugged it, but the well started leaking again Monday, prompting an evacuation of the platform and the shutdown of two adjacent working wells.
Talos Energy, which acquired Energy Resource Technology earlier this year, said the leak is at an older well in a field developed in the 1970s. By 1998, the well was producing mostly water at a low-flowing pressure, so the company decided to abandon it.
The age of the tubing may have contributed to the leak, Talos said, though the Coast Guard said the cause is still under investigation.