Texas Brine Co. of Houston began on Tuesday removing crude oil trapped in a failed company salt cavern inside the Napoleonville Dome in northern Assumption Parish, company and government officials said.
Texas Brine workers began pumping brine through an observational well that had been drilled recently to find the cause of a 4.2-acre sinkhole nearby. The observational well provides access to the salt cavern the company had been using.
Located between Bayou Corne and Grand Bayou, the sinkhole was found the morning of Aug. 3 south of La. 70 South, leading to a mandatory evacuation of 150 homes. The evacuation order remains in place.
Since oil and water do not mix, the brine is a means of pushing crude oil to the top of the cavern, where it can then be collected and shipped away for reuse or disposal, state and parish officials said.
“Every barrel (of crude) taken out is a barrel (of brine) going in,” said John Boudreaux, director of the Assumption Parish Office of Homeland Security and Emergency Preparedness.
Patrick Courreges, Louisiana Department of Natural Resources spokesman, said the replacement brine will be used to maintain stable pressure in the cavern.
Texas Brine is shipping crude removed from the cavern that can be salvaged for reuse to PSC Industrial Outsourcing Inc., Courreges said.
The state Office of Conservation approved the removal plan Tuesday.
Sonny Cranch, Texas Brine spokesman, said brine will be pumped into the well only during daylight hours.
State, parish and company officials said no solid estimates are available on how much oil is in the cavern.
In other developments, Cranch said Texas Brine contractors have largely removed vegetative debris from the surface of the sinkhole and have been vacuuming up crude oil also on the surface for the past two days. Two trees that fell into the south side of the sinkhole overnight Monday have also been removed.
The plan to remove crude oil from the cavern follows the Louisiana Office of Conservation Commissioner Jim Welsh’s order last week saying that the cavern caused the sinkhole.
The order calls on Texas Brine to perform a variety of tests. The company was directed to conduct pressure monitoring on the cavern and set up probes and wells to test and remove natural gas in the aquifer under the area. Part of Welsh’s order also calls on Texas Brine to maintain the stability of the cavern and prevent any more changes.
The Texas Brine cavern is along the western edge of the Napoleonville salt dome, a 1- by 3-mile solid salt deposit used for decades for brine production, hydrocarbon storage and oil-and-gas exploration.
The 449-foot-deep, funnel-shaped sinkhole is not directly over the cavern but about 200 feet northwest. The cavern extends from 3,400 feet to 5,650 feet underground, officials have said.
Scientists think the cavern’s side wall was too close to the edge of the dome and a “side breach” happened on the lower part of the wall, according to Welsh’s order. This “side breach” allowed an estimated 3.3 million cubic yards of material into the cavern, as well as crude oil and gas from natural underground formations next to the dome, the order says.
Courreges said the movement of this material into the cavern released pressure from the tightly compacted underground formations outside the dome, allowing earth to shift and causing the sinkhole.
Oil and gas from those formations also were able to rise to the surface. In addition to crude on the sinkhole’s surface, gas has been found in an underground aquifer in the area and in area waterways.
It is not clear is whether any more oil and gas from the formations outside the dome might continue to enter the cavern once the crude oil is removed by Texas Brine.
Courreges said part of the removal plan involves investigating whether the oil and gas that had moved into the cavern and toward the surface when the cavern failed was a one-time event.
“That is part of what they are trying to figure out,” he said.