Another chunk of land falls into sinkhole

BAYOU CORNE — A shallow well recently drilled into the aquifer underneath the Bayou Corne area has hit natural gas, Shaw Environmental officials said Tuesday.

That well is one of three that contractors for Louisiana Department of Natural Resources drilled to find and vent natural gas believed trapped in the Mississippi River Alluvial Aquifer.

In addition, an earlier boring made separately by Texas Brine Co. LLC of Houston on its leased property also has hit gas, Shaw officials said.

But gas was not on found in another DNR relief well drilled farther west on property west of Bayou Corne.

Along with sampling showing some of the most remote bubble sites are swamp gas from decomposing organic matter, the well findings further support earlier indications that gas is in the aquifer running under the section of northern Assumption Parish but also suggest that the gas has not spread far afield nearer to populated areas.

Parish officials have said they are concerned the gas could build pressure in the aquifer, escape and lead to an explosion risk, though testing has not found that so far.

The DNR vent/relief well with gas inside it is located north of La. 70 South in the vicinity of a 4-acre sinkhole but east of the most-populated portion of the Bayou Corne community. The Texas Brine boring is in the same area but south of La. 70.

Shaw officials working with the Louisiana Department of Natural Resources on the sinkhole told about 100 residents gathered for a community meeting Tuesday that the well north of La. 70 and another drilled on the same site would be linked to a flare to begin removing the gas gradually.

Gary Hecox, a geologist with Shaw Environmental, said releasing the gas too aggressively could damage the well and prevent needed data collection.

“So were going to start off and follow a fairly methodical way of doing it, but we’re doing it as fast as we can, but still keep everybody safe,” he said.

Texas Brine officials also announced Tuesday that they were preparing to drill their own vent well on their property.

The community has been evacuated since the sinkhole was found Aug. 3. DNR scientists have suspected that an abandoned Texas Brine salt cavern failed and caused the sinkhole.

Texas Brine has already announced that the cavern carved from the Napoleonville Dome is 1,500 feet shallower that what it was when it was abandoned in June 2011.

Hecox also said that hydrocarbons pulled from inside the cavern and on top of the sinkhole are virtually identical as far as their chemical makeup.

When asked if that means it is confirmed the failure of the cavern caused the sinkhole, he said, “All the data we’ve looked at so far would lead you to that conclusion, yes.”

But he said there is still evaluation to be done of the cavern collapse and more data is needed.

“One hundred percent in science is a little hard to get to, but right now, the link between what the fill is in the bottom of the cavern and the sinkhole seems to be … the two are linked,” Hecox said.

He explained later that, in contrast to early reports, the hydrocarbons in the sinkhole and the cavern are crude oil, not diesel, and may have come from natural oil-bearing formations along the side of the salt dome.

Bruce Martin, vice president of operations for Texas Brine, told residents that records show all the diesel used in the cavern had been removed before the cavern was plugged and abandoned.

The Texas Brine cavern is near the edge of the dome.

However, questions remain about where the Texas Brine cavern failed, as the roof and the walls at the top portion appear intact, Shaw officials said, and how the crude oil got to the surface.

Hecox said the most likely explanation is that the crude oil went up the side of the salt dome into the sinkhole.

But he also went further in saying that many of the occurrences around Bayou Corne appear to be tied together.

“It is very likely the release of oil and the gas we’re seeing, the cavern collapse, and the sinkhole are all related,” he said.