BY DAVID J. MITCHELL
River Parishes bureau
October 15, 2012
Drilling to locate and remove any natural gas found inside a shallow aquifer underneath the Bayou Corne area could begin as soon as this weekend, Louisiana Department of Natural Resources officials said Thursday.
The 4-acre sinkhole emerged in the same general area Aug. 3 after a two-month period in which earth tremors were reported along with natural gas releases bubbling up in area waterways and at the locations of some land-based water wells.
DNR and other agencies trying to determine the cause of the tremors and bubbles hit natural gas last month during attempts to drill wells into the aquifer in an area to the west of the sinkhole. The drilling was part of DNR efforts to explore underground conditions in the vicinity of the sinkhole.
Gas also was found in the same aquifer above the Napoleonville Dome farther east and deeper underground in the dome’s hard caprock, DNR officials have said.
As a result of the findings, DNR ordered the Napoleonville Dome’s seven operators to find and vent off any gas.
The cavern was hollowed out of the 1-mile by 3-mile Napoleonville Dome after nearly three decades of use for brine production. The dome is a solid salt formation that emerged from deeper deposits left by ancient seas and has been used for oil and gas exploration, brine production and hydrocarbon storage for decades.
The sinkhole is not directly over the cavern, but offset to the northwest about 200 feet.
DNR scientists think a Texas Brine Co. salt cavern inside the dome failed and caused the sinkhole, which forced the evacuation of area residents from 150 homes. The evacuation order remains in force.
Patrick Courreges, DNR spokesman, said Thursday, officials were able to sign contracts earlier this week with a company to drill three shallow wells to further explore the gas-carrying aquifer.
Equipment needed for the drilling is expected to be brought to the site Saturday and Sunday.
The contractor is Frank’s Casing Crew and Rental Tools of Lafayette.
Courreges said the wells would be about 100 feet deep. Two will be located on land between the sinkhole and the Bayou Corne community and another will be located west of Bayou Corne to see if gas is that far west in the aquifer.
Courreges said the wells would tell DNR how much gas is present in the aquifer and how deep the gas is.
The wells will able to be converted to vent, flare off or otherwise safely remove any gas that is found, he said.
He said officials are waiting on fabrication of wellheads designed for safe operation in the environment in which workers will be drilling.
Authorities also are testing air releases from three new bubble sites found in recent weeks farther west toward Pierre Part and beyond any of the 25 other bubble locations in the general vicinity of Bayou Corne and Grand Bayou.
Courreges and parish officials said the samples have been sent off for isotopic tests. It’s not clear if the new bubbling sites are related to the previously known bubbling locations.
Texas Brine also announced Thursday in a statement that about half of the vegetation and debris on the surface of the sinkhole had been removed by a long-reach excavator with assistance from workers in an airboat.
“After sufficient material has been removed, the remaining hydrocarbons will be skimmed from the surface,” Texas Brine officials said.
“Diesel range” hydrocarbons were found on the sinkhole’s surface, as well as the floating debris.
In another aquifer-related development, work to install six geoprobes on land west of Bayou Corne could start as soon as Friday, parish officials said.
Geoprobes are special machines used to make soil borings and to create temporary monitoring wells.
John Boudreaux, director of Assumption Parish’s Office of Homeland Security and Emergency Preparedness, said the geoprobes will allow for monitoring of any gas in the aquifer.
“They should start installing the actual wells tomorrow,” he said Thursday.
Those wells aren’t to be used for venting gas but could provide indications about how future venting programs would remove any underground gas discovered, Boudreaux said.