More than 27,000 abandoned oil and gas wells lurk in the hard rock beneath the Gulf of Mexico, an environmental minefield that has been ignored for decades. No one - not industry, not government - is checking to see if they are leaking.
The oldest of these wells were abandoned in the late 1940s, raising the prospect that many deteriorating sealing jobs are already failing.
An Associated Press investigation uncovered particular concern with 3,500 of the neglected wells - those characterized in federal government records as "temporarily abandoned."
Regulations for temporarily abandoned wells require oil companies to present plans to reuse or permanently plug such wells within a year, but that rule is routinely circumvented, and more than 1,000 wells have lingered in that unfinished condition for more than a decade. About three-quarters of temporarily abandoned wells have been left in that status for more than a year, and many since the 1950s and 1960s - even though sealing procedures for temporary abandonment are not as stringent as those for permanent closures.
As a forceful reminder of the potential harm, the well beneath BP's Deepwater Horizon rig was being sealed with cement for temporary abandonment when it blew April 20. BP alone has abandoned about 600 wells in the gulf, according to government data.
The U.S. Environmental Protection Agency acknowledged Tuesday that it has had to deal with leaks at abandoned wells in shallow state waters of Louisiana and Texas. The U.S. Bureau of Ocean Energy Management, Regulation and Enforcement - which oversees wells in federal waters - also acknowledged Tuesday that it has dealt with "a few" failed abandoned wells farther out in the gulf.
Experts say abandoned wells can repressurize, much like a dormant volcano can awaken. And years of exposure to seawater and underground pressure can cause cementing and piping to corrode and weaken.
"You can have changing geological conditions where a well could be repressurized," said Andy Radford, a petroleum engineer for the American Petroleum Institute trade group.
Whether a well is permanently or temporarily abandoned, improperly applied or aging cement can crack or shrink, independent petroleum engineers say. "It ages, just like it does on buildings and highways," said Roger Anderson, a Columbia University petroleum geophysicist who has conducted research on commercial wells.
Despite the likelihood of leaks large and small, though, abandoned wells are typically not inspected by industry or government.
Oil company representatives insist that the seal on a correctly plugged offshore well will last virtually forever.
"It's in everybody's interest to do it right," said Bill Mintz, a spokesman for Apache Corp., which has at least 2,100 abandoned wells in the gulf.
Added spokeswoman Margaret Cooper of Chevron U.S.A., which has at least 2,700 abandoned wells in the gulf: "It is our experience that the well abandonment process, when performed in accordance with regulation, has been accomplished safely and successfully."
State officials estimate that tens of thousands of wells are badly sealed, either because they predate strict regulation or because the operating companies violated rules. Texas alone has plugged more than 21,000 abandoned wells to control pollution, according to the state comptroller's office.
In deep federal waters, though, the official policy is out-of-sight, out-of-mind.
That means no one really knows how many abandoned wells are leaking - and how badly.
The AP documented an extensive history of warnings about environmental dangers related to abandoned wells:
- The Government Accountability Office, which investigates for Congress, warned as early as 1994 that leaks from offshore abandoned wells could cause an "environmental disaster," killing fish, shellfish, mammals and plants. In a lengthy report, GAO pressed for inspections of abandonment jobs, but nothing came of the recommendation.
- A 2006 Environmental Protection Agency report took notice of the overall issue regarding wells on land: "Historically, well abandonment and plugging have generally not been properly planned, designed and executed." State officials say many leaks come from wells abandoned in recent decades, when rules supposedly dictated plugging procedures. And repairs are so routine that terms have been coined to describe the work: "replugging" or the "re-abandonment."
- A GAO report in 1989 provided a foreboding prognosis about the health of the country's inland oil and gas wells. The watchdog agency quoted EPA data estimating that up to 17 percent of the nation's wells on land had been improperly plugged. If that percentage applies to offshore wells, there could be 4,600 badly plugged wells in the Gulf of Mexico alone.
Capture and containment efforts continue
BP reported Tuesday that its capture systems at the blown-out well collected or burned off 24,980 barrels of oil on Monday. Mark Proegler, a BP spokesman, said preparations continued for hooking a third vessel, the Helix Producer, up to the systems, which would increase the capture capacity from 28,000 barrels a day to 53,000 barrels. Skimming operations across the gulf have scooped up about 23.5 million gallons of oiled water so far.
Oil spotted in Lake Pontchartrain
Oil sheen and tar balls from the spill have been spotted in Lake Pontchartrain, which forms the northern boundary of New Orleans and was rescued in the 1990s from rampant pollution. Response crews placed a combined 600 feet of hard and soft boom in the Rigolets strait to prevent more oil from getting through to the lake. Nineteen manual skimming vessels and four decontamination vessels based out of Orleans and St. Tammany parishes were dispatched to the oiled areas.