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, an Associated Press

investigation shows.

The oldest of these wells were abandoned in the late 1940s,

raising the prospect that many deteriorating sealing jobs are

already failing.

The AP 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 the AP found that the rule is routinely

circumvented, and that 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 - eveb 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, leading to one of the

worst environmental disasters in the nation's history. BP alone has

abandoned about 600 wells in the Gulf, according to government

data.

There's ample reason for worry about all permanently and

temporarily abandoned wells - history shows that at least on land,

they often leak. Wells are sealed underwater much as they are on

land. And wells on land and in water face similar risk of failure.

Plus, records reviewed by the AP show that some offshore wells have

failed.

Experts say such wells can repressurize, much like a dormant

volcano can awaken. And years of exposure to sea water 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, according to government data.

Officials at the U.S. Interior Department, which oversees the

agency that regulates federal leases in the Gulf and elsewhere, did

not answer repeated questions regarding why there are no

inspections of abandoned wells.

State officials estimate that tens of thousands 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.

Offshore, but in state waters, California has resealed scores of

its abandoned wells since the 1980s.

In deeper federal waters, though - despite the similarities in

how such wells are constructed and how sealing procedures can fail

- the official policy is out-of-sight, out-of-mind.

The U.S. Minerals Management Service - the regulatory agency

recently renamed the Bureau of Ocean Energy Management, Regulation

and Enforcement - relies on rules that have few real teeth. Once an

oil company says it will permanently abandon a well, it has one

year to complete the job. MMS mandates that work plans be submitted

and a report filed afterward.

Unlike California regulators, MMS doesn't typically inspect the

job, instead relying on the paperwork.

The fact there are so many wells that have been classified for

decades as temporarily abandoned suggests that paperwork can be

shuffled at MMS without any real change beneath the water.

With its weak system of enforcement, MMS imposed fines in a

relative handful of cases: just $440,000 on seven companies from

2003-2007 for improper plug-and-abandonment work.

Companies permanently abandon wells when they are no longer

useful. Afterward, no one looks methodically for leaks, which can't

easily be detected from the surface anyway. And no one in

government or industry goes underwater to inspect, either.

Government regulators and industry officials say abandoned

offshore wells are presumed to be properly plugged and are expected

to last indefinitely without leaking. Only when pressed do these

officials acknowledge the possibility of leaks.

Despite warnings of leaks, government and industry officials

have never bothered to assess the extent of the problem, according

to an extensive AP review of records and regulations.

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 General 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.

- According to a 2001 study commissioned by MMS, agency

officials were "concerned that some abandoned oil wells in the

Gulf may be leaking crude oil." But nothing came of that warning

either.

The study targeted a well 20 miles off Louisiana that had been

reported leaking five years after it was plugged and abandoned. The

researchers tried unsuccessfully to use satellite radar images to

locate the leak.

But John Amos, the geologist who wrote the study, told AP that

MMS withheld critical information that could have helped verify if

he had pinpointed the problem. "I kind of suspected that this was

a project almost designed to fail," Amos said. He said the agency

refused to tell him "how big and widespread a problem" they were

dealing with in the Gulf.

Amos is now director of SkyTruth, a nonprofit group that uses

satellite imagery to detect environmental problems. He still

believes that technology could work on abandoned wells.

MMS, though, hasn't followed up on the work. And Interior

Department spokeswoman Kendra Barkoff said agency inspectors would

be present for permanent plugging jobs "only when something

unusual is expected." She also said inspectors would check later

"only if there's a noted leak." But she did not respond to

requests for examples.

Companies may be tempted to skimp on sealing jobs, which are

expensive and slow offshore. It would cost the industry at least $3

billion to permanently plug the 10,500 now-active wells and the

3,500 temporarily abandoned ones in the Gulf, according to an AP

analysis of MMS data.

The AP analysis indicates that more than half of the 50,000

wells ever drilled on federal leases beneath the Gulf have now been

abandoned. Some 23,500 are permanently sealed. Another 12,500 wells

are plugged on one branch while being allowed to remain active in a

different branch.

Government records do not indicate how many temporarily

abandoned wells have been returned to service over the years.

Federal rules require only an annual review of plans to reuse or

permanently seal the 3,500 temporarily abandoned wells, but

companies are using this provision to keep the wells in limbo

indefinitely.

Petroleum engineers say abandoned offshore wells can fail from

faulty work, age and drilling-induced or natural changes below the

seabed. Maurice Dusseault, a geologist at the University of

Waterloo in Ontario, Canada, says U