Running a multi-billion dollar energy company isn't easy. Just ask the executives in the corner suites of some of the energy companies that have gone bust over the years. Some, like Enron, were brought down because of insider malfeasance. A few, like ATP, blamed damaging government policies, while others went off the rails due to market forces that left the company and its shareholders flat-footed, deep in debt, and eventually broke. Here are the bankruptcies that will be etched into the tombstones of failed energy fortunes for time immemorial.

1. Enron. Bankrupt December 2, 2001. Assets $65.5 billion

Enron grew from a simple pipeline company into the world's largest energy trader by using the Internet to buy and sell natural gas and electric power to help utilities and industrial power users hedge against price fluctuations. By 2000, Enron was worth an astonishing $68 billion, but when the U.S. Securities and Exchange Commission started investigating, it was revealed that much of the money was based on shady accounting practices and un-recorded losses. In one year, Enron's stock price plummeted from more than $90 to less than $1, resulting in $11 billion in shareholder losses. The subsequent bankruptcy remains the largest in U.S. history. CEO Kenneth Lay and fellow Enron executive Jeffrey Skilling were convicted in 2006 of fraud and conspiracy. Lay died from a heart attack while awaiting sentencing. Skilling is still in prison.

2. Energy Future Holdings. Bankrupt April 29, 2014. Assets $36.4 billion

Energy Future Holdings became the largest power producer in Texas in 2007 after a $45 billion buyout of TXU Corp. But the company struggled under the weight of $40 billion in debt after revenues plunged due to lower prices for natural gas and electricity. Energy Future Holdings was broken up in April under the terms of a restructuring deal.

3. Pacific Gas & Electric Company. Bankrupt April 6, 2001. Assets $36.1 billion

California's largest publicly-owned utility went bust after deregulation led the company to incur billions in debt. After selling its gas power plants, the company had to buy power from other energy companies. Buying at fluctuating prices and selling at fixed prices led to losses and eventual bankruptcy. But according to Time, wholesale prices eventually dropped, and the day the company emerged from bankruptcy in 2004, its stock was worth three times as much as when it filed for protection.

4. Texaco. Bankrupt April 12, 1987. Assets $34.9 billion

Texaco started out in 1901 as the Texas Fuel Company and was independent for 100 years before merging with Chevron in 2001. However, in the 1980s, Texaco became embroiled in a legal battle with Pennzoil, and ended up owing the company $10.5 billion. That led to Texaco filing for bankruptcy, which at the time, was the largest in U.S. history.

5. Calpine Corporation. Bankrupt December 20, 2005. Assets $26.6 billion

In the mid-2000s, Calpine was the biggest owner of natural gas-fired plants in the U.S. But soaring fuel costs led the company to incur more than $22.5 billion in debt. The subsequent bankruptcy filing followed the ouster of top executives after they lost a fight with bondholders to use proceeds from asset sales to buy fuel. The company received $2 billion in financing to allow it to keep its plants supplying customers.

6. ATP Oil & Gas. Bankrupt April 17, 2012. Assets $3.6 billion

In 2009, ATP Oil & Gas, an offshore oil producer, refinanced $1.5 billion in debt, with the goal of doubling its production to 50,000 barrels a day. Then came the BP Deepwater Horizon disaster. A 2010 moratorium on deepwater operations in the Gulf of Mexico meant ATP was not able to complete wells on its Titan production platform. Forced to spin off Titan and borrow $350 million, ATP spiralled downward, crushed by $2.7 billion in debt obligations. In a Forbes article, ATP's CEO blamed the Obama Administration and "its illegal ban on deepwater drilling in the wake of the BP disaster," for the implosion of the company.

7. Patriot Coal. Bankrupt July 9, 2012. Assets $3.6 billion

As the largest producer of thermal coal in the eastern U.S., Patriot Coal was particularly vulnerable to low coal prices, competition from cheap natural gas, a slowing U.S. economy and tougher environmental rules. Patriot Coal lost money every year since 2010, and in 2012 recorded a loss of $198.5 million. To stay afloat during the Chapter 11 bankruptcy process, the company received $802 million from three major banks.

8. James River Coal. Bankrupt April 8, 2014. Assets $1 billion.

Another victim of the U.S. coal downturn, James River Coal declared itself bankrupt in April, 2014, having emerged from a previous bankruptcy in 2004. The company listed $818.7 million in debt after being forced to close a dozen mines. James River Coal was granted a $110-million loan to keep operating under court protection. At the time of the bankruptcy, the company's stock was trading for 36 cents, compared to $60 a share in 2008.

9. OGX. Bankrupt Oct. 30, 2013. Debts $5.1 billion

Darling of Brazilian billionaire Eike Batista, OGX Petróleo e Gas Participações SA filed for bankruptcy protection after failing to reach an agreement with creditors to negotiate part of its $5.1 billion debt. The bankruptcy was the largest in Latin America. The blow to Batista's mining and oil and gas empire came after disappointing output from offshore wells set off a crisis of investor confidence.

10. Suntech. Bankrupt March 20, 2013. Debts $1.6 billion

The Chinese solar panel manufacturer, one of the world's biggest, was forced into bankruptcy court after the company missed a $541 million payment to bondholders. The company's misfortunes were blamed on a glut in the market for solar panels, which collapsed prices. Another solar industry giant, Germany's Q-Cells, was caught in the downturn the year earlier.

Source: http://oilprice.com/Energy/Energy-General/The-10-Biggest-Energy-Company-Bankruptcies.html

By Andrew Topf of Oilprice.com