LONDON -- Royal Dutch Shell, the largest oil company in Europe, disappointed investors Thursday with fourth-quarter earnings that came in well below analysts' forecasts.

The company posted a profit of $5.6 billion after one-time items and inventory changes, up 15 percent from the fourth quarter of 2011. But analysts had expected earnings of about $6.3 billion.

Stuart Joyner, an analyst at Investec Securities in London, described the results as "a substantial miss." The company's shares closed 2.8 percent lower on the London Stock Exchange.

For the full year, Shell reported earnings of $25.1 billion, up 2 percent compared with 2011 results.

Perhaps more than any other energy company, Shell invests in huge oil and gas projects that it hopes will produce steady returns for decades. One example is Pearl GTL in Qatar, which takes natural gas from the emirate's enormous North Field and converts it into liquid fuels like diesel.

Peter Voser, the chief executive of Shell, said production at the gas-to-liquids facility exceeded 90 percent of capacity in the fourth quarter.

Pearl GTL cost around $20 billion, but it looks like it will be a big moneymaker for decades to come. And because its products are pegged to oil prices, it gives Shell and Qatar a hedge against lower gas prices.

"We are on track despite some headwinds in 2012," Voser said in a call with analysts Thursday.

Voser, who comes from a financial background, made his reputation helping to turn around the Swiss machinery-maker ABB a decade ago. He was appointed Shell's chief financial officer in 2004 and was named chief executive in 2009.

Voser said his goal was to deliver $175 billion to $200 billion of total cash flow from operations for 2012-15, a 30 to 50 percent increase over the previous four-year period.

Still, there are reasons to worry about Shell. The fourth-quarter letdown was largely because of lower earnings in Shell's core exploration and production business, mainly caused by weak performance in the Americas.

Shell's prominent, multibillion-dollar Alaska drilling program has encountered several snags and delays, including the running aground of the Kulluk drilling vessel on an uninhabited island in December. Voser said that the Kulluk had been damaged and that another drilling vessel required upgrades. Shell is still considering its next steps in Alaska, he said.

Shell is also being hurt by U.S. natural gas prices, which have been pushed down by the boom in shale gas production. Declining prices have led it to switch strategies and drill for gas deposits that are rich in liquids, which bring in more money than gas.

Low gas prices raise questions about Shell's huge bets on the fuel. Voser said the low prices in North America appeared likely to persist but were an opportunity for Shell's so-called integrated gas business, which is devoted primarily to liquefied natural gas and gas-to-liquids projects. These businesses earned $9.4 billion in 2012, up from $6.4 billion in 2011.