NEW YORK (Bloomberg) - Investors have a message for suffering U.S. oil drillers: We feel your pain.

They've pumped more than US$1.4 trillion (S$1.89 trillion) into the oil and gas industry the past five years as oil prices averaged more than US$91 a barrel. The cash infusion helped push U.S. crude production to the highest in more than 30 years, according to data compiled by Bloomberg.

Now that oil prices have fallen below US$45, any euphoria over cheaper energy will be tempered by losses that are starting to show up in investment funds, retirement accounts and bank balance sheets.

The bear market has wiped out a total of US$393 billion (S$531.7 billion) since June - US$353 billion from the shares of 76 companies in the Bloomberg Intelligence North America Exploration & Production index, and almost US$40 billion from high-yield energy bonds, issued by many shale drillers, according to a Bloomberg index.

"The only thing people are noticing now is that gas prices are dropping," said Sean Wheeler, the Houston-based co-chairman of the oil and gas industry team for law firm Latham & Watkins LLP. "People haven't noticed yet that it's also hitting their portfolios."

The money flowing into oil and gas companies around the world in the last five years came from a variety of sources. The industry completed US$286 billion in joint ventures, investments and spinoffs, raised US$353 billion in initial public offerings and follow-on share sales, and borrowed US$786 billion in bonds and loans.

The crash caught investors and lenders by surprise. Eight months ago, Houston-based oil producer Energy XXI Ltd. sold US$650 million in bonds. Demand was so high that the company more than doubled the size of the offering, company records show. The debt is now trading for less than 50 cents on the dollar, and the stock has declined 88 per cent.

Energy XXI, which has more than US$3.8 billion in debt, is one of more than 80 oil and gas companies whose bonds have fallen to distressed levels, meaning their yields are more than 10 percentage points above Treasury debt, as investors bet the obligations won't be repaid, according to data compiled by Bloomberg.

The stocks and bonds of Energy XXI and other struggling energy firms have been bought up by pension funds, insurance companies and savings plans that are the mainstays of Americans' retirement accounts. Institutional investors had more than US$963 billion tied up in energy stocks as of the end of September, according to Peter Laurelli, a New York-based vice president of research with eVestment, an analytics firm that gathers data on about US$22 trillion of institutional strategies.

Hundreds of smaller banks in states such as Texas, Colorado, Oklahoma and North Dakota have also plunged into energy lending during the oil boom.