West Texas Intermediate crude fell below $90 for the first time in 17 months as fracking drives U.S. output to its highest in four decades.

Futures dropped as much as 1.6 percent to $89.31 a barrel in New York, bringing the decline this year to 9.3 percent. U.S. crude output will rise next year to the highest since 1970, the Energy Information Administration forecast Sept. 9. Saudi Arabia, the world’s largest oil exporter, Wednesday dropped its official selling price for crude to Asia to the lowest level since 2008. Brent crude, the European benchmark, fell 16 percent this year.

The shale boom has turned the U.S. into the world’s largest producer of liquid petroleum, reducing its appetite for imports just as the pace of global demand is slowing. U.S. crude oil production rose to the highest level since 1986 last month, while OPEC output climbed to the highest in a year. The International Energy Agency last month reduced its projections for demand growth this year and in 2015, citing a weakening economic outlook.

“We have more than enough supply out there and demand is not catching up,” said Tariq Zahir, a New York-based commodity fund manager at Tyche Capital Advisors. “U.S. production is just incredible. Fundamentally we are just producing so much oil.”

WTI for November delivery dropped as much as $1.42 to $89.31 a barrel on the New York Mercantile Exchange, trading below $90 for the first time since April 24, 2013. It was at $89.77 at 9:46 a.m. London time. Futures declined 13 percent in the three months to Sept. 30, the worst quarterly performance in more than two years.

Saudi Stance

Brent for November settlement tumbled as much as $1.59, or 1.7 percent, to $92.57 a barrel on the London-based ICE Futures Europe exchange, the lowest since June 29, 2012. Prices decreased 16 percent last quarter. The grade’s premium to WTI was at $3.45 a barrel, little changed from Wednesday.

Saudi Arabia reduced the price for Arab Light to Asia by $1 a barrel to a discount of $1.05 to the average of Oman and Dubai crude, the lowest since December 2008. Official selling prices, or OSPs, are regional adjustments Aramco makes to price formulas to compete against oil from other countries.

The price reduction followed a cut of 408,000 barrels a day in Saudi production in August to 9.6 million a day, according to data the country submitted to the Organization of Petroleum Exporting Countries. The kingdom will maintain output at that level until the end of the year, a person familiar with its policy said Sept. 26.

WTI Options

“The real story seems to me to be that the Saudis want to protect their market share and not act as an OPEC swing producer, as they have done sometimes in the past,” Christopher Bellew, senior broker at Jefferies International Ltd. said by e-mail. “The excess supply of oil in the market is pressuring prices downwards again. It would be a mistake to try to call the bottom of the market.”

Eight of the 10 most-traded WTI options yesterday were puts, which give investors the right to sell oil at a designated price. The most actively traded were contracts to sell WTI at $80 a barrel, according to Nymex data compiled by Bloomberg.

U.S. oil consumption will decline to 18.92 million barrels a day this year from 18.96 million in 2013, the EIA said in the monthly Short-Term Energy Outlook. Demand averaged 19.4 million in the four weeks ended Sept. 19, the lowest since July 25, the Energy Department’s statistical arm said Sept. 24 in a separate weekly report.

Global Demand

Global demand growth slowed in the second quarter to the weakest since 2011, according to the Paris-based IEA. The adviser to 29 nations has cut its 2015 global consumption forecast by 300,000 barrels a day since July to 93.8 million a day.

“What’s pushing oil prices down is probably the steep decline in demand,” said Carl Larry, president of Oil Outlooks & Opinions LLC in Houston. “The weakness in the demand sector is causing a lot of people to sell oil.”

The EIA reduced its price forecasts for WTI in the monthly report. WTI will average $98.28 a barrel this year, down from last month’s projection of $100.45.

The share of total U.S. petroleum and other liquids consumption met by net imports fell to 32 percent in 2013 from 60 percent in 2005, according to the EIA. The rate will decline to 21 percent in 2015, which would be the lowest level since 1968.

Prices also slipped as OPEC output increased in September as Libyan output rebounded to the highest level in more than a year, according to a Bloomberg survey. Production from the 12-member group rose by 413,000 barrels a day to 30.935 million, the survey of oil companies, producers and analysts showed.

OPEC has yet to decide to cut its production target, the United Arab Emirates’ energy minister said on Sept. 23. All 12 members of the group must agree before any reduction in its official limit of 30 million barrels a day, the U.A.E.’s Suhail Al Mazrouei said, a week after OPEC’s secretary-general said it may lower the ceiling in 2015.