Yemenis walk past near oil tankers that were burnt during clashes between Shiite Houthi rebels and their opponents in the capital, Sanaa, in September. Saudi Arabia launched airstrikes this week to counter the Houthis' offensive. Mohammed Huwais/AFP/Getty Images hide caption

itoggle caption Mohammed Huwais/AFP/Getty Images

A platform owned by Mexico's state-run oil company Pemex is seen off the Bay of Campeche in the Gulf of Mexico. The country has recently opened up its energy sector to foreign investors. Victor Ruiz/Reuters/Landov hide caption

itoggle caption Victor Ruiz/Reuters/Landov

A pump-jack sits atop an oil well near downtown Sidney, Mont. The oil boom has brought thousands of new residents to the town, almost all of whom work in the Bakken oil fields in Montana and North Dakota. Sidney sits at the western edge of the Bakken oil patch, one of the most productive drilling areas in the country. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Proponents of the terminal plan say it would bring economic development to the Vancouver area, just across the Columbia River from Portland, Ore. Conrad Wilson/OPB News hide caption

itoggle caption Conrad Wilson/OPB News

Miller Farm, the terminus of Van Syckel's pipeline, in 1868. The oil was pumped to Miller Farm and then transported by railroad. Drake Well Museum/Courtesy of PHMC hide caption

itoggle caption Drake Well Museum/Courtesy of PHMC

Drilling rigs dot the landscape near Calumet, Okla., in April 2013. Oklahoma's economy blossomed during the domestic fracking boom, but as the price of crude oil drops, that could change. Sue Ogrocki/AP hide caption

itoggle caption Sue Ogrocki/AP

An oil well in Garden City, Texas. With prices plunging, oil companies are laying off thousands of workers. Spencer Platt/Getty Images hide caption

itoggle caption Spencer Platt/Getty Images

Libya's oil terminals — like the Brega refinery and oil terminal, pictured in March 11, 2014 — are being fought over by militias and by the nation's two rival governments. The conflict is drying up production, and may have a devastating impact on the nation's battered economy. Abdullah Doma/AFP/Getty Images hide caption

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Tracy Perryman is production manager for his family's small oil company in Luling, Texas. B.J.P. Inc. owns 116 wells that, combined, produce about 100 barrels a day. John Burnett/NPR hide caption

itoggle caption John Burnett/NPR

Tankers are berthed beside the Fawley oil refinery on Jan. 7, in Southampton, England. With low oil prices, some traders are buying oil and storing it in tankers, hoping the price will rise soon so they can sell it at a profit. Matt Cardy/Getty Images hide caption

itoggle caption Matt Cardy/Getty Images

An excavator loads a truck with oil sands at the Suncor mine near the town of Fort McMurray in Alberta, Canada in 2009. Environmental groups that oppose oil sands mining have pointed to delayed and canceled projects as a sign of recent success. Mark Ralston/AFP/Getty Images hide caption

itoggle caption Mark Ralston/AFP/Getty Images

President Vladimir Putin speaks in Moscow on Dec. 23. Russia's current economic crisis stems from Western sanctions and diving oil prices. Maxim Shipenkov/AFP/Getty Images hide caption

itoggle caption Maxim Shipenkov/AFP/Getty Images

A sculpture of oil workers in Caracas, Venezuela. The country is heavily dependent on oil exports, and falling oil prices have had a ripple effect on the country's already troubled economy. Ariana Cubillos/AP hide caption

itoggle caption Ariana Cubillos/AP

Iraqi Finance Minister Hoshyar Zebari announced Tuesday that the Iraqi government and the Kurdistan region have started implementing a deal under which Baghdad resumes funding Kurdish civil servant salaries in return for a share of Kurdish oil exports. Ali Abbas/EPA /LANDOV hide caption

itoggle caption Ali Abbas/EPA /LANDOV