Processing towers stand at the RN-Tuapsinsky refinery, operated by Rosneft Oil Co., in Tuapse, Russia, on Monday, March 23, 2020.

The oil market is facing a "double crisis" with a collapse in the OPEC+ alliance affecting supply and the slowdown in the global economy crushing demand, oil guru Dan Yergin said this week.

"The breakdown of OPEC+ is only part of the picture," the vice chairman of IHS Markit told CNBC's "Capital Connection" on Monday. "The big thing is the coronavirus and the showdown of much of the world economy."

Infections around the world have now crossed 700,000, according to data compiled by the Johns Hopkins University. Nearly 34,000 people have died from COVID-19.

Countries have implemented travel bans and instituted lockdowns to stem the spread of the virus.

"Cars not on the road, airplanes not in the air, factories not working, people not going to work," Yergin said. "We see, in this month of April that's coming, what could be a 20 million barrel a day decline in oil demand."

"It's unprecedented. That's six times larger than the biggest downturn during the financial crisis period (in 2008)," he added.

World oil demand in 2019 stood at around 99.67 million barrels a day, according to OPEC's estimate.