Proven crude oil reserves (bbl):
37.14 billion

Oil has been the dominant source of government revenues in Nigeria since the 1970s. However, the country struggled following last year's collapse in oil prices. And now, Nigeria stands to "face extra competition" from the reintroduction of Iranian oil on the markets.

Source: Barclays Research, CIA Factbook

Proven crude oil reserves (bbl):
48.47 billion

Libya's economy is pretty much completely dependent on energy. Sales of oil and gas plunged sharply in 2014 following huge protest disruptions at oil ports.

Source: Barclays Research, CIA Factbook

Proven crude oil reserves (bbl):
80 billion

Although Moscow stands to benefit geopolitically following the Iran deal, the return of Iranian oil to the markets is bad news for them as Tehran could go after one of Russia's European markets.

“Iran is going to be competing in Europe head-on with Russia,” Ed Morse, head of commodities research at Citigroup Inc. previously told Bloomberg.

Source: Barclays, Business Insider

Proven crude oil reserves (bbl):
97.8 billion

UAE is another energy-dependent state that modernized after the discovery of oil over 30 years ago. Following the late 2014 plunge in oil prices, UAE — one of the biggest producers in OPEC — has been producing record amounts of crude.

Source: Barclays Research, Bloomberg

Proven crude oil reserves (bbl):
104 billion

Petroleum accounts for over half of Kuwait's GDP, and the country plans to increase oil production to 4 million barrels per day by 2020. After the sanctions on Iran in 2012, Kuwait (along with Saudi Arabia) took most of Tehran's "Asian trade."

Source: Barclays Research, CIA Factbook, Bloomberg

Proven crude oil reserves (bbl):
140.3 billion

Iraq's largely state-run economy runs on oil. Consequently, as oil prices fell in late 2014, government revenues fell by approximately 30%.

As of 2015, Iraq — one of the biggest producers in OPEC — was pumping oil at record highs.

Source: Barclays Research, CIA Factbook, Bloomberg

Proven crude oil reserves (bbl):
157.3 billion

Iran's crude oil is the wild card right now. Analysts believe that the return of Iranian oil to the global market could drive prices down. Additionally, there could be increased tension between Iran and Saudi Arabia, as well as Iran and Russia.

Source: Barclays Research, Business Insider

Proven crude oil reserves (bbl):
173.2 billion

Canada exports most of its oil to the US and Europe. Notably, it's the US' largest foreign supplier of oil.

However, a recent reports shows that the oil from Canada's oil sands is about 20% more carbon intensive on average than others. That means that, "if Canada exports more oil sands to the US over time, greenhouse gas emissions from US drivers would rise, even if gasoline consumption remained flat," according to OilPrice.com.

Source: Barclays Research, CIA Factbook, OilPrice.com

Proven crude oil reserves (bbl):
268.4 billion

Saudi Arabia was one of the big players in the oil game over the last year. Most recently, the Kingdom — along with the rest of OPEC — refused to cut oil prices. (Although, notably, the Saudis' rhetoric here has slightly softened.)

Additionally, Iran wants "to double crude exports soon after sanctions are lifted and is pushing other members of [OPEC] to renew the cartel's quota system" — which could soon shake up things for the Saudis.

Source: Barclays, Business Insider, Wall Street Journal

Proven crude oil reserves (bbl):
297.7 billion

"Venezuela remains highly dependent on oil revenues, which account for roughly 96% of export earnings, about 40% of government revenues, and 11% of GDP," according to the CIA Factbook.

Consequently, the plunging oil prices in late 2014, combined with a recession, crushed the Venezuelan economy. And now, the country is looking for allies outside of OPEC in hopes of stabilizing its oil prices.

Source: Barclays Research, CIA Factbook

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