Politically, if Saudi Arabia can't be counted on to fix prices when faced with a threat like Russia and Ukraine, then why does the US keep them as an ally, since they're clearly involved with terrorism?
By contrast, the US added about three million barrels per day in three years ('12,'13,'14).
Most of the oil price damage was caused by the dollar. Oil had been running at significant global oversupply for years before the dollar began to crash the price back in June/July 2014. That same dollar effect threw Canada into a recession, cut Australia's growth rate in half, and crushed emerging markets including Brazil.
Long before Saudi Arabia boosted production, the dollar took off on its greatest run in decades. Oil immediately began to crash from there forward.
The USSR also collapsed due to the strong dollar 30 years ago, which dropped the price of oil substantially. Oil went from $140 inflation adjusted, for three years, to plunging off a cliff to $35 or so, courtesy of Volcker's strong dollar move. And then again Russia nearly imploded during the cheap oil days of 1997-2000, also caused by an extremely strong dollar (gold hit around ~$250).
When the dollar is strong, it takes fewer of them to buy a barrel of oil. ITT there is a lot of talk about the production side of the equation, but the effect of the strong dollar and weaker Chinese demand have played a role too.
China is talking with Russia, Saudi Arabia and Iran about RMB denominated contracts, so that'll be fun. Currency risk will have to factored into contract prices.
This petrodollar conspiracy is baffling.
Countries don't hold dollars solely to buy oil.
The oil and gas industry is only about 4.6% to 6.5% of the global economy.
Countries hold reserve currencies to manage the exchange rate of their currency. Petrodollar conspiracists would be well served by learning about foreign exchange reserves: https://en.wikipedia.org/wiki/Foreign-exchange_reserves
And in any case, only 65% of foreign currency reserves are in the USD.
The US defense of Saudi Arabia has a requirement that Saudi sell oil in US dollars..