Oil prices soared on Friday, extending the sharp gains from the previous session as cold weather threatened to affect large parts of the United States and cut oil supplies.
Brent crude rose 34 cents, or 0.4%, to $91.45 a barrel as of 0206 GMT after rising $1.16 on Thursday.
West Texas Intermediate (WTI) crude rose 46 cents, or 0.5%, to $90.73 after gaining 2.01 cents the previous day and settled above $90 for the first time since October 6, 2014.
Both benchmarks headed for their seventh consecutive weekly gains.
WTI crude rose above $90 after cold air from the Arctic made its way into Texas and disrupted oil production in the Permian Basin. Heavy snow and ice swept through the Midwest and Northeast of the USA, making travel dangerous, if not impossible, thousands of people were without power, and schools were closed in many states.
Tight oil supplies pushed the semi-annual market structure for WTI to a steep backwardation of $8.08 on Friday, 7 cents less than an eight-year high of $8.15 on Nov. 29. Backwardation occurs when fast spot trading prices are higher than future prices, often encouraging traders to get oil out of their stocks.
Market actors and analysts say oil markets are becoming increasingly vulnerable to supply shocks as demand recovers outpaces supply.
Geopolitical tensions in Eastern Europe and the Middle East have also fueled sharp gains in oil, which pushed Brent futures up 17% and WTI futures 20% this year.
The United States mentions that Russia is planning a phased attack as a justification for invading Ukraine. Russian President Vladimir Putin blames NATO and the West for the escalating tension, despite massing thousands of Russian troops on the Ukrainian border.
OPEC+ and its Russia-led allies agreed to stick with modest 400,000 barrels per day (bpd) increases in oil production earlier this week, and the group is currently struggling to meet current targets.
With the geopolitical risk in Ukraine and the planned and controlled production increase implemented by OPEC+, prices are expected to move towards $100 per barrel.
In the medium term, however, some analysts expect supply to stabilize in the coming quarter, helping to curb the recent rise in prices. Meanwhile, concerns remain that any excess will cause an oversupply while trying to stabilize the market.