Oil prices rose more than $1 per barrel today due to growing supply outages, with Norway shutting one oilfield as hundreds of workers began a strike and Libya saying its production more than halved in recent months.
The disruptions add to supply worries around the world. Venezuela's production has collapsed due to a lack of investment and Iranian exports have suffered due to US sanctions.
OPEC has little capacity to fill the gap as demand for oil quickens.
Benchmark Brent oil futures rose by 96 cents, or 1.2%, to $79.03 a barrel this morning, after earlier hitting an intraday high of $79.29. Brent gained 1.2 percent yesterday.
US light crude futures CLc1 were up 38 cents, or 0.5%, at $74.23.
Mounting supply concerns could push Brent above $85 per barrel, analysts said.
Hundreds of workers on Norwegian offshore oil and gas rigs went on strike today after rejecting a proposed wage deal, leading to the shutdown of one Shell-operated oilfield.
That potentially adds to disruptions in other oil producers amid tensions in the Middle East.
Libya's national oil production fell to 527,000 barrels per day from a high of 1.28 million bpd in February following recent oil port closures, National Oil Corp said earlier this week.
The US says it wants to reduce oil exports from Iran, the world's fifth-biggest producer, to zero by November, which would oblige other big producers to pump more.
Saudi Arabia, fellow members of the Organisation of the Petroleum Exporting Countries and allies including Russia agreed last month to increase output to dampen price gains and offset global production losses.
The market has grown concerned that if the Saudis offset the losses from Iran, that will use up global spare capacity and leave markets more vulnerable to further or unexpected production declines.