Brent crude oil was up for a fifth straight session on Thursday – briefly it went above $113 a barrel.
The main reason – investor hopes for more stimulus measures by China to boost its slowing economy.
That would increase demand by the world’s second largest oil consumer.
Other factors include a recent fall in US crude inventories, supply disruptions from a storm in the Gulf of Mexico, lower North Sea output and Middle East tensions.
US crude oil stockpiles fell more than expected last week despite rising imports, federal government data showed. Analysts say the shutdown of an Enbridge pipeline reduced supply.
In the North Sea, oil output is set to plunge 17 percent in September due to oilfield maintenance and natural decline while Mexico has closed two of three main oil export ports in the gulf due to high waves caused by Tropical Storm Ernesto.
Oil could gain more support from geopolitical tensions in the Middle East as the Syrian conflict could intensify other tensions and violence in the region and spill into neighbouring Iraq, Barclays analyst Paul Horsnell wrote in a note.
“If supply tightness accompanied by good fundamental data and shocks such as storms, refinery fires and other outages were behind most of the leg up in crude prices so far, in our view, geopolitical developments look likely to take on the baton from this point,” he said.