OAO Lukoil, Russia's second-largest crude producer, has stress tested its business for oil prices falling to $25 a barrel, according to chief executive Vagit Alekperov.

Brent crude was trading 2.12% higher to $49.55 a barrel at 1240 GMT.

US crude was trading 0.78% higher to 46.67 a barrel following news that Saudi King Abdullah bin Abdulaziz Al Saud had passed away.

But Alekperov told CNBC: "We think that the current trends in the oil market and the global economy are only pushing the world oil to its lower levels. We think the crisis is only at its earliest stages and the demand situation in world market is not really conducive to oil prices going up."

"The sanctions [imposed by Western governments] obviously limit our access to locality and financing. And over the past 25 years, we've been heavily integrated into the international community in terms of technology and financing.

"These will have a telling impact on us," Alekperov told the news channel at the World Economic Forum in Davos on 23 January.

Commerzbank Corporates & Markets said in a note to clients: "Turbulent times on the oil market: after Brent climbed briefly to over $50 per barrel following the ECB's announcement of its massive bond purchasing programme, it dropped back to $48 when the US inventory data were published, only to pick up again in response to news of the death of King Abdullah of Saudi Arabia. As a rule of thumb, high volatility generally heralds a trend reversal, yet we believe it is too early for any real turnaround.

"King Salman, the new King of Saudi Arabia, is a brother of the deceased monarch and has already announced that he will continue his predecessor's policy. That said, the new King may well intervene more actively in his country's oil production policy, having previously headed the petroleum committee. This also raises the question about the future of the current Oil Minister al-Naimi. Uncertainty would probably only increase if he were to resign."

"Too much oil is currently flooding the market, as the enormous rise in US crude oil stocks demonstrated only too clearly yesterday. The increase of a good 10 million barrels recorded last week was the highest in 14 years. At just shy of 400 million barrels, stocks are at their highest level for this time of year in at least 80 years. Given that there is unlikely to be any end in the near future to the news of a huge oversupply, the current period of respite on the oil market could come to an abrupt end," Commerzbank added.

Oil prices could drop to $30 a barrel, Bob Janjuah, co-head of cross-asset allocation strategy at Nomura Securities warned earlier in the month.

The European benchmark, which traded at about $110 a barrel a year ago, has plummeted in recent months amid a supply glut and weak global demand.