The prices for oil rose slightly upward on Tuesday, owing to the strong demand outlook for the coming few weeks. But overall, the markets have continued to remain volatile on the rising output and supply glut in the international market.

Brent crude futures were at $47.07 per barrel at 0359 GMT, up 19 cents, or 0.4 percent, from their last close.

U.S. West Texas Intermediate (WTI) crude futures were at $44.56 per barrel, up 16 cents, or 0.4 percent.

Despite the declining prices, the OPEC commitment to reach their targeted cuts has not been achieved as of yet. The OPEC and some non-OPEC members agreed to cuts in May this year extending the cuts into the coming as the supply glut continues to weaken the prices for oil.

However, the rhetoric of Aramco, Saudi Arabia’s national oil company in a recent report highlighted that the world might be heading for a oil supply shortage following the steep decline in investments and a lack of fresh discoveries.

“If we look at the long-term situation of oil supplies, for example, the picture is becoming increasingly worrying,” Aramco Chief Executive Nasser.

“Financial investors are shying away from making much needed large investments in oil exploration, long-term development and the related infrastructure.  Investments in smaller increments such as shale oil will just not cut it,” Nasser said.

About $1 trillion in investments have already been lost since a decline in oil prices from 2014. Studies show that 20 million barrels per day of new production will be needed to meet demand growth and offset natural decline of developed fields over the next five years, he said. 

Several key OPEC ministers will meet non-OPEC country Russia on July 24 in St Petersburg, Russia, to discuss oil markets.

Kuwait said on Sunday that Nigeria and Libya had been invited to the meeting and their production could be capped earlier than November, when OPEC is scheduled to hold formal talks, according to Bloomberg.

However, Nigeria's oil minister was unable to attend the OPEC meeting because of a previous commitment, the Kuwait Oil Minister Essam al-Marzouq told reporters on Monday.

Libya said on Monday it was ready for talks but added that it’s political, economic and humanitarian situation should be taken into account in talks on caps.

The markets are yet to see any benefit from the OPEC led cuts, as the prices for Brent are below their 2017 level.