Global glut and growth concerns may pressurize the crude oil market further, leading oil prices to fall to as low as $20 a barrel in coming months, according to a global brokerage firm.

Brent oil prices fell nearly 2% or 71 cents to touch an 11-year low of $36.17 a barrel on the London-based ICE Futures Europe Exchange on Monday, while the US Benchmark West Texas Intermediate dropped 32 cents, or nearly 1%, to trade at $34.41 a barrel.

The decline in oil prices comes on the back of growing concerns over the global growth, which could weigh on the oil demand in the coming months. A slowdown in demand may worsen the oversupply conditions that have been rattling the oil market since June 2014.

"We reiterate our concern that 'financial stress' may prove too little too late to prevent the market from having to clear through 'operational stress' with prices near cash costs to force production cuts, likely around $20/barrel," said Goldman Sachs in a note to its clients.

"Our base case remains that the global oil stock build will on aggregate remain shy of storage capacity, although the storage buffer has once again narrowed. But this rebalancing is far from achieved...," Business Standard quoted Damien Courvalin, Abhisek Banerjee, Raquel Ohana of Goldman Sachs, as saying in a report.

Oil prices are also under pressure from an unchanged decision on production levels by the Organisation of the Petroleum Exporting Countries (OPEC) at its recent meeting. The oil cartel remains reluctant to cut the oil output, as it fears loss of market shares to other oil-exporting countries.

"OPEC can't take a unilateral decision, for example, to cut production and others ... raise production. Either we all go to cut production to really defend prices or we have to wait and see," Iraq's oil minister Adel Abdul Mahdi told Reuters on Sunday.

A slowdown in China and resumption in oil exports from Iran are also expected to keep oil prices lower for a prolonged period.