US oil production is approaching record levels again, led by shale projects, potentially foiling efforts by OPEC to support prices. 

Oil prices were boosted this week after Saudi Arabia and Russia signaled they intend to extend an agreement to limit output.  

That raised expectations the Organisation of the Petroleum Exporting Countries will sign off on prolonging the existing production agreement at its May 25 meeting. 

Petroleum exporters' efforts to push prices higher have helped American producers as well, especially shale producers who can react quickly to market developments. 

Oil prices currently trade between $45 and $55 a barrel, up from $26 a barrel in February 2016. 

American shale has been particularly responsive to the higher price range because it is less capital intensive than other ventures. 

Analysts said that shale oil investment decisions and cycles are shorter because it only takes a month to drill and bring a well online. 

They said that as prices either move up or down, the industry can be pretty nimble in terms of responding to that.

US production has risen 850,000 barrels per day (bpd) from its 2016 lows to 9.3 million bpd now, not far from the all-time record set in 2015. 

US producers have streamlined spending and been more selective in the wells they drill.  

The cost to drill for shale has fallen by more than one-third in the last two years, analysts said.

New wells have an average break-even price between $43 and $45 a barrel in the current market, they added.

New techniques to boost the flow of oil means a well in a region like the Permian Basin in Texas and New Mexico "has roughly twice the productivity as the same well in late 2014.

Meanwhile, the US rig count has doubled in a year - the strongest recovery in the last 30 years.

Analysts estimate that every dollar that oil prices rise between $45 and $55 a barrel results in an additional 1.2 billion barrels that become economic to produce.

But too much shale output will threaten to drive down oil prices back down again, and at a certain point more drilling means higher production costs as more operators hire rigs.