This is important because it seems likely Saudi Arabia will continue its war on US unconventionals at Friday's OPEC meeting in Vienna.

Three senior gulf OPEC delegates told Reuters the cartel was likely to keep its output target unchanged when it met on Friday.

"It is unlikely that OPEC will make a decision regarding its production ceiling for two reasons: the first one that Russia and other non-OPEC producers have expressed their non-desire to cooperate in any idea of a production cut," one of the gulf delegate told Reuters.

Then there is the looming threat to oil prices of sanctions being lifted from Iran.

While claims that Iran could increase overseas crude sales by 1 million barrels a day soon after sanctions are lifted are considered an illusion, Iranian economist and Atieh International managing partner Bijan Khajehpour believes the country could boost its oil exports by 400,000pd in the first few months.

Returning to higher, pre-sanctions crude production levels will take about 18 months, Khajehpour told Bloomberg, due to the time lag for sanctions relief to be implemented and for Iran to restore its production capacity.

However, that means Iran could be exporting 2.5MMbpd by early 2017.

Iran has about 20 million barrels of crude stored on tankers that it has been unable to sell due to sanctions that came into effect in mid-2012, which would allow it to rapidly add to its exports.

Meanwhile, Iran is said to be prepared to offer much better commercial terms to foreign companies prepared to invest to help revitalise its ailing oil industry than offered during the last market opening nearly two decades ago.

Despite all this volatility looming, North American shale producers are actually increasing production despite the negative conditions that have led to the shedding of thousands of jobs across both in the exploration and production and supply side of the industry. The onshore rig count has also dropped more than half.

In its latest report on US shale issued yesterday, Rystad said drilling efficiency gains, well performance improvements, a reduction in breakeven prices and a focus on the top US oil plays had caused US production go from strength to strength, last year and this year.

"Even though the oil price dropped significantly in the second half of 2014 and still remains at relatively low levels, hence leading to a considerable reduction in US shale rigs, light oil production from US shale plays has not stopped growing," Rystad analysts Olga Kerimova and Theodora Batoudaki said in the report.

"The main reasons for this are the enhanced drilling efficiencies [pad drilling, reduced drilling time per rig etc] and the improved well performance in the largest US oil plays in 2014.

"Lower unit prices will most likely continue the trend of falling breakeven prices for US shale in 2015, making shale an even more competitive source of production."

The top five plays in the US contributed more than 80% to production growth last year, with the Eagle Ford Shale the largest contributor, followed by the Bakken/Three Forks Shale play.

Light oil production increased more than three-fold from 1.3 million barrels per day in 2011 to 4.4MMbpd in 2014.

Drilling efficiency in Eagle Ford and Bakken improved by more than 10% last year, primarily due to the the introduction of pad drilling in 2009. This allows operators to drill multiple wells from the same drilling location, reducing the time spent for rigging up and down.

As of 2014, more than 80% of all wells in these plays were drilled using this method. Permian Midland is one play where drilling efficiency appears to have been declining since 2013, with a 3% decrease in wells per rig year in 2014 and a 5% decrease in 2015 to date.

"This trend can be explained by the transition to drilling longer laterals with a higher number of frac stages, as well as a shift in activity to deeper parts of the play," the Rystad analysts said.

Rystad's analysis shows breakeven prices are decreasing for most plays.

For the selected plays in the chart shown, the yearly reduction has been 8.7% from 2012 to 2014 -17% in total over the two years.

A yearly reduction of the shale breakeven prices reflects reduction in well cost, an increase in estimated ultimate recovery per well and an increase in light oil content.

Rystad attributed the reduction in well cost to shorter drilling time thanks to increased pad drilling and shorter completion time due to the increased use of zipper fracs.

The analysts said the increase in EUR was due to lower decline rates thanks to better well placement and advances in known completion techniques, such as modified zipper fracs and reduced cluster spacing.