"The impact of productivity gains is likely to be most visible over a longer period of time as it compounds on itself," Goldman said, with the possibility it's more likely to be felt in 2016 than this year.
In January, Goldman cut its oil price forecasts sharply.
On a three-, six- and 12-month basis, Goldman forecasts Brent at $42, $43 and $70 a barrel, respectively, with WTI at $41, $39 and $65 a barrel.
Read More Oil's new normal is lower for longer: Goldman
In Asian trade Wednesday, Brent for March delivery was around $56.30 a barrel, off the low of around $46.40 touched mid-January, while WTI for March delivery was trading around $50.33 a barrel after touching lows of around $43.58 in late January.
"It is premature to translate the recent collapse in the oil rig count into an immediate reduction in output, a tightening in market balances and therefore a bottom in prices," JPMorgan said in a note Wednesday. "Only if there is no offsetting increase in average well productivity – which seems unrealistic – does the drop in rigs imply falling production from mid second quarter of 2015."
JPMorgan estimates that a rise of 15 percent in average initial production rates over the first half, even if the rig count is cut in half, still implies average output growth of more than 215,000 barrels a day for the full year.
JPMorgan expects the recent rally in oil is just position driven and is likely to be reversed over the next few weeks, with CFTC data indicating non-commercial short positions in WTI futures at end-January were at their highest level since 2010.
It expects oil prices will trough in March or April, with Brent futures to hit a low point at around $38 a barrel, with a shallow lower-case-U-shaped recovery to around $58 in the fourth quarter.
Of course, these forecasts aren't as bearish as Citigroup's, which are for WTI to potentially fall as low as $20 a barrel.
"Not only is the market oversupplied, but the consequent inventory build looks likely to continue toward storage tank tops," Citigroup said in a note Monday. Citigroup expects shale producers may cut rig counts by around 50 percent, which combined with some marginal well shutdowns would lower U.S. production growth to around 600,000 barrels a day this year.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1