(Corrects time stamp in paragraph to 0257 GMT not 0558 GMT)
* Record amounts of crude are on ships to customers
* Total CEO warns of further crude price falls
* Murky inventory picture leaves market grappling for clarity
* Oil supplies and crude price curve: tmsnrt.rs/2pElIP6
By Henning Gloystein
SINGAPORE, April 21 (Reuters) - Oil opened the last day of a choppy trading week on a cautious note over doubts that an OPEC-led production cut was having the desired effect of restoring balance to a market that has been dogged by oversupply for more than two years.
Brent crude futures were at $53.03 per barrel at 0257 GMT, up 4 cents from their last close.
U.S. West Texas Intermediate (WTI) crude futures had risen 5 cents to $50.76 a barrel.
The stable prices came after a more-than-3.5 percent fall in both benchmarks earlier this week as doubts emerged over the effect of an effort led by the Organization of the Petroleum Exporting Countries (OPEC) to cut production by almost 1.8 million barrels per day (bpd) during the first half of the year.
Thomson Reuters Eikon data shows that a record 48 million bpd of crude is being shipped across ocean waters in April, up 5.8 percent since December, before cuts were implemented.
The market is taking note: The value of the entire Brent forward curve has slumped steadily since the start of the OPEC-led cuts in January. The average monthly value of a 24-month Brent curve is down by more than $4 per barrel since January to around $54.15 a barrel.
The high supplies are in part a result of other producers, who haven't agreed to cut output, increasing exports.
"The resurgence of U.S shale continues to sabotage the cartel's efforts to stabilise the saturated markets," said Lukman Otunuga, analyst at futures brokerage FXTM.
U.S. production is soaring, jumping by almost 10 percent since mid-2016 to 9.25 million bpd C-OUT-T-EIA. This brings its output close to the world's top two producers, Saudi Arabia and Russia.
The chief executive of France's oil major Total warned this week that crude prices could fall further due to the U.S. production rise.
Attempting to prevent a further ballooning in supplies, some OPEC producers including de-facto leader Saudi Arabia as well as Kuwait are lobbying to extend the pledge to cut production beyond June.
To determine the health of oil markets, analysts say it is important to monitor inventory levels.
Yet outside the United States, where data is plentiful and still shows bloated inventories C-STK-T-EIA, reliable data is difficult to come by.
There are signs that fuel inventories around Asia's oil trading hub of Singapore have fallen, although it is not clear whether this is to meet strong demand or if this is to create storage space in anticipation of more supplies coming.
Reporting by Henning Gloystein; Editing by Kenneth Maxwell