Oil ends down on U.S. inventory surge, doubts on OPEC resolve

* Genscape reports 1.2 mln bbls build at Cushing -traders

* Militants attack oil pipeline in Niger Delta

* Market hit 5-week lows on Wednesday on U.S. stock build (New (KOSDAQ: 160550.KQ - news) throughout, updates prices, market activity and comments to settlement)

By Ethan Lou

NEW YORK, Nov 3 (Reuters) - Oil prices settled down more than 1 percent on Thursday as investors reeled from a record weekly surge in U.S. crude inventories, and remained skeptical about whether OPEC can actually implement its planned output cap.

U.S. crude fell 68 cents, or 1.5 percent, to settle at $44.66 per barrel. At one point, oil had fallen more than $1 a barrel and hit a session low of $44.37.

Brent crude was down 51 cents, or 1.1 percent, at $46.35 a barrel. It hit a session low of 45.99.

Traders said energy monitoring service Genscape reported a weekly build of 1.2 million barrels at the U.S. delivery base in Cushing, Oklahoma.

That kept a lid on oil prices a day after crude fell to a five-week low, when U.S. data on Wednesday showed stockpiles of oil surged a record 14 million barrels last week.

On Thursday, prices were also pressured as U.S. equities fell, with the S&P 500 stock index headed for its longest losing streak since the 2008 financial crisis.

Oil ministers from the Organization of the Petroleum Exporting Countries (OPEC) meet on Nov. 30 in Vienna to agree on a production cap to reduce a global glut and combat low prices.

Market watchers have grown skeptical that a concrete deal can be reached or enforced.

OPEC has not made clear how much each member should cut, and several have been resistant. A Reuters survey this week based on shipping data and industry sources indicated that OPEC output probably set a record high in October.

"We've got this rally a few weeks ago, recent weeks on the expectation that we'll see some cohesive cut coming through from OPEC, but that's been slowly unwound," said Matt Smith, director of commodity research at energy data provider ClipperData.

News (Other OTC: NWSAL - news) of an attack on a Nigerian pipeline, which sources say cut output by at least 200,000 barrels, lent some support to crude prices. Nigeria, Africa's largest crude producer, has been hamstrung in months by rebel activity.

Oil prices have been falling for four days and have not recovered to levels reached in October after the preliminary agreement by OPEC to cap production, reached at a meeting in Algiers.

"If there were broadly three drivers propelling oil prices from about $45 per barrel ahead of Algiers to $53 - OPEC expectations, inventories and a more or less benign macro environment - they suddenly seem spent," Credit Suisse (LSE: 0QP5.L - news) analysts said in a note. (Additional reporting by Sabina Zawadzki in LONDON and Mark Tay in SINGAPORE; Editing by David Gregorio)