By Julia Simon

NEW YORK (Reuters) – Oil prices rose slightly on Friday in volatile trading as the market weighed lower U.S. crude stocks, Nigerian instability and strong global demand growth against a persistently slow rebalancing.

Brent crude <LCOc1> settled up 20 cents or 0.39 percent to $52.10 a barrel.

U.S. West Texas Intermediate crude <CLc1> was up 23 cents or 0.47 percent to $48.82 a barrel.

U.S. crude was down 1.5 percent on the week, while Brent was down 0.6 percent.

The International Energy Agency said it had revised historic demand data for 2015-2016, meaning a lower demand base in 2017-2018 combined with unchanged high supply numbers could lead to lower stock draws than initially anticipated.

On Friday Baker Hughes data showed U.S. drillers added oil rigs for a second time in the last three weeks. However, the pace of additions has slowed in recent months as firms cut spending plans in reaction to declining crude prices.

Drillers added three oil rigs in the week to Aug. 11 bringing the total count to 768, the most since April 2015.

U.S. crude inventories <USOILC=ECI> fell 6.5 million barrels last week, according to the Energy Information Administration.

“As long as we continue to see declining inventories the more we’ll continue to think the OPEC-led cuts are tightening the supply-demand balance,” said Gene McGillian, manager of market research at Tradition Energy in Stamford, Connecticut.

However market watchers caution that declining inventories for gasoline coincide with seasonal draws.

“We may see some headwinds ahead of us with slowing demand as summer driving comes to an end,” said Mark Watkins, regional investment manager at U.S. Bank.

“We’re slowly taking supply out of the marketplace. It isn’t at an accelerated pace,” he said, “This rebalancing is going to take an extremely long time.”

Money managers cut their net long U.S. crude futures and options positions in the week to Aug. 8, the U.S. Commodity Futures Trading Commission (CFTC) said on Friday.

In Nigeria hundreds stormed a crude oil facility and gas plant owned by Royal Dutch Shell Plc <RDSa.L> in the Niger Delta on Friday demanding jobs and infrastructure development, a Reuters witness said.

Nigerian oil exports were scheduled to hit a 17-month high in August, but fell back under 2 million barrels per day (bpd) after Shell declared force majeure on Bonny light.

In the United States, President Donald Trump again stepped up his rhetoric against North Korea again, saying what he called U.S. military solutions were “locked and loaded” as Pyongyang accused him of driving the Korean peninsula to the brink of nuclear war.

(Reporting by Julia Simon in New York and Dmitry Zhdannikov in London; Editing by Jonathan Oatis and Lisa Shumaker)