HOUSTON, July 13 (Xinhua) -- Oil prices increased for the week ending July 12, with the price of West Texas Intermediate (WTI) for August delivery up 4.69 percent and Brent crude oil for September delivery up 3.88 percent.

WTI closed the week at 60.21 U.S. dollars a barrel on the New York Mercantile Exchange, while Brent crude finished the week at 66.72 dollars a barrel on the London ICE Futures Exchange. WTI and Brent have increased 32.59 percent and 24.01 percent, respectively, so far this year.

During the week, WTI and Brent moved in the same directions except Monday. The increase of oil prices showed that oil prices were supported by the more-than-expected drop of U.S. crude stockpile and concerns over potential disruptions to oil and gas production caused by a tropical storm in the Gulf of Mexico.

Oil prices were mixed on Monday amid market concerns over heightening geopolitical risks after Iran crossed the 3.67 percent limit of uranium enrichment purity. WTI gained 0.15 dollar to settle at 57.66 dollars a barrel, while Brent crude lost 0.12 dollars to close at 64.11 dollars a barrel.

On Tuesday, oil prices finished slightly higher as tensions in the Middle East bolstered the market while the gains were trimmed by concerns over a possible slowdown in energy demand. WTI gained 0.17 dollar to settle at 57.83 dollars a barrel, while Brent crude added 0.05 dollars to close at 64.18 dollars a barrel.

On Wednesday, oil prices rallied after newly-released data showed that U.S. crude stockpiles dropped more than expected.

On the day, the U.S. Energy Information Administration (EIA) reported a decrease of 9.5 million barrels of crude oil inventories during the week ending July 5

Oil prices finished lower on Thursday after the Organization of the Petroleum Exporting Countries (OPEC) cut demand forecast for its crude oil next year. WTI lost 0.23 dollar to settle at 60.20 dollars a barrel while Brent crude decreased 0.49 dollar to close at 66.52 dollars a barrel.

However, oil prices finished higher on Friday, as the ongoing tensions in the Middle East lent support while the gains were capped by concerns over a global crude surplus. WTI edged up 1 cent to settle at 60.21 dollars a barrel while Brent crude added 0.20 dollar to close at 66.72 dollars a barrel.

Oil prices have kept gaining momentum since the start of the year due to some geopolitical concerns and OPEC's decision of production cut. The momentum has slowed down recently, mainly because of the concerns over downturn in demand for crude oil.

The slowing global economy continues to be a major headwind for crude oil. The slower economic growth of the world, mainly due to the ongoing trade tensions between the United States and China, will lead to less demand for oil, which in turn would put downward pressure on oil prices.

Moreover, a rising U.S. dollar in the past months has dragged down the greenback-denominated crude futures, as the U.S. Dollar Index has been keeping uptrend since mid-2018.

The dollar index, which measures the greenback against six major peers, fell 0.24 percent to 96.8179 at 3:00 p.m. EST (1900 GMT) on Friday.

Oil is mostly traded in dollar all over the world and a stronger dollar pressures the oil demand.

In the near future, market is expected to weigh on the reports of international organizations on oversupply of crude oil. The International Energy Agency (IEA) said in a statement on Friday that the oil market showed a global surplus of 0.5 million barrels a day (b/d) in the second quarter this year versus previous expectations of a 0.5 million b/d deficit.

In the coming week, analysts believe the oil prices will be supported as major oil firms have evacuated and halted production in the Gulf of Mexico ahead of intensified Tropical Storm Barry.

As of Friday, about 59 percent of crude oil production and about 44 percent of natural gas output were closed down.