On Monday, July 6, investors worried that Greece's exit from Europe would weaken European energy demand. Meanwhile, the development of Iran's nuclear talks affected market nerves, worried that the lifting of trade sanctions against the country would aggravate the risk of oversupply, and international oil prices ended plummeting.

Crude oil, the main contract on the New York Mercantile Exchange, fell $4.40, or 7.73%, to $52.53 a barrel in August.

The ice London Brent crude oil contract fell $3.78, or 6.3%, to $56.54 a barrel in August.

Greece's refusal to accept bailout funds from international agencies after the referendum ended on May 5 has increased the possibility of Greece's exit from the euro zone. Meanwhile, the market is worried that Greece's exit from Europe may have an impact on Europe's energy demand, thus putting pressure on oil prices to fall.

At the same time, Iran's nuclear talks are also a source of market concern. Tuesday, July 7, will be the deadline for Iran's nuclear talks. Investors are worried that once the trade sanctions against Iran are lifted, more cheap Iran crude oil will flow into the market, which will aggravate the risk of oversupply in the crude oil market.

In addition, the fall in oil prices is also attributed to signs that US shale oil developers are gradually resuming production. According to Baker Hughes, the number of active rigs increased slightly last week, the first time since December 2014. But it's not clear whether the recent collapse in oil prices will make oil companies rethink their strategies. After all, many companies need $60 to $65 a barrel to support the operation of new oil wells.

In terms of other energy product prices, in August, the formula gasoline contract fell 11.1 cents, or 5.4%, to $1.924 per gallon; in August, the distillate fuel oil contract fell 13.1 cents, or 7.1%, to $1.709 per gallon. In August, natural gas contract prices fell 6.6 cents, or 2.3%, to US $2.756 per million BTU.