Is the oil surplus caused by the economic slowdown in China?
No. The world consumes about 100 million barrels of oil per day. US consumes 20 million, while China consumes 10 million barrels per day. Thus, whether China is in a recession or not, its economy will not have a significant effect on the world oil price.
Because of new technology (fracking), US production of oil has increased from 5 million barrels in 2008 to 9 million barrels per day in 2015. US now exports oil, and US exports of oil will continue to rise.