Which one is the correct/better way?
1) Although the oil price seems to keep decreasing (Smith 2017), the oil industry is still growing (Watson 2017).
2) Although the oil price seems to keep decreasing, the oil industry is still growing (Smith 2017; Watson 2017).
That depends on where the two separate statements come from. If Smith says the price decreases, while Watson says the industry grows, the first one is correct.
On the other hand, if both authors note the correlation of price and industry, the second is right. It happens very often that the same statement is contained in more than one article, so you need to cite them all.
So that depends where the two statements come from. Both ways are formally correct.
The citation relates to the words immediately before it, I would say. The format for cittions - Name, date - is a good one for many reades.
