From American sanctions on Iran to concerns over oversupply, 2018 seems to be a turbulent year for world's oil market, and uncertainty dominated the markets ahead of those restrictions being enforced in November.

While many analysts predicted it has not drawn the type of price spike, oversupply now appears to be the word of the day, and the game changer for global markets in 2018 might be U.S. production.

Richard Joswick, Managing Director for oil analytics at S&P Global Platts, said the amount of U.S. crude exports impact global markets.

"The growth in U.S. crude exports, crude production, it's light sweet crude, it really has been transformative, it was the real reason that the Organization of Petroleum Exporting Countries [OPEC] had to cut back more. The latest weekly number of U.S. crude exports was over three million now," he said.

Meanwhile, OPEC has been forced to react to a changing landscape. The Middle East's politics has left its mark on OPEC in 2018, notably an ongoing spat that Saudi Arabia and its regional allies such as the United Arab Emirates (UAE) pitted against Qatar. It spilled into OPEC unity, with Doha recently deciding to leave the organization in 2019.

As Qatar is a Liquefied Natural Gas (LNG) powerhouse, analysts doubt it will massively impact OPEC's oil capacity. Robin Mills, CEO of Qamar Energy cited Saudi Russia axis has become very important in terms of managing supply.

"Well, I think Russia has been, which it's never really been before, an active player in collaborating on supply decisions and cutting supply, not cutting as much as the main OPEC countries, but still cutting. And that was really crucial, of course, in making sure that OPEC could actually deliver these cuts, and there are a lot of members, including Saudi Arabia, who didn't want to even come into cuts unless they could be sure they wouldn't be losing market share to Russia and some of the other non-OPEC countries," Mills said. 

Another supply factor set to seep into 2019 concerns waivers granted by Washington to some importers of Iranian crude. On paper they're supposed to be temporary, with the U.S. looking to restrict Iran's energy output further, the slowing global economic growth and an unresolved trade spat between China and the U.S. 

Some of the headwinds moving commodity markets this year look set to leave their mark on 2019.