What: The price of crude oil rallied today, closing up nearly 4% to just under $48 per barrel. Fueling the rally was a surge in gasoline and diesel prices due to robust demand while an industry strike in Brazil and a force majeure in Libya weighed on supply. The rally in crude fueled strong rallies in oil stocks, with Halcon Resources (NYSE:HK), Petrobras (NYSE:PBR), and Cobalt International Energy (NYSE: CIE) among a long list that enjoyed double-digit rallies today.

So what: Among the most interesting catalysts behind today's rally in oil was the oil worker strike in Brazil, which began on Saturday. The strike has reduced the country's output by half a million barrels per in the first day, which pushed Petrobras' daily output down by 25%. However, this output reduction is seen as a net positive by the market because it is reducing the glut of oil in the market, which is why Petrobras' stock is higher along with oil prices.

Meanwhile, Cobalt International Energy's rally is also being fueled by some company-specific news in addition to oil prices. Earlier today, the company reported better-than-expected third-quarter results after reporting a smaller loss. Further, Cobalt International Energy reported encouraging appraisal results from its North Platte, Anchor, and Shenandoah discoveries. In fact, the Anchor discovery could be one of the largest oil accumulations in the deepwater Gulf of Mexico trend where it was discovered. Finally, Cobalt's Heidelberg development in the Gulf is on pace to deliver first oil in the second quarter of next year, which is ahead of the initial guidance.

Finally, today's double-digit move in Halcon Resources is purely fueled by the movement in oil prices. However, Halcon Resources will soon have some news of its own; it's scheduled to report third-quarter results on Thursday after the market closes. That report is an important one for the company, which has been decimated by weak oil prices over the past year. Its investors desperately want to see a strong showing, which would mean it needs to follow Cobalt and report better-than-expected earnings.

Now what: These oil stocks will continue to be volatile until oil prices settle down, which will only happen when supply and demand return to balance. There are, however, a number of signs on the horizon that suggest that balance could be returning to the marketplace, with higher demand for refined petroleum products a key part of that equation. In fact, it suggests that oil prices could head higher in the future, which could lead to more upside for Halcon Resources, Petrobras, and Cobalt International Energy.