Image Source: Transocean.

The price of crude oil seems to have hit a ceiling at $40 a barrel, and has been heading in reverse ever since it topped that mark last week. Just this past week alone, it fell about 6%, closing at just below $37 per barrel. That slump pushed down a whole host of energy stocks, and according to S&P Capital IQ data, some of the worst-performing energy stocks during this week were Transocean (NYSE:RIG), California Resources (OTC:CRC), Tesoro (NYSE:ANDV), Unit (NYSE:UNT), and CARBO Ceramics (NYSE:CRR)

For the most part, oil was the only weight that pushed down these stocks last week. There was no remotely related news regarding Unit, CARBO Ceramics, and California Resources that caused their declines. We can blame the double-digit declines of Transocean and Tesoro on something other than oil prices just to give some variety. 

Transocean, for example, was weighed down after an analyst downgraded two of its peers. In that downgrade, the analyst said that there likely won't be a recovery in the offshore drilling sector until 2018, at the earliest. That implies years of weak business conditions for Transocean and its peers. 

Meanwhile, Tesoro's downward move can partially be blamed on the gasoline market. According to a report by the U.S. Energy Information Administration, the U.S. imported a lot more oil in recent weeks, which is more expensive than domestically produced oil. That suggests that refiners like Tesoro will see their refining margins weaken because they're paying more for oil at a time when demand for gasoline remains strong. 

To learn more about why these stocks moved so sharply, check out the following slideshow.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.