Source: U.S. Energy Information Administration via Facebook.

Following a brutal 2014 for most energy assets, the hope among investors had been that oil and natural gas drillers, as well as the infrastructure and service companies that comprise the energy sector, would see a rebound in 2015. 

But as we sit at the halfway point of 2015, we've seen few glimmers of hope. Oil and natural gas prices remain depressed from where they stood a year ago, and many energy companies are scaling back on projects in order to reduce their expenses.

With this in mind, we asked three of our analysts to suggest one energy stock each that's been a true disappointment in the first half of 2015. Based on their responses, these are the three worst energy stocks of 2015 (so far). 

Matt DiLallo 
Chesapeake Energy (NYSE:CHK) is the worst-performing energy stock in the S&P 500 so far this year. While that broader market was roughly flat during the first half of the year, Chesapeake Energy's stock price was down 43.5%. Talk about an awful start to the year.

Is the sun setting on Chesapeake? Source: Chesapeake Energy via Facebook.

Chesapeake Energy's slide started after it reported weak fourth-quarter results in late February. The company missed estimates rather badly as weak oil and gas prices took a 60% chunk out of its earnings. To make matters worse, it issued 2015 capital spending guidance that would result in its outspending cash flow in 2015. Investors didn't like that news and promptly sold off the stock.

Further pressure has been put on the stock price by the continued weakness in natural gas pricing as the spot price for natural gas is down about 8% for the year to about $2.75 per Mcf. Given that three-quarters of Chesapeake Energy's production is natural gas, this weakness will have an impact on its bottom line in 2015 and beyond. In fact, analysts expect the company to have a free cash flow deficit of $2.1 billion this year and $2.7 billion next year at current projections for Chesapeake's spending and commodity prices. 

In fact, analysts have been particularly hard on Chesapeake Energy this year as it has been the recipient of a number of downgrades. Analysts have pointed out that the company still has too much financial leverage, weak cash flow, bad contracts, and sub-optimal capital allocation as reasons why the stock will continue to underperform its peers. This negative sentiment has certainly weighed on the stock price almost as much, if not more, than weak natural gas prices.

At the moment, there aren't a whole lot of positives for Chesapeake Energy investors to cling to as negativity rules the day. In fact, until there is light at the end of the tunnel on natural gas prices, Chesapeake Energy's stock price will likely remain weak. There's no telling when that might happen as natural gas production continues to hit records as its supply continues to outpace demand. 

Sean Williams
You probably won't have trouble finding worse performers in the energy sector than CONSOL Energy (NYSE:CNX), which dropped 35% through the first half of 2015, but you'll struggle to find a group of more dejected shareholders than you have at CONSOL.

Although there are snippets of bright spots, including its forecast of 30% natural gas production growth in 2015 and 20% natural gas production growth in 2016, and a defined shift among utilities away from coal and toward natural gas-fired plants, CONSOL is staring down a mountain of problems.

Source: CONSOL Energy.

To begin with, natural gas prices aren't working in its favor. Around this time last year, natural gas prices were around $4/MMBtu, whereas today we're looking at prices hovering about 30% lower. Year to date, natural gas prices are lower by a mid-single-digit percentage. Despite fewer rigs in service as a whole, production continues to improve and supply is heading higher. That's not particularly good news for the short- and perhaps intermediate-term picture for natural gas prices, and thus CONSOL's margins.

Also, CONSOL's other business segment, its thermal coal operations, has investors worried. A tightening regulatory environment coupled with cheap natural gas is causing utilities in record numbers to switch over to the cleaner burning fuel. The result has been sharply lower thermal coal prices and a supply glut that doesn't seem to be getting any better. If there is some solace here, research from a columnist at the Pittsburgh Business Times would seem to suggest that CONSOL's exposure to coal order losses from utilities switching to natural gas is just 4% of its production by 2022.

Personally, I believe CONSOL is doing a decent job of controlling its costs and angling itself for success over the long term by focusing its coal production contracts on utilities unlikely to switch to natural gas. But I also recognize that investors' distaste of the coal industry and apathy toward natural gas drillers could easily push CONSOL lower over the near term.

Bob Ciura 
Offshore oil drillers have been hit brutally hard by the collapse in commodity prices over the past year, and one of the worst among them is Diamond Offshore (NYSE:DO). Shares of this stock are down to $25 apiece, which amounts to a 32% decline just since the start of the year.

Source: Diamond Offshore.

The reason for such a precipitous decline, of course, is because Diamond's fundamentals are rapidly deteriorating due to the oil crash. Like most other offshore drillers, it has had to idle rigs to respond to lower demand from its oil and gas customers, which has caused massive writedowns. Diamond lost $256 million last quarter, compared to a $146 million profit in the same quarter last year, and revenue fell 12% year over year. The company took impairment charges on eight rigs, three of which -- the Ocean Saratoga, Ocean Worker, and Ocean Yorktown -- are to be cold stacked in the Gulf of Mexico.

As a result of its crumbling fundamentals, Diamond has had to make some tough decisions to save cash. It did this by cutting its dividend earlier this year. Previously, it typically paid a $0.125 regular quarterly dividend plus a $0.75-per-share supplemental dividend each quarter, which together added up to $0.875 paid per quarter. However, the company recently discontinued its supplemental dividend, and last quarter paid just the $0.125 distribution. This is an 85% reduction from the 2014 quarterly dividends.