Shares in Glencore (LSE: GLEN) Premier Oil (LSE: PMO) and Tullow Oil (LSE: TLW) have risen by between 60% and 80% so far this year.

With oil and other commodities apparently on the rise once more, will these stocks continue to rise and deliver a 100% gain for 2016?

A heavyweight turnaround

Glencore’s share price has risen by 80% so far this year, thanks to a blizzard of debt-reducing asset sales. The ongoing $2bn-plus operating profit from the group’s trading business has also reassured investors who believed this might not be possible at lower commodity prices.

The combination of these achievements and stabilising commodity prices has triggered a big change for Glencore. After a year of downgrades, analysts have turned positive on it over the last month and increased their 2016 net profit forecast by 7.5% to $664.8m. In 2017, net profit is expected to rise by 70% to $1,139m.

This still leaves Glencore shares looking pricey, on 32 times 2017 forecast earnings. However, it’s worth remembering that Glencore’s earnings have averaged around 20 cents per share over the last six years. At the current share price, that’s equivalent to about 12 times earnings.

For investors with a medium-term outlook, I believe Glencore shares aren’t overly expensive and could deliver further gains. A 100% gain in 2016 is definitely possible.

A far riskier play

Premier had net debt of $2.2bn at the end of 2015. To put that in context, it’s almost nine times the firm’s all-time peak profit of $252m from 2012.

Of course, Premier’s profits aren’t going to be anything like that high in 2016 or 2017. Analysts expect the firm to report a loss of $80m for this year, and a profit of just $4.89m for next year.

Premier is planning another $700m of capital expenditure in 2016, mainly to complete the Solan and Catcher projects. The firm doesn’t expect to start generating a meaningful amount of free cash flow to reduce debt until 2018. At this point, production is expected to be 80-90,000 barrels of oil equivalent per day, with an average operating cost of $15/barrel.

This situation could work out well, but it may not. Shareholders may yet face a cash call to help reduce debt levels. In my view, it doesn’t make any sense to buy shares in Premier at the moment. There are too many unknowns.

A strong oil play

Tullow’s position is stronger than that of Premier. The firm is expected to report a profit for this year and next year. However, investors still need to be wary of Tullow’s $4bn net debt. How will this be reduced?

In Tullow’s recent AGM presentation the group said it expects to generate free cash flow in the final quarter of 2016. In 2017, Tullow believes it will be able to start paying down its debt. The firm’s Ghana assets are expected to have operating costs of just $8/bbl at this time, suggesting free cash flow could rise rapidly.

Tullow shares now trade on a 2017 forecast P/E of 16. I suspect they could rise further, although personally I’d rather wait until Tullow’s debt levels fall — or until the shares spike down to provide a buying opportunity.

However, as with Glencore, I believe Tullow shares could double in 2016 if conditions continue to improve.

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Roland Head has no position in any shares mentioned. The Motley Fool UK has recommended Tullow Oil. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.