Shares in mega-miner BHP Billiton (LSE: BLT) may be up by 55% from their January low of 572p, but they are still trading a whopping 46% below their 52-week high of 1,637p.

Frustrated but patient

That means that many investors who bought the stock hoping for a recovery are still underwater. I know I am. And although I’m frustrated that I bought too early, I’m not too concerned about the running loss on my position. I reckon I’ll get my money back if I’m patient.

BHP has used the commodity downturn to take a ruthless look at operating costs and spending plans within its business. Costs have fallen significantly in many areas. For example, unit cash costs in BHP’s main iron ore business fell by 25% during the six months to 31 December. Cash unit costs for Queensland coal fell by 17%.

Despite last year’s drop in the price of iron ore, the red stuff still generates an underlying operating margin of 36% for BHP. When commodity prices start to recover, these low costs mean that profits will rise very quickly indeed.

In the meantime, I’m happy to collect my reduced dividend payment and hold onto my shares.

The debt scare is over

Glencore (LSE: GLEN) stock crashed to a low of 66p in September, prompting the firm’s chief executive Ivan Glasenberg to get serious about reducing Glencore’s debt levels.

The results so far have been impressive. Asset sales worth $1.6bn have been agreed. Net debt has fallen from $30.5bn to $26.9bn. Net debt is expected to fall to $17-18bn by the end of 2016 and a further $4-5bn of asset sales are planned.

Glencore shares have rebounded and are now up by 136% from their September low. The question is how much more is there to come? Unlike BHP, Glencore’s profits come from trading commodities as well as from mining. Although trading profits have proved to be relatively stable, some of Glencore’s mines are less competitive. Costs are higher than those of some peers.

This could slow the speed at which Glencore’s profits rebound with any recovery in commodity prices. Despite this, I think further gains are likely for patient Glencore shareholders.

An outsider with big potential

If you’re interested in smaller firms with the potential to double bag, then one possible choice is Ophir Energy (LSE: OPHR). Ophir’s shares have fallen by 52% over the last year, but offer significant long-term potential.

Ophir owns large stakes in several very large gas deposits off the coast of Africa. The group has 2C resources — a measure of oil and gas that’s known to exist but not yet commercial — of 901 million barrels of oil equivalent off the coasts of Tanzania and Equatorial Guinea.

A decision is due later this year on whether to develop the Equatorial Guinea project. I think Ophir shares are probably worth significantly more than their current price, and could regain last year’s high of 171p.

However, I believe the risk of disappointment is higher than with BHP. This is because Ophir still needs to sell or develop its assets to realise their value. Current production from the former Salamander Energy assets is not enough to justify Ophir’s £554m market cap.

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