My, hasn't this been a fun stretch for investors in energy -- particularly those investing heavily in natural gas plays or energy service stocks? I'm still happy with good old PetroChina (NYSE:PTR), but there seems to be a smoking crater in my portfolio where various energy-service stocks used to be.

Ultra Petroleum (AMEX:UPL), one of the best natural gas independents out there, has had tough times of its own. True, it hasn't been as badly bloodied as Chesapeake (NYSE:CHK), but it has taken a worse hit than the likes of Apache (NYSE:APA), Occidental (NYSE:OXY), or XTO (NYSE:XTO).

Worse yet, Ultra has taken this recent beating despite strong, steady fundamentals. In the company's very good fourth quarter, revenue jumped 87% on the tag-team combo of 25% higher production and 49% higher realizations for gas prices, while operating income and net income both nearly doubled.

I'm very impressed with the expense picture here. If you strip out the higher production taxes that Ultra had to pay, costs per Mcf seem to have risen only about 6%. Given what we're hearing left and right about higher drilling dayrates, service costs, and production expenses, that's an achievement.

Looking at the assorted statistica relevant to energy stocks, we see that finding and development costs were just $0.56 per Mcfe (or about $3.36 per barrel). That's a great number, as is the reserve replacement figure of 773% and the 32% increase in proved reserves.

The hitch here is pretty clear to anybody who's held an energy stock in the past couple of months: It's great when energy is going higher, but not so much fun when prices are heading lower. I'm expecting (or is that hoping?) that this correction in prices will play itself out, letting energy stocks catch their second wind -- but that's just one Fool's thoughts.

I know this will rile up the Ultra Petroleum partisans once again, but this still isn't my favorite pick in the sector. I know they're a great company, but right now, I just don't find the valuation to be compelling relative to the likes of Apache, Occidental, or perhaps XTO.

For more all-natural takes on gas:

Fool contributor Stephen Simpson owns shares of PetroChina, but has no financial interest in any other stocks mentioned (that means he's neither long nor short the shares).