We've poked and prodded Gulfport Energy (Nasdaq: GPOR) extensively over the past two weeks. I think we finally have enough ammunition to take a shot at valuation.

From Louisiana, with love
Let's start with Gulfport's legacy assets on the Gulf Coast -- its West Cote Blanche Bay (WCBB) and Hackberry fields.

Average transaction multiples in the industry are currently running around $65,000 per flowing barrel, or $15 per barrel of proved reserves. The recent purchase of EXCO Resources (NYSE: XCO) assets by Encore Acquisition (NYSE: EAC) is one example.

Applying these multiples, the WCBB is worth $201 million to $214 million. Given the age and location of the field, plus the high percentage of undeveloped and "developed non-producing" reserves, I would discount the midpoint of this range -- but not too heavily, because the WCBB's "oiliness" largely offsets its other shortcomings. Let's knock off 10% and call it $187 million.

Similar multiples applied to Hackberry yield a range of $24 million to $43 million. Gulfport spent $5 million on a 3D seismic survey in 2005, which underlines Hackberry's prospectivity, and makes me inclined to weight the play's reserves more heavily than current production. Giving a two-thirds weighting to our reserves metric provides an estimated value of $37 million. Adding the seismic program (at cost) bumps our estimate to $42 million.

Permian and other production
In putting a price tag on the Permian, we need to consider Gulfport's recent follow-on acquisition, which boosted its acreage position by about 50%. Weighting our reserve and production metrics equally, and increasing July production and 2008 proved reserves by 50% each, yields an estimated value of $122 million.

In May, Gulfport sold 12,270 net acres in the Bakken, producing 190 barrels per day, for $13 million. Applying a similar value to its retained acreage, we get $7 million, and to its retained production, we get $9 million -- so call it $8 million. Talisman Energy (NYSE: TLM) sold Bakken assets at a similar valuation earlier this year, adding confidence to this estimate.

Gulfport's equity investment in a pair of Wexford Capital-controlled ventures in Thailand is carried on the books at $4 million. I'll go along with that.

Our running total sits at $363 million.

Great balls of bitumen
Next is Gulfport's 25% stake in Grizzly Oil Sands. To value Grizzly, which has no production, we'll look at both transaction multiples and public company valuations.

Conveniently, a high-profile deal was recently announcedbetween privately held Athabasca Oil Sands Corp. and PetroChina (NYSE: PTR). The deal sees PetroChina taking a 60% stake in two of AOSC's prized projects for $1.7 billion. That gives the newcomer a net interest in approximately 3 billion barrels of recoverable resources, according to AOSC.

Despite the temptation, it would be a serious mistake to slap this $0.57/barrel transaction multiple on Grizzly's 4 billion barrel estimate, for at least two reasons. First is that this estimate was generated by Grizzly, not independent engineers.

Second, size matters. AOSC's defined resources are highly concentrated within certain flagship properties. MacKay River, for example, is expected to ramp up to 150,000 barrels per day. Dover is even bigger, ranking just behind Suncor 's (NYSE: SU) Firebag and ConocoPhillips ' (NYSE: COP) Surmont project in scope. See deep-pocketed investor drool.

In contrast, Grizzly's properties are diffuse and smaller in scale. The biggest single-property bitumen accumulation that the company has reported, at Silvertip, is only 831 million barrels in place. Economically recoverable reserves would be a sliver of that number. Continued...