Hi, RioDeJaneiro62! I googled very quick declinerates for Haynesville. Here:

http://shale.typepad.com/haynesvilleshale/2009/07/chesapeake-energy-haynesville-shale-decline-curve.html

On the right at this site you can see other links, amoung them "bakken". Here from Chesapeake:

Chesapeake Energy Corporation now believes that its first year decline rate is slightly higher than before at 85%, compared to 81% in the previous release. The company increased its initial production rate for each well during the first 24 hours from 10 mmcfe to 14.1 mmcfe. The Estimated Ultimate Recovery (EUR) for each well remains the same at 6.5 Bcfe.

And here comes the best point, cause the thing is that the well will "pay off" itself much quicker this way:

Since the natural gas is produced quicker from the well, the rate of return that Chesapeake Energy Corporation realizes is higher, assuming that all other inputs are the same.

The company said that its can achieve a rate of return of 42%, excluding any benefit from its partnership deal in the Haynesville Shale with Plains Exploration & Production Company (PXP) The inputs the company uses are:

Ok, this is their numbers and it from july31 last year,2009:

Flat NYMEX natural gas prices of $7.00 per mcf
Well cost of $7.5 million
EUR of 6.5 Bcfe
85% first year decline rate
Initial 24 production rate of 14.1 mmcf

I hope they correct/ajust back the sp. Well, I try to copy the chart:

http://shale.typepad.com/.a/6a011570a2f205970b0115724d2de6970b-pi" />