I am a recent member of this group but I am activitly engaged in Oil and Gas Exploration in the Gulf Coast of Texas. As such I have access to the Drilling Info service in Texas that has an enormous amount of information on permits, drilling wells and production history. I do not have access to the same service in Oklahoma.
Since I have a small mineral interest in Grady County and there is a well in the section next to where I own an interest and other wells permitted neaby I was interested in seeing what a Woodford shale well might produce over the short term and the long term. Having no direct access (except the OCC website which seems a little hard to manage much less download in the first place) I looked at the Barnett shale play just across the river in North Texas and the Eagleford shale play in far South Texas. The Barnett play has some age (10+ years) on it and the Eagleford is much younger. Both these plays are in what is known as "tight reservoirs" which is the same type reseervoir that the Woodford Shale is classified as. The advances in drilling techniques, especially the horiaontal aspect, and the improvement in fracturing techniques has opened up many areas besides Oklahoma to production out of shale reservoirs.
What i have found out is a generalization and will not reflect exactly in the performance of a given well that anybody has a royalty interest in. Since my conslusions are from "out of State", if anyone has some direct information on the decline rate of a given Woodford shale well or wells please chime in.
Looking at the above mentioned reservoirs I find that the declline rate of gas produced declines about 50 to 80% in the first two to three years of initial production and then levels out and can produce for another 10 to 15 years. The oil production seems to decline faster and can be 80 to 90% down in the same two or three year period. I had no break out of condensate with the gas to look at. There will be wells in the Woodford that have more oil with the gas produced and some with less and wells that produce gas only.
Again, I have no direct info on the Woodford except for initial tests. The play in Grady is somewhat new and a better view of the production would be to look in the eastern part of the play that has a longer history if anyone has access to this kind of information. A production result from a 5 or 10 year history in the Woodford shale would be most useful.
I am posting this to demonstrate what happens in the real world of tight shale reservoirs as opposed to what someone may hope happens. The initial tests in a given well may look very promising and that well may live up to the initial results. But overall, the decline curves are a historical fact and, in general, a decline will take place at some rate in any well.
The upside of this is the number of wells that can be drilled in a 640 acre unit. In the Counties north of Grady the spacing may be as small as 80 acres which could put 8 wells into the 640 acre unit. All the wells in the unit would not give exactly the same results as to initial production or decline rates. Some would be better than others. With the forced pooling in Oklahoma all royalty interest owners in that 640 would share in every well drilled there. The operator of that unit would decide how many wells to drill in the unit and when. The royalty owner has no part of this decision by the operator.