Not meaning to offend Bob but it is actually "The Gas Law" (PV=zRT/M) which is applicable in this case because at ~15,000 psi and roughly 825 degrees Rankin natural gas is far from an "ideal gas". (As an aside have you ever had a look at what the supercompressibility factor is for natural gas at those conditions ?? Absolutely amazing !!)
AOF (or absolute open flow) is nothing but a "calculated" rate determined from a 4 point modified isochronal test procedure. Even if the well has an AOF > 100 MMCF/d it does not require a flow at such a rate to determine that AOF. BKP will NOT flow this well at 100 MMCF/d even for 4 hours, Bob. (Besides, the tubulars to be used in the completion are apparently expected to constrain the flow to ~50 MMCF/d.)
Also, the argument which you advance is in fact not directly dependent upon a large "rate" but rather upon a large cumulative "volume". So, whatever could be accomplished with a one day test at 100 MMCF/d can be equally well accomplished with a 5 day test at a lesser rate of only 20 MMCF/d.
I do not know the California regulations with respect to "flaring" on well tests, but I'll be very surprised if their flare license grants BKP a cumulative flare volume exceeding 100 MMCF. It may well be far less than that. As an example, if the well were in Alberta, I would bet on a maximum flare volume of about 50 MMCF.
So, given that the JV will have a flare license restriction to work within, if they really want to learn as much as they can about this reservoir with their flow test, their test will look something like the following (assuming flare permit = 50 MMCF):
1) A 4 hour "cleanup flow" at say 5 MMCF/d following their completion of the well.
2) An overnight shut in.
3) A 4 hour flow at ~5 MMCF/d.
4) A 4 hour shut-in.
5) A 4 hour flow at ~10 MMCF/d.
6) A 4 hour shut-in.
7) A 4 hour flow at ~20 MMCF/d.
8) A 4 hour shut-in.
9) A 4 hour flow at ~40 MMCF/d.
10)A 126 hour flow at about 7 MMCF/d.
11)A shut in of ~260 hours.
Note: I have not performed any calculations to verify that the lower rates (5-7 MMCF/d) are in fact sufficient to prevent liquid loading of the well. If they are marginal, those rates would have to be increased and the final flow period would be shortened.
The pressure\rate\time data of the test will be subjected to a comprehensive transient pressure analysis that will tell the JV lots of very interesting things about their reservoir. BUT unfortunately and although everyone thinks it will, it will tell them nothing very "definitive" about the size of their reservoir UNLESS it is much smaller than everyone seems to be anticipating !! (If you care to understand why, all you need to do is perform an error analysis on "The Gas Law" applied at pre and post test conditions.)
I expect that this might put your calculator in service for an hour or two. <gg>
Have a pleasant evening.
Later,
grayhairs |
