Page 332 - Fundamentals of Reservoir Engineering

REAL GAS FLOW: GAS WELL TESTING 267

If it is assumed that these expressions will not change throughout the producing
lifetime of the well then, for a given plateau rate of 5 MMscf/d, the duration of the
plateau production is determined by the value of p wf. If this pressure drops below the
level

m(p ) − m(p wf n ) p (psia)
i
i
Qn 4300
2
(psia / cp / Mscf/d) 4290
5000 4280

4000
4000

3000
0 10 20 30 40 Q (MMscf/d)
n
Fig. 8.9 Gas well test analysis assuming semi-steady state conditions during each
flow period. Data; table 8.3

required to maintain the minimum allowable wellhead pressure then the rate must be
reduced. Therefore, at this point the values of m(p wf ) in both the above equations must
be equal and

() =
∆ mp 86 Q + .007 Q 2
and for Q = 5 MMscf/d

2
6
×
∆ m () p = .605 10 psia / cp
Also

2p
∆ mp ∆ p
() =
µΖ

and using the data in table 8.1 for p= 1200 psi