Page 347 - Fundamentals of Reservoir Engineering

REAL GAS FLOW: GAS WELL TESTING 282

EXERCISE 8.3 PRESSURE BUILDUP ANALYSIS

Instead of applying a multi-rate flow test, the reservoir described in exercise 8.2 is
tested by producing it for 3 hours at a rate of 40 MMscf/d, closing in for an 8 hour
buildup and finally, by producing for a further 3 hours at a rate of 60 MMscf/d. The
pressures recorded during the flowing and closed in periods are listed in table 8.10 and
8.11, respectively.

Flowing time First Flow Period Second Flow Period
hrs Q 1 = 40 MMscf/d Q 2 = 60 MMscf/d

p wf m (p wf) p wf m (p wf)
2
2
psia psia /cp psia psia /cp
.75 3602 830.45 × 10 6 3076 648.61 × 10 6
1.00 3596 828.38 " 3066 645.16 "

1.25 3591 826.65 " 3059 642.74 "
1.50 3587 825.27 " 3053 640.66 "
1.75 3583 823.88 " 3048 638.93 "

2.00 3580 822.85 " 3043 637.21 "
2.25 3577 821.81 " 3038 635.48 "

2.50 3575 821.12 " 3036 634.79 "
3.00 3570 819.39 " 3029 632.37 "
TABLE 8.10

Closed in time p ws m(p ws) Closed in time p ws m(p ws)
2
2
∆t hrs psia psia /cp ∆t hrs psia psia /cp
.5 4100 1002.61×10 6 3.5 4272 1062.07×10 6
1.0 4255 1056.19 " 4.0 4274 1062.76 "
1.5 4263 1058.96 " 5.0 4276 1063.45 "

2.0 4267 1060.34 " 6.0 4277 1063.80 "
2.5 4269 1061.03 " 7.0 4278 1064.14 "

3.0 4271 1061.72 " 8.0 4279 1064.49 "
TABLE 8.11

Since the fluid properties are the same as in the two previous exercises, equ. (8.48)
can be used as the relationship between real and pseudo pressures. All other data
presented in exercise 8.2 can be used in the current exercise.

1) From the pressure buildup determine p i, k and S′.
1