Tutorials_2_DDT oil and gas industry exp

النفط والغاز المستوى الرابع

1. Drawdown Test
Tutorial-2
By Eng. MAbbas

2. Pore
volume
By Eng. MAbbas

3. Exercise (1)
•A constant-rate drawdown test was run in an oil well with the following data:
Ø= 0.039 B
o=1.136 rbbl/stbC
t=17 10
-6
psi
-1
Q
o=250 STBOPD
µ
O=0.8 cph=69 ft r
w=0.198 ft
Determine:
1-Formation permeability
2-Skin Factor
3-Pressure drop due to skin
4-Flow efficiency and damage ratio
5-Reservoir pore volume
6-Determine the geometry and drainage area
of the test well.
Time(hrs) Pwf(psi)
0 4412
0.12 4272
0.2 4201
0.3 4122
0.4 4057
0.5 3995
0.6 3953
0.7 3912
0.8 3884
0.9 3857
1 3822
1.94 3699
2.79 3653
4.01 3636
4.82 3616
5.78 3607
6.94 3600
8.32 3593
14.4 3573
Time(hrs)Pwf(psi)
17.3 3567
20.7 3561
24.9 3555
29.8 3549
35.8 3544
43 3537
51.5 3532
61.8 3526
74.2 3521
89.1 3515
107 3509
128 3503
154 3497
185 3490
222 3481
266 3472
319 3460
383 3446
460 3429
By Eng. MAbbas

4. 2800
3000
3200
3400
3600
3800
4000
0 50 100 150 200 250 300 350 400 450 500
Pressure ,Pwf,psi
Flowing Time,hrs
DRAW DOWN TEST,Cartesian data plot
3530 psi
By Eng. MAbbas

5. 3400
3450
3500
3550
3600
3650
3700
1 10 100 1000
Pressure ,Pwf,psi
Flowing Time,hrs
DDT,Semi log data plot)
3652 psi
By Eng. MAbbas

6. 100
1000
0.1 1 10 100 1000
(Pi
-
Pwf),psi
flowing time ,hrs
DDT,log-log data plot
WBS
By Eng. MAbbas

7. From log-log plot data:
Time at the beginning of transient period=12 hrs
Time at the end of transient period=150 hrs
From semi-log plot data:
P
1hr=3652psi
The slop of the middle time m =-70 psi/cycle
1-Formation permeability =
2-Skin Factor
By Eng. MAbbas

8. 3-Pressure drop due to skin factor:
4-
Damage ratio is estimated as
2.3
= 1-
386.9
891
=0.43=43%
By Eng.MAbbas

9. 3
5)
By Eng. MAbbas

10. =5.456(−70
−0.222
)+????????????2.303(3652−3530)
−70
EXP
=31.08
From Table 2.1 CA=31.08 corresponds to a well in the center of circle ,square or hexagon
The Drainage area can be calculated as the following
=(3,315,367∗(5.615
43460(0.39)(69)
)
=15.9 acres
A
6)
By Eng. MAbbas

11. Wellbore Storage-Unloading
Bottomhole
Rate
Surface Rate
Rate
Time
0
By Eng. MAbbas

12. Wellbore Storage DefinitionwbwbcVC
Fluid
Expansionwb
wb
c
wb
wb
A
.
g
g
.
A
C


6525
6155
144


Changing
liquid level
By Eng. MAbbas

13. Example-2(Wellbore Storage)
The following data is given for an oil well that is scheduled for a drawdown
test:
•volume of fluid in the wellbore = 180 bbl
•tubing outside diameter = 2 inches
•Wellbore diameter = 7.675 inches
•average oil density in the wellbore = 45 lb/ft3
•h = 50 ft, φ= 15 %, rw= 0. 25 ft, μo = 2 cpk = 30 md, s = 0 ,ct= 20 ×10−6
psi−1, co = 10 ×10−6 psi−1
If this well is placed under a constant production rate,
Calculate:
•the wellbore storage coefficient C.
•How long will it take for wellbore storage effects to end?
By Eng. MAbbas

14. Solution:
1-Calculate the wellbore storage factor caused by fluid expansion:
2-Calculate the wellbore storage factor caused by falling fluid level:
By Eng. MAbbas

15. 3-Calculate the total wellbore storage coefficient:
4-Time required for wellbore storage influence to end:
Solution:
By Eng. MAbbas

16. Any Questions??????????
By Eng. MAbbas