well testing in oil and gas engineering .pdf

All you need to know

1. Network of Excellence in Training
Dominique Bourdet
Introduction to Well
Testing
and Interpretation
WCP1 Course

2. 2
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•Introduction
•Well Testing Procedures and Hardware
•Examples of Typical Flow regimes
•Conclusions
Well Testing and Interpretation

3. 3
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Description of a Well Test
Time, t
Rate, q Pressure, p
t
BU
t
Dd
p
Dd
p
BU
p
i
p(t=0)
drawdown build-up
Drawdown :
Build-up :  pptpt  ()( )0 pppt
i
()

4. 4
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Well Test Objectives
•EXPLORATION WELL
•APPRAISAL WELL
•DEVELOPMENT WELL

5. 5
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Well Test Objectives
•EXPLORATION
–Nature and rate of produced fluid
–Initial pressure
–Reservoir properties

6. 6
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Well Test Objectives
–Reservoir properties
•permeability
•heterogeneity
•reservoir boundaries
–Well productivity
–Fluid properties (sampling)
•APPRAISAL

7. 7
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Well Test Objectives
–Reservoir properties
•drainage mechanism (permanent gauges)
•communication between wells
–Well productivity
–Average pressure
•DEVELOPMENT

8. 8
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Information obtained from Well Testing
–Reservoir responses
•Reservoir in dynamic condition (flow lines are
established)
•Large volume investigated (averaging)p
–Results
•Permeability (horizontal kand vertical k
v)
•Reservoir heterogeneities
–natural fractures,
–layering,
–change of characteristics.
•Pressure (initial p
iand average )
•Boundaries (distance and shape)
•RESERVOIR DESCRIPTION

9. 9
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Information obtained from Well Testing
•WELL DESCRIPTION
–Results
•Production potential
–productivity index PI,
–skin factor S
•Well geometry

10. 1
0
Network of Excellence in Training I S O
input system output
Inverse problem : O / I
=
S
Direct problem : I
* S
=
O
Interpretation Methodology

11. 1
1
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Input Data required for Well Test Analysis
•TEST DATA
–Flow rate (sequence of event)
–Bottom hole pressure
•WELL DATA
–Wellbore radius r
wand geometry
–Depths (formation, gauges)

12. 1
2
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Input Data required for Well Test Analysis
•RESERVOIR AND FLUID PARAMETER
–Formation thickness h(net)
–Porosity 
–Formation volume factor B
–Oil viscosity 
–Compressibility of oil c
o, water c
wand formation
c
f,water saturation S
w 
fwwwot
cScScc 1

13. 1
3
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Types of Well Tests
–Drawdown test
–Build-up test
–Injection test / fall-off test
–Interference test and pulse test
–Gas well test
•Flow after flow test,
•Isochronal test,
•Modified isochronal test
•PROCEDURE

14. 1
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Types of Well Tests
•COMPLETION
–Production test
–Drill stem test (DST)

15. 1
5
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Test Sequence (oil well)
–Clean-up period (drilling and completion fluids, no measurement)
–Initial shut-in (pressure gauge at depth, initial pressure p
i)
–Variable rate (start of rate measurement)
–Stabilized rate (main flow)
–Shut-in: build-up periodTime, t
Clean
up
Initial
shut-in
Variable
rate
Stabilized
rate
Build-up
Time, t
Rate,
q Pressure, p
Clean
up
Initial
shut-in
Variable
rate
Stabilized
rate
Build-up

16. 1
6
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Drill Stem TestFlowhead
BOP Stack
Casing
Tubing
Test tool
Packer
Flowhead
BOP Stack
Casing
Tubing
Test tool
Packer
•ONSHORE
TESTING

17. 1
7
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Drill Stem Test
•OFFSHORE TESTINGFixed Rig (100 m maximum)
Fixed point at
Packer
Fixed Rig (100 m maximum)
Fixed point at
Packer

18. 1
8
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Drill Stem Test
•Cased hole
DST STRINGS
–Open hole
packer
–Barefoot
–Zonal Isolation
•Openhole

19. 1
9
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Surface Equipment
•FLOW HEAD: flowing, killing, wireline
•CHOKE MANIFOLD : positive & adjustable
•HEATER: hydrates, high viscosity
•SEPARATOR: metering of three phases
•TANK: oil rate
•BURNER

20. 2
0
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Surface Equipment
SURFACE SETUP
Burner
Burner
Heater
Separator
Surge
tank
Air
compressor
Water
pump
Rig HP
pump
Gas
OilWater
Choke
maniflod
Flowhead
Transfer pump
Oil
manifold
Gas
manifold

21. 2
1
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Test Separator
•RATE MEASUREMENT
–Oil and water: positive displacement
–Gas: orifice meterEffluent
Water Oil
Gas
Effluent
Water OilWater Oil
Gas
•THREE PHASES: oil, water and gas

22. 2
2
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Down Hole Equipment
•PRESSURE GAUGES : memory or surface read out
•DOWN HOLE VALVE : DST, sampling
•BOTTOM HOLE SAMPLER : PVT analysis
•RFT, MDT: initial pressure, gradient & contacts,
permeability

23. 2
3
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Safety
•EQUIPMENT: pressure, temperature, sour gas
•PROCEDURE: pressure test, emergency shut-
down, day / night, safe area
•ENVIRONMENT: burning, oil drop out

24. 2
4
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Wellbore Storage


 r
rw
pi
pw

25. 2
5
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Wellbore Storage
•
Time, t
Rate, q Pressure, p
q
Surface
q
Sand Face
t
Dd
p
Dd
t
BU
p
BU

26. 2
6
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Wellbore Storageg
V
C
u


non-eruptive well:wo
Vc
p
V
C 



C: wellbore storage coefficient
(Bbl/psi)
with
c
o : fluid compressibility
V
w : wellbore volume

27. 2
7
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Wellbore Storaget
C
qB
p 
24
•Straight lineon linear scale(at the beginning of
the response)Elapsedtime,t
Pressure change,

p
m
WBS
Elapsedtime,t
Pressure change,

p
m
WBS

28. 2
8
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Radial Flow Regime (infinite
homogeneous behavior)




 


 p
wf
r
w r
r
i
p
p
i
S = 0
p
wf
r
w r
r
i
p
p
i
S = 0

29. 2
9
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Radial Flow Regime
(infinite homogeneous behavior)r
w r
p
wf
(S=0)
p
wf
(S>0)
r
i
pskin
p
p
i
S > 0
r
w r
p
wf
(S=0)
p
wf
(S>0)
r
i
pskin
p
p
i
r
w r
p
wf
(S=0)
p
wf
(S>0)
r
i
pskin
p
p
i
S > 0
P
wf
(S<0)
p
skin
p
i
P
wf
(S=0)
S < 0

30. 3
0
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Radial Flow Regime
(infinite homogeneous behavior)Skin
p
qB
kh
S 
2.141
•SKIN:
•DAMAGED WELL(S>0):poorcontactbetween
thewellandthereservoir(mud-cake,insufficient
perforationdensity,partialpenetration)orinvadedzone
•STIMULATED WELL(S<0):surfaceof
contactbetweenthewellandthereservoirincreased
(fracture,horizontalwell)orstimulatedzone

31. 3
1
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Radial Flow Regime
(infinite homogeneous behavior)
Equivalent wellbore radius:S
err
wwe

 w
S
w
S
S
SwSw
r
r
kh
qB
r
r
hk
qB
pp ln
2.141
ln
2.141
0,,


  
w
S
S
SwSw
r
r
k
k
pp
qB
kh
S ln1
2.141
0,, 










Radial steady state flow:
rw
rs
ks
k

32. 3
2
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Radial Flow Regime
(infinite homogeneous behavior)





 S
rc
k
t
kh
qB
p
wt
87.023.3loglog6.162
2


•Semi-log
straight
lineLogt
Pressure change,

p
m
p
(1hr)
Logt
Pressure change,

p
m
p
(1hr)

33. 3
3
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Radial Flow Regime
(infinite homogeneous behavior)
•RESULTS:
1. the semi-log straight line slope m: the permeability km
qB
kh

6.162 









 23.3log151.1
2
hr 1
wt
rc
k
m
p
S

2. the straight line intercept: the skin factor S

34. 3
4
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Radial Flow Regime
(infinite homogeneous behavior)
-Low
permeability
-High
permeability
0
2000
4000
6000
0 10 20 30 40
time, hours
pressure, psi
no skin
moderate skin
0
2000
4000
6000
0 10 20 30 40
time, hours
pressure, psi
high skin
very high skin

35. 3
5
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Radial Flow Regime
(infinite homogeneous behavior)
-Low
permeability
0
1000
2000
3000
0.001 0.01 0.1 1 10 100
time, hours
pressure change, psi
no skin
moderate skin
p skin
-High
permeability
0
1000
2000
3000
0.001 0.01 0.1 1 10 100
time, hours
pressure change, psi
high skin
very high skin
p skin

36. 3
6
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Fractured Well: Linear Flow Regime
•INFINITECONDUCTIVITY FRACTURE
xf

37. 3
7
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Fractured Well: Linear Flow Regimet
kchx
qB
p
tf



06.4 Pressure change,

p
m
LF
t
Pressure change,

p
m
LF
t
•Straight line
with the
pressure versus
the square root
of time

38. 3
8
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Example
•SEMI-LOG ANALYSIS0
500
1000
1500
2000
2500
3000
1.00E-03 1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02
time, hours
pressure change,
psi
Flow rate : 1000 BOPD
Fluid Volume-Factor : 1.2000 vol/vol
Fluid Viscosity :0.500E+00 CP
porosity : 25.0000 %
net thickness : 30.000 FEET
well-bore radius :0.300E+00 FEET
Total Compres:0.185E-04 1/psi
Straight line slope : m = psi/cycle
Straight line pressure at 1 hour : Dp(1hr)= psi
Permeability thickness : kh = md.ft
Skin factor S =

39. 3
9
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•SEMI-LOG ANALYSIS10
-3
10
-2
10
-1
10
0
10
1
3000.
3500.
4000.
4500.
5000.
5500.
Delta-T (hr)
P PSI
SLOPE
Perm-Thickness = 380. MD-FEET
permeability = 12.7 MD
skin = 5.69
prod. time=0. hr at rate=1000.000 STB/D
R(inv) at 22.63 hr = 356. FEET
R(inv) at 1.188 hr = 81.7 FEET
slope of the line = -256.673 PSI/cycle
1996/01/01-1000 : OIL
Example

40. 4
0
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Closed Reservoir: Pseudo Steady
State Regimerrw
pi
re
pw

41. 4
1
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Closed Reservoir: Pseudo Steady State Regime








 rrwpi
re
pw

42. 4
2
Network of Excellence in Trainingrrwpi
re
pw
Closed Reservoir: Pseudo Steady
State Regime

43. 4
3
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Time, t
Pressure, p
p
i
p
-
Closed Reservoir: Pseudo Steady
State Regime
•Straight line on linear scale

44. 4
4
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Closed Reservoir: Pseudo Steady State Regime
–At late time, 








SC
r
A
kh
qB
t
hAc
qB
p
A
wt
87.0351.0log
log6.162234.0
2

 *
234.0
mc
qB
hA
t

–Result:the reservoir pore volume

45. 4
5
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Well Responses
•FLOW REGIMES
–Geometry of the flow lines :
radial, linear, spherical, etc.
–Pressure : (t) =
etc.ttt  1,,log
–Straight line on a specialized pressure versus time plot.

46. 4
6
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Well Responses
•WELL RESPONSES
–Fractured well:
–Well in a channel:
1. Linear
2. Radial
1. Radial
2. Linear

47. 4
7
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Build-up analysis
•Semi-logscale: Horner plot
Pressure,
psia
(tp + t) / t
1 10
1
10
2
10
3
10
4
3000
3250
3500
3750
4000
Pressure,
psia
(tp + t) / t
1 10
1
10
2
10
3
10
4
3000
3250
3500
3750
4000

48. 4
8
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Type Curve analysis
•Log-log ScaleDim ensionless tim e,t
D
C
D
10
-1
1

10 10
2
10
3
10
4
Dim ensionless Pressure, p
D
10
2
10
1
10
-1
C
D
e
2S
Start of sem i-log radial flow

49. 4
9
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Derivative Analysis
1.0E+00
1.0E+01
1.0E+02
1.0E+03
1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02
t, hours

p and

p', psi
derivative
pressure
•Well withwellbore storage& skinin a
homogeneous reservoir

50. 5
0
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Derivative Analysis
Dimensionless pressure, p
D
10
2
10
1
10
-1
10
-1
1 10 10
3
10
4
10
5
C
D
e
2S
10
3
3
10
30
10
20
10
15
10
10
10
6
10
4
0.3
10
2
Approximate
end of
wellbore
storage
DAMAGED
NORMAL
ACIDIZED
10
40
10
50
10
60
10
8
10
1
10
3
10
4
10
6
10
8
10
10
10
15
10
20
10
30
10
40
10
50
10
60
10
30
10
20
10
15
10
10
10
6
10
4
10
2
10
60
10
40
10
3
10
8
10
3
1
0.3
C
D
e
2S
10
50
2
10
1
10
-1
10
-1
1 10 10 10
3
10
4
10
5
Dimensionless time, t
D/C
D
C
D
e
2S
10
3
3
10
30
10
20
10
15
10
10
10
6
10
4
0.3
10
2
Approximate
end of
wellbore
storage
DAMAGED
NORMAL
ACIDIZED
10
40
10
50
10
60
10
8
10
1
10
3
10
4
10
6
10
8
10
10
10
15
10
20
10
30
10
40
10
50
10
60
10
30
10
20
10
15
10
10
10
6
10
4
10
2
10
60
10
40
10
3
10
8
10
3
1
0.3
C
D
e
2S
10
50
10
1
10
-1
10
-1
1 10
2
10
3
10
4
10
5
C
D
e
2S
10
3
3
10
30
10
20
10
15
10
10
10
6
10
4
0.3
10
2
Approximate
end of
wellbore
storage
DAMAGED
NORMAL
ACIDIZED
10
40
10
50
10
60
10
8
10
1
10
3
10
4
10
6
10
8
10
10
10
15
10
20
10
30
10
40
10
50
10
60
C
D
e
2S
10
3
3
10
30
10
20
10
15
10
10
10
6
10
4
0.3
10
2
Approximate
end of
wellbore
storage
DAMAGED
NORMAL
ACIDIZED
10
40
10
50
10
60
10
8
10
1
10
3
10
4
10
6
10
8
10
10
10
15
10
20
10
30
10
40
10
50
10
60
10
3
10
4
10
6
10
8
10
10
10
15
10
20
10
30
10
40
10
50
10
60
10
30
10
20
10
15
10
10
10
6
10
4
10
2
10
60
10
40
10
3
10
8
10
3
1
0.3
C
D
e
2S
10
50
•Well withwellbore storage& skinin a
homogeneous reservoir

51. Network of Excellence in Training
Testing
End of Module