well testing
TRANSCRIPT
Network of Excellence in Training
Dominique Bourdet
Introduction to Well Testing and Interpretation
WCP1 Course
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• Introduction
• Well Testing Procedures and Hardware
• Examples of Typical Flow regimes
• Conclusions
Well Testing and InterpretationWell Testing and Interpretation
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Description of a Well TestDescription of a Well Test
Time, t
Ra
te,
q
P
ress
ure
, p
t BU
t Dd
p Ddp BU
p i
p(t=0)
drawdown build-up
Drawdown :
Build-up : p p t p t ( ) ( )0
p p p ti ( )
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Well Test ObjectivesWell Test Objectives
• EXPLORATION WELL
• APPRAISAL WELL
• DEVELOPMENT WELL
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Well Test ObjectivesWell Test Objectives
• EXPLORATION
– Nature and rate of produced fluid
– Initial pressure
– Reservoir properties
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Well Test ObjectivesWell Test Objectives
– Reservoir properties
• permeability
• heterogeneity
• reservoir boundaries
– Well productivity
– Fluid properties (sampling)
• APPRAISAL
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Well Test ObjectivesWell Test Objectives
– Reservoir properties
• drainage mechanism (permanent gauges)
• communication between wells
– Well productivity
– Average pressure
• DEVELOPMENT
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Information obtained from Well TestingInformation obtained from Well Testing
– Reservoir responses• Reservoir in dynamic condition (flow lines are
established)
• Large volume investigated (averaging)
p
– Results
• Permeability (horizontal k and vertical kv)
• Reservoir heterogeneities– natural fractures,
– layering,
– change of characteristics.
• Pressure (initial pi and average )
• Boundaries (distance and shape)
• RESERVOIR DESCRIPTION
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Information obtained from Well TestingInformation obtained from Well Testing
• WELL DESCRIPTION– Results
• Production potential
– productivity index PI,
– skin factor S
• Well geometry
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I S O
input system output
Inverse problem : O / I = S
Direct problem : I * S = O
Interpretation MethodologyInterpretation Methodology
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Input Data required for Well Test AnalysisInput Data required for Well Test Analysis
• TEST DATA
– Flow rate (sequence of event)
– Bottom hole pressure
• WELL DATA
– Wellbore radius rw and geometry
– Depths (formation, gauges)
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Input Data required for Well Test AnalysisInput Data required for Well Test Analysis
• RESERVOIR AND FLUID PARAMETER
– Formation thickness h (net)
– Porosity – Formation volume factor B
– Oil viscosity
– Compressibility of oil co, water cw and formation cf, water saturation Sw
fwwwot cScScc 1
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Types of Well TestsTypes 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
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Types of Well TestsTypes of Well Tests
• COMPLETION
– Production test
– Drill stem test (DST)
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Test Sequence (oil well)Test Sequence (oil well)
– Clean-up period (drilling and completion fluids, no measurement)
– Initial shut-in (pressure gauge at depth, initial pressure pi)
– Variable rate (start of rate measurement)
– Stabilized rate (main flow)
– Shut-in: build-up period
Time, t
Cleanup
Initialshut-in
Variablerate
Stabilizedrate
Build-up
Time, t
Rat
e, q
Pre
ssu
re, p
Cleanup
Initialshut-in
Variablerate
Stabilizedrate
Build-up
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Drill Stem TestDrill Stem Test
Flowhead
BOP Stack
Casing
Tubing
Test toolPacker
Flowhead
BOP Stack
Casing
Tubing
Test toolPacker
• ONSHORE TESTING
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Drill Stem TestDrill Stem Test
• OFFSHORE TESTING
Fixed Rig (100 m maximum)
Fixed point at Packer
Fixed Rig (100 m maximum)
Fixed point at Packer
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Drill Stem TestDrill Stem Test
• Cased hole
DST STRINGS
– Open hole packer
– Barefoot
– Zonal Isolation
• Open hole
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Surface EquipmentSurface Equipment
• FLOW HEAD: flowing, killing, wireline
• CHOKE MANIFOLD: positive & adjustable
• HEATER: hydrates, high viscosity
• SEPARATOR: metering of three phases
• TANK: oil rate
• BURNER
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Surface EquipmentSurface EquipmentSURFACE 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
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Test SeparatorTest Separator
• RATE MEASUREMENT– Oil and water: positive displacement– Gas: orifice meter
Effluent
Water Oil
Gas
Effluent
Water OilWater Oil
Gas
• THREE PHASES: oil, water and gas
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Down Hole EquipmentDown 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
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SafetySafety
• EQUIPMENT: pressure, temperature, sour gas
• PROCEDURE: pressure test, emergency shut-down,
day / night, safe area
• ENVIRONMENT: burning, oil drop out
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Wellbore StorageWellbore Storage
rrw
pi
pw
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Wellbore StorageWellbore Storage
•
Time, t
Rat
e, q
Pre
ssu
re, p
q Surface
q Sand Face
tDd
pDd
tBU
pBU
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Wellbore StorageWellbore Storage
gV
C u
non-eruptive well:
woVcpV
C
C : wellbore storage coefficient
(Bbl/psi)
with
co : fluid compressibility
Vw : wellbore volume
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Wellbore StorageWellbore Storage
tC
qBp
24
• Straight line on linear scale (at the beginning of the response)
Elapsed time, t
Pre
ssu
re c
han
ge,
p
Elapsed time, t
Pre
ssu
re c
han
ge,
p
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Radial Flow Regime Radial Flow Regime (infinite
homogeneous behavior)
pwf
rw rrip
pi
S = 0
pwf
rw rrip
pi
S = 0
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
rw r
pwf(S=0)
pwf(S>0)
ri
p skin
p
pi
S > 0
rw r
pwf(S=0)
pwf(S>0)
ri
p skin
p
pi
rw r
pwf(S=0)
pwf(S>0)
ri
p skin
p
pi
S > 0
Pwf(S<0)
p skin
pi
Pwf(S=0)
S < 0
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
SkinpqB
khS
2.141• SKIN:
• DAMAGED WELL (S > 0): poor contact between the well and the reservoir (mud-cake, insufficient perforation density, partial penetration) or invaded zone
• STIMULATED WELL (S < 0): surface of contact between the well and the reservoir increased (fracture, horizontal well) or stimulated zone
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
Equivalent wellbore radius: Serr wwe
w
S
w
S
SSwSw r
rkh
qBrr
hkqB
pp ln2.141
ln2.141
0,,
w
S
SSwSw r
rkk
ppqB
khS ln1
2.141 0,,
Radial steady state flow:
rwrs
ks
k
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
S
rc
kt
khqB
pwt
87.023.3loglog6.162 2
• Semi-log straight line
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
• RESULTS:
1. the semi-log straight line slope m : the permeability k
mqB
kh
6.162
23.3log151.1 2
hr 1
wtrc
kmp
S
2. the straight line intercept: the skin factor S
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
- Low
permeability
- High
permeability
0
2000
4000
6000
0 10 20 30 40
time, hours
pre
ssu
re,
psi
no skin
moderate skin
0
2000
4000
6000
0 10 20 30 40
time, hours
pre
ssu
re,
psi high skin
very high skin
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Radial Flow RegimeRadial Flow Regime (infinite homogeneous behavior)
- Low
permeability
0
1000
2000
3000
0.001 0.01 0.1 1 10 100
time, hours
pres
sure
cha
nge,
psi
no skin
moderate skin
p skin
- High
permeability
0
1000
2000
3000
0.001 0.01 0.1 1 10 100
time, hours
pres
sure
cha
nge,
psi
high skin
very high skin
p skin
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Fractured Well: Linear Flow RegimeFractured Well: Linear Flow Regime
• INFINITE CONDUCTIVITY FRACTURE
xf
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Fractured Well: Linear Flow RegimeFractured Well: Linear Flow Regime
tkchx
qBp
tf
06.4
Pre
ssu
re c
han
ge,
p
t
Pre
ssu
re c
han
ge,
p
t
• Straight line with the pressure versus the square root of time
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ExampleExample• SEMI-LOG ANALYSIS
0
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
pre
ssu
re c
han
ge
, psi
Flow rate : 1000 BOPD
Fluid Volume-Factor : 1.2000 vol/volFluid Viscosity :0.500E+00 CPporosity : 25.0000 %
net thickness : 30.000 FEETwell-bore radius :0.300E+00 FEETTotal Compres:0.185E-04 1/psi
Straight line slope : m = psi/cycleStraight line pressure at 1 hour : Dp(1hr)= psiPermeability thickness : kh = md.ft
Skin factor S =
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• SEMI-LOG ANALYSIS
10 -3 10 -2 10 -1 10 0 10 1
3000
.35
00.
4000
.45
00.
5000
.55
00.
Delta-T (hr)
P P
SI
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
ExampleExample
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Closed Reservoir: Pseudo Steady Closed Reservoir: Pseudo Steady State Regime State Regime
rrwpire
pw
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Closed Reservoir: Pseudo Steady State RegimeClosed Reservoir: Pseudo Steady State Regime
rrwpi re
pw
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rrwpi re
pw
Closed Reservoir: Pseudo Steady Closed Reservoir: Pseudo Steady State Regime State Regime
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Time, t
Pre
ssu
re, p
pi
p-
slope m*
pseudo steady state
Closed Reservoir: Pseudo Steady Closed Reservoir: Pseudo Steady State Regime State Regime• Straight line on linear scale
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Closed Reservoir: Pseudo Steady State RegimeClosed Reservoir: Pseudo Steady State Regime
– At late time,
SC
r
Akh
qBt
hAcqB
p
A
wt
87.0351.0log
log6.162234.0 2
*234.0
mcqB
hAt
– Result: the reservoir pore volume
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Well ResponsesWell 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.
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Well ResponsesWell Responses
• WELL RESPONSES
– Fractured well:
– Well in a channel:
1. Linear
2. Radial
1. Radial
2. Linear
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Build-up analysisBuild-up analysis• Semi-log scale: Horner plot
Pre
ssu
re,
psi
a
(tp + t) / t
1 101 102 103 104
3000
3250
3500
3750
4000
slope m
Pre
ssu
re,
psi
a
(tp + t) / t
1 101 102 103 104
3000
3250
3500
3750
4000
slope m
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Type Curve analysisType Curve analysis• Log-log Scale
Dimensionless time,tDCD
10-1 1 10 102 103 104
Dim
en
sio
nle
ss
Pre
ss
ure
, p
D
102
10
1
10-1
CDe2SStart of semi-log radial flow
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Derivative AnalysisDerivative 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 a
nd
p',
psi
derivative
pressure
• Well with wellbore storage & skin in a homogeneous reservoir
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Derivative AnalysisDerivative Analysis
Dim
ensi
onl
ess
pre
ssur
e, p
D
102
10
1
10-1
10-1 1 10 103 104 105
CD e 2S
103
3
1030
1020
1015
1010
106 104
0.3
102
Approximateend ofwellborestorage
DAMAGED
NORMAL
ACIDIZED
104010501060
108
101
103
104
106
108
1010
1015
1020
1030
1040
1050
1060
1030
1020
1015
1010
106
104
102
1060
1040
103
108
103
10.3
CD e 2S
1050
2
10
1
10-1
10-1 1 10 10 103 104 105
Dimensionless time, tD/CD
CD e 2S
103
3
1030
1020
1015
1010
106 104
0.3
102
Approximateend ofwellborestorage
DAMAGED
NORMAL
ACIDIZED
104010501060
108
101
103
104
106
108
1010
1015
1020
1030
1040
1050
1060
1030
1020
1015
1010
106
104
102
1060
1040
103
108
103
10.3
CD e 2S
1050
10
1
10-1
10-1 1 10 2 103 104 105
CD e 2S
103
3
1030
1020
1015
1010
106 104
0.3
102
Approximateend ofwellborestorage
DAMAGED
NORMAL
ACIDIZED
104010501060
108
101
103
104
106
108
1010
1015
1020
1030
1040
1050
1060
CD e 2S
103
3
1030
1020
1015
1010
106 104
0.3
102
Approximateend ofwellborestorage
DAMAGED
NORMAL
ACIDIZED
104010501060
108
101
103
104
106
108
1010
1015
1020
1030
1040
1050
1060
103
104
106
108
1010
1015
1020
1030
1040
1050
1060
1030
1020
1015
1010
106
104
102
1060
1040
103
108
103
10.3
CD e 2S
1050
• Well with wellbore storage & skin in a homogeneous reservoir
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Testing
End of Module