2018 Artificial Lift Strategies for
Unconventional Wells Workshop Cox Convention Center, Oklahoma City, OK
February 4 – 7, 2018
Well Performance Modeling in
Unconventional Oil and Gas
Wells
Adeoluwa Oyewole
Mohan Kelkar
Eduardo Pereyra
Cem Sarica
Outline
Introduction
Approach
Results
Conclusions
References
2 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Nodal Analysis
3 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
∆𝑞
𝑞𝑔 =703 𝑥 10−6 𝑘ℎ 𝑃𝑟
2 − 𝑃𝑤𝑓2
𝑇𝜇𝑧 𝑙𝑛𝑟𝑒𝑟𝑤− 0.75 + 𝑆
PSS IPR
Artificial Lift
Time
What is different for wells in
Unconventional Formations? …
When bottomhole pressure is altered, a new
transient is introduced to the well
performance
The well does not reach pseudo-steady
state for a long period of time
An instantaneous nodal analysis plot cannot
provide information about the future well
performance
4 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Objective
Predict the performance – when the
operating conditions are altered by an
artificial lift system – of a producing well in
an unconventional formation
Simple, analytical solution to complex flow
behavior
Improve on the current methods which use
conventional well performance models for nodal
analysis
5 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Approach
Assumptions
Analytical model
Pseudo-pressure transform
Well performance model
6 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Assumptions
Prior performance of the well is available
By changing the tubing conditions, we do
not change reservoir properties
In general, when artificial lift method is
installed, the bottom hole pressure is
reduced
7 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Assumptions …
An unconventional well is producing under
transient conditions (linear flow)
Linear flow constant-rate pressure transient
for slightly compressible flow 𝚫𝑷
𝒒= 𝒎 𝒕 + 𝚫𝑷𝑺𝑼
8 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Assumptions …
Flow regime validation
9 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
100000
1000000
10000000
1 10 100 1000
∆m(p
)/q
G
Time, days
Assumptions …
Both the rate and pressure can vary
To account for variable rate and variable
pressure, we use the concept of superposition
time
10 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
11 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Assumptions …
“Data Bias in Rate Transient Analysis of Shale Gas Wells” by Agnia (2012)
Superposition time on the
production rate
Analytical model
Linear flow constant-rate pressure transient
with superposition 𝚫𝑷
𝒒= 𝒎 𝒕𝒔𝒑 + 𝚫𝑷𝑺𝑼
Superposition time
𝒕𝒔𝒑 = 𝒒𝒊 − 𝒒𝒊−𝟏𝒒𝒏
𝒕 − 𝒕𝒊−𝟏
𝒏
𝒊=𝟏
12 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Analytical model …
Non-linear change in fluid properties with
pressure
Pseudo-pressure transformation for
Gas production
Multiphase oil & gas production
13 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pseudo-pressure transform …
Real gas pseudo-pressure
𝒎 𝑷 = 𝟐 𝑷
𝝁𝒈𝒛
𝑷
𝟎𝒅𝒑
𝝁𝒈, 𝒛 = 𝒇(𝑷)
𝒎 𝑷 = 𝒇(𝑷)
14 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Pseudo-pressure transform …
In conventional oil wells, gas-oil-ratio (GOR)
behavior is dependent on average reservoir
pressure
For unconventional oil wells, GOR behavior
is a strong function of well flowing pressure
GOR trend also depends on flow regime,
fracture properties, and degree of under-
saturation
15 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
16 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pseudo-pressure transform …
SPE 184397 “Producing-Gas/Oil-Ratio Behavior of Multifractured Horizontal Wells in Tight Oil Reservoirs” by R. Steven Jones Jr.
17 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pseudo-pressure transform …
SPE 184397 “Producing-Gas/Oil-Ratio Behavior of Multifractured Horizontal Wells in Tight Oil Reservoirs” by R. Steven Jones Jr.
18 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pseudo-pressure transform …
SPE 184397 “Producing-Gas/Oil-Ratio Behavior of Multifractured Horizontal Wells in Tight Oil Reservoirs” by R. Steven Jones Jr.
Pseudo-pressure transform …
Pwf < Pb
Multiphase (oil + water + gas) flow
2-phase pseudopressure (oil + gas)
Fetkovich (1973)
𝒎 𝑷 = 𝒌𝒓𝒐(𝒑)
𝝁𝒐𝑩𝒐
𝑷𝒊𝑷𝒘𝒇
𝒅𝒑
𝒌𝒓𝒐 = 𝒇(𝑺𝒐)
𝒎 𝑷 = 𝒇(𝑷, 𝑺𝒐)
19 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
20 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pseudo-pressure transform …
0
2000
4000
6000
8000
10000
0 50 100 150 200 250 300 350
GO
R, S
CF
/ST
B
Time, days
0
1000
2000
3000
4000
5000
0 50 100 150 200 250 300 350
Pw
f, p
sia
Time, days
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.3 0.5 0.8 1.0
krg
kro
So
GAS/OIL
Core Rock and Fluid Properties
(Swir, Sor , Sgc , …)
Corey (1976) 2-phase relative
permeability equations
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.3 0.5 0.8 1.0
krw
kro
Sw
WATER/OIL
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.3 0.5 0.8 1.0
krw
krg
Sw
GAS/WATER
LOOK-UP TABLES
21 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Pseudo-pressure transform …
Constant Composition Expansion (CCE)
𝑘𝑟𝑔
𝑘𝑟𝑜= 𝐺𝑂𝑅 − 𝑅𝑠 ∗
𝜇𝑔𝐵𝑔
𝜇𝑜𝐵𝑜
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.3 0.5 0.8 1.0
krg
kro
So
GAS/OIL
CCE
Assumptions
Conventional Unconventional
Fixed compositon in
multiphase region Constant GOR in
transient linear flow
GOR = f(So) @
Pwf = Pavg
Pwf has greater
effect on GOR
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000 5000
So
Pwf, psia
PRESSURE – SATURATION RELATIONSHIP
Pseudo-pressure transform …
Two-phase pseudo-pressure
𝒎 𝑷 = 𝒌𝒓𝒐𝝁𝒐𝑩𝒐
𝑷𝒊
𝑷𝒘𝒇
𝒅𝒑
22 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Pwf
BAKER (1988) 3-PHASE OIL
RELATIVE PERMEABILITY
EQUATION So kro
𝝁𝒐, 𝑩𝒐
PRESSURE-SATURATION
RELATIONSHIP
PVT CORRELATIONS
Well performance model
Model equation
𝚫𝑷
𝒒= 𝒎 𝒕𝒔𝒑 + 𝚫𝑷𝑺𝑼
𝚫𝒎(𝒑)
𝒒= 𝒎 𝒕𝒔𝒑 + 𝚫𝒎(𝒑)𝑺𝑼
Obtain coefficients defining the past well
performance Slope, m
Intercept
Match past well performance
𝚫𝒎(𝒑)
𝒒= 𝒎 𝒕𝒔𝒑 + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
23 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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24 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Well performance model …
When the bottomhole pressure is changed,
the new rate is calculated by assuming a
new transient in the well is introduced
0
2500
5000
7500
10000
0 500 1000 1500 2000
q o
il o
r g
as
Time
𝑖𝑛𝑐𝑟𝑒𝑚𝑒𝑛𝑡𝑎𝑙 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛
25 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Well performance model …
Forecast future performance
𝒒 =∆𝒎 𝒑 −𝒎( 𝒒𝒊−𝒒𝒊−𝟏 𝒕𝒏−𝒕𝒊−𝟏 − 𝒒𝒏−𝟏 𝒕𝒏−𝒕𝒏−𝟏
𝒏−𝟏𝒊=𝟏 )
𝒎 (𝒕𝒏−𝒕𝒏−𝟏)+𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
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Results
Gas well example
Oil well example
27 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Gas well example
Initial Reservoir Pressure = 5,000 psi
Bottomhole Temperature = 160 deg. F
Gas Gravity = 0.567
0
400
800
1200
1600
2000
0
800
1600
2400
3200
0 200 400 600
qW
, b
pd
qG, M
scfD
Time, Days
qG - MscfD qW - bpd
0
2000
4000
6000
0 200 400 600 800
Pw
f, p
sia
Time, Days
28 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Gas well example …
100000
1000000
10000000
1 10 100 1000
∆m(p
)/q
G
Time, days
29 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Gas well example …
0
300000
600000
900000
1200000
1500000
1800000
0 5 10 15 20 25 30 35 40 45
∆m(p
)/q
G
√tSUP
Slope, m
Intercept
30 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Gas well example …
𝜟𝒎(𝒑)
𝒒= 𝒎 𝒕𝒔𝒑 + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
0
1000
2000
3000
4000
0 100 200 300 400 500 600
qG, M
scfD
Time, Days
qG - Well Data qG - Superposition Fit
0
1000
2000
3000
4000
0 100 200 300 400 500 600 700 800 900
qG, M
scfD
Time, Days
qG - Well Data qG - Model Forecast
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Oklahoma City, OK Feb. 4 - 7, 2018
Gas well example …
Artificial Lift
at ~ 780 days
𝒒 =∆𝒎 𝒑 −𝒎( 𝒒𝒊 − 𝒒𝒊−𝟏 𝒕𝒏 − 𝒕𝒊−𝟏 − 𝒒𝒏−𝟏 𝒕𝒏 − 𝒕𝒏−𝟏
𝒏−𝟏𝒊=𝟏 )
𝒎 (𝒕𝒏 − 𝒕𝒏−𝟏) + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
32 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Gas well example …
𝒒 =∆𝒎 𝒑 −𝒎( 𝒒𝒊 − 𝒒𝒊−𝟏 𝒕𝒏 − 𝒕𝒊−𝟏 − 𝒒𝒏−𝟏 𝒕𝒏 − 𝒕𝒏−𝟏
𝒏−𝟏𝒊=𝟏 )
𝒎 (𝒕𝒏 − 𝒕𝒏−𝟏) + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
0
1000
2000
3000
4000
0 100 200 300 400 500 600 700 800 900
qG, M
scfD
Time, Days
qG - Well Data qG - Model Forecast
33 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example
Initial Reservoir Pressure = 6318 psi.
Bottomhole Temperature = 207 deg. F
Gas Gravity = 0.65
Oil API = 45 deg.
0
1000
2000
3000
4000
0
400
800
1200
1600
2000
0 20 40 60
qG, M
scfD
qO, st
bD
Time, Days
qO - Well Data qG - Well Data
0
2000
4000
6000
8000
0
1000
2000
3000
4000
5000
0 10 20 30 40
Pw
f, p
sia
GO
R,
scf/
stb
Time, Days
GOR Pwf Bubble Point Pressure
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Oil well example …
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.2 0.4 0.6 0.8 1.0
krg
kro
Sg
krg kro
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.2 0.4 0.6 0.8 1.0
krw
kro
Sw
kro krw
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.2 0.4 0.6 0.8 1.0
krw
krg
Sw
krw krg
0.0
0.3
0.5
0.8
1.0
0.0
0.3
0.5
0.8
1.0
0.0 0.2 0.4 0.6 0.8 1.0
krg
kro
Sg
krg kro
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000 5000
Oil
Sa
tura
tio
n,
So
Pwf, psia
35 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
Constant Composition Expansion (CCE)
𝒌𝒓𝒈
𝒌𝒓𝒐= 𝑮𝑶𝑹− 𝑹𝒔 ∗
𝝁𝒈𝑩𝒈
𝝁𝒐𝑩𝒐
36 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
0.1
1
10
1 10 100
∆m(p
)/q
O
Time, days
37 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
0.0
0.5
1.0
1.5
2.0
2.5
0 2 4 6 8 10
∆m(p
)/q
O
√ tsup
Slope, m
Zero-Intercept
38 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
𝜟𝒎(𝒑)
𝒒= 𝒎 𝒕𝒔𝒑 + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
0
500
1000
1500
2000
2500
0 5 10 15 20 25 30 35 40
qO, st
bD
Time, Days
qO - Well Data qO - Superposition Fit
39 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
𝒒 =∆𝒎 𝒑 −𝒎( 𝒒𝒊 − 𝒒𝒊−𝟏 𝒕𝒏 − 𝒕𝒊−𝟏 − 𝒒𝒏−𝟏 𝒕𝒏 − 𝒕𝒏−𝟏
𝒏−𝟏𝒊=𝟏 )
𝒎 (𝒕𝒏 − 𝒕𝒏−𝟏) + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60 70 80
qO, st
bD
Time, Days
qO - Well Data qO - Model Forecast
40 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Oil well example …
𝒒 =∆𝒎 𝒑 −𝒎( 𝒒𝒊 − 𝒒𝒊−𝟏 𝒕𝒏 − 𝒕𝒊−𝟏 − 𝒒𝒏−𝟏 𝒕𝒏 − 𝒕𝒏−𝟏
𝒏−𝟏𝒊=𝟏 )
𝒎 (𝒕𝒏 − 𝒕𝒏−𝟏) + 𝒊𝒏𝒕𝒆𝒓𝒄𝒆𝒑𝒕
0
500
1000
1500
2000
2500
0 10 20 30 40 50 60 70 80
qO, st
bD
Time, Days
qO - Well Data qO - Model Forecast
41 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Conclusions
Traditional nodal analysis methods do not
accurately predict the transient performance
of unconventional wells
Rigorous and simple analytical method is
proposed based on readily-available field
data using the superposition principle
42 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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Conclusions …
In summary, the developed model
Captures past well performance by
assuming the well is producing under
transient linear flow for reasonable period
Matches past well performance with
superposition to determine coefficients
used to predict the future performance
Future performance is predicted under
existing or changing conditions
43 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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References
Baker, L. E. (1988, January 1). Three-Phase Relative Permeability Correlations. Society
of Petroleum Engineers. doi:10.2118/17369-MS
Corey, A.T., Rathjens, C.H., Henderson, J.H. and Wyllie, M.R.J.: "Three-Phase Relative
Permeability," J. Pet. Tech. (Nov. 1956) 8, 63-65; Trans .• , AIME (1956) 20i, 349-351.
Fetkovich, M. J. (1973, January 1). The Isochronal Testing of Oil Wells. Society of
Petroleum Engineers. doi:10.2118/4529-MS.
Jones, R. S. (2016, August 1). Producing Gas-Oil Ratio Behavior of Tight Oil Reservoirs.
Unconventional Resources Technology Conference. doi:10.15530/URTEC-2016-
2460396
Shahamat, Mohammad Sadeq, S. Hamed Tabatabaie, Louis Mattar, and Ehsan
Motamed. "Inflow Performance Relationship for Unconventional Reservoirs (Transient
IPR)." Inflow Performance Relationship for Unconventional Reservoirs (Transient IPR) -
OnePetro. Society of Petroleum Engineers, 20 Oct. 2015.
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44 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
Disclaimer
45 2018 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 4 - 7, 2018
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46 2018 Artificial Lift Strategies for Unconventional Wells Workshop
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