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Introduction to Nodal Analysis
Introduction to Nodal Analysis Instructional Objectives
1. Explain the concept of Nodal Analysis.2. List 4 segments in the reservoir/well system where pressure
loss occurs.3. Define the following terms: inflow performance curve,
outflow performance curve, system graph, solution node.
Pressure Losses in Well System
ΔP1 = Pr - Pwfs = Loss in reservoir
ΔP2 = Pwfs - Pwf = Loss across completion
ΔP3 = Pwf - Pwh = Loss in tubing
ΔP4 = Pwh - Psep = Loss in flowline
Pr PePwfsPwf
ΔP1 = (Pr - Pwfs )ΔP2 = (Pwfs - Pwf )
ΔP3 = Pwf - Pwh
ΔP4 = (Pwh - Psep )
Psep
Sales lineGas
LiquidStock tank
ΔPT = Pr - Psep = Total pressure loss
Adapted from Mach et al, SPE 8025, 1979.
Pwh
Nodal Analysis
ΔP1 = Pr - Pwfs = Loss in reservoir
ΔP2 = Pwfs - Pwf = Loss across completion
ΔP3 = Pwf - Pwh = Loss in tubing
ΔP4 = Pwh - Psep = Loss in flowline
Pr PePwfsPwf
ΔP1 = (Pr - Pwfs )ΔP2 = (Pwfs - Pwf )
ΔP3 = Pwf - Pwh
ΔP4 = (Pwh - Psep )
Psep
Sales lineGas
LiquidStock tank
ΔPT = Pr - Psep = Total pressure loss
Adapted from Mach et al, SPE 8025, 1979.
Pwh
Inflow Performance Curve
0
500
1000
1500
2000
2500
3000
3500
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Production rate, STB/D
Flow
ing
botto
mho
le p
ress
ure,
psi
Inflow (Reservoir) Curve
Outflow Performance Curve
0
500
1000
1500
2000
2500
3000
3500
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Production rate, STB/D
Flow
ing
botto
mho
le p
ress
ure,
psi
Outflow (Tubing) Curve
System Graph
0
500
1000
1500
2000
2500
3000
3500
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Production rate, STB/D
Flow
ing
botto
mho
le p
ress
ure,
psi
Inflow (Reservoir) CurveOutflow (Tubing) Curve
2111 STB/D
1957.1 psi
Solution Node At Wellhead
Pr PePwfsPwf
ΔP1 = (Pr - Pwfs )ΔP2 = (Pwfs - Pwf )
ΔP3 = Pwf - Pwh
ΔP4 = (Pwh - Psep )
Psep
Sales lineGas
LiquidStock tank
Adapted from Mach et al, SPE 8025, 1979.
Pwh
ΔP1 = Pr - Pwfs = Loss in reservoir
ΔP2 = Pwfs - Pwf = Loss across completion
ΔP3 = Pwf - Pwh = Loss in tubing
ΔP4 = Pwh - Psep = Loss in flowline
ΔPT = Pr - Psep = Total pressure loss
System Graph - Wellhead Node
0
200
400
600
800
1000
1200
1400
1600
0 500 1000 1500 2000 2500 3000
Production rate, STB/D
Flow
ing
wel
lhea
d pr
essu
re, p
si
Inflow CurveOutflow Curve
2050 STB/D
500 psi
Nodal Analysis : Uses
• Estimation of Reservoir Parameters e.gSkin
Permeability
Reservoir Pressure
Note : Non unique solutions unless only one unknown
• Evaluation of Potential Stimulation Treatments Primarily through reduction in skin
Parameter sensitivity studies are important
Nodal AnalysisTwo Main Components
• Inflow Performance Curve/Relationship (IPR)
Oil or Gas Flowrate vs Bottomhole Flowing Pressure
Ordinate Origin = Reservoir Pressure (Δp = 0 q = 0)
Abscissa Intercept = Absolute Open Flow Potential
(Δp = pr q = Max)
• Outflow Curve (Tubing Intake)
Function of Hydrostatic, Friction & Acceleration Components
Curves Shifted by Wellhead Pressure & Artificial Lift
• Intercept of Curves Gives FBHP (psi) & Flowrate
Nodal Analysis
Inflow Operating Point
OutflowPressure PWF
Operating Flowrate
Flowrate (stb/d)
Pres
sure
at N
ode
Reservoir Pressure
• Fluid Properties• Oil
– Viscosity, Gas oil Ratio, Bubble Point– Formation Volume Factor, Density
• Gas– Viscosity, Z Factor, Compressibility– Density
• Inflow Correlation Used e.g. Oil - Darcy, Vogel, Gas - Jones, Darcy• Well Geometry i.e. Vertical or Horizontal• Formation Properties
• Reservoir Pressure • Permeability• Skin (Includes deviation, perforation, damage etc)• Net Pay Height
The Inflow Performance Relationship Dependent On:
Outflow
Flowrate
Pres
sure
at N
ode
5 0 -1 -3
SKIN
Inflow(IPR)
qo α
1/ ln re +S rw
Note : Log effect
10
Effect of Skin on IPR
Effect of Pressure Depletion on IPR
Outflow
Flowrate
Pres
sure
at N
ode
8 04
Oil Recovery (% STOIIP)
12
Reservoir with no pressure support
Inflow
• Fluid Properties• Oil
• Viscosity, Gas oil Ratio, Bubble Point• Formation Volume Factor, Density
• Gas• Viscosity, Z Factor, Compressibility• Density
• Outflow Correlation Used e.g. Oil - Duns & Ross, Gas - Gray• Friction• Completion Properties
• Tubing Size • Tubing Restrictions• Tubing Roughness
The Outflow Performance Relationship Dependent On:
Effect of Tubing Size on Outflow
Inflow(IPR)
Outflow
Flowrate (stb/d)
Pres
sure
at N
ode
For a Tubing Restricted Well
2 3/8”
2 7/8”4 1/2”3 1/2”
Solution Procedures for Oil wells
Node location 1. separator3. Pwh6. Pwf8. Pr
8
1
6
3
Solution at bottom of the well
Node location 1. separator3. Pwh6. Pwf8. Pr
8
1
6
3
Step by step solution procedure
• (1) Assume several rates and construct the IPR curve • (2) Assume several flow rates and obtain the required well
head pressures necessary to move the fluids through the horizontal flowline to the separator
• (3) Using the same assumed flowrate as step 2 and the corresponding Pwh determine Pwf
• (4) Plot IPR curve and and Pwf from step 3
• ___ __ ___ _____________ ___ __ __________ __ ________
• _____ __________ ___________ ______
_____ ______
Klik om het opmaakprofiel van de modeltekstte bewerkenTweede niveauDerde niveauVierde niveau
Vijfde niveau
Assumed rate,b/d
Pwf for constantJ, psi
Pwf for Vogel,psi
200 2000 2000400 1800 1800600 1600 1590800 1400 13501000 1200 10671500 700
Pressure 100 psi
Leng
ht, 1
000f
t
Pwh
Assumed rate,b/d
Pwh (requiredhoriz), psi
200 2000400 1800600 1600800 14001000 12001500 700
Pwf
Pressure 100 psi
Depth, 1000 ft
Assumed rate,b/d
Pwh horiz, Psi
Tubing intake(node outflow),
psi200 115 750400 140 880600 180 1030800 230 12251000 275 13701500 420 1840
Rate (Vogel)
Rate (linear)
Solution at top of the well
Node location 1. separator3. Pwh6. Pwf8. Pr
8
1
6
3
Step by step solution procedure
(1) Assume several flowrates as before(2) Start with the separator pressure and find the
required wellhead pressures to move the fluids horizontally
(3) Using the same asumed flow rates and starting from Pr find the corresponding Pwf for the reservoir to produce these rates
(4) Using the flowing pressures obtained in 3 determine the permissible wellhead pressure for these flowrates
(5) plot the wellhead pressures of step 2 vs wellhead pressures of step 4 to obtain the flowrate
• ___ __ ___ _____________ ___ __ __________ __ ________
• _____ __________ ___________ ______
_____ ______
Klik om het opmaakprofiel van de modeltekstte bewerkenTweede niveauDerde niveauVierde niveau
Vijfde niveau
Assumed rate,b/d
Pwf for constantJ, psi
Pwf for Vogel,psi
200 2000 2000400 1800 1800600 1600 1590800 1400 13501000 1200 10671500 700
Pressure 100 psi
Leng
ht, 1
000f
t
Pwh
Pwh
Pressure 100 psi
Depth, 1000 ft
Rate (linear)
Rate (Vogel)
Solution node at the separator
Node location 1. separator3. Pwh6. Pwf8. Pr
8
1
6
3
Step by step solution procedure
(1) Assume various flowrates(2) Start with the other end position at Pr and determine the
flowing borttom hole pressures necessary for the well to produce the assumed flowrates
(3) Start with the Pwf values of step 2 as tubing intake pressure and find Pwh
(4) Starting with Pwh of step 3 find the corresponding permissible separator pressures for each rate
(5) Plot the separator pressure vs rate drawing the constant separator pressure