Introduction to Nodal Analysis
Introduction to Nodal Analysis Instructional Objectives
1. Expl xplai ain n the con concep ceptt of of Nod odal al Ana nallysi ysis. s. 2. List List 4 seg segm men entts in the rese eserrvoi voirr/wel elll system system whe herre pressu pressurre loss occurs. 3. Defi efine ne the fol olllow owiing term erms: s: infl nflow ow pe perrform orman ance ce curve, outflow performance curve, system graph, solution node.
Introduction to Nodal Analysis Instructional Objectives
1. Expl xplai ain n the con concep ceptt of of Nod odal al Ana nallysi ysis. s. 2. List List 4 seg segm men entts in the rese eserrvoi voirr/wel elll system system whe herre pressu pressurre loss occurs. 3. Defi efine ne the fol olllow owiing term erms: s: infl nflow ow pe perrform orman ance ce curve, outflow performance curve, system graph, solution node.
Pressure Losses in Well System P4 = (Pwh - Psep) Pwh
Gas
Psep
Sales line
Liquid
Stock tank
P3 = Pwf - Pwh
Pwf
P1 = Pr - Pwfs
= Loss in reservoir
P2 = Pwfs - Pwf
= Loss across completion
P3 = Pwf - Pwh
= Loss in tubing
P4 = Pwh - Psep
= Loss in flowline
PT = Pr - Psep
= Total pressure loss
Pwfs
P1 = (Pr - Pwfs) P2 = (Pwfs - Pwf)
Pr
Pe
Nodal Analysis P4 = (Pwh - Psep) Pwh
Gas
Psep
Sales line
Liquid
Stock tank
P3 = Pwf - Pwh
Pwf
P1 = Pr - Pwfs
= Loss in reservoir
P2 = Pwfs - Pwf
= Loss across completion
P3 = Pwf - Pwh
= Loss in tubing
P4 = Pwh - Psep
= Loss in flowline
PT = Pr - Psep
= Total pressure loss
Pwfs
P1 = (Pr - Pwfs) P2 = (Pwfs - Pwf)
Pr
Pe
Inflow Performance Curve 3500
Inflow (Reservoir) Curve i 3000 s p , e r 2500 u s s e r p e2000 l o h m o1500 t t o b g n1000 i w o l F 500
0 0
500
1000
1500
2000
2500
3000
3500
4000
4500
Outflow Performance Curve 3500
Outflow (Tubing) Curve
3000
i s p , e r 2500 u s s e r p e2000 l o h m o1500 t t o b g n1000 i w o l F 500
0 0
500
1000
1500
2000
2500
3000
3500
4000
4500
System Graph 3500
Inflow (Reservoir) Curve Outflow (Tubing) Curve
3000
i s p , e r 2500 u s s e r p e2000 l o h m o1500 t t o b g n1000 i w o l F
1957.1 psi
500
2111 STB/D
0 0
500
1000
1500
2000
2500
3000
3500
4000
4500
Solution Node At Wellhead P4 = (Pwh - Psep) Pwh
Gas
Psep
Sales line
Liquid
Stock tank
P3 = Pwf - Pwh
Pwf
P1 = Pr - Pwfs
= Loss in reservoir
P2 = Pwfs - Pwf
= Loss across completion
P3 = Pwf - Pwh
= Loss in tubing
P4 = Pwh - Psep
= Loss in flowline
PT = Pr - Psep
= Total pressure loss
Pwfs
P1 = (Pr - Pwfs) P2 = (Pwfs - Pwf)
Pr
Pe
System Graph - Wellhead Node 1600
Inflow Curve Outflow Curve
1400
i s p1200 , e r u s s1000 e r p d a 800 e h l l e w 600 g n i w o 400 l F
500 psi
200
2050 STB/D
0 0
500
1000
1500
2000
2500
3000
Nodal Analysis : Uses • Estimation of Reservoir Parameters e.g Skin 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 Analysis Two 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 Reservoir Pressure Inflow e d o N t a e r u s s e r P
Operating Point
Pressure PWF
Operating Flowrate
Flowrate (stb/d)
Outflow
The Inflow Performance Relationship Dependent On: • 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
Effect of Skin on IPR
e d o N t a e r u s s e r P
Inflow (IPR)
Outflow SKIN
10
5
0
-1
qo Flowrate
-3 1/ ln re +S rw
Note : Log effect
Effect of Pressure Depletion on IPR Reservoir with no pressure support
e d o N t a e r u s s e r P
Inflow
Outflow
Oil Recovery (% STOIIP) 12
8
Flowrate
4
0
The Outflow Performance Relationship Dependent On: • 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
Effect of Tubing Size on Outflow For a Tubing Restricted Well Inflow (IPR) e d o N t a e r u s s e r P
Outflow 2 3/8” 2 7/8”
3 1/2”
Flowrate (stb/d)
4 1/2”
Solution Procedures for Oil wells
3
1
Node location 1. separator 3. Pwh 6. Pwf 8. Pr
6
8
Solution at bottom of the well
3
1
Node location 1. separator 3. Pwh 6. Pwf 8. Pr
6
8
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
Assumed rate, Pwf for constant Pwf for Vogel, b/d J, psi van de • ___ Klik omhet __ ___ opmaakprofiel _____________ ___modeltekst __ psi 200 2000 2000
te__________ bewerken __ ________ 400
Tweede ______ • _____niveau 600 Derde ____ ______ niveau 800 Vierde _____niveau ______
1000
Vijfde _____niveau ______
1500
1800
1800
1600
1590
1400
1350
1200
1067
700
Pressure 100 psi
Pwh
f t 0 0 0 1 t , h g n e L
Assumed rate, b/d 200
Pwh (required horiz), psi 2000
400
1800
600
1600
800
1400
1000
1200
1500
700
Pressure 100 psi
Pwf
D e p t h , 1 0 0 0 f t
Assumed rate, b/d
Pwh horiz, Psi
200
115
Tubing intake (node outflow), psi 750
400
140
880
600
180
1030
800
230
1225
1000
275
1370
1500
420
1840
Rate (Vogel)
Rate (linear)
Solution at top of the well
3
1
Node location 1. separator 3. Pwh 6. Pwf 8. Pr
6
8
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
Assumed rate, Pwf for constant Pwf for Vogel, b/d J, psi van de • ___ Klik omhet __ ___ opmaakprofiel _____________ ___modeltekst __ psi 200 2000 2000
te__________ bewerken __ ________ 400
Tweede ______ • _____niveau 600 Derde ____ ______ niveau 800 Vierde _____niveau ______
1000
Vijfde _____niveau ______
1500
1800
1800
1600
1590
1400
1350
1200
1067
700
Pressure 100 psi
Pwh
f t 0 0 0 1 t , h g n e L
Pressure 100 psi
Pwh
D e p t h , 1 0 0 0 f t
Rate (linear)
Rate (Vogel)
Solution node at the separator
3
1
Node location 1. separator 3. Pwh 6. Pwf 8. Pr
6
8
