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
ΔP4 = (Pwh - Psep) Pwh Psep
Liquid Gas

Sales line Stock tank

ΔP1= Pr - Pwfs ΔP3 = Pwf - Pwh ΔP2 = Pwfs - Pwf ΔP3 = Pwf - Pwh ΔP4 = Pwh - Psep ΔPT = Pr - Psep

= Loss in reservoir = Loss across completion = Loss in tubing = Loss in flowline = Total pressure loss

Pwf

Pwfs

Pr

Pe

ΔP1 = (Pr - Pwfs) ΔP2 = (Pwfs - Pwf)
Adapted from Mach et al, SPE 8025, 1979.

Nodal Analysis
ΔP4 = (Pwh - Psep) Pwh Psep
Liquid Gas

Sales line Stock tankΔP1 = Pr - Pwfs ΔP3 = Pwf - Pwh ΔP2 = Pwfs - Pwf ΔP3 = Pwf - Pwh ΔP4 = Pwh - Psep ΔPT = Pr - Psep

= Loss in reservoir = Loss across completion = Loss in tubing = Loss in flowline = Total pressure loss

Pwf

Pwfs

Pr

Pe

ΔP1 = (Pr - Pwfs) ΔP2 = (Pwfs - Pwf)
Adapted from Mach et al, SPE 8025, 1979.

Inflow Performance Curve
3500

Inflow (Reservoir) Curve Flowing bottomholepressure, psi
3000

2500

2000

1500

1000

500

0 0 500 1000 1500 2000 2500 3000 3500 4000 4500

Production rate, STB/D

Outflow Performance Curve
3500

Flowing bottomhole pressure, psi

3000

Outflow (Tubing) Curve

2500

2000

1500

1000

500

0 0 500 1000 1500 2000 2500 3000 3500 4000 4500

Production rate, STB/D

System Graph
3500

Flowing bottomholepressure, psi

3000

Inflow (Reservoir) Curve Outflow (Tubing) Curve

2500

1957.1 psi
2000

1500

1000

500

2111 STB/D

0 0 500 1000 1500 2000 2500 3000 3500 4000 4500

Production rate, STB/D

Solution Node At Wellhead
ΔP4 = (Pwh - Psep) Pwh Psep
Liquid Gas

Sales line Stock tank

ΔP1 = Pr - Pwfs ΔP3 = Pwf - Pwh ΔP2 = Pwfs - Pwf ΔP3 = Pwf - Pwh ΔP4 = Pwh - Psep ΔPT = Pr- Psep

= Loss in reservoir = Loss across completion = Loss in tubing = Loss in flowline = Total pressure loss

Pwf

Pwfs

Pr

Pe

ΔP1 = (Pr - Pwfs) ΔP2 = (Pwfs - Pwf)
Adapted from Mach et al, SPE 8025, 1979.

System Graph - Wellhead Node
1600 1400

Inflow Curve Outflow Curve

Flowing wellhead pressure, psi

1200 1000 800

500 psi
600 400 200 0 0 500 1000 1500 2000 25003000

2050 STB/D

Production rate, STB/D

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 PerformanceCurve/Relationship (IPR) Oil or Gas Flowrate vs Bottomhole Flowing Pressure Ordinate Origin = Reservoir Pressure (Δp = 0 Abscissa Intercept = Absolute Open Flow Potential (Δp = pr • Outflow Curve (Tubing Intake) Function of Hydrostatic, Friction & Acceleration Components Curves Shifted by Wellhead Pressure & Artificial Lift • Intercept of Curves Gives FBHP (psi) & Flowrate q = Max) q = 0)

NodalAnalysis
Reservoir Pressure Inflow Pressure at Node Operating Point

Pressure PWF

Outflow

Operating Flowrate

Flowrate (stb/d)

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

Pressure at Node

Inflow (IPR) Outflow SKIN 10 5 0 -1 -3

Flowrate

ln re +S rw Note : Log effect

qo α 1/

Effect of Pressure Depletion on IPR
Reservoir with no...