Analisis Nodal

Copyright 2007, , All rights reserved

NODAL ANALYSIS


NODAL ANALYSIS

Separator

Tubing

Psep

Q

Pwf

FlowlinePwh

ΔPtubing

ΔP flowline GAS

OIL+WATER

ΔPres

Pr, IPR, K

Reservoir

IS A METHODOLOGY TO ANALYZETHE PRODUCTION SYSTEM AS ANUNIT TO CALCULATE ITS CAPACITYWITH THE OBJECTIVE OF:

• DESIGNING EACH COMPONENT OF THE PRODUCTION SYSTEM

• DETECTING PRODUCTION IMPEDIMENTS

• CALCULATING THE EFFECT OF CHANGINGONE OR MORE COMPONENTS ON THECAPACITY OF THE PRODUCTION SYSTEM

ΔP = f(Q)


pp88= = PPwhwh--PPsepsep

PPwfswfs--PPwfwf = = pp22

PPrr PPeePPwfswfsPPwfwf

PPurur

PPuvuv

PPdvdv

PPwhwh PPdsdsPPsepsep

gasgas

SeparatorSeparator

TankTank

ReservoirReservoir

FlowlineFlowline

WellWell

pp11=P=Prr--PPwfswfs

pp33= P= Purur--PPdrdr

pp44= P= Puvuv--PPdv dv

PPdrdr

pp66= P= Pdsds--PPsep sep PPwhwh--PPdsds = = pp55

pp 77

= P

= P w

fw

f-- PPw

h w

h

Surface chokeSurface choke

Safety valveSafety valve

RestrictionRestriction

pp11=P=Prr--PPwfswfs Loss in porous mediumLoss in porous mediumpp22=P=Pwfswfs--PPwfwf Loss across the completionLoss across the completionpp33=P=Purur--PPdrdr ”” ”” restrictionrestrictionpp44=P=Puvuv--PPdvdv ”” ”” safety valvesafety valvepp55=P=Pwhwh--PPdsds ”” ”” chokechokepp66=P=Pdsds--PPsepsep ”” in flow linein flow linepp77=P=Pwfwf--PPwhwh Total loss in tubingTotal loss in tubingpp88=P=Pwhwh--PPsepsep Total loss in flowlineTotal loss in flowline

POSSIBLE PRESSURE LOSSES IN A PRODUCTION SYSTEM


NODE

Pn

INFLOW OUTFLOW

UPSTREAM COMPONENTS

DOWNSTREAMCOMPONENTS

Q Q

Pu Pd

Pnode = Pu – ΔPupstream components (1) = f1(Q)

Pnode = Pd + ΔPdownstream components (2) = f2(Q)

ΔPuΔPd

NODAL ANALYSIS CONCEPT

ΔP = f (Q)


FLOW RATE, Q

NO

DE

PRES

SUR

E, P

node Outflow from node

Inflow to node

SYSTEM FLOW CAPACITY

GRAPHICAL SOLUTION OF THE PROBLEM

NODE PRESSURE

(1)

(2)


EXERCISEILUSTRATION OF NODAL ANALYSIS CONCEPT

Use the following equation to calculate the pressure drop in a pipe

L Q2

ΔP = 3.8 x 10 - 7 x ; D5

where, ΔP is the pressure drop in psi, L is the pipe length in feet, D is the pipe diameter in inches and Q the flow rate in BPD.

Calculate:

1) Actual capacity of the system in BPD.2) Capacity of the system when the diameter of the 2” pipe is increased to 3”.

Select the node at the point where the pipe diameter is reduced from 3” to 2”. Assume flow rates of 2500, 3000 y 3500, 5000, 5500, 6000 BPD.

2000 feet, Ø= 3” 1000 feet, Ø=2”

P1= 200 psi P3= 60 psi

Pnode

WATERSOURCE WATER

SINK

ΔP1 ΔP2



(1) Pnode = P1-ΔP1

(2) Pnode = P3+ΔP2

2000 feet, Ø= 3” 1000 feet, Ø=2”

P1= 200 PSI P3= 60 PSIPnode

WATERSOURCE

WATERSINK

ΔP1 ΔP2

FLOW RATE, Q

NO

DE

PRES

SUR

E, P

node

Outflow performance

Inflowperformance

Actual system flow capacity

Pnode

(1)

(2)2”



(1) Pnode = P1-ΔP1

(2) Pnode = P3+ΔP2

2000 feet, Ø= 3” 1000 feet, Ø=2”

P1= 200 PSI P3= 60 PSIPnode

WATERSOURCE

WATERSINK

ΔP1 ΔP2

FLOW RATE, Q

NO

DE

PRES

SUR

E, P

node

Outflow performance

Inflowperformance

Actual system flow capacity

Pnode

(1)

(2)2”

3”

new system flow capacitySOL


1A

876

5

4

3 21

1B

NODE LOCATION

1 SEPARATOR2 SURFACE CHOKE3 WELLHEAD4 SAFETY VALVE5 RESTRICTION6 Pwf7 Pwfs8 Pr

1A GAS SALES1B STOCK TANK

LOCATION OF VARIOUS NODES


Inflow to node:Pr – ΔPres – ΔPtubing = Pwh (1)

Outflow from node:Psep + ΔPflowline = Pwh (2)

Gas

Flow through porous media

Vertical or inclined tubing

HorizontalFlowline

Separator

Tank

Pr, k, IPR

PwhNODEPsep

ΔPtubing

ΔPres

ΔP flowline

NODAL ANALYSIS APPLICATION IN A SIMPLE PRODUCTION SYSTEM(NODE SELECTED AT THE WELLHEAD)


EFFECT OF THE FLOWLINE SIZE(NODE SELECTED AT THE WELLHEAD)

FLOWRATE, Q

WEL

LHEA

D P

RES

SUR

E, P

wh

d1

d2 > d1

INFLOW

OUTFLOW


Inflow to node:Pr – ΔPres = Pwf (1)

Outflow from node:Psep + ΔPflowline +

ΔPtubing = Pwf (2)

(NODE SELECTED AT THE BOTTOMHOLE)

NODAL ANALYSIS APPLICATION IN A SIMPLE PRODUCTION SYSTEM

Gas

Flow through porous media

Vertical or inclined tubing

HorizontalFlowline

Separator

Tank

Pr, k, IPR

Pwh

NODE

Psep

ΔPtubing

ΔPres

ΔP flowline

Pwf


EFFECT OF THE TUBING SIZE(NODE SELECTED AT THE BOTTOMHOLE)

FLOWRATE, Q

BO

TTO

MH

OLE

FLO

WIN

G P

RES

SUR

E, P

wf

INFLOWIPR

Pr

00

OUTFLOW

d1

d2>d1


TUBING DIAMETER, d

FLO

W R

ATE

, Q

UNSTABLE REGION

DIAMETER FORMAXIMUM FLOW RATE

FINDING OPTIMUM TUBING SIZE

Copyright 2007, , All rights reservedFLOW RATE, Q

BO

TT

OM

OL

E F

LO

WIN

G P

RE

SSU

RE

, Pw

f Pr

00 PRODUCTION INCREASE

1

2

d1

d2>d1

2**

2*

WELL WITHSKIN EFFECT

WELL WITHOUT SKIN EFFECT

SIMULTANEOUS EFFECT OF MINIMIZING FLOW RESTRICTIONSIN THE RESERVOIR AND IN THE PIPING SYSTEM

(NODE AT THE BOTOMHOLE)


LIQ

UID

PR

OD

UC

TIO

N R

ATE

, QL

GAS INJECTION RATE, Qgi

Available gasvolume

Economic Optimum

Maximum liquid production

LIQUID PRODUCTION RATE, QL

BO

TTO

M H

OLE

FLO

WIN

G P

RES

SUR

E, P

wf

Inflow PerformanceIPR

Pr

GLR

Excessive GLR

GAS LIFT WELL PERFORMANCE

(a) Gas lift well analysis (b) Effect of gas injection rate


FLOWRATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf

Pr

00

EFFECT OF PERFORATING DENSITY ON INFLOW

N1

N1>N2

N3>N2

N = NUMBER OF PERFORATIONS PER FOOT

OUTFLOW

INFLOW


NUMBER OF PERFORATIONS PER FOOT, N

FLO

WR

AT

E, Q

EFFECT OF PERFORATING DENSITY ON FLOW RATE


NODAL ANALYSIS APPLICATIONS

•Selecting tubing size.•Selecting Flowline size.•Gravel pack design.•Surface choke sizing.•Analyzing an existing system for abnormalflow restrictions (production impediments).

•Artificial lift system design.•Well stimulation evaluation.•Analyzing effects of perforating density.•Predicting the effect of depletion on productioncapacity.

•Allocating injection gas among gas lift wells.•Analyzing a multiwell producing system.


1. Determine which components in the system can be changed.

2. Select one component to be optimized.

3. Select the node location.

4. Develop expressions for the inflow and outflow.

5. Obtain required data to calculate the pressure drop versusflow rate fall components.

6. Determine the effect of changing the characteristics of the selected component by plotting inflow versus outflow and readin the intersection.

7. Repeat the procedure for each component that is to be optimized.

SUGGESTED PROCEDURE FORNODAL ANALYSIS APPLICATION


HISTORY CASENODAL ANALYSIS FOCUSED ON ARTIFICIAL LIFT

FLOW RATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf

Pr

00 PRODUCTION

INCREASE

1

2

GAS LIFT

ELECTRICAL SUBMERSIBLEPUMP (ESP)

PbBUBBLE PRESSURE

ESP FAILED DUE TOEXCESSIVE GAS RATE

Pwf<<<<Pb

Pwf


Pr

00

1

2

GAS LIFT

Pb

PRODUCTION INCREASE

WELL WITH AVERY STRONGSKIN EFFECT

3

IPR IMPROVED BY REPERFORATION +STIMULATION JOB

ZERO GAS INTHE PUMP

Pwf > Pb


FLOW RATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf

BUBBLE PRESSURE

HISTORY CASENODAL ANALYSIS FOCUSED ON ARTIFICIAL LIFT


Pr

00

2

BEAM PUMPING

WELL STIMULATED WITH STEAM SOAK

1

VERY SMALL INCREASEIN PRODUCTION WAS ACHIEVED

HISTORY CASENODAL ANALYSIS FOCUSED ON INFLOW RESERVOIR PERFORMANCE

FLOW RATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf


Pr

00 PRODUCTION INCREASE

3

1

1000 BPD

BEAM PUMPING

FLOW RATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf


HISTORY CASENODAL ANALYSIS FOCUSED ON INFLOW RESERVOIR PERFORMANCE


WELL RESTRICTED BY PIPING SYSTEM AND NEAR WELLBORE SKIN EFFECT

FLOW RATE, Q

BO

TT

OM

HO

LE

FL

OW

ING

PR

ESS

UR

E, P

wf

Pr

00

OUTFLOW

INFLOW

1

2

3

4

NEAR WELLBORE

RESTRICTION (SKIN)

TUBING OR FLOWLINE

RESTRICTION

BOTH


ANALYZING MULTIWELL SYSTEMS

• Working over individual wells• Placing some wells on artificial lift• Add new wells• Shutting in some of the existing wells• Changes in producing characteristics with time• Effect of surface line sizes• Instalation of pumps or compressors• Effect of the final outlet pressure

A change made in any component in the system would affect the producingcapacity of the total system, Some of the changes that could be consideredare:


Well 1

Well 2

A B

Well 3

Pwf2

Q2

Pwf3

Q3

Pwf1

Q1

QA=Q1+Q2+Q3

PASystemCapacity

ANALYZING MULTIWELL SYSTEMS

Analisis Nodal

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