GAS LIFT DESIGN

Muhammad Akhtar UET Lahore

CONTENTS Introduction Need of Gas LiftDesign ConsiderationsManual Design PIPESIM DesignResults Comparison Synopsis

Gas Lift

Continued… Gas is injected continuously or

intermittently at selected locations, resulting in the lifting(decreasing density) of the produced fluids to the surface

The lowering of the bottom hole pressure is accomplished to increase the drawdown between reservoir and wellbore

When We need Gas Lift?

Producing wells that can’t flow naturally

Initial unloading of a well that will flow on its own later

Increasing the production rate of a flowing well

Continued…Accommodating deviated and

horizontal well boresUnloading a well affected by

adjacent well drilling and fracturing

Removing solids by back flowingProducing wells with sand or

scale problems

7

Data Required

1. Well Data: a.- Casing or liner size b.- Tubing size, type & thread c.- Perforated or open hole

interval d.- Pump setting depth

8

2. Production Data:

a.- Wellhead tubing & casing

pressure

b.- Present production rate

c.- Static & dynamic fluid level

d.- GOR & W/C

e.- Datum point

f.- BHT

g.- Desired production rate

9

3. Well Fluid Properties: a.- Water specific gravity b.- Oil API or specific

gravity c.- Gas specific gravity d.- Bubble-point pressure e.- Oil viscosity f.- PVT data

10

4. Possible Problems: a. Sand b.- Deposition c.- Corrosion d.- Paraffin e.- Emulsion f.- Gas g.- Abnormal temperature

Design ConsiderationsGas injection depth, pressure and GLR

for desired production Principles of unloading operations Well Gradients Gas lift valve spacing principles Types of gas lift valves Mechanics of gas lift valve operation Factors that affect efficiency (injected

gas)

LimitationsNot feasible if no source of gas

present. High initial capital purchase cost.Maintenance intensive.Difficult to operate

GAS LIFT VALVESThe heart of any gas lift system is the gas lift

valve.

Gas lift valves are basically downhole pressure regulators

Practically all gas lift valves use the effect of pressure acting on the area of a valve element (bellows, stem tip, etc.

Tubing pressure operated valves (r-25p, r-25p1, etc.)

Casing pressure operated valves (r-20, altec, etc.)

GAS FLOW

FROM CASINGGAS FLOW

FROM CASING

GAS FLOW

INTO THE TUBING

GAS FLOW

INTO THE TUBING

CASING PRESSURE OPERATED

GAS LIFT VALVE (IPO)

TUBING PRESSURE OPERATED

GAS LIFT VALVE (PPO)

REVERSE FLOW

VALVE

GAS LIFT VALVES

UNLOADING PROCEDURE

Obtain the design details of the gas lift string. The kick-off pressure, estimated gas injection rate during unloading

Bleed the tubing pressure to the oil manifold. This should be done very slowly.

Start injecting +/- 500 mscfd gas. Slowly control the lift gas rate so that it takes 10-12 minutes for 50 psi buildup in the casing pressure.

CONTINUED….• Increase the gas injection rate slowly to allow the casing pressure to buildup 100 psi in every 10 minutes till the gas is passing through the orifice.

• Once the well has cleaned up and unloaded to the orifice, adjust the gas injection rate as per the recommendation.

Case StudyDATA:

Well depth=Gas injec depth= 13250 ft Tubing id= 4.89 inch Water Cut= 60% Tsc= 60 F API= 35.7 degree Formation GLR = 500 scf/STB psep= 190 psig P.G= 0.465 psi/ft

Test Data: pr=SIBHP= 3100 psig Pb = 3600 psig

P.I=6.1 STB/D-psi T= 200 F pinj= 1800 psia

Manual DesignP.I method was used for IPR plottingHagedorn Brown Correlation was used to

generate pressure traverse curve using tubing data

Then the qL and pwf values were plotted on same graph of IPR

The point with maximum value of qL is taken as operating flow rate

Optimization of Gas Injection Rate

Microsoft Office Excel Worksheet

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 200000

500

1000

1500

2000

2500

3000

3500

4000

4500 GAS LIFT OPTIMIZATION

IPR, WCUT=60%

GLRinj= 0 mmscfd

GLRinj= 0.4 mmscfd

GLRinj= 0.8 mmscfd

GLRinj= 1.2 mmscfd

GLRinj= 1.4 mmscfd

GLRinj= 1.6 mmscfd

GLRinj= 1.8 mmscfd

GLRinj=2.0 mmscfd

GLRinj= 2.2 mmscfd

qL (STB/D)

pw

f (p

sig

)

Operating Flow RatesGLRTotal(scf/STB) qL (STB/D)

500 7000900 8350

1300 87001700 88001900 88502100 8850

Optimization of Gas Injection Rate

0 5 10 15 20 250

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000qinj Optimization

qinj (MMSCF/D)

qL (

STB

/D)

Valve Setting Depth Calculations Following are the steps used for

drawing gradient lines and calculating valce setting depths:

Microsoft Office Word Document

VALVE SETTING DEPTH CALCULATIONS

0 500 1000 1500 2000 2500 3000 35000

2000

4000

6000

8000

10000

12000

14000

P, psig

Depth

TV

D(f

t)

STATIC GRADIENT 0.465 PSI/FT

DEPTH OF WELL

CA

SING

PRE

SSUR

E G

RA

DIE

NT

(S.G=0.65)

SIBHP

FLOWING GRADIENT 400 BPD, 0% W

CUT, ,200GLRFLOW

ING GRADIENT 8700BPD, 0% WCUT, , 1300 GLR

Mandrel#1 @ 3600 ft

Mandrel#2 @6400 ft

Mandrel#3 @8400ft

Mandrel#4 @9800 ft

Mandrel#5 @10700 ftMandrel#6 @11350 ftMandrel#7 @11800 ft

0.465 psi/ft

0.465 psi/ft

0.465 psi/ft

0.465 psi/ft

FBHP

DRAWDOWN CREATED BY GAS INJECTION

Valve Setting DepthVALVE DEPTH , ft

1. Unloading Valve3600

2. Unloading Valve6400

3. Unloading Valve8400

4. Unloading Valve9800

5. Unloading Valve10700

6. Unloading Valve11350

7. Operating valve11800

PIPESIM DESIGN

OPTIMIZATION OF GAS INJECTION RATE

GAS LIFT OPTIMIZATION

Operating Flow ratesqinj MMSCF/D qL STB/D

1 4400

2 5700

3 6500

4 7000

5 7400

6 7700

7 7800

Results Analysis

qL STB/D qinj MMSCF/D RECOVERY

MANUAL DESIGN

7000 0 NATURAL

8700 6.9 GAS LIFT

PIPESIM DESIGN

4000 0 NATURAL

7800 6.9 GAS LIFT

Conclusions Manual Calculations give us

overestimated resultsPIPESIM is a very helpful tool in

determining the efficiency of artificial lift methods

Gas Lift is remarkably beneficial in increasing productivity

ANY QUESTION?

THANK YOU FOR BEING PATIENT