© Schlumberger 2001

GAS LIFT WELL KICK-OFF

© Schlumberger 2001

0 1000 2000

0

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10000

PRESSURE (PSIG)D

EP

TH F

TTV

D

S.I.B.H.P.

DEPTH OF WELL (MID PERFS)

STATIC GRADIENT (0.465 PSI/FT)

TEMPERATURE F100 150 200

CAMCO GAS LIFT TECHNOLOGY

SLIDE 2

© Schlumberger 2001

0 1000 2000

0

1000

2000

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PRESSURE (PSIG)D

EP

TH F

TTV

D

S.I.B.H.P.

DEPTH OF WELL (MID PERFS)

STATIC GRADIENT (0.465 PSI/FT)

F.B.H.P.

FLOW

ING

GR

ADIEN

T 2000 BLPD, 99%

W.C

., 1000:1

GLR

TEMPERATURE F100 150 200

CAMCO GAS LIFT TECHNOLOGY

SLIDE 5

FLOWING GRADIENT 2000 BPD, 99% W.C., 0 GLR

CA

SIN

G P

RE

SS

UR

E G

RA

DIE

NT 0.65 S

.G.

© Schlumberger 2001

GAS LIFT WELL KICK-OFF• Unload well carefully

– 50 - 100 psi (3.5 bar) per 10 min– 1 - 2 bbl per min

• Maximize production choke opening• Gradually increase gas injection rate• Monitor well clean up and stability• Get to target position• Perform step rate production test• Optimise gas injection rate• Note - when unloading all valves open!

© Schlumberger 2001

GAS CALCULATIONS RELATED TO GAS LIFT SYSTEMS

• Gas injection pressure at depth

• Gas volume stored within a conduit

• Temperature effect on bellows-charged dome pressure

• Volumetric gas throughput of a choke or GL Valve port

© Schlumberger 2001

GAS CALCULATIONS RELATED TO GAS LIFT SYSTEMS

GAS INJECTION PRESSURE AT DEPTH

S.G. x L 53.34 x T x Z

P@L = P@S x e

Where: e = 2.71828P@L = Pressure at depth, psiaP@S = Pressure at surface, psiaS.G. = Gas Specific GravityL = Depth, feetT = Average Temp Degrees RZ = Average Compressibility for T and average pressure

© Schlumberger 2001

GAS CALCULATIONS RELATED TO GAS LIFT SYSTEMS

GAS INJECTION PRESSURE AT DEPTH

“Rule of thumb” Equation based on S.G. of 0.65,a geothermal gradient at 1.60F/100ft and a surface temperature of 700F

P@L = P@S + (2.3 x P@S x L ) 100 1000

Where: P@L = Pressure at depth, psiaP@S = Pressure at surface, psiaL = Depth, feet

© Schlumberger 2001

GAS VOLUME STORED WITHIN A CONDUIT

Internal capacity of a single circular conduit

Q(ft3/100ft.) = 0.5454 di2

Q(barrels/100ft.) = 0.009714 di2

Annular capacity of a tubing string inside casing

Q(ft3/100ft.) = 0.5454 di2 - do2

Q(barrels/100ft.) = 0.009714 di2 - do2

Where: di = inside diameter in inchesdo = outside diameter in inches

© Schlumberger 2001

GAS VOLUME STORED WITHIN A CONDUIT

To find the volume of gas contained under specificwell conditions):

P x Tb

b = V x ---------------- Z x Pb x T

Where: b = gas volume at base conditionsV = capacity of conduit in cubic feetP = average pressure within conduitTb= temperature base in degrees RankinZ = compressibility factor for average pressure and temperature in a conduit (see Figure 3.2)Pb= pressure base (14.73 psi)T = average temperature in the conduit in degrees Rankin

© Schlumberger 2001

TEMPERATURE EFFECT ON CONFINED BELLOWS CHARGED DOME PRESSURE

Major Advantages of Nitrogen

•Availability•Non-explosive•Non- corrosive•Predictable compressibility•Predictable temperature effect

© Schlumberger 2001

TEMPERATURE EFFECT ON CONFINED BELLOWS CHARGED DOME PRESSURE

P2 = P1 X Tc

Where: P1 = Pressure at initial temperatureP2 = Pressure resulting from change of temperatureTc = Temperature correction factor

and

1 + 0.00215 x (T2 - 60)Tc = --------------------------------

1 + 0.00215 x (T1 - 60)

Where : T1 = Initial temperature, Deg FT2 = Present temperature, Deg F

© Schlumberger 2001

VOLUMETRIC GAS THROUGHPUT OF A CHOKE OR A GAS LIFT VALVE PORT

Equation based on Thornhill-Craver Studies

Page 3-13

Since this equation is so complex the chart in page 3-16 provides a means of quickly obtaining an approximate gas passage rate for a given port size

© Schlumberger 2001

GAS PASSAGE THROUGH ORIFICE VALVE

ORIFICE VALVE PERFORMANCE CURVE

PRESSURE

GA

S RA

TE

CRITICAL FLOW SUBCRITICAL FLOW

© Schlumberger 2001

GAS PASSAGE THROUGH UNLOADING VALVE

UNLOADING VALVE PERFORMANCE CURVE

PRESSURE

GA

S RA

TE Orifice FlowThrottling Flow

© Schlumberger 2001

RDO-5 Orifice Valve, 24/64" Port, Cd = 0.86

0.00

0.50

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Downstream Pressure (psig)

Gas

Flo

wra

te (m

msc

f/d)

Calculated Flowrate Measured Flowrate

Calculated Flowrate Measured Flowrate

Calculated Flowrate Measured Flowrate

Calculated Flowrate Measured Flowrate

© Schlumberger 2001

APPLICATION OF FLOWING PRESSURE GRADIENTS / EXERCISES