4 kickoff and gas laws aberdeen 10-03
TRANSCRIPT
© Schlumberger 2001
GAS LIFT WELL KICK-OFF
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0 1000 2000
0
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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)
TEMPERATURE F100 150 200
CAMCO GAS LIFT TECHNOLOGY
SLIDE 2
© Schlumberger 2001
0 1000 2000
0
1000
2000
3000
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6000
7000
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9000
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)
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.
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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!
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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
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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
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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
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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
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TEMPERATURE EFFECT ON CONFINED BELLOWS CHARGED DOME PRESSURE
Major Advantages of Nitrogen
•Availability•Non-explosive•Non- corrosive•Predictable compressibility•Predictable temperature effect
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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
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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
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GAS PASSAGE THROUGH ORIFICE VALVE
ORIFICE VALVE PERFORMANCE CURVE
PRESSURE
GA
S RA
TE
CRITICAL FLOW SUBCRITICAL FLOW
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GAS PASSAGE THROUGH UNLOADING VALVE
UNLOADING VALVE PERFORMANCE CURVE
PRESSURE
GA
S RA
TE Orifice FlowThrottling Flow
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RDO-5 Orifice Valve, 24/64" Port, Cd = 0.86
0.00
0.50
1.00
1.50
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2.50
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3.50
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4.50
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0.00 200.00 400.00 600.00 800.00 1000.00 1200.00 1400.00 1600.00 1800.00 2000.00
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
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APPLICATION OF FLOWING PRESSURE GRADIENTS / EXERCISES