5. Gas Ligt - Diseño y Analisis
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Transcript of 5. Gas Ligt - Diseño y Analisis
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EX 5 1
Example 5
FloSystem User Course
Gaslift Design and Analysis
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EX 5 2
Gaslift Design
Overview
A Gaslift design for a well that does not flow naturally
Select Data Preparation and check : Reservoir data
Fluid data
Deviation data - Well data
Equipment Data - Well Data
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EX 5 3
Reservoir DataEnter Reservoir Data
Fluid Type is Black Oi l
Entry Model is Manual
PI = 1.3 STB/day/psia
IPR model = Vogel
Reservoir Pressure = 5100 psia
Reservoir Temperature = 230 F
Fluid Parameters for Black Oil
API = 27.5 GOR = 320
Water cut = 20 %
Gas specific gravity = 0.74
Water salinity = 200 kppm
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EX 5 4
Deviation Data
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EX 5 5
Equipment Data
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EX 5 6
Analysis :Operating Point
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EX 5 7
No operating point:Natural flow
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EX 5 8
Gaslift Data
Select Data Preparation - Gaslift Data
Use the following design parameters :
Casing Injection Pressure = 1200 psia
Gas Specific Gravity = 0.65
Differential pressure across the Valve = 100 psia
Lift gas injection rate 1.5 MMscf/day
Deepest point of injection = 40 ft above tubing shoe
These are the minimum data to calculate the
Operat ing Poin tfor the
Deepest Point of Injection
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EX 5 9
Gaslift Design :Deepest Injection Point
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EX 5 10
Gaslift Design Rate2513 STB/day
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EX 5 11
Pressure vs DepthInjection Depth: 8120 ft TVD
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EX 5 12
Gaslift Design
The design parameters used gives : Liquid rate = 2513 STB/day
Oil rate = 2010 STB/day
Water rate = 503 STB/day
Gaslift Valve Depth at 8121 ft. for given Qgi, CHP.
Sensitivity studies can now be made
gaslift injection rate 1.5, 2, 2.5 MMscf/day etc.
water cut increasing to 20, 30, 50, 70 % etc.
At this stage the design parameterscould also be revised (e.g. Casing injectionpressure, wellhead pressure)
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EX 5 13
Sensitivity of lift gasinjection rate
Note PaybackRatio
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EX 5 14
Sensitivity of anincreasing water cut
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EX 5 15
Gaslift Design :Final Parameters
The final parameters for the optimum design willdepend of the actual operating restrictions.
The initial lift gas injection rate, casing injection
pressure and valve differential pressure will be usedfor the Gasl i f t Design
Select Analys is - Gasl i f t Design....
Revise the parameters again and set the top node orChristmas tree pressure and the specific gravity ofthe fluid in the annulus
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EX 5 16
Gasl ift Des ign ....
Design Margins...
Design
Sizing...
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EX 5 17
Gaslift Design....
When click the Designbutton
First:
The temperature profile is calculated using the
model selected
Object ive tubing f lowing gradientis computedtop down
The gas is forced at the specified MD of
injection (Data Preparation -Gasli ft data...)Second:
Space unloading valves and define operatingvalves. Below operating valve space dummy
valves according to minimum spacing
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EX 5 18
Des ign Marg ins ....Casing Controlled Valves + Valve
Number
Casing Controlled Valves and Valve Number
Additionally
The fluid in the annulus is brine of 0.45 psi/ft
Minimum valve spacing below the operating valve =
450 ft. (100 psi)
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EX 519
Gasli f t Design ...Design Marg ins...
Kickoff Pressure
Casing closing
pressure margin
Margin at valve 1
Increment per valve
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EX 520
Gasli f t Des ign ...Gaslift Valves Spacing
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EX 521
Gasli f t Design ...Gaslift Valves Spacing
Operating Valve with all
design margins
Design Operating valve
Minimum valve spacing
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EX 522
Gasli f t Des ign ...Spacing ofDesign Operat ingValve
The position of the Design Operat ing valvedepends ifthe spacing finds the following constraints:
1. Next position less than minimum valve spacing
Last valve is marked as Operating valve and valvespacing below equal to minimum spacing.
The Design Operat ing valveis marked at depth with
enough differential pressure (relative to uncorrectedtubing pressure)
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EX 523
Gasli f t Des ign ...Spacing ofDesign Operat ingValve
2. Pcasing- Ptubing< differential pressure
Move up until it reaches a depth where the
differential pressure is met The new position is the Design operat ingvalveif spacing greater than minimum valvespacing
If the new position is less than minimumvalve spacing the Design Operating valve ismarked at the valve above
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EX 524
Gasli f t Design ...Spacing ofDesign Operat ingValve
3. Next position is below Max MD of in ject io n
The Design Operat ing valvewill be positioned at MaxMdprovided Pcasing-Ptubing> valve differentialpressure
If Pcasing-Ptubing
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EX 525
Gaslift Design Results
Active valves 6 and dummy valves 12
5 unloading valves
1 operating valve : Valve Depth = 7621 ft TVD (8068 ft MD)
Casing Pressure = 1300 psia
Tubing Pressure = 1195 psia
Temperature = 212.4 oF
12 Dummy valves below the operating valve spacedat 450 ft (TVD)
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EX 526
Gaslift Design Results
A new casing injection operating pressure of1131 psia can be selected
However this new injection pressure will give a
liquid rate = 2434 STB/day because If the casing injection pressure is kept at 1200
psi, then the liquid rate = 2491 STB/day(compared with design value of 2513 STB/day)
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EX 527
Sizing.... Facility
1. Port Size calculation using the Thornhill Craverequation.
2. Opening and Closing pressures computation for
each valve3. Dome and Test Rack Opening pressures
computation for each valve
4. Valve type selection :
Gas Charged Spring
Orifice
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EX 528
Sizing....Facility
Gasli f t Design ... results transferred to Sizing...:
Column name
Gaslift rate Qgi Valve depths MD and TVD
Wellbore temperature Temp
Tubing transfer pressure Pt P tubing
Casing pressure Pvo P open valve
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EX 529
Sizing.... Facility
1. Port Size
Valve type and Port Size
Critical Flow Flag
Pt
Pvo
F ilit
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EX 530
Sizing.... Facility
1. Port Size
Thornhill-Craver is solved with:
Pt (downstream pressure)
Pvo (upstream pressure)
Temp
Qgi
Discharge coefficient (Disch Coeffcolumn) default
value is 0.865All these values can be edited independent of the
previous gaslift design results
The column Critshows whether the valve is oncritical flow
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EX 531
Sizing.... Casing controlled
2. Opening and Closingpressures
Two methods to determine Opening and Closingpressures:
A. Use Pvo (from Gaslift Design)
B. Specify a surface closing pressure Psc
(P close sur f, column)
Update ratio R = tubing port area /bellows area
R in the order of 0.1 i.e. most of the bellows feel thecasing pressure
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EX 532
Sizing.... Casing controlled
2. Opening and Closingpressures
A. Use Pvo by setting NOin Calc by P closespreadsheet column
B. Use P close surf by sett ing YESin Calc by P close
spreadsheet column
Select calculation method
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EX 533
Sizing.... Casing controlled
2. Opening and Closingpressures
A. Use Pvo:
The Dome pressure is calculated from:
Pd = Pvo(1- R)+Pt(R)
The Valve Closing pressure Pvc is equal to Pd.
Pd & Pc valvecolumn in spreadsheet
The surface Closing pressure Psc follows bycorrecting Pvc for the gas gradient
P close sur fcolumn in spreadsheet
The surface Opening pressure Pso follows bycorrecting Pvo for the gas gradient
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EX 534
PvcPsc
Sizing.... Casing controlled
2. Opening and Closingpressures
Pt
R
Pvo Pso
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EX 535
Sizing.... Casing controlled
2. Opening and Closingpressures
B. Use P close surf(Psc)
Enter the Psc in the spreadsheet (e.g. 1300 for thefirst valve)
The Pvc is computed by using the gas gradientand Psc. By definition this is the in-situ domepressure Pd
Pd & Pc valvecolumn in spreadsheet
The valve Opening pressure Pvo is calculated fromPd, R and Pt:
Pvo= (Pd-Pt*R) /(1-R)
P open valvecolumn
P open sur f(Pso) follows by correcting Pvo for the gas
gradient
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EX 536
B. Use P close surf (Psc)
Sizing.... Casing controlled
2. Opening and Closingpressures
YesPsc
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EX 537
Sizing.... Casing controlled
3. Pd and TRO openingpressures
The in-situ (Pvo, Pvc) and surface (Psc, Pso) and thedome pressure (Pd) have been calculated at the valvetemperature
Pd is converted to its value at 60 oF
P dom e at 60oFcolumn
The Test Rack Opening TRO is derived from:
TRO= (Pdome at 60oF- 14.65*R) /(1-R)
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EX 538
Sizing.... Casing controlled
3. Pd and TRO
opening pressureP dome at 60F
Pd at valve Temp
TRO
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EX 539
Gaslift DesignSummary
Example of Gaslift design for a well that does notflow naturally
Design Margins
Casing-controlled valves
Fluid-controlled valves
Sizing Facility
Port size
Opening and closing pressures Dome and Test Rack Opening pressure
Valve type selection