downhole gas separation performance lynn rowlanalrdc.org/workshops/2017_2017gaswellworkshop... ·...
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Gas Well Deliquification Workshop
Sheraton Hotel, Denver, Colorado
February 20 – 22, 2017
Lynn Rowlan
Downhole Gas Separation Performance
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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Overview • Free gas interfering with liquid filling the pump is a major
operational problem producing Sucker Rod Lifted wells.
• Gas interference is when free gas at the pump intake
pressure enters the pump filling displacement volume
with gas in place of liquid, then significant loss in liquid
production and reduced drawdown occurs
• Downhole Gas Separator Simulation program predicts
how a separator will perform in the field so that the
proper gas separator and pump can be selected.
• Operators can analyze a particular separator
configuration and view how the gas separator separates
the liquid from the gas and also determine separator
capacity.
•
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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Efficiency of the Downhole Gas Separation Process
• Efficiency of the downhole gas separation
process expressed by two different methods:
1) Effective Pump Fillage % - EPF%
2) Gas Separator Efficiency %.
• Effective Pump Fillage % represents the ratio of
effective plunger travel divided by maximum
plunger travel expressed as a percent.
• Gas Separator Efficiency % percentage of free
gas at the pump intake pressure condition
vented up the casing not entering the pump
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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K Coefficient Determines Free Gas into Pump - Schmidt & Doty – May 1989
SPE 15426 Prod Engr
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado 5
Liquid Velocity Should be Less Than ~6”/sec Bubble Rise Velocity from Laboratory Testing
Effect of Liquid Velocity
5 inch/sec
243 BPD
6 inch/sec
275 BPD9 inch/sec
420 BPD
OK FAIL
FAIL 5 inch/sec 243 BPD
6 inch/sec 275 BPD
9 inch/sec 420 BPD
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Separator OK Downward Flow rate 243 BPD 5 inches /Second
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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Separator Fails Due Downward 420 BPD Flow at Velocity of 9 inches /Second
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Bubbles Must Exit Gas Separator When SV Ball on Seat During SR Pumping Cycle
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado 9
Collar Sized Separator OK
Production of 100 BPD
with a Full Pump
Poor Boy Separator Fails
34.4” Effective
Plunger Stroke with
34% Pump Fillage
Separator Fails 141 BPD
Displacement Greater than
96 BPD Separator Capacity
Separator OK 141 BPD
Displacement Less than 242
BPD Separator Capacity
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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161 Capacity Poor Boy Separator Fails Net Pump Displacement = 168 BPD @ 6.82 SPM
10
Gas Bubble Rise is
4.6 inch/sec
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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161 Capacity Poor Boy Separator OK Net Pump Displacement = 140 BPD @ 6.14 SPM
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Gas Bubble Escapes
Separator @ 4.6 inch/sec
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
Low Capacity Gas Separator 2 7/8 inch Poor-Boy Separator with 60 foot dip tube 324 BPD Pump Capacity EXCEEDS 147 BPD Separator capacity
Seating Nipple
6 foot 2 7/8 sub
6 foot 2 7/8 Perforated Sub
60 Foot 1 ¼ inch dip tube
Tubing Plug
6 foot Perforated sub
Baker Latch Assembly
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Longer is NOT better
FAILS.
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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$125K 147 BPD Poor Boy Separator Fails 60 Ft Long Dip tube Does NOT Help
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Tubing Anchors & Liner Tops
Tubing anchor with the
gaseous fluid column
combine to create a
choke mechanism that
regulates gas flowing
up the casing annulus
Gas Separation FAILS
due to problem of TAC
restricting annular gas
flow causing pump
filled with gas
The gaseous
liquid column
above the
TAC is 28 %
liquid with 53
MCF/D of gas
flowing
upward
through the
gaseous
liquid column.
Gas flow is
restricted
from below
the TAC.
Casing
Tubing
Liquid
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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High Capacity 420 BPD Pump in the Rat Hole FAILS TAC restricts annular gas flow
Full Partial fillage
Stroke 1 Stroke 9
Dynamometer Test After 10 Minute Shut down
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Separation FAILS if Pump EPF% Less than % Liquid in Annulus
Gas Separation
FAILS
Gas Separation
OK
Casing Size Limits
Gas Separation
Maximum Capacity
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Separators for 4 1/2 inch Casing
Separator Type, size, inches Capacity
Natural Gas Separator 420 BPD
Collar Size Gas Separator 2 3/8 275
Poor Boy Separator 2 3/8 96
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Separators for 5 1/2 inch Casing
Separator Type, size, inches Capacity
Natural Gas Separator 580 BPD
Collar Size Gas Separator 2 7/8 443
Heavy Wall Gas Separator 2 7/8 372
Packer Type Separator 444
Poor Boy Separator 2 7/8 190
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Separators for 7 inch Casing
Separator Type, size, inches Capacity
Natural Gas Separator 1200 BPD
Collar Size Gas Separator 4 ½ 1044
Collar Size Gas Separator 4 833
Collar Size Gas Separator 3 ½ 644
Collar Size Gas Separator 2 7/8 443
Heavy Wall Gas Separator 2 7/8 372
Packer Type Separator 1089
Poor Boy Separator 2 7/8 190
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
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Gas Separation Efficiency Determined by Gas Produced Up the Tubing and Casing
Gas Produced Up the Tubing Is Determined
From the Pump Card Calculations
Free Gas Produced Up the Tubing/Casing
Annulus Is Determined Form the Acoustic
Fluid Level Test Performed While Acquiring
the Dynamometer Test Data
Total Gas Produced Can Be Determined
System Gas Separation Efficiency Can Be
Determined By Comparing the Gas
Produced Up the Casing to the Total Gas
Produced.
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
21
Well’s System Gas Separation Efficiency is 51.2% Equal to 9.1/17.8 MscfD
21
9.1
MscfD
8.7
MscfD
Feb. 20 - 22, 2017
2017 Gas Well Deliquification Workshop
Denver, Colorado
22
Gas Separator Recommendations
1. Use a Natural Gas Separator unless well conditions are
unfavorable.
2. When the separator is above the producing zone, the outer
barrel of the gas separator should be about 80% of the casing
internal diameter in high producing rate wells.
3. The gas separator capacity should exceed the pump capacity.
4. Use the Echometer Gas Separator Simulator Software
Program to determine gas separator capacity.
5. Use dynamometer and fluid level analysis to determine pump
fillage and separator efficiency.
6. Determining gas separator efficiency from pump fillage when
using high slippage pumps can be very misleading since the
separator may be separating very little liquid from gas and the
actual liquid production rate may be very low.
7. The bottom of the dip tube should extend below the bottom of
the gas separator inlet ports approximately 200/SPM inches.
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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Conclusion
• Both of these gas separation efficiency methods can be
misleading and result in the operator not identifying a
well having a gas separation problem.
• Expected performance of downhole gas separators can
be calculated based on net pump displacement, size of
separator, planned SPM and a gas bubble rise velocity.
• Using K Gas Separator Performance Factor with PVT
properties does Model Field Separator Performance
• To effectively produce sucker rod lifted wells Gas
Separators should be used to within their operational
limits.
• What aout Horizontal Wells?
Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
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Copyright
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Feb. 20 - 22, 2017 2017 Gas Well Deliquification Workshop
Denver, Colorado
25
Disclaimer
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