2019 Artificial Lift Strategies for
Unconventional Wells Workshop Cox Convention Center, Oklahoma City, OK
February 11 - 14, 2019
Analysis of Gas-Lift Wells in
Unconventional Reservoirs –
A Case Study based on SPE-190950-MS
Luis E. Gonzalez
Rajan Chokshi
Introduction
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Oklahoma City, OK
Gas lift has become a predominant, intermediate term, artificial lift system in majority of basins.
For over 3 years, most operators have been moving to gas lift after experiencing the high failure rates and significant downtime associated with other artificial lift systems.
The major cause of high failure rates and expenses can be attributed to the dynamic nature of these wells, specifically, the rapid decline of pressure and production rates in combination with slugging.
Source: Gas-Lift Workshop Key Note, Noonan, 2017
Gas Lift Equipment
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Oklahoma City, OK
• Use of conventional
mandrels is the most
common in unconventional
• Restrictions to use side
pocket mandrels:
• Use of plunger lift in future
• Size of casing (5 1/2”) and
tubing (2 7/8”).
• Losing the ability to
optimize the well.
Gas Lift Design
Shows a sample gas lift
design.
Number of mandrels : 10-18.
Dome-charged valves are
used as operating valves.
Dummy valves are active
valves.
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Oklahoma City, OK Feb. 11 - 14, 2019
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Oklahoma City, OK
Reservoir – Pressure & PI – Behavior
is not well understood
SPE 171768
Reservoir pressure and PI – very important elements for effective gas-lift design and efficient operation – are mostly unknown over life cycle.
For shale reservoirs pseudo-steady state or steady state IPR curves are not applicable.
Transient IPR models – found in the literature – are based on initial pressure.
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Oklahoma City, OK
Pressure & PI Behavior
Graphic shows PR and PSRV behavior in a shale well. PSRV may be calculated by
reservoir simulation or Rate Transient Analysis. A complex approach for
production application like gas-lift.
Dynamic Nodal Analysis (DNA) – SPE 190950
Efficient, faster and practical algorithm to calculate the PSRV and PI using operation data
Time (days)
Pw
s
PI
Time (days)
PR
PSRV
Reservoir Pressure
Figures show examples of IPRs using Pinitial & PSRV.
PIs obtained are different and can significantly affect optimization-decisions for a gas-lift well.
Dynamic Nodal Analysis (DNA) – SPE 190950
Efficient, faster and practical algorithm to calculate the PSRV and PI using operation data.
Feb. 11 - 14, 2019 7 2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK
SPE 171768
Case Study: Delaware Gas Lift Well
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Oklahoma City, OK
Figure shows the completion of “Shale01”:
MD/TVD: 16,650’/11,089’
KOP/HEEL=10,655’/11,664’
Production Casing = 7 5/8”
Production Tubing = 2 7/8”
Lateral = 5,553’
Case Study: Production Data
40-months’ history analyzed
for this gas-lift well Top-left production & injection
rate trends, and
on the bottom-right, wellhead
pressures, and injection choke
trends.
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Oklahoma City, OK
SPE-190950-MS
Case Study: Operation Data
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Oklahoma City, OK
• Dynamic Nodal Analysis (DNA) algorithm was developed to infer Pws & PI for the 40-months’ production history.
• Once the DNA is performed, traditional Nodal Analysis can be completed with high confidence at any time step. SPE-190950-MS
-
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
-
500
1,000
1,500
2,000
2,500
3,000
9/18/2014 7/15/2015 5/10/2016 3/6/2017 12/31/2017
Liq
uid
Ra
tes
(B
LP
D)
Time
Measured & Calculated Liquid Rates
QLMeasure QLCal PI
-
2,000
4,000
6,000
8,000
10,000
12,000
9/18/2014 7/15/2015 5/10/2016 3/6/2017 12/31/2017
Pre
ss
ure
(P
SI)
Time
Static & Flowing Pressure
Pwfcalc1 Pwh Pwfcalc2 Pgauge PSRV
Case Study – Nodal Analysis
11 Feb. 11 - 14, 2019 2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK
• Figure shows Nodal Analysis for date-stamp 09-16-2016.
• Five upper valves are closed. • Where and
how much
gas is being
injected?
SPE-190950-MS
Case Study – Advanced GL Valve
Modeling
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Oklahoma City, OK
• Looking at the Valve 6 performance for Pcsg values of 882, 936 and 1,000 psi.
• Results indicate no gas being injected in the well for Pcsg of 882 psi, but the operations show 679 MSCFD of gas being injected. • Wrong calculations?
• What is happening?
Valve Performance curve
for 1,000 Psi
Valve Performance curve
for 882 Psi
Valve Performance curve
for 936 Psi
Case Study – Dynamic G/L Analysis
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• A dynamic gas-lift
model is created and
ran for the same
timestep with the
following results:
− top 5 valves are
closed
− 2 valves act as
operating valves
(Multi-point
injection)
SPE-190950-MS
2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK
Operation
Data
Dynamic
Model
Pwh 199.40 200.70
Pcsg 881.71 935.70
Pwf 2,491.47 2,522.00
Ql 767.87 763.00
Qo 125.87 125.00
Qw 642.00 638.00
Qginj 678.94 614.00
Qtg 1,188.06 1,118.00
Case Study – Dynamic G/L Analysis
Feb. 11 - 14, 2019
If we force-open the
Valve no. 5, the
simulations show a
better match with
operation results.
Operation
Data
Dynamic
Model
Pwh 199.40 208.70
Pcsg 881.71 887.70
Pwf 2,491.47 2,571.70
Ql 767.87 751.00
Qo 125.87 123.00
Qw 642.00 628.00
Qginj 678.94 679.00
Qtg 1,188.06 1,177.00
SPE-190950-MS
2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK 14
2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK
0.00
0.20
0.40
0.60
0.80
1.00
1.20
0
500
1,000
1,500
2,000
2,500
9/18/14 7/15/15 5/10/16 3/6/17 12/31/17
Liq
uid
Ra
tes
(B
LP
D)
Time
Measured & Calculated Liquid Rates
Liquid Measures QLCal PI
Feb. 11 - 14, 2019
Dynamic G/L Analysis @ Various Time Steps
Conclusions
Gas lift design procedures applicable for
conventional wells cannot necessarily be
applied to unconventional wells without
considering the dynamic changes in
behavior.
Understanding dynamic reservoir behavior
of unconventional wells is a must in order to
efficiently design, effectively operate and
troubleshoot gas lift.
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Conclusions
A new workflow, to analyze unconventional gas-lift wells, using dynamic nodal analysis has been presented.
This novel DNA-based workflow offers
Efficient calculation of dynamic PI and PWS using production data over large time-periods.
Validation and troubleshooting of gas-lift well behaviors.
Better understanding of dynamic pressure and PI behavior will help improve design and operation of future gas-lift wells.
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18 2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 11 - 14, 2019
Disclaimer
19 2019 Artificial Lift Strategies for Unconventional Wells Workshop
Oklahoma City, OK Feb. 11 - 14, 2019
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