gas lift applications for mature fields
TRANSCRIPT
Gas Lift Applications for Mature Fields
Objective:
Present a list of alternatives to prolong the economic life of the Gas Lift Method in Mature Fields before considering other types of Artificial Lift Methods
Contents:
• Introduction• 1st Stage Optimization (no Work Over required)• 2nd Stage (Alternative Completions)• Automation (Control and Data Acquisition)• Surface Facilities (Adapting to a New Reality)• Conclusions
Introduction
Accumulated Production (Bb)
Inje
ctio
n G
as
Liqu
id R
ati
o (
SC
F/B
b)
Liqu
id F
low
Rate
(B
b/D
)Max. Economical GLR
Accumulated Production (Bb)
Inje
ctio
n G
as
Liqu
id R
ati
o (
SC
F/B
b)
Liqu
id F
low
Rate
(B
b/D
)Max. Economical GLR
Compressors, pipe line gas distribution networks and current gas lift completions are by themselves expensive.
But it might be even more expensive (if not economically impossible) to invest in new electric generators and cables, pumps and new completions, training personnel… for mature fields.
….Can we extend the life of an old gas lift field?
1st Stage Optimization (no Work Over Required)
Trouble Shooting (System Approach)
o Find QL vs. Qgi (measure flowing bhp at different Qgi)
Do not take computer models as the indisputable truth!
o Identify where and why wells are not optimize
GAS INJECTION FLOW RATE
LIQ
UID
FLO
WR
ATE
Max Ql point
Opt. economic point
Assessment of current “best possible” Injection GLR
UNSTABLE WELLS
POINT OF INJ ECTION
COMPLETION INTEGRETY
OR
FORMATION DAMAGE, SAND...
GAS INJECTION FLOW RATE
LIQ
UID
FLO
WR
ATE
Max Ql point
Opt. economic point
Assessment of current “best possible” Injection GLR
UNSTABLE WELLS
POINT OF INJ ECTION
COMPLETION INTEGRETY
OR
FORMATION DAMAGE, SAND...
Shift from Continuous to Intermittent Gas Lift o Aim: to reduce Inj. GLR (not necessarily to increase liquid
production) o When?
There is no theoretical approachRule-of-thumb: static liquid level = 1/3 total depth
o Where?Avoid extreme tubing sizes (4-1/2 or < 2-3/8 in tubing)Avoid extreme annulus volume Surface facilities
o How?1-1/2 in vs. 1 in valvesSpring loaded or nitrogen charged valves / single element or pilot v.Surface controllers or choke control / Use plungers or notOptimum cycle time to maximize QL / Correct gas inj. per cycle
2nd Stage Optimization (Alternative Completions) Reduce Tubing size
Aim: prolong continuous gas lift while reducing Inj. GLR
Continuous GL is operationally always better than intermittent GL specially in small fields with few operating wells
Use other type of completionsLast resourceThe only way to extend GL to ultimate depletion
CHAMBER INSTALLATIONS
More liquid can be accumulated for a given flowing bottom hole pressure
Double Packer Chamber
• Can reduce IGLR• Might increase liquid
production (high P.I.)• Max. liquid capacity
than any other type of chamber
Attention to:
• Bleed valve port size• Gassy wells• Sand (difficulty to
pull the completion and wire line jobs)
• The completion is more complex. This increases the risk of any production inefficiency due to completion failure
Insert Chamber
• Can reduce IGLR
• Might increase liquid production (not necessarily high P.I.)• Max. Draw-down • Especially suitable for wells with long perf. Intervals.
Attention to:
• Bleed valve port size (chamber and outer annulus)• Gassy wells (but perform better than DPC)• Sand (difficulty to pull the completion and wire line jobs)• The completion is even more complex than double packer
chambers
ACUMULATORS
Compared with simple completion, more liquid can be accumulated for a given flowing bottom hole pressure but with less complex
completions
Simple Type Accumulator
• Can reduce IGLR• Might increase liquid
production (high P.I.)• Suitable for gassy
wells• Not as complex as
chamber
Attention to:
• Liquid capacity is always lower than any type of chambers
• I.D. of accumulator cannot be too large
UNLOADINGVALVE
OPERATINGVALVE
UNLOADINGVALVE
PACKER &STANDING VALVE
SIMPLE TYPEACCUMULATOR
Insert Type Accumulator
• Can reduce IGLR• Increases liquid
production (long perf. intervals) due to high draw-down
• Suitable for gassy wells
• Not as complex as chamber
Attention to:
• Gas lift valve should be at upper mandrel
• I.D. of accumulator cannot be too large
GAS LIFT GASMULTIPHASE FLOW
FORMATIONGAS INLET(Y-TOOL)
MANDREL
SPECIALPACKER
STANDING VALVE
INYECTION POINT
COILED TUBING
• Bleeb port should handle two-phase flow
Automation (Control and Data Acquisition)
An automation system can:• Help the gas-lift Operator to optimize each gas-lift well and
keep it optimized all of the time.• Help to optimize the performance of an entire gas-lift system:
by automatically coordinating injection cycles, it can reduce the occurrence of system upsets that may happen when two or more wells are injected at the same time
• Keep stable condition during a compressor trip or restart, a production station trip or restart, or the trip or restart of large wells on the system
• Continuously monitors all wells and the system to provide surveillance and troubleshooting information to the gas-lift Operators
Its major drawback is COST, but new technologies are reducing it
Surface Facility (Adapting to a New Reality)
• Lower well head pressure (use of low pressure booster might be necessary)
• Oversize tests separator (test accuracy)• Undersize separators (ability to handle gas for intermittent gas
lift, use chokes)• Gas handling (moisture[Dp], debris[old pipes] etc)• Well heads free of restrictions (streamlined wellhead free of
choke box)• Use of valves instead of orifices as the operating point to reduce
the impact of compressor shut-downs• Use abandoned wells to storage either high or low pressure gas
to increase the stability of the whole system
CONCLUSIONS
• The injection gas liquid rate can be kept within an economical level if proper steps are taken
• Long term planning for surface and subsurface equipment replacement can extend the Gas Lift Method up to ultimate depletion
• New technologies in automation equipment should make its implementation economically feasible even for low producing wells
• Training personnel for present and future operation requirements is essential for extending the life of the Gas Lift Method.
Stage Optimization (Alternative Completions)
Insert Chamber with Hanger Nipple
Insert Chamber with Combination Operating-Bleed Valve
Extremely long Insert Chamber
Insert Chamber for Tight Formations
Gas Chamber Pumps
• Increase liquid production by reducing fall back losses in wells with low API oil
• Can handle gassy wells and high temperatures (steam injection)
Attention to:
• Higher cost in surface controller equipment than in Gas Lift• For complex designs, parts are subject to wear and replacement• A High-Pressure gas source is required• Gas liquid ratios can be high for some designs due to venting of
high pressure gas
AdjChoke
Inj. Gas &vent string
AdjChoke
Vent motor valve
Pilot Control System
Inj. gas motor valve
Inj.Gas line
Flowline
Csg
InsertChamber
Perfs Intake check
valve
Discharge check valve
Chamber dip tube
Prod conduit