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Plunger lift safety
considerations
• Presentation is meant to bring awareness to safety set points and shut
downs
• Is it ok for “heavy” plungers to be “allowed” to travel as fast as light ones?
• Should metal selection play a role in shut down settings?
• Are your shut down settings enabled?
• Are your shut down settings “blanket ordered”?
Every time a plunger well is shut in for whatever the reason – the situation is
worsened the longer the well is shut in.
800.0
1000.0
1200.0
1400.0
1600.0
1800.0
2000.0
2200.0
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
0.000 13.889 27.778 41.667 55.556 69.444 83.333
Is your logic set up ok?
Is this why plungers break?
Too Slow Target
Gas Slips By Plunger
May Never Reach Surface
Too Fast
Wastes Well psi
Damages Equipment
How fast is too fast for the lighter plungers?
How fast is too fast for the heavy plungers? Arrivals faster than 1000 ft./min is mostly a waste of energy not necessarily a
point of damage.
Gas velocity/pressure Velocity increases
significantly as pressure is
reduced
Point – If it becomes
necessary to blow the
well be aware of the
impact that has on the
velocity of the gas and
therefore the plunger.
Point – If the well has
been shut in for an
extended period and is
going to be brought on
to a low pressure
system be cautious of
the plunger travel
speed
Things we can control to Reduce Impact
Energy
1. Mass (Reduction in Mass = Reduction in Impact energy)
2. Ensure your well is “optimized”
3. Improvement to materials and springs
4. Preventing “lifts” during high energy situations
5. * mass reduction is often overlooked as a means of impact force reduction
Assessing Dangerous
Arrival Speeds
• In order to assess when an arrival is going to cause damage
or a catastrophic failure we should consider
• Spring in Lubricator/Spring in Bottom Hole
• Weight of Plunger (focus area)
• Material of Lubricator
• This will become important in the case that the spring is
damaged
Assessing Dangerous
Arrival Speeds Example
Operating
Window – In
this case the
spring is
collapsed at 14
m/s and force
on the
Lubricator
begins, this ties
directly to the
weight of the
plunger.
Assessing Dangerous
Arrival Speeds Once the Spring has
been damaged you rely
on the yield strength of
the material which can
vary from manufacturer,
best practice is to
contain the Kinetic
Energy of the plunger
by reducing speed and
weight where possible
however for safety
lubricator material
should be reviewed.
A 9.8 Lbs plunger @ 1000 Ft/min has the same Kinetic
energy as a 3.2 Lb plunger @ 1700 Ft/Min
1700
ft/min
1000
ft/min
psi
Do plungers need “speed limits” specific to mass?
Presentation is centered on mass and not specific to
lubricators or liquid brought to surface. It is about
the “ones that get away”
2000
ft/min
600
ft/min
A 30 Lbs plunger @ 600 Ft/min has the same Kinetic
energy as a 3.2 Lb plunger @ 2000 Ft/Min
Should plunger mass be considered in determining
shut down settings? Red Line represents constant
energy.
psi
Similar looks Some plungers may look the
same but different metals “can”
equal impact force reduction.
1000 ft./min = 2282 lbs. impact force [steel]
1000 ft./min = 1548 lbs. impact force
[titanium]
Different looks 1000 ft./min impact force 2338 lbs
2 7/8 Venturi ti
1000 ft/min. impact force 8510 lbs
2 7/8 triple pad
800.0
1000.0
1200.0
1400.0
1600.0
1800.0
2000.0
2200.0
-1.5
-1.0
-0.5
0
0.5
1.0
1.5
0.000 13.889 27.778 41.667 55.556 69.444 83.333
Pressure required for
large slug
Large slugs can promote high energy situations
Pressure required for
“optimized” slug
SCADA systems and stand alone controllers have shut down
settings in place that address fast arrival conditions. Should 1000
ft/min apply for everything including 2 1/16 – 3 ½ inch plungers?
Below is a list of average plunger weights traveling at 1000ft./min
• 2 3/8 Venturi ti – impact force = 1337lbs
• 2 3/8 viper – impact force = 3317lbs
• 2 3/8 dual pad – impact force 4257lbs
• 2 7/8 triple pad plunger – impact force 8510lbs
So what can you do to
minimize impact forces?
• Ensure your well is optimized. Maintain small liquid slugs and only shut in long enough
to meet the MINIMUM pressure required for a lift.
• Consider metal specs on surface facilities. Sometimes you get what you pay for.
• Consider plunger mass when setting your safety shut down settings. Mass reduction
alone can have positive impacts on production if liquid slugs are kept small, as well as
having drastic benefits to arrival impact forces.
• Make sure your safety shut down settings are “enabled”
• Regarding high speed shut down settings – is the concern the number? Consecutive
values? Or cumulative values?
• Is shutting the well in required?
Safety/profit
• With plunger lift wells – “the lower the flowing
bottom hole pressure, the more gas you make”
• With plunger lift wells – “the lower the flowing
bottom hole pressure, the SAFER you system
is”
• With plunger lift wells – “optimization and
safety work well together”
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