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?
Is your logic set up ok? Is this why plungers break? 2200.0 1.5 2000.0 1800.0 1600.0 1400.0 1200.0 1000.0 1.0 0.5 0-0.5-1.0 800.0 0.000 13.889 27.778 41.667 55.556 69.444 83.333-1.5 Every time a plunger well is shut in for whatever the reason the situation is worsened the longer the well is shut in.
Hydrates
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. Too Slow Target Too Fast Gas Slips By Plunger May Never Reach Surface Wastes Well psi Damages Equipment
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.
Weight vs velocity
A 9.8 Lbs plunger @ 1000 Ft/min has the same Kinetic energy as a 3.2 Lb plunger @ 1700 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 1700 1000 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 2000 600 ft/min
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
Large slugs can promote high energy situations 2200.0 2000.0 Pressure required for large slug 1.5 1.0 1800.0 1600.0 1400.0 1200.0 Pressure required for optimized slug 0.5 0-0.5 1000.0-1.0 800.0 0.000 13.889 27.778 41.667 55.556 69.444 83.333-1.5
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