Gas Well Deliquification Workshop Sheraton Hotel, February 20 22, 2017 Using Kinetic Energy for Plunger Lift Safety and Maintenance Mark Scantlebury, President and CEO Extreme Telematics Corp.
THE CHANGING PLUNGER LIFT INDUSTRY A new standard 2
Impacts at Surface Impact at surface is critically important Spring and lubricator together absorb the energy at surface Repetitive fast plunger arrivals lead to broken plungers and springs If spring is compromised, energy is transferred to lubricator 3
API 11 PL Specification Covers Plunger Lift Lubricators and Related Equipment Operators and equipment manufactures collaborate to create a common set of standards for the plunger lift industry Helps identify quality manufacturers that properly design, construct, and test plunger lift equipment for reliable, safe operation Manufacturers are required to provide a kinetic energy rating, shifting the way plunger wells are monitored and controlled 4
THE IMPORTANCE OF KINETIC ENERGY An essential measurement for safety and maintenance 5
Kinetic Energy The energy of a plunger is transferred to the spring and lubricator The kinetic energy can be calculated just before this contact KE = 1 2 mv2 Units are kg m2 ss or joules 1 joule = 0.73756 ft lb Doubling the mass of the plunger doubles the kinetic energy Velocity is squared, greatly affecting the energy absorbed by the lubricator and spring 6
Kinetic Energy Can be used by the control system for safety when compared to user defined values for: Hard Hit Dangerous Hit Operation is stopped after a user defined number of hard hits or a single dangerous hit. Sum kinetic energy long term for predictive maintenance 7
Kinetic Energy Need an accurate kinetic energy for each plunger arrival regardless of how it will be used To use Kinetic Energy, we need accurate: ratings from manufacturers plunger mass plunger surface velocity 8
AVERAGE PLUNGER VELOCITY A Flawed Approach 9
Calculating Average Plunger Velocity Most systems still rely on average plunger velocity Simply use the well depth and arrival time v = d/t System Parameters Depend on Plunger Type and Lubricator Target of 750 ft/min Fast Trip > 1000 ft/min Dangerous Trip > 2000 ft/min Well Depth Feb. 20-22, 2017 10
Average Velocity Issues Assumes that the plunger was at bottom Ignores acceleration and deceleration Potential damage to plunger, lubricator, and spring without knowing it The plunger is not entering the lubricator at the velocity you think it is 11
MEASURING SURFACE VELOCITY A first step 12
Geomagnetic sensing technology Operation Velocity measured as plunger passes Switch closed once velocity is available Logs all arrivals even when control system has moved on Modbus port used to retrieve velocity and access settings and logs Interfaces Dry contact switch RS-485 Modbus slave 13
Surface Velocity Diagnostic Kit Sasquatch Plunger Velocity Sensor Link Device Connection Vision Device Management Software 14
Surface Velocity Capture 15
ANALYZING SURFACE VELOCITY DATA What can we learn? 16
Kinetic Energy on Venting 7.5 lb (3.4 kg) Plunger Average Velocity calculated at 400 ft/min (122 m/min) Estimated KE = 7.02J Surface Velocity recorded as 2025 ft/min (617 m/min) Actual KE = 180 J Over 25x more energy than expected Was occurring once every few hours 17
Consistent High Kinetic Energy 9 lb (4.1 kg) Plunger Average Velocity of 750 ft/min (229 m/min) Estimated KE = 29.76 J Surface Velocity regularly 1200 ft/min (366 m/min) Actual KE = 76.18 J Over 6 months (4300 arrivals) spring has absorbed 200 kj more than anticipated Feb. 29 Mar. 2, 2016 2016 Gas Well Deliquification Workshop 18
Dangerous Hit 10 lb (4.54 kg) Plunger Average Velocity of 250 m/min (820 ft/min) Estimated KE = 39.4 J Surface Velocity peaks 1714 m/min (5623 ft/min) Actual KE = 1853 J Single arrival may be enough to collapse spring completely 19
UNDERSTANDING LUBRICATOR SPRINGS Infinite life vs certain failure 20
Compression Spring Background Most springs designed for infinite life or 1x10 7 cycles Spring manufacturers typically recommend that the spring is not pushed beyond 85% of the maximum deflection. Springs are typically designed to withstand 40% - 45% of tensile stress before fully collapsing Design is typically based on ideal conditions 21
Spring Cycle Life Many factors affect the life of a spring Stress Material Quality Corrosion Cyclic Frequency Impact Loading Any rating for a spring must be greatly reduced As technology is developed, regular spring inspections are a must 22
Spring Example The following spring is an example only Name Material Wire Diameter Rate Coil OD Coil Mean Diameter Length Max Deflection Parameter Chrome Silicon 0.476 in 410 lbf/in 2.555 in 2.074 in 14.25 in 3.694 in 23
Kinetic Energy to Move Spring We can evaluate the amount of maximum amount of energy based on the spring rate k = 410 lbf = 71839.7 N/m Energy to move the spring is E = 1 2 k d2 100% travel is 3.695 in (0.0939 m) E = 316 J 85% travel is 3.1408 in (0.0798 m) E = 229 J 24
Plunger Velocity and Mass We should always operate this plunger well under 229 J and stop operation at 316 J to inspect the spring We can calculate the velocity of each based on plunger mass % Deflection Energy 10 lb (4.54 kg) Plunger 15 lb (6.80 kg) Plunger 85 229 J 1978 ft/min (603 m/min) 1616 ft/min (492 m/min) 100 316 J 2324 ft/min (708 m/min) 1898 ft/min (578 m/min) This will vary greatly for each spring. These numbers are shown just for illustrative purposes. 25
ADVANCING SAFETY AND PREDICTIVE MAINTENANCE Developing a model for spring failure 26
Pilot Projects ETC is currently running several pilot projects with plunger lift well operators Activities include: Monitoring of surface velocity over time Calculation of Kinetic Energy Regular spring inspections Build model to relate kinetic energy to spring wear Test model against empirical data Goals Predict spring wear Predict spring failure 27
Conclusions Kinetic energy is the most important factor for safety and maintenance in plunger lift wells We can use kinetic energy for safety today More work needs to be done to model spring fatigue and failure The more operators and manufacturers that embrace kinetic energy, the better off the industry will be. 28
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