using kinetic energy for plunger lift safety and...

Gas Well Deliquification Workshop

Sheraton Hotel, Denver, Colorado

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

Feb. 20 – 22, 2017 2017 Gas Well Deliquification Workshop

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Impacts at Surface


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• 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

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


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THE IMPORTANCE OF KINETIC ENERGY An essential measurement for safety and maintenance


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Kinetic Energy


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• The energy of a plunger is transferred to the

spring and lubricator

• The kinetic energy can be calculated just

before this contact

– 𝑲𝑬 =𝟏

𝟐𝒎𝒗𝟐

– 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

Kinetic Energy


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• 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

Kinetic Energy


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• 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

AVERAGE PLUNGER VELOCITY A Flawed Approach


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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 2017 Gas Well Deliquification Workshop

Denver, Colorado

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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


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MEASURING SURFACE VELOCITY A first step


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• 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


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Surface Velocity Diagnostic Kit


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• Sasquatch Plunger

Velocity Sensor

• Link Device Connection

• Vision Device

Management Software

Surface Velocity Capture


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ANALYZING SURFACE VELOCITY DATA What can we learn?


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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


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Consistent High Kinetic Energy

Feb. 29 – Mar. 2, 2016 2016 Gas Well Deliquification Workshop

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• 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

Dangerous Hit


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• 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

UNDERSTANDING LUBRICATOR SPRINGS Infinite life vs certain failure


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Compression Spring Background

• Most springs designed for “infinite life” or 1x107

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


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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


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Spring Example

• The following spring is an example only


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Name Parameter

Material Chrome Silicon

Wire Diameter 0.476 in

Rate 410 lbf/in

Coil OD 2.555 in

Coil Mean Diameter 2.074 in

Length 14.25 in

Max Deflection 3.694 in

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


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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

• This will vary greatly for each spring. These

numbers are shown just for illustrative purposes.


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% 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)

ADVANCING SAFETY AND PREDICTIVE MAINTENANCE Developing a model for spring failure


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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


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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.


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Copyright

Rights to this presentation are owned by the company(ies) and/or author(s) listed on the title page. By submitting this presentation to the Gas Well Deliquification Workshop, they grant to the Workshop, the Artificial Lift Research and Development Council (ALRDC), and the Southwestern Petroleum Short Course (SWPSC), rights to:

– Display the presentation at the Workshop.

– Place it on the www.alrdc.com web site, with access to the site to be as directed by the Workshop Steering Committee.

– Place it on a CD for distribution and/or sale as directed by the Workshop Steering Committee.

Other use of this presentation is prohibited without the expressed written permission of the author(s). The owner company(ies) and/or author(s) may publish this material in other journals or magazines if they refer to the Gas Well Deliquification Workshop where it was first presented.


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The Artificial Lift Research and Development Council and its officers and trustees, and the Gas Well Deliquification Workshop Steering Committee members, and their supporting organizations and companies (here-in-after referred to as the Sponsoring Organizations), and the author(s) of this Technical Presentation or Continuing Education Training Course and their company(ies), provide this presentation and/or training material at the Gas Well Deliquification Workshop "as is" without any warranty of any kind, express or implied, as to the accuracy of the information or the products or services referred to by any presenter (in so far as such warranties may be excluded under any relevant law) and these members and their companies will not be liable for unlawful actions and any losses or damage that may result from use of any presentation as a consequence of any inaccuracies in, or any omission from, the information which therein may be contained.

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