Setting Plunger Fall Velocity u - Rick Nadkrynechny

8/9/2019 Setting Plunger Fall Velocity u - Rick Nadkrynechny

1/24

SETTING PLUNGER FALL VELOCITUSING VENTURI PLUNGERSRick Nadkrynechny, T-Ram CanadaDavid Green, Well Master CorporationLynn Rowlan, Echometer


2/24

Venturi plunger bydefinition

• noun pl. ven·tu·ris A short tube with a constricted throatused to determine fluid pressures and velocities bymeasurement of differential pressures generated at thethroat as a fluid traverses the tube.

• A constricted throat in the air passage of a carburetor,causing a reduction in pressure that results in fuel vapor

being drawn out of the carburetor bowl.


3/24

What the Venturi is NOT…. • A version of the Capillary Plunger

from the early 1980’s • A hollowed plunger with an

opening at the upper end of astandard fish neck

• A simple means of bypassing gasthrough the body of the plunger

(Reference Dr. J.F. Lea, private correspondence,from an internal report for Amoco, 1984)


4/24

Venturi history – whenand why?

• Testing began in 2007 after numerous encounters with damaged bypass plungers

• “hollow sleeves” from damaged bypass plungers would still

sometimes surface without the internals• Industry misconceptions surrounding fall velocities and conventional

vs continuous applications are still a problem• There was a need to create a “fast falling” plunger without any

moving parts to assist with improper lubricator plunger piping

arrangements• Patent pending status granted in 2010.• Testing still ongoing to further evaluate design enhancements

including shift valve arrangements.


5/24

The Concept

LowerChamber

UpperChamber

InternalFish Neck

Venturi Orifice


6/24

How does the venturiconcept work in a plunger?

• The orifice provides the mechanism for the effect to occur• A pressure differential is created across the orifice while the plunger

is rising causing an accelerated flow regime inside the tool.• The accelerated flow regime interacts via the exit of the tool “helping

lift” • The upper chamber is at a lower pressure than the lower chamber and

the accelerated flow through the orifice creates hydrodynamic lift•

The upper chamber also collects liquid from the liquid column abovethe plunger and from the tubing wall as it ascends• The upper chamber then acts as a mixing chamber, where gas and

liquid are intensely mixed, creating a “traveling gas lift valve “effect.


7/24

CFD – VelocityPlot of FullCross Section


8/24

CFD View of Venturi Action – CrossSection at VenturiOrifice VelocityPlot


9/24

CFD Flow Vectors Shows Strong Mixing Action in Upper Chamber


10/24

Venturi set up considerations• Determine if the well is a conventional/continuous candidate• Orifice selection based on expected gas velocities and casing

pressure build rates• Strong wells allow for larger orifices thus increasing fall velocities as

a result• Weaker wells require smaller orifices thus enhancing the venturi

effect – fall velocities become less important• Material selection to address risk management – especially low

pressure wells• Auto catch/dual outlet considerations – based on length of after flow

periods


11/24

imilar looks Some plungers may look the same

but different metals can reduceimpact force.

1000 ft./min = 2282 lbs. impact force [steel]

1000 ft./min = 1548 lbs. impact force [titanium]


12/24

Orifice selection


13/24


14/24

Orifice selection to address build rate

Foss & GaulPcMax

By-pass

Bypass or10 mm

8 or 4.7 mm

4.7 mm, Barstock or Pad


15/24

Venturicontinuous/bypass considerations

• Dual outlet required to guaranteeshift pin behavior

• Auto catch required to prevent“freewheeling” and to ensure shift

pin behavior• Not a good fit for wax/debris• Ensure 12-15 ft./second at the

bottom of the well• Fall velocity against flow can be

controlled through orifice selectionas well as material selection.

• Fall rates on bypass plungers can be controlled to avoid exceeding bumper spring limits under “worstcase scenarios”


16/24

STEP 1 – BUILD WELL BOREUsing ProdOp Program – Dr. J.F. Lea


17/24

Step 2 – input expected conditionsUsin ProdO Pro ram – Dr. J.F. Lea


18/24

Using ProdOp Program – Dr. J.F. Lea

Case 1: 250 MCF 1000 PSI – 4.7MMORIFICE


19/24

Case 2: 250 MCF 200 PSI - 8MMORIFICE OR SMALLERUsing ProdOp Program – Dr. J.F. Lea


20/24

Case 3: 250 MCF 75 PSI - CONTINUOUS OR

LARGE ORIFICE VENTURI?Using ProdOp Program – Dr. J.F. Lea


21/24

Pinedale Anticline High Pressure, low velocity well, switch from Barstockto 4.7 mm Venturi, 60 Day window, typical result

Venturi Dropped

Casing P drops 100 psi

Gas up 50 mcf/d

Operators report steadieroperation than Barstock,faster recovery from linepressure spikes with lessintervention

f


22/24

Change from Barstock to 8 mm

Venturi (2- 7/8”)

Flowrate increase from 14 to 18.2 e3m3/d(494 to 643 mcf/d)

Tubing Pressure increases by 300 kpa (44psi)


23/24

Change from Single Pad to 8

mm Venturi

Increase flowrate from 4.5 to 14.9 e3m3/d(159 to 526 mcf/d)


24/24

Conclusions

• The Venturi Plunger is a new and unique concept for plunger design• The Venturi concept produces a “traveling gas lift valve effect” on

the liquid column• Plunger selection can now be made more easily based on well

readiness• Venturi Plungers can have different orifice sizes to tailor the fall rate

to the well• Gas rise velocity is a very important parameter in selecting an

appropriate plunger• Plunger velocity on both fall and rise is controllable and desirable for

optimization and safety• Plunger mass is an important factor for safety and operation,

particularly in low line pressure wells

Documents

Setting Plunger Fall Velocity u - Rick Nadkrynechny