Setting Plunger Fall Velocity Using Venturi Plungers

Transcription

1 Gas Well Deliquification Workshop Sheraton Hotel, February 27 March 2, 2011 Setting Plunger Fall Velocity Using Venturi Plungers Rick Nadkrynechny, T-Ram Canada David Green, Well Master Corporation Lynn Rowlan, Echometer

2 Venturi Plunger Definition noun pl. ven tu ris A short tube with a constricted throat used to determine fluid pressures and velocities by measurement of differential pressures generated at the throat 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. 2

3 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 a standard fish neck A simple means of bypassing gas through the body of the plunger (Reference Dr. J.F. Lea, private correspondence, from an internal report for Amoco, 1984) 3

4 Venturi History When And 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 Testing still ongoing to further evaluate design enhancements including shift valve arrangements. 4

5 The Concept Internal Fish Neck Upper Chamber Venturi Orifice Lower Chamber 5

6 How Does The Venturi Concept 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 above the 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. 6

7 CFD Velocity Plot of Full Cross Section 7

8 CFD View of Venturi Action Cross Section at Venturi Orifice ~ Velocity Plot 8

9 CFD Flow Vectors Shows Strong Mixing Action in Upper Chamber 9

10 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 10

11 SIMILAR LOOKS Some plungers may look the same but different metals can reduce impact force ft./min = 2282 lbs. impact force [steel] 1000 ft./min = 1548 lbs. impact force [titanium] 11

12 ORIFICE SELECTION 10 mm 8 mm 4.7 mm 0 mm 12

13 13

14 Orifice Selection To Address Build Rate By-pass Bypass or 10 mm 4.7 mm, Barstock or Pad Foss & Gaul PcMax 8 or 4.7 mm 14

15 Venturi Continuous/Bypass Considerations Dual outlet required to guarantee shift pin behavior Auto catch required to prevent freewheeling and to ensure shift pin behavior Not a good fit for wax/debris Ensure ft./second at the bottom of the well Fall velocity against flow can be controlled through orifice selection as well as material selection. Fall rates on bypass plungers can be controlled to avoid exceeding bumper spring limits under worst case scenarios 15

16 STEP 1 BUILD WELL BORE ProdOp Program Dr. J.F. Lea 16

17 STEP 2 EXPECTED CONDITIONS INPUT ProdOp Dr. J.F. Lea 17

18 Case 1: 250 MCF 1000 PSI 4.7MM ORIFICE ProdOp Program Dr. J.F. Lea 18

19 Case 2: 250 Mcf 200 Psi - 8mm Orifice Or Smaller ProdOp Program Dr. J.F. Lea 19

20 Case 3: 250 Mcf 75 Psi - Continuous Or Large Orifice ProdOp Program Dr. J.F. Lea 20

21 Pinedale Anticline High Pressure, low velocity well, switch from Barstock to 4.7 mm Venturi, 60 Day window, typical result Casing P drops 100 psi Gas up 50 mcf/d Venturi Dropped Operators report steadier operation than Barstock, faster recovery from line pressure spikes with less intervention 21

22 Change from Barstock to 8 mm Venturi (2-7/8 ) Flow rate increase from 14 to 18.2 e3m3/d (494 to 643 mcf/d) Tubing Pressure increases by 300 kpa (44 psi) 22

23 Change from Single Pad to 8 mm Venturi Increase I flow rate from 4.5 to 14.9 e3m3/d (159 to 526 mcf/d) 23

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 24

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