Recording Dynagraph on Bent / Misaligned Polished rod.

Transcription

1 8 th Annual Sucker Rod Pumping Workshop Renaissance Hotel Oklahoma City, Oklahoma September 25-28, 2012 Recording Dynagraph on Bent / Misaligned Polished rod. Avinav Kumar, Atul D Patil Oil and Natural Gas Corporation ( ONGC ), India

2 Introduction Dynamometer card used for years to establish and optimize rod pump system efficiency. Proper analysis of dynamometer important to ascertain surface and sub-surface pumping problems. Predominantly used dynamometer Polished rod transducer ( PRT ) and Horse shoe load cell Sucker Rod Pumping Workshop 2

3 Introduction Both PRT and Horse shoe load cell records load at the polished rod ( plotted along Y axis ) as a function of polished rod displacement ( plotted along X axis ). An ideal surface & sub-surface cards usually rectangular in shape Sucker Rod Pumping Workshop 3

4 Dynamometers Load Cell General three types of dynamometers used to acquire dynamometer data : Dynamometer Mechanical Hydrualic Electronic Polished Rod transducer Horseshoe Load cell Electronic dynamometers being used predominantly 2012 Sucker Rod Pumping Workshop 4

5 Polished Rod Transducer (PRT) PRT is attached 6 8 below the carrier bar. Unit not stopped during installation. Position of plunger in the pump barrel not changed during installation Sucker Rod Pumping Workshop 5

6 Polished Rod Transducer (PRT) PRT measures change in diameter / elongation in polished rod due to stress in axial direction and converts corresponding strain to change in load on polished rod Sucker Rod Pumping Workshop 6

7 Polished Rod Transducer (PRT) Load measurement Radial Strain (Ɛ)=(δd)/D Axial Strain ( )= Radial Strain ( ) / Poisson s Ratio ( ) Axial Stress = Polished rod load (PRL) / cross sectional area (A) = Axial Strain (Ɛ ) * Young's modulus ( E ) PRL =[(δd ) /( D)*E *A]/ ( ) Position measurement : using accelerometer Load at various position plotted against position to generate surface and sub-surface dyna cards Sucker Rod Pumping Workshop 7

8 Polished Rod Transducer (PRT) Bent Polished rod will not have uniform change in diameter at all the points along the rod diameter at particular distance from carrier bar. At point A and B diameter change not uniform. Dyna cards shapes different at point A and B Sucker Rod Pumping Workshop 8

9 Polished Rod Transducer (PRT) Dyna cards shapes different at point A and B. Sloped /aberrantly shaped Sucker Rod Pumping Workshop 9

10 Polished Rod Transducer (PRT) 2012 Sucker Rod Pumping Workshop 10

11 Polished Rod Transducer (PRT) Inherent bent in polished rod not visible to naked eye. Bent induced in the polished rod : Misaligned carrier bar. Unit not centered properly. Unit too far forward / back Sucker Rod Pumping Workshop 11

12 Polished Rod Transducer (PRT) Misaligned carrier bar 2012 Sucker Rod Pumping Workshop 12

13 Polished Rod Transducer (PRT) Unit not centered properly 2012 Sucker Rod Pumping Workshop 13

14 Polished Rod Transducer (PRT) Unit too ahead or back 2012 Sucker Rod Pumping Workshop 14

15 Horse shoe load cell is attached between pumping unit carrier bar and polished rod clamp. Unit stopped during installation. Position of plunger in the pump barrel changed during installation. Horse Shoe Load Cell 2012 Sucker Rod Pumping Workshop 15

16 Horse Shoe Load Cell Measures the load directly, unknown or inaccurate physical properties of polished rod have no influence 2012 Sucker Rod Pumping Workshop 16

17 PRT vs. Horse shoe load cell Polished Rod Transducer Horse shoe Load cell Load measurement Converts strain to load on the polished rod during the stroke. Horse shoe load cell measures the load directly Installation Installed 6 8 below carrier bar. Unit not stopped during installation Betweenclampandcarrierbar.Unit stopped for installation 2012 Sucker Rod Pumping Workshop 17

18 PRT vs. Horse shoe load cell Polished Rod Transducer Horse shoe Load cell Plunger position Position of plunger in pump is not changed Position of plunger in pump changed during horse shoe installation Bent / misaligned polished rod Inherent bent in polished rod or misaligned polished rod affects recording of load by PRT Hose shoe load cell measures load directly 2012 Sucker Rod Pumping Workshop 18

19 Case Studies Well A Completion details: Production Details Tubing 2 7/8 Liquid (bbls/day) 80 Pump depth / diameter 1000 mts / 2.25 Water cut 90% SRP unit API 160D Oil rate (bbls/day) 8 Pump operating Parameters Echo meter results Stroke length 71.4 Static liquid level NA SPM 2.2 Dynamic liquid level NA Envisaged production at 100% pump efficiency = 90 bbl./day. Actual production = 80 bbl./day 2012 Sucker Rod Pumping Workshop 19

20 Case Studies Well A With Polished Rod Transducer Fig 1 Fig Sucker Rod Pumping Workshop 20

21 Case Studies Well A With Polished Rod Transducer Fig 3 Fig Sucker Rod Pumping Workshop 21

22 With Horse shoe load cell Case Studies Well A Fig Sucker Rod Pumping Workshop 22

23 Case Studies Well A Production Parameters : Stroke length : 74 ; Production : 85 bbl./day Figure Load Cell used Surface Stroke Length Subsurface Stroke Length PPRL (lbs.) MPRL (lbs.) Pump displacement (bbls/day) from Dynacard Fig 1 PRT Fig 2 PRT Fig 3 PRT Fig 4 PRT Fig 5 Horse Shoe Sucker Rod Pumping Workshop 23

24 Case Studies Well A Pumping unit not centred properly : 2012 Sucker Rod Pumping Workshop 24

25 Case Studies Well A Polished Rod not straight : 2012 Sucker Rod Pumping Workshop 25

26 Case Studies Well B Completion details: Production Details Tubing 2 7/8 Liquid (bbls/day) 120 Pump depth / diameter 1000 mts / 2.25 Water cut 80% SRP unit C Oil rate (bbls/day) 24 Pump operating Parameters Echo meter results Stroke length 71.3 Static liquid level NA SPM 3.7 Dynamic liquid level 75 mts Envisaged production at 100% pump efficiency = 135 bbl./day. Actual production = 120 bbl./day 2012 Sucker Rod Pumping Workshop 26

27 Case Studies Well B With Polished Rod Transducer Fig 6 Fig Sucker Rod Pumping Workshop 27

28 Case Studies Well B With Polished Rod Transducer Fig Sucker Rod Pumping Workshop 28

29 Case Studies Well B Production Parameters : Stroke length : 74 ; Production : 120 bbl./day Pump displacement Figure Load Cell used Surface Stroke Length Subsurface Stroke Length PPRL (lbs.) MPRL (lbs.) (bbls/day) from Dynacard Fig 6 PRT Fig 7 PRT Fig 8 PRT Horse shoe load cell could not be used due to unavoidable reason 2012 Sucker Rod Pumping Workshop 29

30 Case Studies Well B Unit too back : 2012 Sucker Rod Pumping Workshop 30

31 Conclusion Though Polished rod transducer is quick and easy to install, it may not represent actual pump action every time. Any inherent bent or bent induced in polished rod will affect load recording by PRT. Horseshoe measures load directly, any inherent bent or any induced bent will have no effect on recording of load Sucker Rod Pumping Workshop 31

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