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Foam Flow Meeting, January 23, 2014 1 Liquid Loading Current Status, New Models and Unresolved Questions Mohan Kelkar and Shu Luo The University of Tulsa.

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Presentation on theme: "Foam Flow Meeting, January 23, 2014 1 Liquid Loading Current Status, New Models and Unresolved Questions Mohan Kelkar and Shu Luo The University of Tulsa."— Presentation transcript:

1 Foam Flow Meeting, January 23, 2014 1 Liquid Loading Current Status, New Models and Unresolved Questions Mohan Kelkar and Shu Luo The University of Tulsa

2 Foam Flow Meeting, January 23, 2014 2 Outline Definition of liquid loading Literature Survey Our Data Model Formulation Model Validation Program Demonstration Summary

3 Foam Flow Meeting, January 23, 2014 3 What is liquid loading? Minimum pressure drop in the tubing is reached The liquid drops cannot be entrained by the gas phase (Turner et al.) The liquid film cannot be entrained by the gas phase (Zhang et al., Barnea) The answers from different definitions are not the same

4 Foam Flow Meeting, January 23, 2014 4 Traditional Definition OPR IPR Transition Point Stable Unstable Liquid Loading

5 Foam Flow Meeting, January 23, 2014 5 Traditional Definition

6 Foam Flow Meeting, January 23, 2014 6 Definition Based on Mechanisms Two potential mechanisms of transition from annular to slug flow  Droplet reversal  Film Reversal Models are either based on droplet reversal (Turner) or film reversal (Barnea)

7 Foam Flow Meeting, January 23, 2014 7 Literature Data Air-water data are available The data reported is restricted to 2” pipe Very limited data are available in pipes with diameters other than 2” No data are available for other fluids

8 Foam Flow Meeting, January 23, 2014 8 Generalized Conclusions (2” pipe)

9 Foam Flow Meeting, January 23, 2014 9 Liquid Film Reversal Westende et al., 2007

10 Foam Flow Meeting, January 23, 2014 10 Liquid Film Reversal Westende et al., 2007 At 15 m/s, liquid starts to flow counter current with the gas stream

11 Foam Flow Meeting, January 23, 2014 11 Liquid Film Reversal Zabaras et al., 1986 Minimum is at 20 m/s (blue line) Residual pressure reaches a zero value at lower velocity

12 Foam Flow Meeting, January 23, 2014 12 Entrained Liquid Fraction Alamu, 2012

13 Foam Flow Meeting, January 23, 2014 13 Inception of Liquid Loading Belfroid et al., 2013 For vertical pipe OLGA = 12 m/s Exptl = 14 m/s

14 Foam Flow Meeting, January 23, 2014 14 Our Data

15 Foam Flow Meeting, January 23, 2014 15 Air-Water Flow Skopich and Ajani conducted experiments in 2” and 4” pipes The results observed are different based on film reversal and minimum pressure drop – consistent with literature However, the experimental results are very different for 2” versus 4” pipe

16 Foam Flow Meeting, January 23, 2014 16 Calculation Procedure Total pressure drop is measured and gradient is calculated Holdup is measured and gravitational gradient is calculated Subtracting gravitational pressure gradient from total pressure gradient to get frictional pressure gradient By dividing the incremental pressure gradient by incremental gas velocity, changes in gravitational and frictional gradients with respect to gas velocity are calculated.

17 Foam Flow Meeting, January 23, 2014 17 dP G vs. dP F Air-Water, 2 inch, v sl =0.01 m/s Minimum

18 Foam Flow Meeting, January 23, 2014 18 Total dp/dz Air-Water, 2 inch, v sl =0.01 m/s Film Reversal

19 Foam Flow Meeting, January 23, 2014 19 dP/dz) G vs. dP/dz) F Air-Water, 2 inch, v sl =0.01 m/s dp/dz) F is zero

20 Foam Flow Meeting, January 23, 2014 20 dP T - dP G Air-Water, 2 inch, v sl =0.01 m/s Transition at 16 m/s

21 Foam Flow Meeting, January 23, 2014 21 Pressure at Bottom Air-Water, 2 inch, v sl =0.01 m/s Pressure build up No pressure build up

22 Foam Flow Meeting, January 23, 2014 22 dP/dz) G vs. dP/dz) F Data from Netherlands (2 inch) dp/dz) F is zero

23 Foam Flow Meeting, January 23, 2014 23 What should we expect for 3” or 4” pipeline?

24 Foam Flow Meeting, January 23, 2014 24 dP G vs. dP F Air-Water, 4 inch, v sl =0.01 m/s Minimum

25 Foam Flow Meeting, January 23, 2014 25 Total dp/dz Air-Water, 4 inch, v sl =0.01 m/s Film Reversal

26 Foam Flow Meeting, January 23, 2014 26 dP/dz) G vs. dP/dz) F TUFFP (3 inch, v sl =0.1 m/s) dp/dz) F is zero

27 Foam Flow Meeting, January 23, 2014 27 dP/dz) G vs. dP/dz) F Air-Water, 4 inch, v sl =0.01 m/s dp/dz) F is zero Film reversal

28 Foam Flow Meeting, January 23, 2014 28 Effect of Diameter on Liquid Loading

29 Foam Flow Meeting, January 23, 2014 29 Why diameter impacts? Film thickness? Skopich et al., SPE 164477

30 Foam Flow Meeting, January 23, 2014 30 Liquid Loading Definition Liquid loading starts when liquid film reversal occurs We adopt the model of film reversal to predict inception of liquid loading The reason for this adoption, as we will show later, is because we are able to better predict liquid loading for field data using this methodology.

31 Foam Flow Meeting, January 23, 2014 31 Background Turner’s Equation The inception of liquid loading is related to the minimum gas velocity to lift the largest liquid droplet in the gas stream. Turner et al.’s Equation: This equation is adjusted upward by approximately 20 percent from his original equation in order to match his data.

32 Foam Flow Meeting, January 23, 2014 32 Background Drawbacks with Turner’s Equation Turner’s equation is not applicable to all field data. Coleman et al. proposed equation (without 20% adjustment ) Veeken found out that Turner’s results underestimate critical gas velocity by an average 40% for large well bores. Droplet size assumed in Turner’s equation is unrealistic based on the observations from lab experiments. Turner’s equation is independent of inclination angle which is found to have great impact on liquid loading.

33 Foam Flow Meeting, January 23, 2014 33 Approach Film Model Two film models are investigated to predict liquid loading:  Zhang et al.’s model(2003) is developed based on slug dynamics.  Barnea’s model(1986) predicts the transition from annular to slug flow by analyzing interfacial shear stress change in the liquid film.

34 Foam Flow Meeting, January 23, 2014 34 Approach Barnea’s Model Constructing force balance for annular flow and predict the transition from annular to slug flow by analyzing interfacial shear stress changes. The combined momentum equation: Interfacial shear stress with Wallis correlation: Schematic of Annular Flow

35 Foam Flow Meeting, January 23, 2014 35 Approach Barnea’s Model Transition Solid curves represent Interfacial shear stress from combined momentum equation Broken curves represent Interfacial shear stress from Wallis correlation Intersection of solid and broken curves yields a steady state solution of film thickness and gas velocity at transition boundary Another transition mechanism is liquid blocking of the gas core.

36 Foam Flow Meeting, January 23, 2014 36 Model Formulation In inclined wells, the film thickness is expected to vary with radial angle Vertical WellInclined Well

37 Foam Flow Meeting, January 23, 2014 37 Original Barnea’s Model at Different Inclination Angles

38 Foam Flow Meeting, January 23, 2014 38 Non-uniform Film Thickness Model

39 Foam Flow Meeting, January 23, 2014 39 Non-uniform Film Thickness Model Let A 1 =A 2, we can find this relationship. If film thickness reaches maximum at 30 degree inclination angle

40 Foam Flow Meeting, January 23, 2014 40 Non-uniform Film Thickness Model

41 Foam Flow Meeting, January 23, 2014 41 Non-uniform Film Thickness Model Only maximum film thickness will be used in the model because thickest film will be the first to fall back if liquid loading starts. Find critical film thickness δ T by differentiating momentum equation. δ T equals to maximum film thickness δ(π,30).

42 Foam Flow Meeting, January 23, 2014 42 Non-uniform Film Thickness Model

43 Foam Flow Meeting, January 23, 2014 43 Other Film Shape

44 Foam Flow Meeting, January 23, 2014 44 Interfacial Friction Factor Critical gas velocity calculated by Barnea’s model is conservative compared to other methods. Fore et al. showed that Wallis correlation is reasonable for small values of film thickness and is not suitable for larger film thickness liquid film. A new correlation is used in the new model :

45 Foam Flow Meeting, January 23, 2014 45 Turner’s Data 106 gas wells are reported in his paper, all of the gas wells are vertical wells. 37 wells are loaded up and 53 wells are unloaded. 16 wells are reported questionable in the paper. Current flow rate and liquid loading status of gas well are reported.

46 Foam Flow Meeting, January 23, 2014 46 Turner’s Model Results Turner’s Data V g < V g,c V g > V g,c

47 Foam Flow Meeting, January 23, 2014 47 Barnea’s Model Results Turner’s Data

48 Foam Flow Meeting, January 23, 2014 48 New Model Results Turner’s Data

49 Foam Flow Meeting, January 23, 2014 49 Coleman’s Data 56 gas wells are reported, all of the wells are also vertical wells. These wells produce at low reservoir pressure and at well head pressures below 500 psi. Coleman reported gas velocity after they observed liquid loading in gas wells.

50 Foam Flow Meeting, January 23, 2014 50 Turner’s Model Results Coleman’s Data

51 Foam Flow Meeting, January 23, 2014 51 Barnea’s Model Results Coleman’s Data

52 Foam Flow Meeting, January 23, 2014 52 New Model Results Coleman’s Data

53 Foam Flow Meeting, January 23, 2014 53 Veeken’s Data Veeken reported offshore wells with larger tubing size. 67 wells, which include both vertical and inclined wells, are presented. Similar to Coleman’s data, critical gas rate was reported. Liquid rate were not reported in the paper. We assumed a water rate of 5 STB/MMSCF.

54 Foam Flow Meeting, January 23, 2014 54 Turner’s Model Results Veeken’s Data

55 Foam Flow Meeting, January 23, 2014 55 Barnea’s Model Results Veeken’s Data

56 Foam Flow Meeting, January 23, 2014 56 New Model Results Veeken’s Data

57 Foam Flow Meeting, January 23, 2014 57 Chevron Data Production data:  Monthly gas production rate  Monthly water and oil production rate 82 wells have enough information to analyze liquid loading Two tubing sizes: 1.995 and 2.441 inch Get average gas and liquid production rate when cap string is installed from service history. Assume liquid loading occurred at this point.

58 Foam Flow Meeting, January 23, 2014 58 Production Data

59 Foam Flow Meeting, January 23, 2014 59 Turner’s Model Results Chevron Data

60 Foam Flow Meeting, January 23, 2014 60 New Model Results Chevron Data

61 Foam Flow Meeting, January 23, 2014 61 ConocoPhillips Data Daily production data and casing and tubing pressure data are available Select 62 wells including 7 off-shore wells Two tubing size: 1.995 and 2.441 inch Determine liquid loading by casing and tubing pressure divergence.

62 Foam Flow Meeting, January 23, 2014 62 ConocoPhillips Field Data P c and P t diverge Liquid Loading starts at 400 MCFD liquid loading starts

63 Foam Flow Meeting, January 23, 2014 63 Turner’s Model Results ConocoPhillips Data

64 Foam Flow Meeting, January 23, 2014 64 New Model Results ConocoPhillips Data

65 Foam Flow Meeting, January 23, 2014 65 Future Improvements Better interfacial f i correlation

66 Foam Flow Meeting, January 23, 2014 66 Improvements Liquid Entrainment  Impact on the inception of liquid loading Collection of 5” data Pressure drop inspection for larger diameter pipes Incorporation of foam data in model

67 Foam Flow Meeting, January 23, 2014 67 Summary Liquid film reversal is the most appropriate model for defining liquid loading The effect of diameter on liquid loading is significant and is related to square root of diameter The film reversal can be detected either by observation of film or residual pressure drop

68 Foam Flow Meeting, January 23, 2014 68 Thank You! Questions…


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