Lesson 9

1. Lesson 9 Gasified Liquid Hydraulics Read: UDM Chapter 2.7 pages 2.131-2.179

2. Gasified Liquid Hydraulics • Reynolds Number • Multi-phase flow • Pressure prediction • HSP • Circulating pressure • Bit pressure drop • Hole Cleaning Harold Vance Department of Petroleum Engineering

3. Reynolds Number • In practice the flow of gasified liquid is almost always turbulent (Reynolds number > 4000) • Example water flowing up an 8 1/2” hole with 5” drillpipe. • AV of 7 ft/min would be turbulent • AV’s > 100 ft/min are common Harold Vance Department of Petroleum Engineering

4. Reynolds Number • Equation 2.58 Harold Vance Department of Petroleum Engineering

5. Reynolds Number • The consequenses of turbulance in the annulus is that the rheology of gasified fluids has little effect on the annular pressure profile. • This is at least true with un-viscosified base fluid. Harold Vance Department of Petroleum Engineering

6. Multi-phase flow • At least three phases are present in the wellbore • Liquid, gas, and solids • Liquids could be: • Mud • Oil • Water Harold Vance Department of Petroleum Engineering

7. Flow Regimes Harold Vance Department of Petroleum Engineering

8. Flow Regimes Harold Vance Department of Petroleum Engineering

9. Flow Regimes Harold Vance Department of Petroleum Engineering

10. Pressure prediction • HSP • Annular Friction • Bit pressure drop • Mud • Gasified mud • Drillstring pressure drop • Mud • Gasified mud Harold Vance Department of Petroleum Engineering

11. HSP Harold Vance Department of Petroleum Engineering

12. HSP Harold Vance Department of Petroleum Engineering

13. HSP Harold Vance Department of Petroleum Engineering

14. Gas Volume Harold Vance Department of Petroleum Engineering

15. Friction forces Harold Vance Department of Petroleum Engineering

16. Fanning Friction Factor Harold Vance Department of Petroleum Engineering

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18. Reduced Reynolds Number Harold Vance Department of Petroleum Engineering

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20. Gas volume • This correlation and equation 2.66 were used to compute the required air injection rate to give a BHP of 2497 psi at 6000’ in an 8 1/2” X 4 1/2” annulus at 350 gpm. • Required 14.9 scf/bbl Harold Vance Department of Petroleum Engineering

21. Gas volume • Equation 2.63 was used to calculate the volume of air to give the same BHP static. • Required 13.4 scf/bbl. • Poettmann and Bergman concluded that the difference is insignificant and a reasonable calculation of air rate for the desired BHP could be done assuming a static fluid column. Harold Vance Department of Petroleum Engineering

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23. Bit pressure drop • Mud • Gasified Mud Harold Vance Department of Petroleum Engineering

24. Bit pressure drop - Mud • Red book Harold Vance Department of Petroleum Engineering

25. Bit pressure drop - Gasified Mud • This relationship neglects any energy loss through the nozzles due to frictional effects and any change in potential energy. Harold Vance Department of Petroleum Engineering

26. Bit pressure drop - Gasified Mud • Substituting equation 2.44 for the density of a lightened fluid this becomes Harold Vance Department of Petroleum Engineering

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30. Fig. 2.41 Harold Vance Department of Petroleum Engineering

31. Hole Cleaning • Settling velocity • Critical velocity • Settling Velocity • Cuttings Transport ratio Harold Vance Department of Petroleum Engineering

32. Settling velocity Harold Vance Department of Petroleum Engineering

33. Critical velocity • Guo assumed that the cuttings concentration in the annulus should not exceed some critical value if hole cleaning problems were to be avoided. • vc = ROP/60Cc • vc = critical velocity, ft/min • ROP = Rate of penetration, ft/hr • Cc = Cuttings concentration, fraction Harold Vance Department of Petroleum Engineering

34. Critical velocity • Taking the critical concentration as 4%, cuttings would need to travel uphole with a velocity 25 times greater than the penetration rate. • For a penetration rate of 30 ft/hour, this corresponds to a velocity of 12.5 ft/min. Harold Vance Department of Petroleum Engineering

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36. Settling Velocity • With a large annulus, the AV may not be such that turbulent flow can be achieved. • We would then need to alter the viscosity of the fluid. Harold Vance Department of Petroleum Engineering

37. Settling Velocity • For a 0.25” cutting with a density of 21 ppg falling through a fluid of density of 5 ppg. • Maximum AV = 15 ft/min. • Settling velocity would have to be restricted to 17.4 ft/min at a penetration rate of 30 ft/hr. • This would require an effective viscosity of 160 cP. Harold Vance Department of Petroleum Engineering

38. Cuttings Transport Ratio Harold Vance Department of Petroleum Engineering

39. Cuttings Transport Ratio • The velocity of the system is normally the mean velocity in the annulus determined by dividing the total flow rate of the various phases of the fluid by the cross-sectional area of the annulus. Harold Vance Department of Petroleum Engineering

40. Cuttings Transport Ratio • The CTR should be calculated throughout the annulus to ensure that adequate hole cleaning takes place at all points and that the cuttings are not packing off in the hole somewhere. • A CTR of 1.0 implies perfect hole cleaning. • If CTR>0 cuttings are moving upward. • CTR should be >0.55 Harold Vance Department of Petroleum Engineering

41. Example Harold Vance Department of Petroleum Engineering

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46. The End Harold Vance Department of Petroleum Engineering