Gasified Liquid Hydraulics

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Lesson 9

• Gasified Liquid Hydraulics
• Read UDM Chapter 2.7
• pages 2.131-2.179

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Gasified Liquid Hydraulics

• Reynolds Number
• Multi-phase flow
• Pressure prediction
• HSP
• Circulating pressure
• Bit pressure drop
• Hole Cleaning

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Reynolds Number

• In practice the flow of gasified liquid is almost
  always turbulent (Reynolds number gt 4000)
• Example water flowing up an 8 1/2 hole with 5
  drillpipe.
• AV of 7 ft/min would be turbulent
• AVs gt 100 ft/min are common

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Reynolds Number

• Equation 2.58

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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.

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Multi-phase flow

• At least three phases are present in the wellbore
• Liquid, gas, and solids
• Liquids could be
• Mud
• Oil
• Water

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Flow Regimes
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Flow Regimes
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Flow Regimes
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Pressure prediction

• HSP
• Annular Friction
• Bit pressure drop
• Mud
• Gasified mud
• Drillstring pressure drop
• Mud
• Gasified mud

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HSP
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HSP
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HSP
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Gas Volume
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Friction forces
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Fanning Friction Factor
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Reduced Reynolds Number
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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

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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.

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Bit pressure drop

• Mud
• Gasified Mud

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Bit pressure drop - Mud

• Red book

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Bit pressure drop - Gasified Mud

• This relationship neglects any energy loss
  through the nozzles due to frictional effects and
  any change in potential energy.

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Bit pressure drop - Gasified Mud

• Substituting equation 2.44 for the density of a
  lightened fluid this becomes

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Fig. 2.41
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Hole Cleaning

• Settling velocity
• Critical velocity
• Settling Velocity
• Cuttings Transport ratio

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Settling velocity
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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

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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.

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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.

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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.

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Cuttings Transport Ratio
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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.

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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 CTRgt0 cuttings are moving upward.
• CTR should be gt0.55

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Example
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The End