Bit Hydraulics Optimization

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Purposes

Control formation pressuresDrive motor/turbineCool the bitClean cuttings from the hole bottomClean cuttings from the bitTransport cuttings to surface

Drilling Fluid Circulation

BitHydraulics

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Nozzle Flow Area (TFA - sq.in.)Nozzle Pressure Drop (psi)Nozzle Horsepower (HSI)Nozzle Impact Force (lbf)Nozzle Velocity (ft/sec)

Bit Hydraulics OptimizationFluid PressureFluid Flow RateFluid Density and Viscosity

PHP= PxQ1714

BHP=PxQ

1714

FrictionalPressureLosses

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Pressure Loss Factors

Equipment and Wellbore Geometry– Flow Area– Length– Constrictions

Flow RateMud Properties

– Weight– Plastic Viscosity– Yield Point

Pressure InPressure Out

Flow In Flow Out

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PStdpipe=PSurf.Eq.+PDrill String+PMWD/Motor+PBit+PAnnulus

Pressure LossesSurface Equipment

– Standpipe– Kelly Hose– Swivel– Kelly

Drill String– Pipe– Collars– BHA

Motor/TurbineBit NozzlesAnnulus

Drill String– Pipe– Collars– BHA

Surface Equipment– Standpipe– Kelly Hose– Swivel– Kelly

Motor/TurbineBit NozzlesAnnulus

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Case Stand Pipe Hose Swivel Kelly

Length(Ft.)

ID(In.)

Length(Ft.)

ID(In.)

Length(Ft.)

ID(In.)

Length(Ft.)

ID(In.)

1 40 3.0 45 2.0 4 2.0 40 2.25

2 40 3.5 55 2.5 5 2.5 40 3.00

3 45 4.0 55 3.0 5 2.5 40 3.25

4 45 4.0 55 3.0 6 3.0 40 4.0

Pressure Losses Surface EquipmentSurface Equipment

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Drill PipeDrill Pipe DD11 DD22

Pressure Losses Drill StringDrill String

ID (in.)OD(in.)

Nominal Weight(lb/ft) Body Tool Joint

3 ½ 15.5 2.992 2 1/8 – 2 9/16

5 19.5 4.276 2¾ – 3¾

5 25.6 4.000 3¼ – 3¾

6 5/8 25.2 5.965 4 5/8 - 5

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Pressure Losses Drill StringDrill String

Heavy Weight Drill PipeHeavy Weight Drill Pipe

ID (in.)OD(in.)

Nominal Weight(lb/ft) Body Tool Joint

3 ½ 25.3 2 1/16 2 3/16

4 ½ 41.0 2 ¾ 2 7/8

5 49.3 3 3 1/16

DD11 DD22Drill PipeDrill Pipe

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IDOD(in.)

Weight(lb/ft)

OD(in.)

Weight(lb/ft)

ID(in.)

4 ¾ 54.0 1 ½

4 ¾ 44.0 2 ½

8 165.0 1 ½

8 143.0 3 ¼

Pressure Losses Drill StringDrill StringHeavy Weight Drill PipeHeavy Weight Drill PipeDD11 DD22

Drill PipeDrill Pipe

Drill CollarsDrill Collars

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Pressure Losses MWD andMWD andDownhole DrivesDownhole Drives

MWDPDMTurbineRSS

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Pressure Losses BitBit

Flow RateMud WeightNozzle TFA

Pressure Drop

HSIJIF

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Pressure Losses AnnulusAnnulus

Flow RateMud WeightCasing IDDrill String ODLength

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Example of Pressure LossesHole Size =8-1/2"Depth Out = 15,000 feetMax. Standpipe Pressure = 3000 psi Flow Rate = 238 GPMMud Weight = 14.5 ppg

At Maximum HSISurface Equipment Loss = 20 psiInternal Drill String Loss = 968 psiMWD/Motor Loss = 0Bit Pressure Drop = 1890 psiAnnulus Loss = 122 psiTotal Loss = 3000

PStdpipe=PSurf.Eq.+PDrill String+PMWD/Motor+PBit+PAnnulus

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Hydraulics Optimization3000 psi Standpipe Pressure

Standpipe HP

JIF/sq. in.Bit Nozzle HPSystem Loss HP

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Flow Rate RequirementsFlow Rate RequirementsHydraulic Recommendations

Flow Rate must be high enough to transport cuttings. Back-reaming, bit body balling and lack of chips at surface indicate cuttings transport or sloughing problems.

Flow Rate must be low enough to avoid hole erosion, equipment wear, and excessive standpipe pressure.

High flow rates often require large or open nozzles.

Bits with large junk slots, high open face volume, widely spaced teeth/inserts and numerous jets are helpful.

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Maximum Hydraulic HorsepowerMaximum Hydraulic HorsepowerHydraulic Recommendations

Maximize nozzle HSI when cutting structure or bottom hole balling is the limitation.

Deep holes, high mud weights, water-based mud and reactive formations, cuttings packed on teeth indicate static or dynamic chip hold down problems.

Maximum HSI obtained when nozzle pressure drop is 65% of standpipe pressure.

Aggressive designs with widely-spaced blades and teeth are helpful.

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Maximum Jet Impact ForceMaximum Jet Impact ForceHydraulic Recommendations

Maximize JIF in shallow holes where cuttings return and bit/hole balling are both potential limitations.

Common in shallow holes with high ROP in reactive formations.

Obtained when the pressure drop across the bit is 50% of the total pump pressure.

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Other GuidelinesOther GuidelinesHydraulic Recommendations

30 to 50 gpm per inch of hole diameter.

3 to 7 HSI recommended (not always possible).

18% or less flow through centerjet (=18% of TFA).

Blank nozzles generate crossflow. Blank the nozzle pointing to the cone with fewest gauge row inserts.

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Hydraulic Program DesignGoal: Determine nozzle sizes and flow rate

to deliver maximum HSI or JIF within specified operating constraints.

1. Maximum Standpipe Pressure2. Minimum and Maximum Flow Rate3. Maximum Pump Horsepower4. Mud Weight5. MWD and Motor Considerations6. Fixed Flow Rate7. Fixed TFA

Constraints:

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Hydraulic Program Calculation Method

1. Identify Maximum Standpipe Pressure.2. Specify HSI or JIF optimization and TFA/GPM constraints.3. Find GPM giving maximum HSI or JIF based on frictional losses.4. Derive Nozzles from TFA at optimum GPM.

Nozzles ?Flow Rate ?

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Hydraulic Program Cases

Case 1 Case 2

Case 3 Case 4 Case 5

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Hydraulic Program Demo

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Field ResultsHydraulic OptimizationHydraulic Optimization

Carboniferous FormationOil Base Mud in North Sea

Shale FormationWater Base Mud in Columbia