DRILLINGHYDRAULICS

Courtesy of Baker Hughes

Goal of Drilling Hydraulics

Enhance Bit PerformanceLower Over-all Drilling Cost

Drilling Hydraulics

Bit HydraulicsClean the Bit And Hole BottomCool the Bit

Annular HydraulicsLift Cuttings and CavingsLimit Annular Pressure DropLimit Hole Erosion

Downhole Tool Hydraulics

How to achieve these Goals?

ActualSituation

"Optimization"

Recommend

EvaluateCommunicate

Factors which Affect Pump Pressure

Flow RateFlow AreaLength of Circulation SystemFluid Properties

Pump Pressure

Flow Rate

Pressure Required (psi)Flow Rate (gpm)

400

800

41

147 (3.6 times 41)

10 lb/gal mud 1000 ft of 5" XH 19.50 drill pipe

∆p0.1582 L⋅ ρ

0.8⋅ µ a

0.2⋅ v

1.8⋅

d1.25

= Friction loss for Bingham Plastic

14.4 in.2

11.5 in.2

Pressure Required (psi)

5" XH 19.50 lb/ft

4-1/2" XH 16.60 lb/ft41

67 (63% more)

Pipe Size Flow Area (in.2)

400 gpm 10 lb/gal mud 1000 ft of 5" and 4-1/2" drill pipe

Flow Area

∆p0.1582 L⋅ ρ

0.8⋅ µ a

0.2⋅ v

1.8⋅

d1.25

= Friction loss for Bingham Plastic

Length of Circulation Loop

Pressure Required (psi)Length (ft)

1000

2000

41

81 (twice as much)

400 gpm 10 lb/gal mud 5" XH 19.50 drill pipe

∆p0.1582 L⋅ ρ

0.8⋅ µ a

0.2⋅ v

1.8⋅

d1.25

= Friction loss for Bingham Plastic

Fluid Properties

Pressure Required (psi)Mud Weight (lb/gal)

10

12

41

49 (20% more)

400 gpm 10 lb/gal mud 1000 ft of 5" XH 19.50 drill pipe

∆p0.1582 L⋅ ρ

0.8⋅ µ a

0.2⋅ v

1.8⋅

d1.25

= Friction loss for Bingham Plastic

Pump Pressure Distribution

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pressure (psi)

System Losses

Available for bitAs flow rate increases, the amount of pressure available for the bit decreases

Optimization of Hydraulic System

Reduce System Losses

Optimum Flow Rate

Large Flow Area

Optimum Lengths

Low Mud Weight

Low Viscosity

MaximumHydraulic Energyat the Bit

Two Optimization Methods

Jet Impact Force – Maximum force at bit

Hydraulic Horsepower – Maximum energy at bit

0 100 200 300 400 500 600 700 800 900Flow Rate (gpm)

IF (lb)

Max. Impact Force

Maximum Impact Force

Jet impact force is maximized when momentum is maximized. This occurs when the bit losses are 49% of the available pump pressure.

M = m v

mass ρ q⋅= q

velocityqAt

=q

F jρ q

2⋅

A t=

qF j q ρ ∆p b⋅⋅= q

Jet Impact Force

1342 psi - 48%Bit

System

2800

1456 psi - 52%

Maximum Force at the Bit

P H ∆p b q⋅= ∆p b P Hρ q

3⋅

A t2

=q

0 100 200 300 400 500 600 700 800 900Flow Rate (gpm)

HHP (hp)

Max. HHP

Maximum HHP

Hydraulic Hp is maximized when the energy dissipated at the bit is maximized. This occurs when 65% of pump pressure is dissipated at the bit.

Hydraulic Horsepower

1820 psi - 65%Bit

System

980 psi - 35%

Maximum Energy at the Bit

2800

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pump Pressure (psi)

HHP

35%

Impact Force

52%

Design Pump Pressure

Pressure used by the System

System Losses

Bit Loss

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pump Pressure (psi)

System Losses

Bit Loss

HHP

35%

65%

Impact Force

52%

48%

Design Pump Pressure

Pressure remaining for the Bit

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pressure loss through the bit (psi) IF,HHP

System LossesBit Loss

Max. Impact Force

Max. HHP

Design Pump Pressure

Maximum HHP and Impact Force

100%92% 93% 100%

0%

20%

40%

60%

80%

100%

120%

Max. HHP Max. Impact Force

Comparison at Maximum Conditions

HHP Impact Force

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pressure loss through the bit (psi) IF, HHP

System LossesBit Loss

Max. HHP

Max. Impact Force

20% Higher

Design Pump Pressure

Higher Flow Rate at Impact Force

0 100 200 300 400 500 600 700 800 9000

400

800

1,200

1,600

2,000

2,400

2,800

Flow Rate (gpm)

Pressure at the bit (psi) IF, HHP

System Losses

Bit Loss

Max. HHP

Max. Impact Force

35% Higher

Design Pump Pressure

Higher Pressure at Hydraulic Horsepower

ShallowLarger Diameter Hole

DeeperSmaller Diameter Hole

Which one to use?

Hydraulic Horsepower14% Higher Jet Exit Velocities35% Higher Pressures

Jet Impact Force20% Higher Flow Rates

90% of Maximum HHP

0 0.2 0.4 0.6 0.8 10%

20%

40%

60%

80%

100%

120%

Fraction of Surface Pressure across Bit

% of Maximum HHP

90%

65%

Optimization of Hydraulic System

Choose equipment to keep system losses at minimum for the anticipated range of flow rates and depthSelect Optimization Method - Impact Force or Hydraulic HorsepowerDetermine optimum flow rateAdjust flow rate to meet requirements or limitsDetermine TFA

Rules of ThumbFlow RateFlow rate should be maintained at 30 to 60 gpm per inch of bit diameter

Hydraulic HpAim at 2.5 to 5 hydraulic Hp per square inch of bit diameter.

Bit Pressure dropDesign for 48% to 65% Pressure drop across bitIf system losses are greater than 48% of pump pressure then optimize for jet velocity.

Jet VelocityMaintain jet velocity above 250 feet per second

Flowrate LimitsAnnulusHole ErosionHole CleaningLoss of Circulation

Downhole ToolsPDMTurbineMWD

PumpSPMLiner Size

Cuttings AnalysisErosion vs. chip formation

Roller ConeBit Hydraulics

Three Major Mechanismsof Bit Hydraulics

• Remove the drilled-up particles to the surface

• Clean the cones and cutting structures

• Remove the layer of filter cake and crushed• material from the borehole bottom

Factors Which Determine Which Mechanism will become the Dominant

Problem

nFormation

nBorehole Bottom Condition

nHydraulic and Mechanical Operating Parameters

nProperties of Drilling Fluid

Hydraulic Mechanism Neededto Improve Mechanical Efficiency of

Roller Cone Bit

* Remove the drilled-up particles to the surface

APPROXIMATELY 20 TO 30 FT/HR* Remove the layer of filter cake and crushedmaterial from the borehole bottom

* Clean the Cones and Cutting StructuresHigh ROP

Low ROP

Development of the Crushed ZoneAs the cutting element penetrates into a formation, the formation directly below the element is crushed and compacted.

The process continues, forming a pocket of crushed, permeable material until the stress level is sufficiently high to propagate cracks and generate major chips.

As the high stress is released, the large chips are removed leaving behind a pocket of crushed formation.

Crushed Formation

Uniform Layer of Fines

IMPERMEABLE FORMATION

FILTER CAKE

PERMEABLECRUSHED ZONE

MUD PRESSUREWELLBORE

FORMATION

Improve Bottomhole Cleaning byIntensifying Jet Velocity and

Pressure on Bottom

Jet Flow

POTENTIAL CORE100% EXIT VELOCITY AND PRESSURE

CREATED BY ENTRAINING SURROUNDING FLUID

TURBULENCE

Velocity and Pressure on Bottomis Increased by

Increasing Nozzle Diameter

Decreasing Distance Off Bottom

Asymmetrical Nozzle ArrangementThe larger size nozzle has an effect on the jet flow due

to the larger potential core delivering more of the available power to the bottom before it dissipates into the surrounding fluid.

X

LargerPotentialCore

D 2 D

Nozzle Distance Off Bottom

The nozzle distance off bottom has an effect on the jet flow due to the jet having less distance available to entrain the surrounding fluid and dissipate the available power.

X

2 XPotential Core

Increase the Jet Action by Concentrating the Available Power

3 Identical Size Nozzles Asymmetrical Arrangement1 Large Nozzle with 2 Smaller Nozzles

Measure of Jet Intensity

7.710

15

20

X/D Ratio

100%77%

51%

38%

Velocity

100%59%

26%

15%

Pressure

X/D Ratio Needed to Produce Desired Hydraulic Mechanism

High Flow Rates for Bit Cleaningand Dispersing Shale - High ROP

APPROXIMATELY 20 TO 30 FT/HR

High Velocities for Bottom ScouringLow ROP

X/D Ratio

Less Than 7.7

7.7-15

Hydraulic Mechanism Neededto Improve Mechanical

Efficiency of Roller Cone Bit

IncreasingHydrostatic Pressure

High Flow Rates for Bit Cleaning and Dispersing Shale – High ROP

APPROXIMATELY 20 TO 30 FT/HR

High Velocities for Bottom-ScouringLow ROP

IncreasingHydraulic Horsepower

PDC Bit Hydraulics

Junk Slot Area Face Volume

Nozzle Orientation

TILT

OFFSET

FLOWVECTOR

OFFSET

Ports

• Ports are used when space limitations prevent the use of nozzles.

• Ports help to distribute hydraulic energy to areas of the bit that may not be adequately covered by nozzles.

• Ports provide a larger potential TFA in high flow rate or low standpipe pressure applications.

• Ports can be specified in any equivalent nozzle size.

Reverse Impinging Hydraulics

• Remove bit body material so cuttings have no surface to stick to.

• Impact the chip from the rear stressing it across the weakest axis.

• Provide large open face volume and smooth transition to annulus.

Chipmaster Hydraulic Concept

Original Concept Refined Version

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