What Drilling Fluid (Mud) Does

An Introduction to Drilling Fluid- And Making Deep Holes

Michael A. Freeman, PhD Scientific Advisor/R&E Fellow

1 9/6/2010 What Drilling Fluid (Mud) Does

Seal rocks to prevent loss Prevent of fluid hole collapse

Prevent rock dispersion

PreventPrevent the the flow flowofildf oil of an oil d gasand whilegas drillingwhile drilling

Remove Lubricate drill cuttings the drill string

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2 9/6/2010 To Get To The MoHo, You Must Make a Hole.

Drill with a pipe, and pump fluid down the center

Rock is broken by the bit and lifted to the surface

3 9/6/2010 Water Can Not Lift Cuttings as Holes Go Deeper

Mud (clay suspension) cleans the hole!

4 9/6/2010 Lifting Rock Up the Hole Requires Overcoming Gravity

Stokes Law d ² (ρ - ρ ) V = kG c s m s µ

Vs = Settling velocity GG==Gravitational Constant kk==Parametric Constant

dc = Particle diameter

ρs = Density of Rock

ρm = Density of Fluid µ = Viscosity of Fluid

Mud provides viscosity and density

5 9/6/2010 Drilling Fluid Viscosity Decreases with Velocity

Fluid thickens as motion slows down, so settling is slowed

6 9/6/2010 KTB SuperDeep Well Drilled with Mud

7 9/6/2010 KTB Had Problems

Six Casing Strings Run- Smallest 5 ½” 8 9/6/2010 Boreholes Fail Because of Stresses

3

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/R 0 r

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-3 -3 -2 -1 0 1 2 3 r/R

Weigggpht of overburden and shifting of formations put stresses on rocks and fluids in them

9 9/6/2010 Hydraulic Pressure Counters Stresses

Pore Pressure Pushes Fluid and Rock Into the Hole, Balanced by the Pressure Exerted by Mud Density

Fracture Gradients Limit Mud Density

Limits of FG and PP Set Casing Points

10 9/6/2010 4.2 sg Barite Provides Density

Barite Also Settles

11 9/6/2010 The ‘Window’ Is Narrower In Deeper Water

12 9/6/2010 Viscosity + Density Create ‘ECD’- Pressure While Drilling

Pressure and Temperature Change Static Density, “ESD”

Resistance to Flow Adds On to Make ECD When Pumping.

14 9/6/2010 Circulating Temperature with a Riser- 40 °F Offset at Bit

15 9/6/2010 Riserless Drilling Reduces Pressure

16 9/6/2010 Without Further Cooling Formation -

But will you therma lllly frac ture the roc k ?

17 9/6/2010 Stress Cage Treatment of Fractures

 Estimate fracture width using Rock Mechanics  Picks WSM blend with particle size distribution required to bridggppe, prop and seal the fracture

19 9/6/2010 20

DESIGN OF WSM

ON-SITE PARTICLE SIZE WSM RECOVERY DISTRIBUTION

PARTICULATE WSM CHEMICAL WSM

RIGSITE WELLBORE STABILITY MODEL

20 9/6/2010 FRACTURE FILLING, BRIDGING & PLUGGING TESTS Questions?

21 9/6/2010