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PART ONE

Liquid Drilling Systems

Liquid is widely used as a circulating fluid to drill oil and gas wells, water
wells, geotechnical boreholes, and mining boreholes. This type of drilling
fluid is most commonly suspensions of clay and other materials in water
and is thus called drilling mud. Since it usually has a density ranging from
8.33 to 18.33 ppg (1.0–2.2 S.G.), drilling mud is used for drilling rock
formations with normal to abnormal fluid pressure gradients (>0.433 psi/ft
or 0.01 MPa/m). Because the bottomhole pressure is greater than the for-
mation pore pressure, mud drilling is an overbalanced drilling operation.
Compared to gas drilling and two-phase drilling (see Parts II and III), mud
can be used to drill various types of formation rocks with better control of
formation fluids and borehole stability.
Part I provides drilling engineers with basic knowledge about mud circu-
lating systems and techniques that are used for optimizing drilling hydraulics
to achieve the maximum drilling rate. Materials are presented in the first
four chapters:
Chapter 1: Equipment in Mud Circulating Systems
Chapter 2: Mud Hydraulics Fundamentals
Chapter 3: Mud Pumps
Chapter 4: Mud Hydraulics Optimization

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