Basic Concepts of Hydraulics – Average fluid velocity, – Fluid velocity through the annulus Vf (ft/min) v f 24 51 ∗ Q = d 22 − d 12 – Fluid velocity through the drill string Vf (ft/min): v. MWD/LWD – Bit nozzle pressure loss, – Annular pressure losses 10 © COPYRIGHT 2001, All Rights Reserved Hydraulics. From the pump to the standpipe, kellyhose, Kelly or top drive, to the top of the drill pipe – Pressure loss through the drill string, – Downhole tool pressure loss:. Circulating System Pressure Loss – Pressure loss through the surface equipment,. Circulating System Mud pump Mud pit Casing & cement Drill pipe Annulus Drill bit Open hole Drill collar © COPYRIGHT 2001, All Rights Reserved Hydraulics. Hole Cleaning – Annular Velocity, – Rate of penetration (ROP), – Viscosity, – Hole Angle, – Mud Weight, – Hole washout © COPYRIGHT 2001, All Rights Reserved Hydraulics. Importance of Hydraulics – Cuttings removal in the annulus, – Hydrostatic pressure to balance pore pressure and prevent the wellbore from collapsing, – ECD (Equivalent Circulating Density), – Surge/swab pressures during tripping, – Limitation of pump capacity, – Optimization of the drilling process (Max HHP or Max Jet Impact), – Pressure and Temperature effects © COPYRIGHT 2001, All Rights Reserved Hydraulics. This requirement for flowrate may adversely affect optimization of HHP © COPYRIGHT 2001, All Rights Reserved Hydraulics. Manufacturer often recommend a minimum flowrate in an attempt to ensure the bit face is kept clean and cutter temperature is kept minimum,. The effects of increased hydraulic horsepower at the bit are similar to their effect on the roller cone bits,. Hydraulic efficiency © COPYRIGHT 2001, All Rights Reserved Hydraulics – Hydraulic Efficiency:. Mud properties, – In order to prevent an influx of formation fluids into the wellbore, mud hydrostatic pressure should be slightly higher (safety margin),. 
Roller Cone Bit: – Penetration rate is function of many parameters including:.The increased fluid flowrate may however cause excessive erosion of the face and premature bit failure © COPYRIGHT 2001, All Rights Reserved Hydraulics.
These requirements may be satisfied by increasing the fluid flowrate,.Circulation across the bit face must be designed to remove the cuttings efficiently and also cool the bit face,.Select bit nozzles to optimize bit hydraulics © COPYRIGHT 2001, All Rights Reserved Hydraulics – Fluid Circulation:.Understand basic concept of bit hydraulics,.Lecture Objectives – By the end of this lecture YOU should be able to:.Lecture Contents, – Lecture Objectives, – Basic concepts of Hydraulic, – Pressure Losses and ECD, – Bit nozzle selection, – Hydraulic optimization © COPYRIGHT 2001, All Rights Reserved Hydraulics.Network of Excellence in Training Bit Hydraulics © COPYRIGHT 2001, NExT All Rights Reserved Hydraulics
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