PDC Bit Hydraulics
Since PDC bits are formation specific (best used in plastic formations), the formation characteristics will determine the hydraulic energy required. The drilling fluid will dictate the HSI, for water-based drilling fluids it will be between 2.5 and 4.5, while for oil-based drilling fluids it will be between 1.5 and 3.0.
The HSI, calculated at the jet nozzle orifices, will have several characteristics which will directly affect hydraulic energy:
1. the fluid velocity decreases rapidly once it leaves the nozzles
2. high vertical velocity and low horizontal velocities are achieved across the bit face
3. for higher volumes of fluid pumped, horizontal velocities will increase, but not necessarily HSI
The increased horizontal velocities provide better cuttings removal, better cooling, and possibly better drill rates.
Nozzle velocity is calculated in the same manner as with rollercone bits.
Since PDC bits are formation specific (best used in plastic formations), the formation characteristics will determine the hydraulic energy required. The drilling fluid will dictate the HSI, for water-based drilling fluids it will be between 2.5 and 4.5, while for oil-based drilling fluids it will be between 1.5 and 3.0.
The HSI, calculated at the jet nozzle orifices, will have several characteristics which will directly affect hydraulic energy:
1. the fluid velocity decreases rapidly once it leaves the nozzles
2. high vertical velocity and low horizontal velocities are achieved across the bit face
3. for higher volumes of fluid pumped, horizontal velocities will increase, but not necessarily HSI
The increased horizontal velocities provide better cuttings removal, better cooling, and possibly better drill rates.
Nozzle velocity is calculated in the same manner as with rollercone bits.
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