The basic system means the drill string consisting of drill pipe, drill collar and a bit (no downhole tools). The process for drilling hydraulic optimization is simple. The following steps demonstrate how to optimize drilling hydraulics for the basic system.
• Select drill pipe and drill collar which provide pressure loss at a minimum for the range of depth and flow rate.
• Decide the methods to optimize drilling hydraulics. If you drill a shallow hole section, the maximum impact force is recommended. However, if you drill a deeper section, the maximum hydraulic horsepower is better than the maximum impact force.
• Determine flow rate to meet your optimization requirement at the end of the bit run. The curve below gives you a idea how you can get the flow rate from the char at each particular optimization method.
• Determine the total bit nozzle area (total flow area) which can meet the requirement within the maximum constraint of equipment.
Reference: Drilling Hydraulic Books