I update some useful drilling formulas into the drilling formulas spread sheet called version 1.1.
Please feel free to download.
Drilling Formula Calculation Sheet V1.1
The following drilling formulas are added:
Hydrostatic Pressure Loss Due to Gas Cut Mud
Maximum pit gain from gas kick in water based mud
Maximum Surface Pressure from Gas Influx in Water Based Mud
You can read how to use this work sheet via this topic > Drilling Formula Calculation Sheet
Ref book: 
Formulas and Calculations for Drilling, Production and Workover, Second Edition
Vry nyc web site…
hello dear sir
thanks for your all guidlines.how we can calculate back reaming rate.
I don’t have the formula to determine back ream rate. It depends on experience in that area, condition of the well, etc to identify how fast you will back ream.