A new method for defining the rock drilling resistance: five-parameter method

The accurate evaluation on the characteristic parameters of rock mechanics of strata is the base of bit selection. Field cores were tested in the laboratory, and a model to calculate the parameters of rock drilling resistances was established by means of regression analysis method. Then, the five-parameter radar map of formation drilling resistance was plotted by means of normalization processing method according to the relationships of interval transit time vs. rock hardness, internal friction angle, uniaxial compressive strength, abrasiveness grade and rock drillability grade. In this map, the effects of rock’s petrophysical property, mechanical property and pore characteristics on its drilling resistance parameters, as well as the aggression and abrasiveness of bit are taken into consideration. Finally, the radar map was plotted and applied to the bit type selection for the Yuyang Formation in X Oilfield. It is indicated that when the bit selected on the basis of the radar map is applied, average drilling footage, average rate of penetration (ROP) and average net drilling time are increased by 188%, 7% and 160%, respectively. In conclusion, this bit selection method can be used to instruct the field construction.