Method for predicting rate of penetration using bit-specific coefficients of sliding friction and mechanical efficiency as a function of confined compressive strength

摘要

A method for predicting the rate of penetration (ROP) of a drill bit drilling a wellbore through intervals of rock of a subterranean formation is provided. The methoduses an equation based upon specific energy principles. A relationship is determinedbetween a bit-specific coefficient of sliding friction µ and confinedcompressive strength CCS over a range of confined compressive strengths CCS.Similarly, another relationship for the drill bit is determined between mechanicalefficiency EFF and confined compressive strength CCS over a rangeof confined compressive strengths CCS. Confined compressive strength CCS isestimated for intervals of rock through which the drill bit is to be used to drilla well bore. The rate of penetration ROP is then calculated utilizing the estimatesof confined compressive strength CCS of the intervals of rock to be drilled andthose determined relationships between the bit-specific coefficient of slidingfriction µ and the mechanical efficiency EFF and the confinedcompressive strengths CCS, as well as using estimated drill bit speeds N (RPM)and weights on bit (WOB).