Method for measuring bit wear during drilling

Claim 1

A method of monitoring the wear of the teeth of milled tooth bits while drilling in formations that drill by a gouging and a scraping action comprising the steps of measuring the weight on the bit, the torque required to rotate the bit, and the speed of rotation of the bit; calculating the rate of penetration R in distance drilled per unit of time; calculating the dimensionless torque T D from the equation, T D =M/Wd, where M is the measured torque, W is the weight on the bit, and d is the bit diameter using appropriate dimensions to produce a dimensionless T D ; calculating the dimensionless rate of penetration R D from the equation, R D =R/Nd, where R is the rate of penetration, N is the rate of rotation of the drill pipe, and d is the diameter of the bit, using appropriate dimensions to produce a dimensionless R D ; empirically determining the values of constants a 1 and a 2 for a sharp drill bit by plotting T D vs R D from data collected for a sharp drill bit, with a 1 being the intercept of the T D axis and a 2 being the slope of the line through the plotted points; and determining bit efficiency from the equation E D =(T D -a 2 R D )/a 1 ; and pulling the bit when the bit efficiency drops to a preselected amount.

Claim 2

A method of monitoring the wear of the teeth of milled tooth bits while drilling in formations that drill by a gouging and a scraping action comprising the steps of measuring the weight on the bit, the torque required to rotate the bit, and the speed of rotation of the bit; calculating the rate of penetration R in distance drilled per unit of time; calculating the dimensionless torque T D from the equation, T D =M/Wd, where M is the measured torque, W is the weight on the bit, and d is the bit diameter using appropriate dimensions to produce a dimensionless T D ; calculating the dimensionless rate of penetration R D from the equation, R D =R/Nd, where R is the rate of penetration, N is the rate of rotation of the drill pipe, and d is the diameter of the bit, using appropriate dimensions to produce a dimensionless R D ; empirically determining the values of constants a 1 and a 2 for a sharp drill bit by plotting T D vs R D from data collected for a sharp drill bit, with a 1 being the intercept of the T D axis and a 2 being the slope of the line through the plotted points; and determining bit efficiency from the equation E D =(T D -a 2 R D )/a 1 ; and pulling the bit when the bit efficiency drops to a preselected amount.

Claim 3

A method of monitoring the wear of the teeth of milled tooth bits while drilling in formations that drill by a gouging and a scraping action comprising the steps of measuring the weight on the bit, the torque required to rotate the bit, and the speed of rotation of the bit; calculating the rate of penetration R in distance drilled per unit of time; calculating the dimensionless torque T D from the equation, T D =M/Wd, where M is the measured torque, W is the weight on the bit, and d is the bit diameter using appropriate dimensions to produce a dimensionless T D ; calculating the dimensionless rate of penetration R D from the equation, R D =R/Nd, where R is the rate of penetration, N is the rate of rotation of the drill pipe, and d is the diameter of the bit, using appropriate dimensions to produce a dimensionless R D ; empirically determining the values of constants a 1 and a 2 for a sharp drill bit by plotting T D vs R D from data collected for a sharp drill bit, with a 1 being the intercept of the T D axis and a 2 being the slope of the line through the plotted points; determining bit efficiency from the equation E D =(T D -a 2 R D )/a 1 ; pulling the bit when the bit efficiency drops to a preselected amount; calculating the dimensionless tooth flat F D by calculating the dimensionless weight on the bit W D from the equation W D =R D /(4a 1 E D ), and calculating F D from the equation F D =W D (1-E D ).

Claim 4

A method of monitoring the wear of the teeth of milled tooth bits while drilling in formations that drill by a gouging and a scraping action comprising the steps of measuring the weight on the bit, the torque required to rotate the bit, and the speed of rotation of the bit; calculating the rate of penetration R in distance drilled per unit of time; calculating the dimensionless torque T D from the equation, T D =M/Wd, where M is the measured torque, W is the weight on the bit, and d is the bit diameter using appropriate dimensions to produce a dimensionless T D ; calculating the dimensionless rate of penetration R D from the equation, R D =R/Nd, where R is the rate of penetration, N is the rate of rotation of the drill pipe, and d is the diameter of the bit, using appropriate dimensions to produce a dimensionless R D ; empirically determining the values of constants a 1 and a 2 for a sharp drill bit by plotting T D vs R D from data collected for a sharp drill bit, with a 1 being the intercept of the T D axis and a 2 being the slope of the line through the plotted points; determining bit efficiency from the equation E D =(T D -a 2 R D )/a 1 ; pulling the bit when the bit efficiency drops to a preselected amount; calculating the dimensionless tooth flat F D by calculating the dimensionless weight on the bit W D from the equation W D =R D /(4a 1 E D ), and calculating F D from the equation F D =W D (1-E D ).