Method for measuring bit wear during drilling
First Claim
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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 ofmeasuring 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 TD from the equation, TD =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 TD ;
calculating the dimensionless rate of penetration RD from the equation, RD =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 RD ;
empirically determining the values of constants a1 and a2 for a sharp drill bit by plotting TD vs RD from data collected for a sharp drill bit, with a1 being the intercept of the TD axis and a2 being the slope of the line through the plotted points; and
determining bit efficiency from the equation ED =(TD -a2 RD)/a1 ; and
pulling the bit when the bit efficiency drops to a preselected amount.
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Abstract
A method for measuring the wear of milled tooth bits during oilwell drilling uses surface and subsurface wellsite sensors to determine averaged values of penetration rate, rotation speed and MWD (measurements-while-drilling) values of torque and weight-on-bit to obtain a real time measurement of tooth wear, drilling efficiency and the in situ shear strength of the rock being drilled.
113 Citations
4 Claims
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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 TD from the equation, TD =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 TD ; calculating the dimensionless rate of penetration RD from the equation, RD =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 RD ; empirically determining the values of constants a1 and a2 for a sharp drill bit by plotting TD vs RD from data collected for a sharp drill bit, with a1 being the intercept of the TD axis and a2 being the slope of the line through the plotted points; and determining bit efficiency from the equation ED =(TD -a2 RD)/a1 ; and pulling the bit when the bit efficiency drops to a preselected amount.
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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 TD from the equation, TD =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 TD ; calculating the dimensionless rate of penetration RD from the equation, RD =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 RD ; empirically determining the values of constants a1 and a2 for a sharp drill bit by plotting TD vs RD from data collected for a sharp drill bit, with a1 being the intercept of the TD axis and a2 being the slope of the line through the plotted points; determining bit efficiency from the equation ED =(TD -a2 RD)/a1 ; pulling the bit when the bit efficiency drops to a preselected amount; calculating the dimensionless tooth flat FD by calculating the dimensionless weight on the bit WD from the equation WD =RD /(4a1 ED), and calculating FD from the equation FD =WD (1-ED). - View Dependent Claims (3, 4)
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Current AssigneeSchlumberger Technology Corporation (Schlumberger NV)
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Original AssigneeSchlumberger Technology Corporation (Schlumberger NV)
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InventorsLesso, William G. Jr., Burgess, Trevor M.
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Primary Examiner(s)Levy, Stewart J.
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Assistant Examiner(s)Raevis, Robert R.
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Application NumberUS06/686,851Time in Patent Office712 DaysField of Search73/151.5, 73/151, 73/84, 73/104, 175/39, 175/50US Class Current73/152.44CPC Class CodesE21B 12/02 Wear indicatorsE21B 44/00 Automatic control systems s...
