Title:
METHOD FOR DETECTING ROLLER BIT BEARING FAILURE
United States Patent 3581564
Abstract:
A method for detecting failure of bearings in roller drill bits used in rotary drilling. Two drilling parameters--rotary torque and drilling rate--are measured and plotted with a third parameter (ψ) equals ratio of the parameter of rotary torque divided by the parameter of drilling rate. A sharp increase in the third parameter ψindicates bearing failure.
US Patent References:
System for recording work done during rotary drilling operations
Hildebrandt - January 1967 - 3298226
System and method for optimizing drilling operations
Brooks et al. - June 1967 - 3324717
Method and apparatus for measuring rock bit wear while drilling
Arps - October 1967 - 3345867
System for recording work done during rotary drilling operations
Hildebrandt - January 1967 - 3298226
System and method for optimizing drilling operations
Brooks et al. - June 1967 - 3324717
Method and apparatus for measuring rock bit wear while drilling
Arps - October 1967 - 3345867
Application Number:
04/824497
Publication Date:
06/01/1971
Filing Date:
05/14/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
175/39, 73/152.590
International Classes:
E21B12/02; E21B44/00; E21B45/00; E21B12/00; E21B45/00
Field of Search:
175/39,50 73/151,151.5,152,136
Primary Examiner:
Myracle, Jerry W.
Claims:
Having fully described the objects, advantages, apparatus and operation of my invention, I claim
1. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising:
2. A method as recited in claim 1 including displaying also said parameter of rotary torque and said parameter of penetration rate.
3. A method as recited in claim 2 including plotting on a chart said ratio parameter ψ.
4. A method as recited in claim 3 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.
5. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising:
6. A method as recited in claim 5 including plotting on a chart said ratio parameter ψ.
7. A method as recited in claim 6 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.
1. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising:
2. A method as recited in claim 1 including displaying also said parameter of rotary torque and said parameter of penetration rate.
3. A method as recited in claim 2 including plotting on a chart said ratio parameter ψ.
4. A method as recited in claim 3 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.
5. A method for detecting roller bit bearing failure of a roller drill bit attached at the lower end of a rotatable drill pipe string when drilling boreholes through earth formations comprising:
6. A method as recited in claim 5 including plotting on a chart said ratio parameter ψ.
7. A method as recited in claim 6 including plotting on said chart said parameter of rotary torque and said parameter of penetration rate.
Description:
FIELD OF THE INVENTION
Background of the Invention
When drilling boreholes with rotary well-drilling rigs, the time to roller bit bearing failure is difficult to predict. In the drilling of nonabrasive formations, the achievement of minimum drilling cost per foot is obtained by maximizing hours of rotation of the drill bit. The prediction of bit bearing failure is, therefore, critical since under such conditions, drill bits are totally consumed as a result of bit bearing failures.
It has been observed that drill pipe torque increases rapidly upon cone lockup. However, other drilling conditions such as hole deviation and gauge may give rise to premature high values of torque which can be misinterpreted. By observing the response of both torque and drilling rate during the life of the drill bit, it is possible to distinguish between bit bearing failure and other spurious torque responses.
SUMMARY OF THE INVENTION
Briefly, the invention concerns use of two drilling parameters, (1) rotary torque or torsional stress in the drill string and (2) drilling rate or rate of penetration of the drill bit to evaluate bit bearing failure. The method involves determining a third parameter ψ=T/R; where T = rotary torque and R = penetration rate of the drill bit. At bit bearing failure, T increases, but R decreases, thereby defining a uniquely high value of ψ.
BRIEF DESCRIPTION OF THE DRAWING
The sole FIG. is a schematic illustration of a system capable of performing the method of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the FIGURE, there is shown a well 10 that penetrates subsurface hydrocarbon-containing formation 11. Well 10 has a surface casing 13 installed and cemented in place in accordance with conventional procedures. The well is drilled by means of a conventional rotary drill bit 15 rotated by means of a drill string 16 which extends to the surface where it passes through a conventional wellhead 18 that includes suitable blowout preventers and other equipment well known to those skilled in the art of rotary well drilling. Drill string 16 is rotated by a rotary table 20. The upper end of drill string 16 is connected by a swivel 21 and hooks 22 to a traveling block 23 supported from a stationary crown block 24 mounted on table 25. A cable or follow-line 30 connected at one end to traveling block 23 extends over pulley 31 to a takeup reel 32, both supported from table 25 along with an optical tachometer 33 moveable by cable 30 and capable of generating an electrical signal proportional to rate of rotation of tachometer 33.
Rotary drive motors 40 drive rotary 29 through the belt and shaft transmission generally designated 41. Low resistant shunts are placed in series with generators 42 which supply power to rotary drive motors 40. Low voltage signals are developed by the current passing through these shunts. These signals are amplified and calibrated so that the measurement of voltage drop across the shunt becomes proportional to the torsional stress in the drill pipe. The signals proportional to the torsional stress are sent along line 45 to a pen operator 46 connected to a pen 47 mounted on a chart 58, rotated by a drive 49. Signals indicative of the torque are also sent to an electronic divider means 50, e.g., an operational amplifier. The electrical signals proportional to rate of penetration resulting from movement of cable 30 downwardly in response to movement of block 23 are transmitted along line 55 to a pen operator 56 connected to a pen 57 mounted on chart 48. Signals indicative of rate of penetration are also transmitted to divider means 50 which functions to divide the torque by the rate of penetration and send a signal proportional to ψ=T/R along line 60 to a pen operator 61 connected to a pen 62 arranged on chart 48. Thus, line 63 on chart 48 indicates torque; line 64 on chart 48 indicates rate of penetration of the drill bit; and line 65 on chart 48 indicates ψ, the relation of torque divided by rate of penetration.
In operation, as indicated in the drawing, the ratio of torque divided by penetration rate is essentially constant throughout the life of the drill bit up to the point of bearing failure. As the hard metal surfaces on the roller race spall, torque increases as a result of the cone lockup and the rate of penetration is reduced. There could be several reasons for a reduction in penetration rate, but when a cone locks, efficiency of the drilling mechanism is reduced by one-third. In soft formations, when torque increases, penetration rate normally increases also, but at a slower rate, Conversely, in harder formations, such as dense shale, where penetration rate is slower, torque is reduced but, again, disproportionately. Accordingly, the ratio of torque divided by penetration rate remains constant up to the point of bearing failure. As indicated at 66 on the chart, a substantial increase in ψ indicates bearing lock.
Field practice will result in defining a maximum value of ψ. The parameter ψ may be computed by means of an analog or digital computer programmed for solution using feedback values of torque and drilling rate. It also may be conveniently displayed or recorded for observation.
Other techniques are available for obtaining signals--electrical or pneumatic--proportional to torsional stress in the drill pipe and rate of penetration other than those illustrated and described above. Thus, another method for obtaining electrical signals proportional to torsional stress is shown and described in U.S. Pat. No. 3,298,226, issued to Hildebrandt, Jan. 17, 1967, entitled, "System for Recording Work Done During Rotary Drilling Operations." In this method, a load-cell device measures the stress in the chain which drives the rotary table and also generates a signal calibrated in terms of rotary torque. A third technique uses an electronic device installed on the drilling equipment, shown and described in U.S. Pat. No. 3,295,367, issued to Rundell, Jan. 3, 1967, entitled, "Sensitive Torque Meter."
Background of the Invention
When drilling boreholes with rotary well-drilling rigs, the time to roller bit bearing failure is difficult to predict. In the drilling of nonabrasive formations, the achievement of minimum drilling cost per foot is obtained by maximizing hours of rotation of the drill bit. The prediction of bit bearing failure is, therefore, critical since under such conditions, drill bits are totally consumed as a result of bit bearing failures.
It has been observed that drill pipe torque increases rapidly upon cone lockup. However, other drilling conditions such as hole deviation and gauge may give rise to premature high values of torque which can be misinterpreted. By observing the response of both torque and drilling rate during the life of the drill bit, it is possible to distinguish between bit bearing failure and other spurious torque responses.
SUMMARY OF THE INVENTION
Briefly, the invention concerns use of two drilling parameters, (1) rotary torque or torsional stress in the drill string and (2) drilling rate or rate of penetration of the drill bit to evaluate bit bearing failure. The method involves determining a third parameter ψ=T/R; where T = rotary torque and R = penetration rate of the drill bit. At bit bearing failure, T increases, but R decreases, thereby defining a uniquely high value of ψ.
BRIEF DESCRIPTION OF THE DRAWING
The sole FIG. is a schematic illustration of a system capable of performing the method of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the FIGURE, there is shown a well 10 that penetrates subsurface hydrocarbon-containing formation 11. Well 10 has a surface casing 13 installed and cemented in place in accordance with conventional procedures. The well is drilled by means of a conventional rotary drill bit 15 rotated by means of a drill string 16 which extends to the surface where it passes through a conventional wellhead 18 that includes suitable blowout preventers and other equipment well known to those skilled in the art of rotary well drilling. Drill string 16 is rotated by a rotary table 20. The upper end of drill string 16 is connected by a swivel 21 and hooks 22 to a traveling block 23 supported from a stationary crown block 24 mounted on table 25. A cable or follow-line 30 connected at one end to traveling block 23 extends over pulley 31 to a takeup reel 32, both supported from table 25 along with an optical tachometer 33 moveable by cable 30 and capable of generating an electrical signal proportional to rate of rotation of tachometer 33.
Rotary drive motors 40 drive rotary 29 through the belt and shaft transmission generally designated 41. Low resistant shunts are placed in series with generators 42 which supply power to rotary drive motors 40. Low voltage signals are developed by the current passing through these shunts. These signals are amplified and calibrated so that the measurement of voltage drop across the shunt becomes proportional to the torsional stress in the drill pipe. The signals proportional to the torsional stress are sent along line 45 to a pen operator 46 connected to a pen 47 mounted on a chart 58, rotated by a drive 49. Signals indicative of the torque are also sent to an electronic divider means 50, e.g., an operational amplifier. The electrical signals proportional to rate of penetration resulting from movement of cable 30 downwardly in response to movement of block 23 are transmitted along line 55 to a pen operator 56 connected to a pen 57 mounted on chart 48. Signals indicative of rate of penetration are also transmitted to divider means 50 which functions to divide the torque by the rate of penetration and send a signal proportional to ψ=T/R along line 60 to a pen operator 61 connected to a pen 62 arranged on chart 48. Thus, line 63 on chart 48 indicates torque; line 64 on chart 48 indicates rate of penetration of the drill bit; and line 65 on chart 48 indicates ψ, the relation of torque divided by rate of penetration.
In operation, as indicated in the drawing, the ratio of torque divided by penetration rate is essentially constant throughout the life of the drill bit up to the point of bearing failure. As the hard metal surfaces on the roller race spall, torque increases as a result of the cone lockup and the rate of penetration is reduced. There could be several reasons for a reduction in penetration rate, but when a cone locks, efficiency of the drilling mechanism is reduced by one-third. In soft formations, when torque increases, penetration rate normally increases also, but at a slower rate, Conversely, in harder formations, such as dense shale, where penetration rate is slower, torque is reduced but, again, disproportionately. Accordingly, the ratio of torque divided by penetration rate remains constant up to the point of bearing failure. As indicated at 66 on the chart, a substantial increase in ψ indicates bearing lock.
Field practice will result in defining a maximum value of ψ. The parameter ψ may be computed by means of an analog or digital computer programmed for solution using feedback values of torque and drilling rate. It also may be conveniently displayed or recorded for observation.
Other techniques are available for obtaining signals--electrical or pneumatic--proportional to torsional stress in the drill pipe and rate of penetration other than those illustrated and described above. Thus, another method for obtaining electrical signals proportional to torsional stress is shown and described in U.S. Pat. No. 3,298,226, issued to Hildebrandt, Jan. 17, 1967, entitled, "System for Recording Work Done During Rotary Drilling Operations." In this method, a load-cell device measures the stress in the chain which drives the rotary table and also generates a signal calibrated in terms of rotary torque. A third technique uses an electronic device installed on the drilling equipment, shown and described in U.S. Pat. No. 3,295,367, issued to Rundell, Jan. 3, 1967, entitled, "Sensitive Torque Meter."