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Characterisation of the Wear of the Roller Cone Drill Bit Caused by Improperly Chosen Drilling Regime

Jurij Šporin
Jurij Šporin
   | 23 mars 2021
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Article Category: Original scientific article
Publié en ligne: 23 mars 2021
Pages: 91 - 102
Reçu: 07 déc. 2020
Accepté: 11 déc. 2020
DOI: https://doi.org/10.2478/rmzmag-2020-0013
Mots clés
© 2020 Jurij Šporin, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Characteristic dull of the roller cone bit after drilled interval.
Characteristic dull of the roller cone bit after drilled interval.

Figure 2

Scanning electron microscope (SEM) image of tip of the bit tooth. Position 1 – carbide material; Positions 2 and 3 – carbide coating matrix; Position 4 – tooth body and Position 5 – mixed zone.
Scanning electron microscope (SEM) image of tip of the bit tooth. Position 1 – carbide material; Positions 2 and 3 – carbide coating matrix; Position 4 – tooth body and Position 5 – mixed zone.

Figure 3

DSC heating curve of the steel of the tooth body.
DSC heating curve of the steel of the tooth body.

Figure 4

DSC heating curve of carbide coating.
DSC heating curve of carbide coating.

Figure 5

Dilatometric heating curve of the steel of the carbide coating and the steel of the tooth: 1 – tooth steel material (blue), 2 – carbide coating (black).
Dilatometric heating curve of the steel of the carbide coating and the steel of the tooth: 1 – tooth steel material (blue), 2 – carbide coating (black).

Figure 6

Display of measurement positions of Vickers hardness tests.
Display of measurement positions of Vickers hardness tests.

Figure 7

Microscopic photo of the tip of the tooth.
Microscopic photo of the tip of the tooth.

Figure 8

A view at the tip of tooth that was in contact with the rock.
A view at the tip of tooth that was in contact with the rock.

Figure 9

Photography of tooth steel material. Position 1 – carbide coating; Position 2 – mixed zone and Position 3 – tooth steel (body).
Photography of tooth steel material. Position 1 – carbide coating; Position 2 – mixed zone and Position 3 – tooth steel (body).

Figure 10

Photography of cracks through carbide coating.
Photography of cracks through carbide coating.

Figure 11

Erosion channels at the top of the tooth.
Erosion channels at the top of the tooth.

Drilling regime parameters

Parameters Units Value Value
Depth m 1535.15–1600.00 1600.00–1623.04
Rotary speed rpm 35 45
Load on drill bit kN 30 40
Pump pressure MPa 5.5 5.5
Pump capacity m3/min 0.845 0.845

Results of the rock properties – limestone

Parameters Units Value
Cohesion MPa 5.50
Elastic module MPa 28125
Angle of internal friction ° 38.42
Compressive strength MPa 75

The elemental composition of carbide coating material (Figure 2 – Position 1)

Elements Concentration
at.% wt.%
W 55.415 79.539
Co 42.380 19.500
Fe 0.807 0.962

The elemental composition of the tooth body (Figure 2 – Position 4)

Elements Concentration
at.% wt.%
Fe 95.427 95.385
Ni 3.164 3.323
Mn 0.660 0.649
Mo 0.218 0.375
Si 0.531 0.267

Chemical analysis of the tooth material – body

Elements Mas. %
Mn 0.79
Ni 0.74
Cr 0.60
Mo 0.50
Cu 0.27
Si 0.26
C 0.17
S 0.016
P 0.011

The properties of drilling fluid

Parameters Units Value
Density kg/m3 1150–1170
Viscosity (Fann Funnel) s 45–48
Plastic viscosity (Fann Viscosimeter) mPas 16–18
pH – 9.5
Filtration mL/30 min 9.8–10

Results of the rock properties – carbonatic siltstone

Parameters Units Value
Cohesion MPa 0.722
Elastic module MPa 9375
Angle of internal friction ° 20.94
Compressive strength MPa 25

The elemental composition of the carbide coating matrix (Figure 2 – Position 2)

Elements Concentration
at.% wt.%
Fe 86.096 68.599
W 1.709 29.094
Ni 1.921 1.608
Mn 0.892 0.699

Results of the Vickers hardness test

Diagonals (mm) Hardness (HV0.5) Average Note
d1 d2
37.23 46.24 532.3198 594.5670 Tip of the tooth
36.22 37.55 681.5125
36.4 40.81 622.1374
37.99 41.33 589.4786
37.54 41.66 591.2662
37.43 39.54 626.0232
37.57 39.86 618.6071
36.33 42.41 598.1947
38.87 42.45 560.8396
38.48 42.45 566.2580
39.01 42.84 553.6000
44.99 47.95 429.3664 433.5184 Tooth body
44.44 48.37 430.5701
44.61 47.78 434.4937
44.09 47.10 446.0042
45.14 48.04 427.1575
33.28 37.13 748.1087 784.1543 Carbide coating—matrix
31.73 34.04 857.3887
33.64 36.53 753.2349
34.58 36.51 733.8654
30.41 36.51 828.1739 1458.984 Carbide coating—base
24.67 25.96 1446.830
24.43 25.78 1471.137

The elemental composition of the carbide coating matrix (Figure 2 – Position 3)

Elements Concentration
at.% wt.%
Fe 86.117 68.616
W 11.103 29.124
Ni 1.511 1.265
Mn 1.269 0.995
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