English Edition (6 MB pdf) - Saudi Aramco

Bit Control
158
160
Drilling Torque (lbs - ft)
113
53
13
-38
-58
-138
-158
Bt C
Bt D
Torque Variations (lbs - ft.)
140
120
100
80
60
40
20
0
0
Bit C
Bit D
1 2 3 4 5
The greater the Torque flucuation
the less the Bit Face Control
DLS (deg/100 ft)
Fig. 20. Bit tool face control.
Bit Walk
Walk Angle
Walk Angle
Bit Name
Bit Walk Force (lb)
BitWalk Rate (100 ft)
Bit Walk Angle (deg)
Bit C
-151.15
-1.59
-17.64
Bit Name
Bit Walk Force (lb)
BitWalk Rate (100 ft)
Bit Walk Angle (deg)
Bit D
-102.25
-1.75
-19.32
Fig. 23. Bit D + PRSS performance in the Hawiyah zone.
Fig. 21. Bit walk tendency.
Fig. 24. Bit D + PRSS performance in the ‘Uthmaniyah zone.
Fig. 22. Bit D + PRSS performance in the Haradh zone.
Bit walk tendency is another comparative analytical tool
incorporated in the DxD software. To calculate the bit walk
tendency, the program calculates the forces in the bit cone
area vs. the forces on the shoulder and bit gauge.
Fundamental studies on which the DxD is based
demonstrates that the bit walk tendency also depends on the
drilling mode; if the bit is building or dropping, the bit walk
tendency will change. With the point-the-bit system, the gauge
pad and gauge cutters generate a large walk force, which
drives bit walk to the left 3 . Figure 20 shows that both bits
have a slight bit walk tendency to the left, as expected. Bit D
tends to be more neutral, which reflects improvements of the
bit design.
Bit tool face control for Bit D also shows improvements
because the variation of the torque on the bit is less than that
of Bit C. The sensitivity analysis shows the same results at
different DLS, Fig. 21.
The field results of Bit D were optimum, and the bit was
used in the entire Ghawar field with excellent results. The
54 SUMMER 2010 SAUDI ARAMCO JOURNAL OF TECHNOLOGY