English Edition (6 MB pdf) - Saudi Aramco

Bit Design Iteration 2 (Bit C)
By the time the team was ready for a bit new design iteration,
the Saudi Arabia operations bit designer used new analytical
tools, including the energy balance and transition drilling
modules. The cutting structure was optimized using the new
tools, which further reduced the force imbalance and obtained
minimum energy balance values. It was adjusted to obtain
smooth transition drilling, simulating hard rock (35,000 psi
compressive strength) and soft rock (10,000 psi compressive
strength). Figure 14 shows the ability of the bit to return to an
imbalance stage (flat lines) after drilling through a formation
change, and Fig. 15 shows its maximum value at the bit nose,
which is the right trend.
Because the major challenge was to increase the bit life
without sacrificing the ROP, Bit C implemented the use of a
new PDC cutting element, R1 cutters. The R1 cutters act as
a secondary cutting structure to assist cutting after the
primary cutting structure begins to show some degree of wear.
In addition to the additional diamond volume, the R1 cutters
help to prevent impact damage and to control the depth of cut
when the cutting structure is still in perfect condition. Figure 16
illustrates the R1 cutter geometry.
An additional improvement made to Bit C includes the
rearrangement of the bit nozzle after the CFD indentified
some interference zones in which the flow coming from the bit
was re-circulated around the bit face before it was evacuated
through the annulus space.
Bit C provided many good runs in all Ghawar zones,
completing the directional section in one run in 95% of cases.
The bit condition at the end of the run improved substantially,
and the bit achieved the optimum ROP while completing the
interval. Figure 17 shows the smooth wear at the end of the
run and the performance of the R1 cutters after the main
cutting structure began to wear.
Bit Design Iteration 3 (Bit D)
In the last quarter of 2008, two new technological advances
made it possible to increase the bit performance standard in
the Saudi Arabia deep gas drilling operations. The devel -
opment of the cutters for extreme drilling conditions, which
Fig. 14. The ability of the bit to return to an imbalance stage (flat lines) after
drilling through a formation change.
Cutter Torque Change
7
6
Percent Torque Change
5
4
3
2
1
0
0 10 20 30 40 50
Cutter Number
Fig. 15. The maximum value at the bit nose.
Fig. 16. R1 cutter implemented on Bit C.
52 SUMMER 2010 SAUDI ARAMCO JOURNAL OF TECHNOLOGY