R
ecord footage increases in hard, abrasive formations
are being achieved across a variety of bit sizes
and configurations with an application specific
diamond-impregnated (DI) bit. The design enables fit-for-purpose
optimisation and fast-paced refinement to achieve significant
performance improvements in durability and ROP. In recent
applications in Canada and Oman, the design has set new
standards for footage drilled and drill out capabilities.
The Varel Fusion® bit is a matrix body design with
diamond-impregnated segments on each blade and
thermo/abrasion resistant PDC cutters in the bit centre. The
optimised segment geometry maximises bit durability without
impacting efficiency. Benefits are achieved through several
advances, including diamond pelletisation, high density segments,
a low heat infiltration process, and a cutting structure design
programme that allows placement of individual segments in the bit
face to be customised for the application needs.
Customisingthebit
A key aspect of Fusion design concept is ensuring the diamond
grit mix is the correct one for the bit’s specific application. Grit
mix refers to the actual diamond size and/or mixture of diamond
sizes that are used. The best performance is typically achieved
when grit is optimised over subsequent runs for the specific target
formation. This is a very significant factor in the ROP but also
impacts diamond volume, wear characteristics, durability, and the
bit’s ability to drill through varied lithologies such as carbonates
and/or changing shale content.
One of the main advantages of the Varel design is its ability
to be quickly modified based on the dull bit characteristics. Hot
isostatic pressing (HIP) inserts can be moved, made bigger, and
adjusted to maximise diamond volume at a particular radius if so
required (Figure 1).
BRUNO CUILLIER, AURELIEN MANGENY,
BRAD TAKENAKA & DANNY TILLEMAN,
VAREL OIL & GAS DRILL BITS,
EVALUATE THE PERFORMANCE OF
APPLICATION-SPECIFIC DIAMOND
IMPREGNATED BIT DESIGNS IN
CHALLENGING DRILLING CONDITIONS.
WITH DIAMONDS
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