Obviously, the days of any one drilling technology meeting a variety of applications
are over. Considering that the average nonproductive time in drilling operations
worldwide remains about 20%, and adding the extra cost that will undoubtedly
arise from further control and oversight of deepwater operations, the value of
differentiated drilling technologies can only increase.
However, the development of drilling technology has largely been as a series of
separate components. And while their individual performance has been optimized,
similar optimization of the entire system, from rig floor to drill bit, must now be
targeted in an integrated manner. Only then will it be possible to make the required
step change in performance that the future supply of oil and gas requires. But
engineering this combination goes beyond the integration of drilling technologies
and requires optimization of the entire drilling workflow—from research and
engineering to operational execution.
Improving Drilling Performance—The Need for Integration
Today, a large part of the energy input at the drilling rig floor may never reach the
drill bit. Instead of cutting rock, energy is lost through friction, mechanical shock,
and vibration—all of which can lead to premature failure of downhole equipment,
longer drilling times, and higher economic and technical risks. Indeed, the motion
of thousands of meters of spaghetti-like pipe in a wellbore a few tens of centimeters
in diameter is prone to all manner of mechanical behavior that is only becoming
understood today. In fact, studies have shown that improvement in the management
of energy input at the surface can increase downhole tool reliability by a factor of
two or three.
At the same time, drilling performance is constrained by the ability to understand
and control the downhole environment—including reservoir characteristics, rock
properties, drilling fluid behavior, and borehole pressure. Real-time data transmitted
from the bottomhole drilling assembly already provide much valuable information,
but the integration and control of drilling components require a wider range of
recorded parameters in addition to measurement continuity from the drill bit to the
rig floor. After all, what cannot be measured cannot be controlled or improved.
Achieving a step change in drilling performance begins with recognizing the three
key objectives of the workflow. The first of these is increasing overall drilling
efficiency, which is a function of the rate of penetration and the overall time actually
spent drilling. The second is precise well placement and formation evaluation to
maximize production and provide quantitative reservoir characterization. The third
objective is wellbore evaluation and assurance, defined as the need to protect the
integrity of the well throughout its productive life.
Reaching these objectives requires a move from regarding drilling as an art form
to thinking of it as a science. As such, a much greater degree of optimization is
necessary across the drilling workflow, from the development of technology through
its application in the field.
Optimizing the Workflow—From Technology to People
Optimizing the drilling workflow is a complex and multidimensional challenge. It
begins with a commitment to research and development, which must be approached
in an integrated multidisciplinary manner because the technical solutions span an
entire spectrum of scientific disciplines. Indeed, experience has already shown that
testing drilling concepts in the laboratory with computer simulation or through the
use of scale models can dramatically reduce technology development times.
Drilling—Optimizing Bit Design
The rate of penetration, or the
speed at which a well is drilled while
maintaining good directional control, is
largely dependent on the efficiency at
which the drill bit is able to cut or grind
the rock. This in turn depends on the
weight applied to the bit, the rate of its
rotation, and the manner in which the
bit addresses the rock.
The design engineers at Smith Bits
use the IDEAS* integrated dynamic
engineering analysis system to
understand how the cutting structure
interacts with the rock and its behavior
as an integral part of the total drilling
system. Even small changes in cutter
position and orientation can have
significant effects on drilling
performance and reliability.
Using the IDEAS system, the designer
can arrive much more quickly at an
optimal design and then certify the
performance capabilities of each bit
through a simulation and modeling
methodology that takes into account
not just the lithology but also the
drillstring, drive system, bottomhole
assembly, and total system influence
on drillbit behavior.
By combining the Smith engineering
workflow with information detailing
the exact steering process for the latest
Schlumberger rotary steerable tools,
a new range of drill bits matched to
both drilling environment and rotary
steerable system can be developed.
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