Improving Borehole
Quality With New Suite of Drilling Tools has Significant
Effect on Drilling Efficiencies
By
Rick Russel1, Adel Youssef2
(1) Halliburton, Dubai, Dubai, United Arab Emirates (2) Halliburton, Egypt, Cairo, Egypt
This paper presents a suite of drilling tools that have been designed to
eliminate bit side-forces, even while drilling directional wells. The mechanisms
that cause unwanted bit side-forces are outlined and the techniques and
principles used to eliminate them are described. Examples of the improved
borehole
quality that results from their elimination and the overall improvement
in drilling efficiencies will be cited both from international and Middle-East
operations.
In an ideal world a borehole
would be a perfect cylinder with a smooth,
frictionless interior and retain the original diameter of the drill bit.
However, in the real world this can never be achieved. A number of factors
contribute towards this less-than-perfect
borehole
, such as formation
instability, and interactions between the drilling and formation fluids. Another
major contributor is the actual mechanics of the drilling process itself and the
resulting effect this has on the
borehole
geometry.
The phenomena of borehole
spiraling is being increasingly recognized to be a
result of the inefficiencies of conventional drilling assemblies. This
short-pitch micro-tortuosity and the mechanisms that cause it are responsible
for many of the problems described above. It has been found that
borehole
spiraling can largely be eliminated by adopting a ‘point-the-bit’ design rather
than utilizing bit side forces.
The application of this range of tools can have a significant effect on drilling operations, especially in the field of horizontal and extended-reach drilling, where the improvement in hole quality can impact well design and economics.