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.