Abstract

Horizontal wellbores typically encounter inefficiencies due to friction during both drilling and completions operations. In severe cases, further advancement of the bit or downhole tools is almost impossible due to the inability of existing technology and methods to overcome downhole friction forces. This problem, seen in drilling, completions, and intervention activities, is particularly acute in coil tubing deployed bottom hole assemblies (BHA). Fluid hammer tools are often used in an attempt to mitigate this friction, with varying degrees of success. Current commercially available fluid hammer tools are preset mechanical systems operating at relatively high frequencies from 12 to over 40 Hz. These tools, which cannot be deactivated once installed in the BHA, typically exhibit a large pressure drop which can rise even further with increased flow. It is proposed that a downhole pressure oscillation tool be developed that provides the capability to manage downhole pressure oscillation amplitude independent of flow rate. It is also proposed that such a tool, operating at low frequencies, could simultaneously encode downhole measurements within the pressure pulse signal. This paper presents experimental data collected in the development of such a system and further explores the theory that high amplitude oscillations at lower frequencies impart significant motive force to the BHA enabling extended reach.

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