Abstract
Abstract Development and diversification of directional-drilling tools continues, as do the applications in which they operate. As a result, there is continual demand for development and refinement of drill bits and string tools to meet the latest challenges and issues faced. One such challenge is the ability to reliably deliver consistent directional performance in very soft formation applications. Issues such as hole washout, inappropriate drilling parameters, stabilization, and hole quality can all contribute to poor directional-drilling performance. Several commercial projects are reviewed where technical merit has justified use of rotary steerable systems (RSSs), but because of the very soft lithologies, these systems have been unable to deliver the required directional control. In each example, a separate engineered solution is introduced. These include An innovative concentric string reamer (CSR), featuring a mid reamer section that enables effective stabilization of the reamer even if the pilot borehole is of poor quality or is over gauge.A soft formation fixed-cutter drill-bit design with an engineered hydraulic configuration to avoid hole washout and extended circumferential gauge geometry.A near-bit stabilizer incorporating a full ring gauge that delivers 360° circumferential coverage, thus providing greater contact with the wellbore and higher potential for deviation.A specific bicenter design that uses a secondary component configuration on the face of the pilot to enable appropriate drilling parameters to be used for efficient directional control. The gauge geometry and profile is also tailored to suit soft formation drilling. Global case studies document where these solutions, in combination with both push and point RSSs, have proven extremely successful. These have provided greater flexibility with regard to tool selection, well planning options, and delivering lower cost per foot in rotary-steerable projects.
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