Summary
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.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
8 November 2007
- Meeting paper published:
13 February 2008
- Revised manuscript received:
6 November 2008
- Manuscript approved:
25 November 2008
- Published online:
9 July 2009
- Version of record:
23 December 2009
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