Technical Discussions

IADC/SPE 112670 (Copyright 2008, ADC/SPE Drilling Conference) Concurrent Rotary-Steerable Directional Drilling and Hole Enlargement Applied Successfully: Case Studies in North Sea, Mediterranean Sea and Nile Delta

Steve Jones and Junichi Sugiura — PathFinder Energy Services

Abstract

Concurrent rotary-steerable directional drilling and hole enlargement utilizing concentric underreamers is becoming more commonplace. Significant cost savings can be obtained enlarging the hole while drilling with a rotary-steerable system (RSS) as opposed to using a designated hole-opener run after the pilot has been drilled. However, RSS underreamer assemblies are often challenged with BHA instability, excessive vibration and stick-slip problems when the two different cutting structures (bit and underreamer) interact with significantly different formations. This paper describes case histories of directional wells that have been drilled with both point-the-bit and push-the-bit RSS underreamer assemblies in the North Sea, Mediterranean Sea and Nile Delta (Egypt). In particular, RSS underreamer assemblies opening from 13" to as large as 17 ½”, using 12 ¼” pilot holes will be discussed.

A unique sensor system, integrated into this specific RSS provides measurements of near-bit borehole caliper, stick-slip and vibration. While drilling, borehole quality and downhole vibrations were monitored in real-time at the rig site and from a remote operating center. The real-time data was used to optimize drilling parameters and provide enhanced performance from the RSS underreamer assembly. The RSS solution to simultaneous wellbore enlargement has been analyzed in terms of vibration, efficiency, performance, directional objectives and cost. The physical components, operational aspects and limitations of RSS underreamer technology will be discussed. The combination of a specific RSS and underreamer with a balanced cutting structure has resulted in excellent ROP and directional control, while reducing reaming-related vibration and potential failures. Further, an automated directional drilling feature and real-time drilling process monitor have enabled optimum directional drilling performance.