Concurrent Rotary-Steerable Directional Drilling and Hole Enlargement Applied Successfully: Case Studies in North Sea, Mediterranean Sea, and Nile Delta

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. Introduction Hole enlargement while drilling using RSS and underreamers is becoming widely accepted on directional projects worldwide. Conventionally, steerable motors with bi-center bits were the only practical option for directional hole enlargement where casing pass-through was a restriction. Today, BHAs utilizing a combination of RSS and underreamers are commonly used on wells that require directional hole enlargement. Slim well casing programs, casing whipstocks or re-drilling around a fish all commonly use RSS underreamer technology. Common problems associated with bi-center bits are: poor directional control, inconsistent directional results in soft formations, low ROP, excessive vibration, and irregular and/or spiraled holes1–3. All these problems lead to the need for an alternative method of hole enlargement, with the ability to enlarge the hole beyond the size of existing casing. The RSS underreamer BHA has become the obvious solution to this problem.

Improving Rotary-Steerable Borehole Quality Using Innovative Imaging Techniques

“…11,12 Near-bit sensors also have been used to make comparative analyses of drill bit and BHA performance among different assemblies and wells. 11,12 Near-bit sensors also have been used to make comparative analyses of drill bit and BHA performance among different assemblies and wells.…”

“…While testing, concurrent near-bit caliper and vibration data enabled the engineers and researchers to make comparative analyses of bit/BHA stability and borehole quality among different bit/BHA configurations 11,12,13 . Bit gauge design and cone profile come into play in this aspect.…”

The Use of the Industry's First 3-D Mechanical Caliper Image While Drilling Leads to Optimized Rotary-Steerable Assemblies in Push- and Point-the-Bit Configurations

“…BHA instability can have a significant negative effect on the RSS directional performance and reliability. While testing, concurrent near-bit caliper and vibration data enabled the engineers and researchers to make comparative analysis of bit/BHA stability and borehole quality among different bit/BHA configurations 3,14,15 . Table 2 shows the near-bit vibration severities observed with different bits.…”

Integrated Approach to Rotary-Steerable Drilling Optimization Using Concurrent Real-time Measurement of Near-bit Borehole Caliper and Near-bit Vibration

“…The real-time data has helped to better understand complex downhole dynamics and to mitigate for undesirable downhole conditions and failures in challenging drilling conditions. For example, this real-time measurement has been successfully used for RSS runs with simultaneous hole enlargement [9]. Comprehensive real-time vibration and caliper data was delivered in real time to a multi-disciplinary drilling optimization team consisting of engineers and researchers through a secure web-based real-time monitoring and data delivery system.…”