Abstract
This paper will describe the concept study, pre-planning and drilling of test-well BETA BHB-11 and Njord well 6407/7-A-9 AH, which is the world's first Through Tubing Rotary Drilling (TTRD) well drilled from a floating platform, where specific technology developments for a TTRD Bottom Hole Assembly (BHA) were required.
The challenges to maintain the integrity of the existing sub-sea well completion, and pass through of the Down Hole Safety Valve (DHSV) with an nominal ID of 5 7/8", together with the specific BHA requirements to drill in this highly depleted reservoir, were addressed by the application of a TTRD BHA built up by bi-centre bit, 3D Rotary Steerable System (RSS), or Rotary Closed Loop System (RLCS), real time hole caliper, enhanced bit rotation from an integrated modular Positive Displacement Motor (PDM), real time pressure, vibration and bending moment monitoring sub. Low flow BHA setup, and a Dog Leg Severity (DLS) capability of 6-8°/30m.
