Thorough Analysis and Commitment for Improvement Led to a Step Change in the Drilling Performance on Valemon Field, North Sea

Abstract

This case study aims to share the experience and improve the understanding of downhole shock and vibration and demonstrate how it can be prevented using thorough offset analysis, an advanced bit design, downhole mechanics module, and detailed drilling roadmap. The new approach delivered a step change in the performance of the 17 ½-in. section in Valemon field, in the Norwegian sector of the North Sea. Employing a one-run strategy through this extremely demanding section could eliminate the need for a dedicated motor run to withstand high shocks through the sandy interval with interbedded limestone and cemented sand layers. Using a point-the-bit bottomhole assembly (BHA) with a detailed drilling roadmap for every group of formations secured smooth drilling, pull out, and running of the intermediate 14-in. × 13 3/8 in. casing to provide integrity to drill 12 1/4-in. section. An advanced bit design balanced drilling with low aggressiveness through sand without compromising the performance through the interbedded limestone stringers and claystone. The conical-shaped cutter placed behind the main PDC conventional cutters successfully controlled the depth of cut through the sandy intervals and mitigated the downhole shocks. A detailed drilling roadmap was developed to define formation-specific drilling parameters to mitigate the shock-related failures on similar lithology. A downhole drilling mechanics module was used to provide real-time axial, lateral, and torsional shock and vibration data, which enabled adjustment of surface drilling parameters accordingly.