Abstract

This paper details the step by step process undertaken by a dedicated focus group established to provide a solution to inconsistent drilling performance with the 16" section in a deep gas field on the Arabian Peninusular. The paper reviews the analysis undertaken as well as focusing on new design concepts and improved technology introduced.

Drilling in these deep gas fields, especially the 16" sections has always been a challenge for Polycrystalline Diamond Compact (PDC) drill bits due to the complex lithology that consists of a variety of carbonates with high interfacial severity, followed by a highly abrasive sandstone and dense dolomite formations. Despite improving the ability to consistently drill the 16" sections in a single run over the past few years, the new challenge is to make further improvements to the consistency while at the same time providing further improvements in rate of penetration.

Having experienced inconsistent performance and a series of premature PDC bit failures in these applications over the last few years the vendor assembled an integrated project team to investigate the issue. This team carried out an in depth analysis of all the available field data and identified several factors that were responsible for PDC bit damage, such as bit/BHA whirl, poor operating parameters with their associated vibrations and the limited ability of existing PDC cutters to drill such formations.

The findings led to the development of a new PDC bit design solution with high lateral and torsional stability capable of drilling with high drilling efficiency, the introduction of new cutter technology; along with optimised operating parameters. The successful implementation of the new drill bit and recommended drilling parameters has enabled the operator to more consistently drill these challenging 16" sections in a single run at higher ROPs than previously achieved. This has resulted in significant cost saving for the operator.

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