Back to the Drawing Board - Bit Failures Investigation and Remediation

Abstract Modern drilling operations rely on optimization of all drilling variables to provide the most cost effective and timely well delivery. To drive continuous improvement there has been a focus on shoe-to-shoe drilling of each section. During 2023, it was observed that in Field A, there were many PDC bit failures with partial to total ring outs observed in the 16″ and 17-1/2″ sections, resulting in additional trips and, in turn, impacting the bottom line. This paper presents the approach taken for investigating these failures and recommending concrete actions to remedy the issue and strive for continuous improvement. The investigation was carried out to determine the common causes for these repeated failures. The investigation was conducted with the following approach: Data was reviewed for all 17-1/2″ and 16″ drilled sections during the last 5 years.The rate of failure for each year was investigated.The failures were plotted on the field map to determine any geological correlation.Formation where bit was most likely damaged was reviewed.Failure rates for each manufacturer were compared.Rock strength analysis of 17-1/2″ and 16″ section lithology was reviewed.The role of BHA type associated with failures was reviewed.The role played by the number of bit repair/refurbishments in the failure was investigated. The results of the investigation were intriguing as they broke preconceived notions of the major contributing factors to these repeated failures. It was found that the failures were mapped across the field rather than only in the North of the field which was earlier suspected. Additionally, it was found that the number of repairs did not play a significant role in the repeated failures. Most of the failures were discovered to have taken place in Anhydrite 1 & Limestone 2. The year with the least amount of failure was the one where the wells were more equally distributed between multiple manufacturers. Encountering chert and high compressive strength formations were the major contributors towards failures. Based on the results of the investigation, recommendations were provided regarding drilling parameters in the transition zones to save damage to the bit. Three new technology bits from different manufacturers were identified to tackle this issue, they were field tested and proved to be a promising solution. The number of such failures in 2024 in runs with the new proposed bits has reduced from 2 failures per 9 runs to 1 failure per 15 runs so far. Such in-depth investigations help provide a road map for excellence and would be valuable to other companies investigating similar failures.