To ensure the continuation of safe and reliable well operations diagnosing well health issues becomes increasingly necessary. Having access to the right technology can provide greater confidence in diagnostics data; enabling more effective well management and risk mitigation. As a prudent operator, bp is proactive and rigorous in monitoring the health of its well stock and is continuously introducing new technology and methods to increase the effectiveness of its surveillance capabilities.

Traditionally, a combination of passive acoustics and temperature has been deployed in such investigations, but historically this has yielded limited success in offshore wells due to the combination of complex overprints. Whilst it is still acknowledged that passive acoustic logging does have limitations, chiefly due to their inability to characterize sporadic signals, next generation passive acoustics technology equipped with spectral sensor arrays have significantly enhanced abilities to measure subtle acoustic signals. This paper details an approach utilized offshore Azerbaijan for such diagnostics work, using these latest passive acoustic technologies, teamed with conventional temperature and distributed fibre optics.

As part of routine and ongoing data gathering, different tools were tested across a multi-well campaign in a variety of environments and different well states; static, active annular bleed and whilst applying pressure to annuli. Previous logging programs have deployed passive acoustic tools to confirm pre-existing notions of well issues. The logging programs described in this paper used higher sample densities and longer station intervals to enable a detailed and objective view of well health. There were thousands of stations acquired in more than 10 runs across production, water and gas injector wells. The acquired dataset generated a vast number of data points across different fluid types, completions and well conditions which allowed a more robust assessment of tool repeatability, sensitivity and spectral response. Highly sensitive hydrophones in modern spectral passive acoustic logging tools along with temperature and fibre measurements integrated with other information helped our understanding of the dynamics behind the casing, allowing us to make better informed decisions about wells operations.

As the datasets grew in size, quick-look processing methodology was developed to identify and characterize acoustic anomalies. The paper will demonstrate how the techniques developed have generated more confidence in passive acoustic technology. It will show how both acquisition procedures and data processing techniques were optimized to ensure the best quality answer products were delivered.

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