Sustained Annulus Pressure Diagnostics in Offshore Wells by Multisensory Spectral Acoustics

The monitoring of sustainable annulus pressure (SAP) in offshore wells plays an important role in the development of an oil reservoir with a massive gas cap. The method of spectral noise logging and high-precision temperature logging used to identify SAP source presented in work (Shtun 2020) proved to be good in determining the intervals of gas movement, however, the method is limited in answers. The most significant limitation of the spectral noise logging method is associated with the impossibility based on power spectrum to distinguish the zones of gas flow in the annular space and gas inflow zones from reservoir contributing SAP. This information is critical for proper workover planning to eliminate SAP. This limitation relates to the fact that the amplitude and frequency of the resulting signal depend on not only the aperture of space fluid flow through and depend on the turbulence of the fluid flow. The paper describes a novel technology of multisensory passive acoustics of radial location that is designed to differentiate far and near acoustic sources in wells to accurately define the sources of SAP. The results of laboratory and field cases in offshore oil wells were presented in this paper as well as the comparison between single sensor spectral noise logging and multisensory passive acoustics of radial location answers was given at the end of the paper based on real case studies. As shown in the paper the described technology provides a more accurate determination of the source of SAP and the geometry of fluid movement in the near-wellbore zone.