New Prospects of SAP Investigation using Multisensory Passive Spectral Acoustics

Sustained Annulus Pressure (SAP) monitoring on offshore stationary platforms plays an important role in the development of oilfields with the massive gas cap. Conventional SAP diagnostic techniques is significantly limited primarily by the complexity of unwanted flowpaths in annular space and the presence of multiple pipe barriers. Multisensory passive acoustics is the novel approach evaluating SAP. Several accurately synchronized high-definition acoustic sensors measuring acoustics wave time arrival shift of the signal generating by active flow source. To take into account acoustic wave reflections in multiple strings of well construction 3D modelling of acoustic propagation is applied. The logging campaign of five wells was surveyed using slickline. Both conventional single sensor and multisensory spectral acoustics were used in the same toolstring. The multisensory acoustic data indicated active SAP sources and estimated the distance to the SAP source and flowpath separately, differentiation of that is impossible using single sensor spectral acoustics data. As a result of the campaign multisensory passive spectral acoustic instrument demonstrated additional important features on SAP source identification over conventional single sensor spectral acoustics. The most important feature is the differentiation of SAP source and flowpaths behind multiple casings. This significantly improves workover planning on SAP source isolation