Passive Acoustic Monitoring of Underwater Well Leakages with Machine Learning: A Review

Abandoned oil and gas wells pose significant environmental risks due to the potential leakage of hydrocarbons, brine and chemical pollutants. Detecting such leaks remains extremely challenging due to the weak acoustic emission and high ambient noise in the deep sea. This paper reviews the application of passive sonar systems combined with artificial intelligence (AI) in underwater oil and gas leak detection. The advantages and limitations of traditional monitoring methods, including fibre optic, capacitive and pH sensors, are compared with those of passive sonar systems. Advanced AI methods that enhance signal discrimination, noise suppression and data interpretation capabilities are explored for leak detection. Emerging solutions such as embedded AI analogue-to-digital converters (ADCs), deep learning-based denoising networks and semantically aware underwater optical communication (UOC) frameworks are also discussed to overcome issues such as low signal-to-noise ratio (SNR) and transmission instability. Furthermore, a hybrid approach combining non-negative matrix factorisation (NMF), convolutional neural networks (CNN) and temporal models (GRU, TCN) is proposed to improve the classification and quantification accuracy of leak events. Despite challenges such as data scarcity and environmental change, AI-assisted passive sonar has shown great potential in real-time, energy-efficient and non-invasive underwater monitoring, contributing to sustainable environmental protection and maritime safety management.