Subsea pipelines are the heart of the oil transportation system. Oil leakages from subsea pipelines is one of the principal risks associated with oil transportation. An experimental test rig was designed to identify a range of scenarios that could cause leakage, and consequently marine pollution. The Acoustic Emission (AE) technique was employed to sense the flow behaviour inside the pipeline through quantifying and analysing key parameters, such as; energy, amplitude, and the counts number. Although, the size and location of the oil leakage were acquired experimentally utilising highly sensitive acoustic sensors. Two series of numerical simulations utilising Computational Fluid Dynamics (CFD) – Reynolds-Averaged Navier-Stokes (RANS) model, were performed to accurately predict the rate of the oil spill and the corresponding trajectory to the free-surface at Reynolds number Re range from 0.3702 × 103 to Re 9.775 × 103 for flow inside pipeline. The computed results showed good agreement with the experimental data. The results demonstrated that the current experimental measurements analysis could determine the leakage location and the leakage hole capacity, then the numerical calculations could predict the leaked oil volume and the leaked oil route to prevent oil diffusion and mitigate its harmful impact. The findings of this work is a step forward for preventing and controlling oil pollution to protect the marine environment.