Decommissioning of subsea oil and gas production pipelines: hydrodynamic modeling for preliminary assessment of sediment resuspension and burial onto benthic organisms

Abstract

Many offshore oil and gas fields in Brazil are reaching the end of their economic productive life, which has increasing the demand for decisions about decommissioning of the offshore exploration structures such as subsea pipelines. However, removing, retaining or relocating subsea infrastructure have potential impacts on the marine environment caused by seabed perturbation. Using the MOHID hydrodynamic software, this study simulated resuspension, similar to those caused by pipelines recovery operations, and estimated the deposited particle layer onto rhodoliths and deep-water coral in continental shelf and slope in different sediment grain-size typologies. According to the proposed scenarios, simulation of resuspension indicated that particle deposition exceeded the burial thresholds (5.0 mm to rhodoliths and 6.3 mm for deep-water corals), while only in the continental shelf with fine sand seabed, the subsea pipeline removing didn’t represent burial risk for considered benthic organisms.