Explosives Use in Decommissioning—Guide for Assessment of Risk (EDGAR): II Determination of Sound Exposure Levels for Open Water Blasts and Severance of Conductors and Piles from below the Seabed

Alison M Brand

doi:10.3390/modelling2040028

Abstract

A simple underwater noise model suitable for use with explosive severance of well conductors and piles during the decommissioning of oil and gas subsea structures is introduced and evaluated against data from five projects in the US. This study focuses on a novel model for the determination of sound exposure levels. The model has been developed to enable determination of impact areas for marine mammals and fish. Simulated received underwater sound exposure levels were significantly correlated with measurements for all scenarios. The maximum total error achieved between simulations and measurements was 2.6%, suggesting that predictions are accurate to within 3% of the average measurement. A low relative bias was observed in the simulations when compared to measured values, suggesting only a small systematic underestimate (≤0.5% of average measurement) for most severance operations and a small overestimate (0.14%) for open water blasts.

Highlights

Oil and gas platforms in the Gulf of Mexico (GOM) are often decommissioned using the predictability and cost effectiveness of explosives to sever legs and piles [1]
Abrasive and mechanical cutters are less reliable than explosives for pile severance, and can lead to delays in vessel spreads, which are the primary reason for budgetary overspend
A simple, but dynamic, underwater noise model driven by only simple, minimal input data has been described and estimates of the underwater noise

Summary

Introduction

Oil and gas platforms in the Gulf of Mexico (GOM) are often decommissioned using the predictability and cost effectiveness of explosives to sever legs and piles [1]. In the UK, the Department for Business, Energy and Industrial Strategy (BEIS) is responsible for licensing offshore operations after consideration of their effectiveness with respect to safety and environmental impact. Several of these activities require the underwater detonation of bespoke explosive charges designed to perform specific functions (for example conductor and pile severance) during the decommissioning of offshore structures and wells

Methods

Results

Conclusion