Oil spill trajectory simulation for the Saltpond oilfield, Ghana, West Africa

Abstract

Abstract The exploration and production of petroleum resources is not without environmental consequences and these remain an important factor in contemporary global oil industry. As an emerging oil producing nation, very little or nothing is known about the behaviour of Ghana’s sweet light crude in water under varying environmental conditions. This is crucial for an efficient management of accidental spills. Therefore, this study designed a deterministic model for oil spill trajectory simulation using the Saltpond oilfield (Ghana) as study location. The main objectives were to: (a) design a diagnostic GNOME model to configure and generate localised oil spill scenarios; (b) model different oil spill scenarios and weathering profiles for varying environmental conditions e.g. wet/dry seasons, different currents and wind conditions; and (c) Predict the ‘minimum regret’ Splots as a precautionary principle. A combined Eulerian-Lagrangian approach involving a hydrodynamic model containing localised environmental parameters from the Saltpond oilfield was utilised. The General NOAA Operating Modelling Environment (GNOME) based on a C++ programming language was used to execute the analyses. In addition, the ADIOS2 oil weathering tool was used to estimate the oil budget for different spill quantities based on the physical and chemical properties of Ghana’s sweet light crude at Saltpond field. The key findings are: 5000 and 10,000 barrels of spilled oil beached after a minimum of 12 hours in 97% of the scenarios under the influence of winds from the South. Wind speeds leading to beaching were 35.7% for 14 and 16 knots, 14.3% for 17 knots and 7.1% for 15 and 20 knots respectively. Weathering results showed a maximum of 43% of spilled oil evaporated after 116 hours with a minimum and maximum dispersal of 1% and 7% respectively. This study, for the first time, has provided hitherto unavailable analysis and information on oil spill transport forecasting and trajectory simulation for the Saltpond Oilfield in Ghana which environmental managers/engineers would find readily useful in responding to future oil spill disasters. The approach and methodology used in this study could also be adapted for other offshore regions in Ghana and West Africa.