Oil Spill Fate and Trajectory Simulation for Sierra Leone's Offshore Exploration Basin, Using the Savanah-1X Well as the Focal Point

Abstract

The demand for crude oil and petroleum products have subsequently led to an increase in the likelihood of occurrence of oil spills. It is therefore imperative to understand the impacts of these spills on humans and the environment. Developing appropriate oil spill response and remediation techniques can be achieved by understanding the fate and likely trajectory of different types of oils, once they come in contact with the sea surface. Though still at the nascent stage of oil and gas exploration, the Sierra Leone basin is known to hold large undeveloped hydrocarbon reserves which are being exploited with the aim of contributing to national development. With the availability of oil spill modelling tools, and owing to the fact that environmental conditions vary over time, there is the need to carry out routine studies on the likely behavior of a spill offshore Sierra Leone. This study aims to develop a prediction model that would aid in understanding the fate, trajectory and uncertainties of oil spilled on Sierra Leone waters in the dry, rainy, and harmattan seasons. In order to analyze the trajectory of a spill in the Sierra Leone basin, the GNOME software was used. Furthermore, ADIOS2 was also employed to analyze the weathering processes of the spill. The results obtained from GNOME showed that during the dry and rainy seasons, approximately 15% of oil would be stranded on the shores of Sierra Leone, within three – five days. Owing to the permanently warm water temperatures in the Gulf of Guinea basin, a high percentage of the oil is expected to evaporate and disperse within few days of the spill. The weathering models from ADIOS2 reveal that 34% of oil would be lost to evaporation in the dry season, and 36% and 38% will be lost in the rainy and harmattan seasons respectively. Furthermore, it can be seen that dispersion accounts for 2.5% of oil lost in the dry season, 7.8% during the rainy season and 6.2% in the harmattan period. Within 5-days, ADIOS2 reveals a stable water-in-oil emulsion, leading to an increase in viscosity and density. Airborne benzene concentration is expected to be high on the first day of the spill, but would decrease as the days go by. Based on these results, it is recommended that oil spill response personnel are professionally trained, and equipment must be available to respond to spills in a timely and efficient manner.