Oil spill modeling for environmental risk assessment and mitigation in East Kalimantan offshore waters

Oil spills pose a persistent threat to marine ecosystems, particularly in East Kalimantan, one of Indonesia's major oil exploration regions where crude oil distribution and production activities are intensive. However, limited research has quantitatively integrated oil spill trajectory modeling with probabilistic risk assessment for this area. This study aims to fill that gap by modeling oil spill distribution patterns and evaluating their environmental risks under seasonal monsoon conditions. Historical spill records, wind and current data, oil characteristics, and spill parameters were incorporated into the modeling framework. Oil spill dispersion was simulated and validated using Root Mean Square Error (RMSE), which yielded an initial viscosity of 905.88 centipoise, while calibration with the Mean Absolute Percentage Error (MAPE) adjusted the viscosity to 84.3 centipoise. Spill probability was estimated using the Relative Frequency method applied to historical data, and consequences were quantified with Orifice and Bernoulli equations. The results indicate that during the West Monsoon (February 2024), oil tended to spread southwest and northwest, whereas in the East Monsoon (May 2024), the dispersion shifted toward the northwest, north, and northeast. The risk assessment categorized spill probability in the range of 0.1-0.01, with very high consequences due to spill volumes of 10-100 barrels. The novelty of this study findings contribute scientifically by offering a reproducible framework for integrating hydrodynamic modeling and risk analysis, while also providing practical insights for stakeholders such as companies, policymakers, and local communities to design targeted and proactive environmental mitigation strategies.