A Semi-Markov Model for the Analysis of Crude Oil Spills in Niger Delta Region, Nigeria

This paper developed a three-state Semi-Markov model with Weibull waiting time distribution to analyse crude oil spill occurrences in the Niger Delta region of Nigeria. Oil spills were categorized into minor, medium, and major categories based on the volume of spill. An empirical data from the National Oil Spill Detection and Response Agency (NOSDRA), Nigeria from January, 2006 to March, 2020 with particular consideration of crude oil spill incidences due to CHEVRON Nigeria Ltd and Nigeria Agip Oil Company (NAOC) was used in the analysis. In the case of NAOC, the stationary distribution of the Semi-Markov process was obtained as 0.6954, 0.2461 and 0.0585 for minor, medium and major oil spills respectively, with corresponding mean waiting times before transition of 2.5438, 2.7429 and 3.6204 days. For CHEVRON Nigeria Ltd, the stationary distribution of the Semi-Markov process was found to be 0.9373, 0.0393 and 0.0234 for minor, medium and major oil spills respectively with corresponding mean waiting times of 6.4609, 6.0408 and 8.7861 days. Further results reveal that crude oil spills due to NAOC occurred once in every 3 days while that of CHEVRON Nigeria Ltd was once in every 6 days. The study recommends further investigation on the associated risk factors to oil spills of all categories in the Niger Delta region.