Nowadays, oil is the world’s primary energy supply and plays a key role in stimulating economic expansion by meeting growing energy needs, particularly in industry and transport. However, the growing global demand for petroleum products is leading to a number of negative consequences. The extraction of crude oil and the occurrence of spills and leaks have the potential to contaminate soils and alter their physical, mechanical and chemical properties. This study involves the laboratory evaluation of the physical properties of clayey soils and the change in shear strength properties of soil samples obtained from 6 different sites within the Maysan Refinery in Iraq, which were affected by the crude oil spill. The six sites were selected for comparison based on their proximity to the refinery and the availability of clean, uncontaminated soil. The results of the research indicate that the release of crude oil into the surrounding environment had a significant impact on sites within a two-kilometer radius of the refinery. The geotechnical properties of the soil are significantly affected by the presence of oil, resulting in a reduction in undrained shear strength and bearing capacity. Negative effects on soil physical parameters, including bulk density and specific gravity, have been observed. This makes them unsuitable for various engineering purposes.