Where did the organisms live later become crude oil?

The organisms that later became crude oil primarily lived in ancient marine environments, such as oceans and seas, millions of years ago. When these organisms, mainly microscopic plankton and algae, died, they sank to the ocean floor and were buried under layers of sediment. Over time, heat and pressure transformed these organic materials into hydrocarbons, resulting in the formation of crude oil. This process typically occurs in sedimentary basins where conditions are favorable for preservation and transformation.