When and where did petroleum form?

Petroleum formed over millions of years from the remains of ancient marine organisms, primarily zooplankton and phytoplankton, that settled on the ocean floor. This process began in the Mesozoic Era, around 252 to 66 million years ago, and continued through the Cenozoic Era. The organic material was buried under layers of sediment, subjected to heat and pressure, transforming it into hydrocarbons. Significant petroleum deposits are found in sedimentary basins around the world, particularly in regions like the Middle East, the Gulf of Mexico, and parts of Russia and the North Sea.