Over time, layers of mud and sand covered this organic debris, creating an oxygen-poor environment that prevented complete decay. Above them, a caprock—often composed of shale or salt—acts as a seal, preventing the oil from escaping.
How Salt Domes Trap Crude Oil Reserves Beneath the Surface
However, it rarely reaches the surface. Instead, it becomes trapped beneath impermeable rock formations, such as salt domes or dense shale, where it accumulates in reservoirs that can be extracted today.
Reservoir Rocks and Caprocks: The Storage and Seal For an oil field to be commercially viable, two key geological features must align. Heat and Transformation: The Role of Temperature Deeper burial meant increasing temperatures, typically rising about 25°C for every kilometer of depth.
How Salt Domes Trap Crude Oil Reserves Beneath Impermeable Rock Formations
Complex organic molecules gradually transformed into a waxy substance called kerogen, and with further heat and time, kerogen converted into liquid and gaseous hydrocarbons. When plankton, algae, and other organic material died in ancient oceans, they settled on the seabed, mixing with sediments.
More About How are crude oil formed
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