petroleum reservoir

A petroleum reservoir is a permeable rock formation that holds oil or natural gas in significant quantities. These reservoirs are crucial for the extraction of hydrocarbons. The formation of petroleum involves hydrocarbons originating in fine-grained sedimentary rocks, such as clays and shales, where geothermal heat acts on kerogen. This process, known as primary migration, releases oil and gas, which then move through the rock.123

Petroleum accumulations are typically found in porous and permeable reservoir rocks like sandstones and siltstones, or in carbonate rocks like limestones and dolomites. These rocks must be sealed by an impermeable cap rock to form a trap, preventing the hydrocarbons from escaping. Stratigraphic traps, related to sediment deposition or erosion, are another major type, often formed by features like ancient reefs or sandbars. Exploration for these reservoirs involves various techniques, including seismic surveys, gravity and magnetic surveys, and geochemical analysis.456