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How are natural gas, oil, and water arranged inside a petroleum trap?

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Multiple large offshore petroleum oil rigs with cranes and equipment stand in the ocean, connected by walkways above the water. — petroleum Liquid petroleum (crude oil)—which is refined into gasoline, diesel, heating fuels, asphalt, plastics, and other useful chemical compounds—is often extracted from the ground using a series of drills and pumps.

Inside a petroleum trap, natural gas, oil, and water are arranged based on their relative densities. Because natural gas is the lightest, it occupies the highest portion of the trap. Beneath the gas layer lies the oil, and at the bottom of the reservoir is the formation water.12

This vertical stratification occurs because the specific gravity of the water is significantly higher than that of oil and natural gas, causing the hydrocarbons to float to the top of the water-saturated environment. This accumulation is contained within porous and permeable sedimentary rock and is sealed by an impermeable cap rock to prevent further migration. While this arrangement is typical, the presence of moving water can sometimes displace the pool down the side of the trap due to hydrodynamic pressure.213