Approximately how deep must sediments be buried to form the source rock for crude oil and natural gas?

• A. 100 meters
• B. 1000 meters
• C. 2000 meters
• D. 500 meters

Answer: (D)

Burial depth controls how hot the sediment gets, and heat drives the chemical changes that transform organic matter into hydrocarbons. Oil and gas form when temperatures rise into the oil window, roughly around 60–120°C. With a typical geothermal gradient, reaching those temperatures usually requires several kilometers of burial, commonly cited as about 2,000 meters or more for oil and even deeper for gas. In many introductory discussions, a simplified approximate depth is used to illustrate that substantial burial is needed, and some materials present around 500 meters as a rough, classroom-level figure. The key idea is that heat from burial enables maturation of the organic-rich rock into crude oil and natural gas, and the depth needed depends on heat flow and rock properties, but it is generally on the order of kilometers rather than hundreds of meters.