kerógen

Kerogen is a complex mixture of organic molecules, insoluble in common organic solvents, that is found in sedimentary rocks. It is the precursor to petroleum and natural gas. Kerogen is formed from the remains of ancient organisms, such as plants, algae, and bacteria, that were buried and subjected to heat and pressure over millions of years. As these organic materials are buried deeper within the Earth's crust, they undergo a process called catagenesis, which transforms them into kerogen. The specific type of kerogen formed depends on the original organic matter and the conditions of burial, including temperature, pressure, and time. Kerogen is classified into three main types: Type I, Type II, and Type III. Type I kerogen, also known as alginite, is derived from lacustrine (lake) algal material and is typically rich in hydrogen, making it a good source of oil. Type II kerogen, or sapropelite, is derived from marine plankton and is intermediate in hydrogen content, yielding both oil and gas. Type III kerogen, or humite, is derived from terrestrial plant material and is rich in carbon, primarily yielding natural gas. When kerogen is subjected to sufficient heat and pressure, it breaks down through a process called pyrolysis into liquid hydrocarbons (oil) and gaseous hydrocarbons (natural gas), which can then migrate and accumulate in porous rock formations, becoming economically viable petroleum reservoirs. The study of kerogen is crucial for understanding the formation and distribution of fossil fuels.