Final answer:
The quality of oil and gas in source rock depends on organic content and maturation; oil shale contains kerogen and requires extensive processing to extract synthetic oil, yielding lower net energy values and posing significant environmental risks compared to conventional oil.
Step-by-step explanation:
The quality of oil and gas in place (kerogen) in source rock varies depending on the levels of organic matter and thermal maturity. Kerogen is a mixture of organic compounds found in sedimentary rock, which transforms into oil and gas under high temperature and pressure over millions of years. Oil shale, which is sedimentary rock containing organic matter, can be considered a type of source rock; it contains kerogen that has not yet been fully transformed into crude oil. Oil shale requires processing, such as pyrolysis, to produce liquid petroleum, and during this process the kerogen is converted into synthetic oil and gas. The extended processing of oil shale differs from conventional oil drilling, where liquid oil is pumped from reservoirs and typically has higher net energy values than oil from oil shale. Additionally, oil shale extraction can have severe environmental impacts, including high water use and potential chemical pollution from fracking processes.