Heat combined with increased pressure aids the transformation of organic
matter into petroleum products. But too much heat or too much
pressure can prevent any oil from forming. Many geologists use petroleum
formation to guide them on how much heat was in an area. For example, if
oil is found, the temperature never exceeded 200E
C or (392E F).
As oil is being produced in source rocks like diatomite or
limestone, the oil and gas will move into reservoir rocks that
can trap the oil as shown in the diagram below.