Petroleum industries and exploration started and grew large without the use of organic geochemistry. Today, however, organic geochemistry has its place in the petroleum industry. Geochemistry is needed to explain and understand the problems of petroleum generation and migration. In recent years the enormous refinement of analytic tools and their higher speed resulted in a steadily growing flux of information about the chemistry of petroleum and its precursors. This information combined with geologic knowledge produced a fair, but by no means complete, understanding of the complex processes of petroleum generation, maturation, and to some extent of petroleum migration. We can predict fairly well where to expect heavy or light oil. We can establish maturity sequences. We ha e means to differentiate between marine and nonmarine oils and we can recognize migrational directions. This basic knowledge is a prerequisite to finding a solution for the problems of oil-oil and oil-source bed correlation, source-bed identification, and a better understanding of petroleum migration. Modern organic geochemistry is prepared to attack these problems.

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