Thoughts on the Birth, Evolution, and Current State of Petroleum Geochemistry

IN THE LAST 20 to 30 years, petroleum geochemistry has evolved from a fledgling science into a fully-accepted member of the multi-disciplinary team involved with hydrocarbon exploration. The birth of present-day petroleum geochemistry perhaps occurred with the early classic studies of Phillipi (1965) andTissotetal. (1971). However, the twin papers of Dow (1 974) and Williams (1974), which cannot be considered separately, are possibly the two most significant papers ever published in this field, when normalized to time of publication. This early Amoco study, far ahead of its time, gave us petroleum systems and other concepts with powerful oil-exploration applications. However, at inception, and for some time thereafter, these concepts were scornfully derided by many explorationists (Wally Dow, pers. cornmun., June, 1996). Now, with AAPG Memoir 60 (Magoon and Dow, 1994), the concept of petroleum systems is finally universally recognized as the powerful exploration tool it is. In the last 20 years, petroleum geochemistry has evolved into what many view as a mature science. This evolution culminated in the use of powerful computer models wherein basin evolution, including HC generation, expulsion, and fluid migration are modelled, yielding specific predictions accepted as reasonable portrayals of Nature by many explorationists and researchers. Because of these achievements, it appeared that there was less need for basic “new-topic’’ petroleum-geochemical laboratory and fieldbased research. This apparent decrease in a need for basic petroleum-geochemical research coincided with a general “downsizing” within the oil industry, as oil prices dropped from historic highs. Geochemistry was particularly affected by this downsizing for two reasons. First, as stated, this discipline is largely viewed as a mature science where accurate computer models yield realistic portrayals of Nature. Second, analytical and experimental petroleum geochemistry are expensive. Geochemical research was thus a prime candidate for overhead reduction by decreasing laboratory studies. Thus, much of the petroleumgeochemical HC exploration effort is now carried out by computer modelling. In fact,