Review Early developments in petroleum geochemistry John M. Hunt a , R. Paul Philp b, *, Keith A. Kvenvolden c a Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA b School of Geology and Geophysics, University of Oklahoma, Norman, OK 73019, USA c US Geological Survey, Menlo Park, CA 94025, USA Received 3 January 2001; accepted 6 May 2002 (returned to author for revision 16 April 2001) Abstract Petroleum geochemistry is the outgrowth of the application of the principles and methods of organic chemistry to petroleum refining and petroleum geology. This paper reviews 120 years of petroleum geochemistry, from about 1860 to 1980, and includes a discussion of the formal recognition of petroleum geochemistry as an earth-science discipline starting in 1959 when a general petroleum geochemistry symposium was first organized at Fordham University, New York. A chronology of significant events, including concepts, techniques, and textbook publications, is presented. Because petroleum geochemistry has been a tool for petroleum exploration from the beginning, the early developments of surface prospecting, source-rock identification, and oil/oil and oil/source correlation are discussed, along with the application of geochemistry to petroleum migration, accumulation, and alteration. In addition the paper deals with the biomarker revolution, which began in earnest about 1964, and with early models of geothermal history. Concepts in petroleum geochemistry have continually evolved, enhanced by the development of new analytical techniques, leading to new discoveries concerning the origin and occurrence of petroleum. # 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction The roots of petroleum geochemistry go back to the last part of the nineteenth century, when petroleum was recognized to be an important natural resource, and to the first part of the twentieth century, when develop- ments in organic chemistry provided a means to deter- mine the complex composition of petroleum. Concurrent with the latter was the application of chemical principles to the geology of petroleum, including its origin, migra- tion, accumulation, and alteration; the goal was to enhance petroleum exploration and production. This practical combination of petroleum chemistry and petro- leum geology became known as petroleum geochemistry. Petroleum is understood here to mean crude oil, crude-oil products, natural gas, and related bitumens. This paper reviews (1) the early history of the field of petroleum geochemistry, (2) some of the major advances prior to about 1980, and (3) how the early history and major advances laid the foundation for present practices in the field. 2. Chronology of significant events to 1980 Although the roots of petroleum geochemistry go back to the nineteenth century, mankind knew of the occurrence and use of some forms of petroleum as early as 3800 BC (Rossini, 1960). Since then, natural seeps of both oil and gas have been found in various places on earth, including China, Burma, Azerbaijan, Romania, Iran, India, Trinidad, Cuba, and North America. In many places, surface wells and shafts were drilled or dug to increase the flow rate of petroleum to the surface for collection purposes (Hunt, 1979). By the end of the eighteenth century an oil field with over 500 wells had been developed in Burma, and the last half of the next century saw the early development of a petroleum 0146-6380/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0146-6380(02)00056-6 Organic Geochemistry 33 (2002) 1025–1052 www.elsevier.com/locate/orggeochem * Corresponding author. Tel.: +1-405-325-4469. E-mail address: pphilip@hoth.gcn.ou.edu (R.P. Philp).