A recent visit to the Soviet Union confirms impressions from the literature that Soviet geochemists continue to be the most active in geochemical prospecting technology. The All Union Scientific Institute of Nuclear Geophysics and Geochemistry in Moscow has the prime responsibility for research and development of near-surface geochemical prospecting for practical application as a rapid reconnaissance tool, especially in new areas and for stratigraphic traps, in support of geophysics and geology exploration. The major topics of investigation include: vertical migration mechanisms, radiometry, geomicrobiology, soil gas analysis, and gas logging.

In the United States, geochemical prospecting has had an erratic history of research and application, and although credited in whole or in part with some discoveries, it is not generally accepted as a commercially useful tool.

Successful application of near-surface geochemical prospecting requires (1) migration of hydrocarbons from the accumulation to the near-surface zone, (2) detection and identification of these migrated hydrocarbons in micro quantities, and (3) correlation of the observed near-surface distribution of these hydrocarbons with their subsurface source. Modern analytical methods for detecting micro quantities of hydrocarbons in rocks, soil, or soil gas samples are accurate and definitive. Factors complicating the use of geochemical prospecting involve the vertical migration process with the associated complex environmental productive zones, non-commercial occurrences, and intervening source rocks. Field tests indicate that where hydrocarbons succeed in reaching the near-surface zones, they u ually do so in the form of seeps of restricted areal extent even at the micro concentration level.

From the initial work of United States and Soviet geochemical investigators 25 years ago, there has developed a sophisticated geochemical technology now making important contributions to petroleum exploration through source bed evaluation, crude oil correlation, formation water analyses, and origin and migration investigations.

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