Abstract

Research on the generation and presence of hydrocarbons in sediments has been in progress for several years. The aims of this review of the literature have been to compile some of these basic concepts involved in a geochemical source-bed evaluation and show how the resulting studies can be utilized in an exploration program.

Geochemistry can play a major role in evaluating the hydrocarbon potential of basins and stratigraphic sequences. By direct analysis of well cuttings and cores, it can be established whether commercially significant quantities of hydrocarbons have been generated and preserved in the sediments represented by the samples. Thermal maturation analyses can aid in determining the subsurface depths at which oil and gas might be generated from the kerogens present in those sediments and preserved in reservoirs. Used as an exploration tool, geochemistry, therefore, can aid the explorationist in his quest to assess the areas favourable for producing hydrocarbons.

The term “source bed” should be restricted to those nonreservoir rocks that contain significant quantities of hydrocarbon mixtures similar to those characteristic of crude oils. Since only a relatively small amount of the oil generated within a sediment ever migrates from it, a source bed can be recognized by the petroleum left behind. Thus, extraction of the soluble organic matter (EOM) present in a sediment followed by detailed chemical analysis of this extract, will establish whether significant amounts of petroleum-like hydrocarbons are present, i.e., the likelihood of a source of oil.