Kerogen studies and geological interpretations

Abstract

Abstract Kerogen is defined as the portion of organic matter in sedimentary rocks that is insoluble in organic solvents. It is formed from formerly living organic materials by diagenetic processes in the first few hundred meters of burial and is partially converted, under the influence of temperature and time, into petroleum by a series of complex, first-order reactions, termed catagenesis. The quantity and quality of petroleum formed is controlled by the concentration, type, and thermal maturity of the kerogen present in source beds and these parameters comprise the basis of all source bed studies. Catagenesis of hydrogen-rich algal and liptinitic kerogen accounts for most of the oil and gas generated in sedimentary rocks. Hydrogen-deficient, humic kerogen can yield only limited quantities of dry gas and some components of kerogen have little or no capacity to generate petroleum. The convertibility of any specific kerogen to petroleum can be estimated from its elemental composition and thermal maturity as defined by the reflectance of vitrinite. Kerogen studies play an important role in identifying effective source beds in order to predict the amount, type, and distribution of petroleum that can be expected in a basin. Maturity data is also useful in identifying certain geological features in wells, defining the provenance of sediments, unravelling the sedimentary and tectonic history of basins, and determining the boundaries between diagenesis, catagenesis, and metamorphism. Incorporation of kerogen studies and other geochemical data into conventional exploration programs will become essential as the search for petroleum becomes more difficult and expensive.