Source-Rock Geochemistry: Organic Content, Type, and Maturity

Petroleum generation and storage in unconventional shale reservoirs is primarily controlled by the organic-matter present within shales. While organic richness is very important for acting as unconventional petroleum reservoirs, their hydrogen content and thermal maturity levels, critically influences the petroleum generation potential. Ideally, with increasing thermal maturity levels, petroleum compounds are liberated from organic-matter with concomitant creation of secondary organic-porosity. However, depending upon the type of kerogen present and its chemical composition, petroleum compounds may be generated even at lower thermal maturity levels. Organic petrologic techniques allows identification of organic-matter type and abundance within shales (mainly in dispersed state), as well as measure their thermal maturity levels and thereby enabling detailed petroleum generation modeling and interpretation. Herein utilizing organic petrology as a tool, we discuss the fundamentals of source-rock geochemistry comprising of organic content, type, and maturity.