System and method to determine volumetric fraction of unconventional reservoir liquid

A system determines a volumetric fraction of oil in a formation penetrated by a borehole, the formation comprising an unconventional reservoir. The system includes a carrier configured to be conveyed through the borehole and a geochemical tool disposed at the carrier and configured to determine a mineral makeup of the formation and excess carbon not apportioned to any mineral of the mineral makeup, the excess carbon being associated with kerogen and oil in the formation. An NMR tool disposed at the carrier determines porosity of fluid in the formation, the fluid excluding the kerogen in the formation. A density tool disposed at the carrier determines bulk density of the formation, and a processor determines the volumetric fraction of oil in the formation based on the excess carbon, the porosity of the fluid in the formation, and the bulk density of formation.