Organic Geochemical Probes of Subsurface Migration in Morrow Formation Crude Oils

Abstract

Distributions of petroleum compounds in crude oils can be altered during secondary migration by adsorption and other chromatographic processes. Trends in distributions of alkanes and nitrogen-containing compounds among oils may indicate migration pathways when used in conjunction with structural and lithologic maps. Several crude oils which were produced from reservoir sans of the Morrow Formation in western Kansas and eastern Colorado were analyzed for hydrocarbons and nitrogen-containing organic compounds. Deasphalted oils were fractionated into saturate, aromatic, and polar fractions using a thermionic specific detector, which responds specifically to nitrogen-containing organic compounds. Lithologically Morrow sands and shales contain abundant clay minerals which potentially expose active adsorptive surfaces to petroleum compounds as migration of the crude oil proceeds. The fluvio-deltaic depositional environment of the sands provides clay minerals along probable flow paths in the form of clay drapes or a s gradational facies changed in silt and clay content. Differences in both alkane and nitrogenous compound profiles of crude oils from the study area exhibit possible migration-induced alteration of the oils.