Porphyrin Research and Origin of Petroleum

Abstract

Several analytical and physical methods for porphyrin research recently have been developed or applied to problems of the petroleum industry. Methods for isolating metal-porphyrin complexes from bituminous materials include solvent extraction or precipitation, emulsification, chromatography, and molecular volatilization. The classical method of Treibs and Groennings remains the basic method for extracting porphyrin aggregates from bituminous materials. Analytical methods for determining the metal contents of extracts rich in porphyrin complexes include emission spectroscopy and spectrography, colorimetry, flame photometry, and X-ray spectrography. The results of porphyrin research have several important implications on the geochemistry of petroleum. The widespread occurrence of porphyrin materials in bituminous materials is evidence of their biological origin. The carboxylated porphyrin contents of some crude oils indicate that these oils, and presumably others, have a low-temperature history. Correlations of porphyrin studies indicate that the common nickel- and vanadium-porphyrin complexes are formed by metal exchange reactions with animal and plant metabolic pigments such as hemoglobin and chlorophyll which were present during the early stages of petroleum formation. Porphyrin studies offer considerable support for the current theories that petroleum is formed slowly in marine or brackish environments from marine and terrest ial plant and animal matter and that the asphaltic constituents of crude oils are of primary formation. During the evolution of the oil these simplify to form the clean, paraffinic oils commonly associated with older formations.