Composition changes in vanadyl porphyrins in oil filtering through porous media.

Previous experiments on property changes in petroleum during filtration have shown that trace elements provide reliable migration parameters for hydrocarbon fluids. The porphyrins in petroleum and the major part of the trace elements are associated with the heavy fractions and tend to be taken up by the rock during infiltration, which tends to produce compositional differentiation in the vanadyl porphyrins; the overall vanadyl porphyrin concentration decreases along the migration path, while the proportion of nonpolar porphyrin compounds increases, as does the alkylation index. The changes in the vanadyl porphyrins have been examined by simulating migration under laboratory conditions, and the results are confirmed by research on the vanadyl porphyrins in petroleum from deposits in the Surgut petroliferous region in W Siberia. -Authors