Observation of hydrocarbon generation and migration of highly-matured carbonates by means of laser-induced fluorescence microscopy

Some important information on hydrocarbon generation, inclusion and migrati on in highly-matured carbonates of lower Palaeozoic age from the Ordos Basi n and Tarim Basin has been analyzed by a newly-combined laser-induced fluor escence microscope (LFM) designed by our laboratory. The following informat ion has been obtained from the lower Ordovician lamellar carbonates with eq uivalent vitrinite reflectance (R-o) as high as 1.6%-1.7% and residual TOC of 0.14%-0.35% from the Ordos Basin: wide occurrences of oil and source mac erals with strong fluorescence, including G.Prisca alginite, lamalginite, t elalginite and algae-detrinite; fluorescing asphalt among mineral crystals; some groundmass and spheroid-like reservoir bitumen with high maturation l evels in the pores of dolomites. Various kinds of fluorescing organic inclu sions and asphalt have been found in the carbonates, calcareous shales and silt-shales with high maturation levels from the Cambrian-Ordovician strata in the Tarim Basin. All this helps us find and evaluate significant and ex cellent source rocks for large- and middle-scale gas fields. The net and mi cro-net systems for hydrocarbon generation, expulsion and migration in carb onates have been revealed by the highly-powered laser-induced fluorescence microscopy.