MULTIPLE PHASES OF HYDROCARBON GENERATION AND MIGRATION IN THE TAZHONG PETROLEUM SYSTEM OF THE TARIM BASIN, PEOPLES-REPUBLIC-OF-CHINA

Organic petrology, organic geochemical analysis and fluid inclusion me thods were employed to investigate a series of core samples from the T azhong Uplift. Bitumens and organic inclusions were found to occur wid ely in Paleozoic rocks, especially carbonates, and both can be subdivi ded into three groups. The reflectance ranges of the three bitumen gro ups are: 1.30-1.60% (I); 0.50-0.80% (II); and 0.15-0.40% (III), respec tively, and the corresponding organic inclusion groups are: dark yello w fluorescence organic inclusions with a homogenization temperature of 200-240 degrees C; blue-green fluorescence organic inclusions with a temperature of 160-200 degrees C; and the strong yellow fluorescent or ganic inclusions with a temperature of 80-130 degrees C. The wide occu rrence of the three group bitumens and organic inclusions in the Tazho ng Uplift reveals that there were three periods of large-scale oil mig ration and accumulation in this area. The analysis of hydrocarbon-gene rating history based on paleotemperature and burial history of source rocks shows that they underwent three oil-generating peaks, in Early O rdovician, Triassic and Cenozoic, respectively, which led to three pha ses of hydrocarbon generation and migration. It is believed that the T azhong Uplift is an old uplift rich in oil and gas, and has been fed w ith oil and gas from nearby source areas during a long geological hist ory, and also that it has great hydrocarbon potential. (C) 1997 Elsevi er Science Ltd.