Abstract: Baigang Formation and Nadu Formation in Tertiary of Baise Basin are lacustrine source rocks. After contrasting and analyzing the results of liquid hydrocarbon and gaseous hydrocarbon productivity and component from hydrous pyrolysis of two typical immature samples of black mudstone, it is discovered that their differences are still remarkable. The hydrocarbon analysis result of the samples from Nadu Formation shows it is basically liquid in low mature-mature stage(simulating temperature between 230 to 350℃),accumulative productivity of low mature oil takes up some 60%. Liquid hydrocarbon productivity is little bigger than gaseous hydrocarbon at low mature stage in samples of Baigang Formation, but at mature stage, the hydrocarbon is basically gaseous one. In the component of thermal simulation gaseous matter, the content of gaseous hydrocarbon in the samples of Nadu Formation is significantly double peak with the increase of simulating temperature. In the thermal simulation liquid hydrocarbon，the distribution of C₂₇,C₂₈,C₂₉regular steranes is in the form of letter "V", the steranes ratio of C₂₇/C₂₉, pristane／phytane and the content of gammacerane changes in a small range with the increase of simulating temperature, but the ratio of Ts/Tm changes in a great range with the increase of simulating temperature.

Key words: thermal simulation experiment, low mature oil, gaseous hydrocarbon, Baise Basin, Tertiary