Organic petrology is a marginal science that is quite practicable. At present, it has developed into a routine research tool that is widely applied in petroleum exploration and assess ment. Based on several years’research of the authors, this paper presents the advances in organic petrological studies on immature source rocks, including the classification and characteristics of macerals, the composition of macerals and types of organic matter, the abundance and evolution of organic matter, oil2prone macerals, hydrocarbon generation and expulsion. All these results show that organic petrology is of considerable value pertaining to its application in the assessment of immature oil and gas. The immature source rocks consist of various macerals with obvious heterogeneity, contain different hydrocarbon-generating macerals with different oil thresholds and oil peaks, and show a two-staged evolutionary pattern of organic matter.

The modelling of carbon isotope kinetics of natural gas is a leading research direction in oil and gas geochemistry at home and abroad1 Combined with basin sedimentary burial and geothermal histories, the modelling of carbon isotope kinetics provides a new and effective means for evaluating the origin and accumulation history of natural gas pools1 In this paper, we briefly introduce the modelling of carbon isotope kinetics of natural gas formation and its applications to the assessment of natural gas maturity, the determination of gas source, the history of gas migration and accumulation, and the oil-gas ratio1 We show that this approach is of great value for those applications1 The carbon isotopic characteristics of natural gas are not only affected by gas source and maturity, but also are related to accumulation conditions and the geothermal gradient in a basin1 There are obvious differences in the characteristics of carbon isotope ratios between instantaneous gas and cumulative gas1 The kinetic model of carbon isotope fractionation may be different for different basins, which depends on gas source condition, accumulation history and sedimentary-tectonic history1 Since the origin of natural gas pools in the superposed basins of our country is very complicated, and because natural gas pools have features of multiphase and variable gas-sources, this paper may provide new thought s for the study and evaluation of natural gas1