Successive generation of natural gas from organic materials and its significance in future exploration

The mechanism of natural gas successive generation from organic materials means that the organic material converts with development of geothermal evolution from the kerogen thermal degradation to the thermal cracking of liquid hydrocarbon or soluble organics specifically in coal measures, leading to the relay contribution of natural gas generation from kerogen degradation to liquid hydrocarbon cracking at different stages of thermal evolution. The successive generation model of natural gas contains two aspects of ideas: ①The gas generated from kerogen thermal degradation generally takes place earlier than those from liquid hydrocarbon or soluble organic cracking. The gas generative dynamics of different organic matter shows that the major gas generation period from Ⅰ,Ⅱ and Ⅲ types of kerogen occur respectively in the thermal evolution stages of R_o1.6% (Ⅰ,Ⅱ) and R_o1.3%. The major thermal cracking gives from liquid hydrocarbon or soluble organics are mainly occurred in the thermal evolution stages at R_o1.6% and R_o(1.3%), respectively; ②Liquid hydrocarbon generated from kerogen degradation can only expel partially from source rocks and accumulated in appropriate place of reservoirs. A big portion of the liquid hydrocarbon still remains scattered in source rocks, which will be thermally cracked into gas with the increase of geothermal evolution, especially in high to super-maturation stages with the R_o2.0%.The model will help to understand the mechanism of natural gas accumulation with the feature of late gas generation from highly matured source rocks, and it is of great importance with the setup of this model to reveal the valuable potential of further exploration in the regions and intervals with high to super-high maturation.