沉积与特提斯地质2024，Vol.44Issue(3)：630-640,11.DOI:10.19826/j.cnki.1009-3850.2024.08003
页岩气保存条件的碳同位素约束:以上扬子板块五峰—龙马溪组页岩为例
Shale gas preservation conditions and their carbon isotope constraints:A case study of the Wufeng-Longmaxi Shale in the Upper Yangtze Block
摘要
Abstract
The carbon isotope composition of natural gas provides significant insights into the preservation conditions of oil and gas.This study focuses on the Wufeng-Longmaxi Formation in the Changning,Fuling,and Zheng'an areas,analyzing shale gas components and the carbon isotopes of monomer hydrocarbons to understand the variation in alkane carbon isotope reversal(δ13C1-δ13C2)in different areas.We reconstruct the spatial and temporal evolution of preservation conditions in the Wufeng-Longmaxi Shale of the Yangtze Block and explore how preservation conditions affect shale gas enrichment.The results show that:(1)Carbon isotope reversal of hydrocarbons is commonly observed in the Wufeng-Longmaxi Shale,primarily caused by the mixing of secondary cracking gas with primary cracking gas during the high or post-maturation stage.(2)The mixing ratio of these two types of cracking gases is the major factor controlling the degree of carbon isotope reversal.As the proportion of secondary cracking gas increases,the extent of carbon isotope reversal and shale gas content gradually increase from the periphery towards the interior of the Sichuan Basin,indicating relatively good sealing conditions within the basin.(3)A quantitative evaluation model based on δ13C1 shows that the system openness(θ)of the Wufeng-Longmaxi shale ranges from 66%to 82%in the Zheng'an area,70%to 77%in the Fuling area,and 65%to 70%in the Changning area.(4)Differential structural deformation of the Meso-Cenozoic strata in the Upper Yangtze Region has severely damaged the sealing conditions outside the Sichuan Basin,facilitating hydrocarbon migration and expulsion,and the preservation conditions are relatively poor.Therefore,good preservation conditions are crucial for shale gas enrichment,particularly in regions that have undergone extensive deformation.关键词
页岩气/保存条件/碳同位素倒转/含气性/五峰—龙马溪组页岩Key words
shale gas/preservation conditions/carbon isotopic reversal/gas content/Wufeng-Longmaxi Shale分类
天文与地球科学引用本文复制引用
徐璐,刘睿,张康斌,唐余锋,陈增裕..页岩气保存条件的碳同位素约束:以上扬子板块五峰—龙马溪组页岩为例[J].沉积与特提斯地质,2024,44(3):630-640,11.基金项目
国家自然科学基金项目(42072184,41702157) （42072184,41702157）
中国石油—西南石油大学创新联合体项目(2020CX010302) （2020CX010302）
