Carbon isotope fractionation during methane transport through tight sedimentary rocks:Phenomena,mechanisms,characterization,and implications  

作　　者：Wenbiao Li Jun Wang Chengzao Jia Shuangfang Lu Junqian Li Pengfei Zhang Yongbo Wei Zhaojing Song Guohui Chen Nengwu Zhou 

机构地区：[1]Sanya Offshore Oil&Gas Research Institute,Northeast Petroleum University,Sanya 572025,PR China [2]Ministry of Education Key Laboratory of Continental Shale Hydrocarbon Accumulation and Efficient Development,Northeast Petroleum University,Daqing 163318,PR China [3]School of Geosciences,China University of Petroleum(East China),Qingdao 266580,PR China [4]Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,PR China [5]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,PR China

出　　处：《Geoscience Frontiers》2024年第6期255-276,共22页地学前缘（英文版）

基　　金：the National Natural Science Foundation of China(Grant Nos.42302170,42302160);the Innovation Platform for Academicians of Hainan Province(YSPTZX202301);the National Postdoctoral Innovative Talent Support Program(Grant No.BX20220062);the National Science Foundation of Heilongjiang Province of China(Grant No.YQ2023D001);the Project of Sanya Yazhou Bay Science and Technology City(Grant No.SCKJ-JYRC-2023-01);CNPC Innovation Found(Grant No.2022DQ02-0104).

摘　　要：The phenomenon of carbon isotopic fractionation,induced by the transport of methane in tight sedimentary rocks through processes primarily involving diffusion and adsorption/desorption,is ubiquitous in nature and plays a significant role in numerous geological and geochemical systems.Consequently,understanding the mechanisms of transport-induced carbon isotopic fractionation both theoretically and experimentally is of considerable scientific importance.However,previous experimental studies have observed carbon isotope fractionation phenomena that are entirely distinct,and even exhibit opposing characteristics.At present,there is a lack of a convincing mechanistic explanation and valid numerical model for this discrepancy.Here,we performed gas transport experiments under different gas pressures(1–5 MPa)and confining pressures(10–20 MPa).The results show that methane carbon isotope fractionation during natural gas transport through shale is controlled by its pore structure and evolves regularly with increasing effective stress.Compared with the carbon isotopic composition of the source gas,the initial effluent methane is predominantly depleted in^(13)C,but occasionally exhibits^(13)C enrichment.The carbon isotopic composition of effluent methane converges to that of the source gas as mass transport reaches a steady state.The evolution patterns of the isotope fractionation curve,transitioning from the initial non-steady state to the final steady state,can be categorized into five distinct types.The combined effect of multi-level transport channels offers the most compelling mechanistic explanation for the observed evolution patterns and their interconversion.Numerical simulation studies demonstrate that existing models,including the Rayleigh model,the diffusion model,and the coupled diffusion-adsorption/desorption model,are unable to describe the observed complex isotope fractionation behavior.In contrast,the multi-scale multi-mechanism coupled model developed herein,incorporating diffusion and adsorption/desorp

关 键 词：Natural gas Carbon isotope fractionation Mass transport Numerical modeling Combined effect 

分 类 号：P618.13[天文地球—矿床学]