基于碳氢同位素的深层煤岩气成因分析及沉积环境响应

——以渝西地区龙潭组为例

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中图分类号：P618.13 文献标识码：A 文章编号：2097-5465（2026）02-0058-11

Abstract：Inrecentyears，significantnaturalgasshowshavebeenencounteredinthedeepcoalmeasuesofthePermianLongtan FormationinthewesternChongqingarea，preliminarilyconfimingconsiderableresourcepotentialfordeepcoal-measuregasinthis interval.Torevealthegeochemicalcharacteristicsandclarifythegenetictypeandoriginofthedeepcoal-measuregasinthis region，studieswereconductedonthecompositionofnaturalgasandthecarbonandhydrogenisotopiccharacteristicsofmethane， ethane，and CO2 .The research results indicate：1）The Longtan Formation coal-measure gas in western Chongqing is predominantly CH4 ，accompanied byminor CO2 and N2 ，with low heavy hydrocarbon content. Compared to Permian coal-measure gas from adjacent areas of the Yangtze Platform，the N2 and CO2 contentsare significantly higher，indicatinga high thermal evolutiondegreeofthecoalmeasuresandfavorablepreservationconditios.2）Thecarbonisotopesofalkanegasessuggesthatthe deepcoal-measuregasisover-maturecrackedgas.Hydrocarbongenerationhistoryandtheralhistoryanalysesindicatethatthemaingasaccumulationinthestudyareaformedduring theEarlyCretaceous，representinganearlychargingandaccumulation event.3）The δD 1 values of the coal-measure gas in the study area exhibit agradual decrease from bottom to top，apattern closely related to sea-level fluctuations and paleoclimate variations during the coal deposition period.Spatially， 8D1 values in the eastern Sichuanregionshowanincreasingtrendfromsouthwesttonortheast，overallcontrolledbythedepositionalenvironmentandalso influenced bythe degree of thermal evolution.Under similar thermal evolutionconditions，marine SD -1 values are more negative thanteestrialvalues，whilethemarine-continentaltransitionalfaciesexhibitabroaderrangeofvalues.Thestudydemostrates thatthegeochemicalcharacteristicsofcoal-measuregasarecloselylinkedtotheformationandevolutionofthecoalseams， providing a scientific basis for selecting favorable targets and assessing resource potential.

Keywords：deepcoal-measure gas；C-H isotope；natural gas composition；thermal evolution；depositional environment

煤岩气是近年来我国非常规天然气资源勘探的热点领域，其成因机制厘定与资源潜力评价一直是油气地质学研究的前沿方向[。（剩余13220字）